Does This System Make Sense?

RWBRWB Solar Expert Posts: 168 ✭✭✭✭✭
Hi I'm wanting to build a system that is rather small but not to small for doomsday situations. I'm wanting to build something that would power a few CFL's, 2 laptop's, 1 hour quick AA charger, Some Radios, a fan here and there and have 1500w True Sine Inverter that is able to power the microwave, drill, saw type of loads. Yes, I know I would have to conserve and could only run the large loads rarely.

I have a Kill A Watt meter and have taken readings on all the devices I would want to run and for how long per day to try to get a ruff reading on what I would need to supply that load. Here is what I was playing with:

Laptop#1 .68amps x 10 hours a Day = 6.5 Amp Hours
Laptop#2 .45amps x 10 hours a Day = 4.5 Amp Hours
13Watt CFL .18 amps x 12 Hr a Day = 2.16
13Watt CFL .18 amps x 12 Hr a Day = 2.16
13Watt CFL .18 amps x 12 Hr a Day = 2.16
Satellite .19 amps x 12 Hr a Day = 2.28
Sony Big TV 2.5 amps x 3 Hr a Day =7.5
Amplifier .45 amps x 12 Hr a Day = 5.4
AA Charger .33 amps x 3 Hr a Day = .99

Total Amp Hours = 33 Amp Hours

So is there anything wrong with the above Amp hour total?

Here is the system that I was thinking would be able to supply the above daily needs.

2 or 3 - Sharp ND 224U1F Panels
Outback FM60 SCC (Mainly so I can upgrade later & its a good controller)
2 - Concord SunxTender PVX-2120 AGM 4D batteries, 212 Amp Hours Each
1 - 1500 Watt Pure Sine Wave Inverter (Hoping it will start Vacume motors)

I attached a printout on what these panels could produce.
2 panels could produce - 29adc per hour max
3 panels could produce - 44adc per hour max

So I'm thinking that 2 panels could do the job but 3 panels would do it quicker but I'm budgeting for 2 right now.

I live in Indianapolis Indiana and from what I have come up with its looking like we get:

Low Solar Hours Per day = 2.7
High Solar Hours Per day = 6.3
No Tracking Average = 4.6
1 Axis Tracking Average = 5.8

It looks to me that this system would work pretty good for the loads that I'm am looking at running in an emergency situation.

What am I missing out on? I'm sure I'm off somewhere on something with this setup. I know the inverter is not very efficient.

Please let me know what you pros think about this setup, I expect it would cost me 4500 for the setup, and 5600 for the 3 panel setup. I would like to expand it as time goes on and money permits but right now I just want a system that is semi portable and is able to produce a decent amount of power for lights, laptops, and recharging Scanners, AA Battries that run radios, and the occasional microwave, or anything else that I might need to power for very short periods. I know a system this size can not run large loads long at all.

Please let me know what you think.

Comments

  • BB.BB. Super Moderators, Administrators Posts: 32,814 admin
    Re: Does This System Make Sense?

    First, a minor issue... With your kill-a-watt meter, you would be better off to measure watts rather than amps. Measuring amps can over estimate the amount of power your system will need to supply. Especially for motors and some electronic devices.

    Power=Voltage*Current is the common equation. For DC, that is pretty much always true. For AC, the shape of the current wave forms and the "phase" between the voltage and current wave form force us to use the more correct equation for power:

    Power (AC) = Voltage*Current*Cos Angle between voltage and current
    Power (AC) = Voltage*Current*Power_Factor (power_factor~Cos Angle)

    For "resistive" loads, Cos 0 degrees = 1 = Power_Factor
    For "Motor/Inductive" loads, Cos 53 degrees = 0.6 = Power Factor
    For "CFL's", PF can equal ~0.6 because of non-sine current wave form

    So, just using AC Amps, can, in some cases, cause you to think that watts used is actually 1/0.6=1.67 or to estimate 67% more power usage than there really is (inverters, to a large degree, don't care about P=V*I, they care about P=V*I*PF=Watts).

    Now, the other big issue (if I understand your data correctly) is that you measured and calculated everything in Amps... The data you took is (I presume) amps at ~120 Volts... But the panels you are looking at are amps at ~29.3 volts.

    Power=33 amphours * 120 volts = 3,960 Watt*Hours
    Power=33 amphours * 29.3 volts = 966 Watt*Hours

    Or, you are undersizing your system by 120/29.3=4 .

    But--if you take into account the "hours of sun" per day... You are getting 3-6 hours per day... So, if you are taking that into account, then in summer you will have excess power and in winter, you will have to cut the load/use alternatives to recharge your batteries.

    But, there is also another issue--overall system efficiency vs "name plate" ratings... In the end, a good starting point for an off-grid system's efficiency (from solar panel to charge controller, to battery, to inverter, to load) is around 0.52... Meaning that you will have to multiply your estimated power requirements by 1/0.52=1.92 -- or approximately 2x more solar panels than you would estimate from using the solar panel name plate ratings.

    So--working things the way I am normally used to:

    Load=3,960 Watt*Hours per day
    Location: Indianapolis Indiana
    Off-Grid: derate factor = 0.52
    Using this website to estimate your power output (everything else default)

    A 1kW array will generate a minimum of 69 kWhrs per month or 1/30=2.3 kWhrs per day minimum 9 months out of the year...

    So, your system panel requirements would be:

    (3.96kWH/2.3kWH)*1kW=1.72 kWatts of solar panels
    1,720 Watts/224 watts per panel=7.6~8 solar panels of the model you are looking at

    Now, I see that you are looking at AGM batteries--so the derating factor would be ~0.58 (80% eff for flooded cell, 90% eff for AGM)... Allowing you to round down to 7 panels instead.

    Sizing of the battery bank...

    1/85% inverter eff * 3,960 watts / 12 volts = 388 amp*hours at 12 volts

    Using our 6x rule of thumb (3 days of no-sun, 50% discharge level):

    6x388*AH=2,328 amp*hours of batteries are 12 volts.

    2,328 AH/212AH per battery = 11 AGM batteries (of the rating you looked at)

    Lastly, looking at your inverter--If you are going to want more than 1kW from your inverter, I would suggest that you look at either a 24 volt or 48 volt inverter. I recommend trying to keep your DC current below 100 amps for your wiring... (keeps costs down, and reduces dealing with really heavy cables).

    Cost wise, you are already looking ~$8,000 of solar panels ($5 per watt) and ~$5,000 for the batteries.

    I will stop here--because this is a whole bunch more money than you were initially planning on spending. And it is possible I miss-understood your information in places here.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarusicarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Does This System Make Sense?

    It "aint" what you want to hear, but once again Bill has it dialed!

    Tony

    Bill, Do you ever get tired of doing those calcs over and over again?
  • BB.BB. Super Moderators, Administrators Posts: 32,814 admin
    Re: Does This System Make Sense?

    So far... Not yet... It helps me keep in practice typing. :cool:

    Notice that I have not done a copy and paste on the formulas yet... At this point, everyone asks the "solar question" a bit differently--so giving a "canned" answer for people just starting would seem to be a bit frustrating for everyone involved.

    I have stopped the "derivation" of derating and battery factors... I think that this probably confusing to new users--and we are always ready to go off the deep end in discussing any detailed questions (see the "3 day battery rule" thread :p ).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • RWBRWB Solar Expert Posts: 168 ✭✭✭✭✭
    Re: Does This System Make Sense?

    Thanks for the breakdown I was expecting that :)

    I guess what I'm really looking to find out is:

    What is the system capable of producing & storing in the batteries per day do ya think. A ruff estimate would be good if ya can do that.

    I'm not really concerned with the 3day storage factor for cloudy days. This is for backup only.

    Lets forget about the loads I mentioned.

    What do you pro's think a 2 and 3 panel system is able to produce daily max and then average, and Lets throw out the 3 day reserve.

    Thanks for the help BB :)

    I just want to have something ready incase I'm ever without the grid for long periods of time.
  • icarusicarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Does This System Make Sense?

    You are asking a question that really doesn't have an answer. For example, if you are looking for an emergency solution, but don't want to include a reserve it is kind of pointless. If, as you say, you "are without the grid for long period of time" you have to estimate the loading and the the time to give any meaning to your answer.

    We use ~ 500 wh/day with ~200 watts of panel. Some of that is used while generating, some drawn from the battery, so it isn't a direct correlation, but it gives you an idea.

    In your case, I suppose with ~450 watts of panel you could draw somewhere around 1200wh/day all things being similar. If you were willing to draw your batteries down to close to zero, you could perhaps draw 6kwh for one day, but depending on your battery it would be dead.

    Tony
  • BB.BB. Super Moderators, Administrators Posts: 32,814 admin
    Re: Does This System Make Sense?

    Say I had $4,500 and I use our host's store (shipping and handling extra).

    3x $1,030 = $3,090 Sharp 224 watt panels (remember, S&H can be very expensive for glass solar modules)

    1x $584 Outback Flexmax 80 Amp MPPT Solar Charge Controller

    1x $140-$350 battery monitor (really recommended to prevent battery damage from over/under charging and over discharging)

    Inverter wise, I would suggest a good, small, true sine wave inverter. The Morning Star 300 watt ($300) is a really nice unit. Others on this page are fine too (and available for 24+ volt battery systems). If you need to power larger loads on occasion (well pump, vacuum cleaner)--get one of those 1,000 watt MSW (modified sine/square wave) inverters for $50-$100.

    That pretty much uses up your budget... I would suggest that you get some "cheap golf cart batteries" and setup the system with them... Once they have worn out (after 3-7 years), you can make the decision to buy the 2-3x as expensive AGM batteries. If you get the flooded cell batteries, then a few accessories (like hydrometer and water saver type battery caps) will help.

    How much will your array output... 3x224 watt panels, grid tied, 52% efficient:
    Month SunHrs/Day kWH/Month kWH/day
    1    3.18    34.9    1.2
    2    4.14    41.0    1.4
    3    4.44    46.4    1.5
    4    5.15    50.4    1.7
    5    5.73    56.4    1.9
    6    5.84    53.1    1.8
    7    5.92    55.1    1.8
    8    5.67    53.8    1.8
    9    5.20    48.4    1.6
    10    4.7    47.7    1.6
    11    3.07    30.2    1.0
    12    2.37    25.5    0.9
    ===========================
    Year    avg sun  4.62   kWH/year 541.6
    

    Assuming that I formatted this post correctly and did the Excel conversions to 672 watts of solar panel (program uses 1,000 watts of solar panels as the minimum panel size)...

    So roughly, 1-1.8 kWhrs per day over the year... I would still size your batteries for 6x the daily production/load of your system... Pick 1.5kWhrs

    6x1.5kWhrs=9kWhrs of storage.

    Using 12 volt batteries:

    9,000 Watt*Hours / 12 volts = 750 amp hours of batteries...

    You could probably drop down to 350 Amp*Hours of batteries (referenced to 12 volts) and still be just fine. Still gives you a day or two of "emergency storage"

    350 AH * 12 volts * 50% (max battery discharge)=2,100 Watt*Hours of useful storage

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.BB. Super Moderators, Administrators Posts: 32,814 admin
    Re: Does This System Make Sense?

    Forgot to add the mounting discussion...

    Don't bother with tracking array mounting of your solar panels. The trackers are expensive, unreliable, easy to fail during wind storms, and require lots of maintenance/replacement parts.

    Just take the money you "save" on not buying a tracker and buy more solar panels.

    If you have the area--look at (and/or build) solar mounts that would let you tilt the panels for summer/winter use... You have only a few panels so this would be easy for you to adjust for the seasons.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarusicarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Does This System Make Sense?

    Bill,

    It is interesting that your full calc. corresponds almost exactly with my real world system, adjusted for size!

    T
  • RWBRWB Solar Expert Posts: 168 ✭✭✭✭✭
    Re: Does This System Make Sense?

    Dam Bill ya make it look so simple :) I can't thank you enough for all the advice.

    Ok so let me get this straight with the 3 - Sharp ND 224U1F Panels and the Outback Flexmax 80 Amp MPPT Solar Charge Controller together are able to output roughly, 1-1.8 kWhrs or (1,000-1,800 Whrs) per day over the year.

    And these are realistic numbers I can actually expect for this area correct.

    I want to have as few parts in this system as possible and would like to only have 2 batteries that are large but not so large they would be to heavy for a single man to move around. I was thinking that the AGM batteries took a charge quicker and they last longer when they are taken down to 50% DOD, which I would do if needed only.

    Assuming that price was not a factor which battery do you think is better suited for this type of application where I only would like to have 2 batteries max and would like to use a 50% DOD even though it will shorten the life of the battery to just a few years.

    If I went with the 2 Sunextender 212amh batteries how many watt hours do you think I could store if 50% was my DOD?


    I have quite a few questions but we will start with this one :)

    Thanks for the help guys :)
  • BB.BB. Super Moderators, Administrators Posts: 32,814 admin
    Re: Does This System Make Sense?

    RWB,

    Yes, more or less, you can expect those numbers... I ran the same program against my homes 3.5kW of solar panels (Grid Tied) and the results where very close.

    As always, these are estimate and your local conditions (for example, 12 miles away is the Pacific Ocean and we get 4 day of clouds and 2 days of sun) and any local shading (power line, trees, buildings, etc.) can dramatically reduce your real outputs.

    But, if you have good exposure, and no shadows from 9am to 3pm, you will get good results.

    Also, if you are curious, look up your state/city on these PDF's of the data... The graphs have approximately 20 years of data and they show min/max/average energy production (some place, the difference between high and low in a month can be a factor of 2x of the twenty years--because of weather?, other places, the differences are much less).

    I left out a few details--Highly recommend that you get the Remote Battery Temperature Sensor option for the charge controller. Battery charging voltages change quite a bit based on the battery's actual temperature. For the Outback FM 80, there is a "Mate" programming/monitoring interface you may want/need (I am not the expert on the details of the equipment--I would suggest you download the manuals and read them before buying).

    Others, like Xantrex, also make nice MPPT charge controllers. There are other 60 amp controllers--A bit small for your 3x224 watt panels--but could work fine too--read the manuals to be sure.

    I am not sure I would go with the AGM batteries... My two cents--They are expensive (2-3x as much), and I wonder if they would last any longer than a good quality flooded cell battery--especially in a "stand by off-grid" system... And for a new system/user--it is very easy to over charge (or over discharge) an off-grid system--a typical mistake for a new user. If you are careful--you could use AGM's first. If you overcharge a flooded cell battery--you just add distilled water. AGM's, you cannot add water if overcharged/vented.

    AGM's are very nice for off-grid systems. No maintenance (adding of water), and no acid fumes to eat your wiring, and no hydrogen gas production during normal operation (you do still need to properly vent the box in the event the batteries overcharge and vent).

    Regarding useful storage... At 50% and 80% (yes, 80% should be OK with the SunExtender AGMs--but less cycle life with deeper discharge):

    2x212 AH * 12 volts * 50% (max battery discharge)=2,544 Watt*Hours of useful storage
    2x212 AH * 12 volts * 80% (max battery discharge)=4,070 Watt*Hours of useful storage

    And lastly, for an emergency system, test it once per year or so... Nothing like finding your batteries won't hold any more power than six "D Cells" in a real emergency.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • RWBRWB Solar Expert Posts: 168 ✭✭✭✭✭
    Re: Does This System Make Sense?
    Also, if you are curious, look up your state/city on these PDF's of the data... The graphs have approximately 20 years of data and they show min/max/average energy production (some place, the difference between high and low in a month can be a factor of 2x of the twenty years--because of weather?, other places, the differences are much less).

    That's where I got my numbers from, so sounds like they should be most realistic.
    I left out a few details--Highly recommend that you get the Remote Battery Temperature Sensor option for the charge controller. Battery charging voltages change quite a bit based on the battery's actual temperature. For the Outback FM 80, there is a "Mate" programming/monitoring interface you may want/need (I am not the expert on the details of the equipment--I would suggest you download the manuals and read them before buying).

    Yes I will certainly have a RBT sensor for the Outback. I like the Outback Flex SCC better than anything else I see avaliable right now.

    After seeing that a being able to monitor the battery's state of charge is an important thing not to mention all the other data it provides I decided that the items below will keep me totally informed of whats going on:

    Outback Flexnet DC
    The Mate2 Remote Monitor
    Others, like Xantrex, also make nice MPPT charge controllers. There are other 60 amp controllers--A bit small for your 3x224 watt panels--but could work fine too--read the manuals to be sure.

    Yea the Xantrex is a nice looking unit but I like the outback better. I think its better to go with the Flex 80amp unit for future expansion and its only 50 bucks more.
    I am not sure I would go with the AGM batteries... My two cents--They are expensive (2-3x as much), and I wonder if they would last any longer than a good quality flooded cell battery--especially in a "stand by off-grid" system... And for a new system/user--it is very easy to over charge (or over discharge) an off-grid system--a typical mistake for a new user. If you are careful--you could use AGM's first. If you overcharge a flooded cell battery--you just add distilled water. AGM's, you cannot add water if overcharged/vented.

    AGM's are very nice for off-grid systems. No maintenance (adding of water), and no acid fumes to eat your wiring, and no hydrogen gas production during normal operation (you do still need to properly vent the box in the event the batteries overcharge and vent).

    Yea the main thing I'm liking about the batteries is that they are sealed, no gasses, no need to keep them topped up water. I'll be taking care of the batteries for sure. I'll make sure everything is taken care correctly considering the cost.
    Regarding useful storage... At 50% and 80% (yes, 80% should be OK with the SunExtender AGMs--but less cycle life with deeper discharge):

    2x212 AH * 12 volts * 50% (max battery discharge)=2,544 Watt*Hours of useful storage
    2x212 AH * 12 volts * 80% (max battery discharge)=4,070 Watt*Hours of useful storage

    Yea I have looked at the DOD chart for these batteries and at 50% its in the 3 year range if I remember correctly. I would only deeply discharge when needed.

    I do understand that the I will be cutting the batteries life short by discharging so deeply if I did do it but for this system I'm no planning on a very long battery life. 3 years life would be fine with me.
    And lastly, for an emergency system, test it once per year or so... Nothing like finding your batteries won't hold any more power than six "D Cells" in a real emergency.

    Absolutely, I will set this system up and will be using it to power small loads until I have a power outage or emergency. So it will be up and running correctly from setup.

    Won't the Charge controller properly charge my batteries correctly once setup correctly providing that we have an average amount of sun? Is there anything I am forgetting BB assuming its setup right and temps are not extream in either direction?


    Now the one thing that I am trying to get a grip with is the AC to DC Inverter equation for correctly measuring what the DC Load is gonna be on the battery when power stuff via DC to AC converter.

    I have attached a picture of an equation out of the Sun extenders PDF document on sizing your batteries. But its still confusing to me.

    I have a KillaWatt Meter here are my watt and Amp readings if ya could help me understand how to correctly calcuate the correct DC load.

    Laptop#1 45watt - .68amps x 10 hours a Day = 6.5 Amp Hours
    Laptop#2 40watt - .45amps x 10 hours a Day = 4.5 Amp Hours
    13Watt CFL 11watt - .18 amps x 12 Hr a Day = 2.16
    13Watt CFL 11watt - .18 amps x 12 Hr a Day = 2.16
    13Watt CFL 11watt - .18 amps x 12 Hr a Day = 2.16
    Satellite 14watt - .19 amps x 12 Hr a Day = 2.28
    Sony Big TV 200watt - 2.5 amps x 3 Hr a Day =7.5
    Amplifier 39watt - .45 amps x 12 Hr a Day = 5.4
    AA Charger 22watt - .33 amps x 3 Hr a Day = .99


    Thanks again for all the help :)
  • BB.BB. Super Moderators, Administrators Posts: 32,814 admin
    Re: Does This System Make Sense?

    I think you have the basics down down...

    Read the manuals, and somebody who knows the Outback family better than I (Jim/Crewzer here, the Outback Forums, or the retailer you purchase the equipment from) will be able to address those "little details" that can kill you in the end.

    The link to the program that calculates the solar power output is probably a bit more accurate than the charts (both probably use the same data set) when estimating output... But I like the charts because they show the variability and other options right there (like comparing tilting an array up in the winter vs just leaving it fixed all year round).

    I don't know much about the new Flexnet battery monitor--read through the manual for both (Flexnet and other brands/models) to make sure they give you the information you need.

    It is interesting, the "3 day battery rule" thread--I went through the calculations of running of charging a battery every day, vs letting it discharge for 3 days then recharging--and from the cycle charts, the battery may have ~1/3 the number of cycles, but because there are 1/3 the number of cycles, the difference adds up to being almost equal (with in a first order guess) vs using a generator to make up loss in sunlight (charging after 1 day vs charging after 3 days).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarusicarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Does This System Make Sense?

    Using your numbers, 120 volts ~34 amp hours=4080 watt hours
    12 volts 340 amp hour=4080 watt hours
    24 volts 170 amp hour=4080 watt hours

    It is all watt in the net, regardless of the voltage used to power it.

    Volts X amps = Watts

    Tony
  • RWBRWB Solar Expert Posts: 168 ✭✭✭✭✭
    Re: Does This System Make Sense?
    Read the manuals, and somebody who knows the Outback family better than I (Jim/Crewzer here, the Outback Forums, or the retailer you purchase the equipment from) will be able to address those "little details" that can kill you in the end.

    Yea good idea.
    The link to the program that calculates the solar power output is probably a bit more accurate than the charts (both probably use the same data set) when estimating output... But I like the charts because they show the variability and other options right there (like comparing tilting an array up in the winter vs just leaving it fixed all year round).

    Yea them charts are nice, especially for beginners.
    I don't know much about the new Flexnet battery monitor--read through the manual for both (Flexnet and other brands/models) to make sure they give you the information you need.

    Yea I read through that manual and I have to say that the Battery Monitor is a slick piece of equipment. I like what I see at least.
    It is interesting, the "3 day battery rule" thread--I went through the calculations of running of charging a battery every day, vs letting it discharge for 3 days then recharging--and from the cycle charts, the battery may have ~1/3 the number of cycles, but because there are 1/3 the number of cycles, the difference adds up to being almost equal (with in a first order guess) vs using a generator to make up loss in sunlight (charging after 1 day vs charging after 3 days).

    Not quite sure what you are saying here, but would like to understand.
    It is all watt in the net, regardless of the voltage used to power it.

    Volts X amps = Watts

    Thanks Tony, that did help out :)


    Now questions about inverters :)

    I would just go with a 1750watt Xantrex Modified Sine Wave inverter off Amazon.com for $200 to power up everything even the large loads like the occasional vacume, microwave, stuff like that.

    I don't want to be limited to what I can power up because of having to small of an inverter. But I also do not want to damage stuff by powering it from a Modified Sine wave either.

    I had a Xantrex 1200watt inverter but when I tested it out hooked up to one of those portable car battery jumper systems it would trip every time I tried to power up a Shop Vac or my Dyson vacuum cleaner. The drill, tv, stereo, satellite all worked at the same time.

    Do you guys think the Xantrex 1750watt Modified inverter hooked up to these 2 batteries would run start and run these vacuum motors?

    Do motors run just as fine on Modified Sine Wave as Pure wave?

    I would rather have 1 inverter than 2 (Morning Star 300 & 1750w Xantrax) so I was thinking that spending alittle more on a Pure Wave inverter would be a better investment if I was worried about harming the devices I would be powering in the case of an long term loss of power. I'm thinking if its a dooms day scenario then I think that running a pure wave inverter I have less chance of ruining the very the equipment that I would be surviving with.

    What are you thoughts on this?
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Does This System Make Sense?

    rwb,
    modsine inverters tend to have more power drawn when you are dealing with loads that are motors be they fans, drills, or even sweepers. this extra power gets dissipated in the motor as extra heat and can cause a shortened lifespan to the motor with some blowing out in a short timespan. also, some chargers like for some power tools(but not limited to power tools) and other wall wart devices have been known to blowout too. this type of an inverter may do fine on lights, radios, and even most tvs. if you want to run a sweeper i suggest a sinewave inverter and one that has plenty of room for the surge power such devices can draw. running multiple devices with motors at the same time may not work well for you without going even larger on the inverter and battery capacities. it is my opinion those 2 concorde batteries should handle the sweeper.
    btw, if it's a "dooms day scenario" nobody will be around to use it even if it should survive whatever caused the doomsday scenario. i think you mean an emergency situation.
  • BB.BB. Super Moderators, Administrators Posts: 32,814 admin
    Re: Does This System Make Sense?

    Regarding the whole 3 day rule, 50% max discharge, whether it is better to only cycle a battery by 10% and using a generator to recharge in bad weather vs letting the battery discharge 50% and at that point, decide whether to use the generator to recharge the bank.

    In the end, when I went through a few of the senarios in the "3 day rule thread"--it appeared that within a margin of error of +/-20% (there is probably no way we could predict typical battery life any closer than that), it turned out that turning on the generator after the first day of no sun would give a longer cycle life; ~3x longer, but letting the battery go 3 days and then recharging used 1/3x the number of charging cycles--pretty much becoming a wash in battery life (charging every day life gave only marginally longer battery life vs charging every three days). When you add the price for fuel (vs the "free power" that may be available from the sun to recharge your bank in day 2 or 3; the cost of the fuel/generator maintenance may have well equaled the costs vs a buying a new battery bank marginally sooner because of the deeper cycling).

    The other thing to look at... Designing a battery bank to cycle an average of 10% Depth of Discharge (DOD) vs designing a battery bank for an average of 50% DOD---the 10% bank is 5x larger (and 5x more costly) than the 50% DOD designed bank.

    If the 10% bank lasts 5+x longer, but costs 5x as much--have you really saved any money. Add to that the cost of money (if a loan) vs positive of the ever upwards price pressures on buying ever more expensive batteries vs the "cheap" batteries you have been using for 10+ years... :confused:

    In the end, from what I have seen, just take care of your bank (properly charged: Keeping batteries above 75% SOC (state of charge) for long term storage, don't overcharge/boil batteries--especially for AGM/Sealed batteries, and keep the water up--in flooded cell, and keep the installation clean, etc...

    Don't over think the system design and usage, and you can easily move the "3 day rule" around by 1/2x to 2x (for battery capacity) and still have a very usable system that does not (typically) violate any basic system no-no's...

    -Bill

    PS: I would still highly recommend (if your budget can justify) a "small" true sine wave (TSW) inverter for the smaller loads, and get the cheap, big, MSW inverter for large loads/backup... 300 watts is more than enough to power a laptop and (smallish) TV/Sat system (perhaps one at a time). Bigger inverters have much more losses when running small equipment and are less efficient in many applications (because of the MSW behaviour in many appliances). Plus, you will have a backup inverter.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarusicarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Does This System Make Sense?

    Here is the way that I see it. Properly sizing batter banks is important. Erring on the side of too big (ie sized for ~10% discharge rate) allows the occasional deeper discharge without damage. I realize this comes at an added cost of the bank. The danger is that if you have a bank that is over large, them temptation is, when it gets down below ~80% for a couple of days, the reaction can be , "Oh well, we can draw down to 50% without a problem". This of course leading to not bringing the battery up full in a timely manner.

    My battery gives me a 3 day reserve to 20% dod, and the panels are sized such that it will bring them back from that in 1 good day of sun. I, as a matter of course always run the generator on the third day unless I am absolutely convince that I will have perfect sun on the fourth.

    Tony
  • RWBRWB Solar Expert Posts: 168 ✭✭✭✭✭
    Re: Does This System Make Sense?
    niel

    rwb,
    modsine inverters tend to have more power drawn when you are dealing with loads that are motors be they fans, drills, or even sweepers. this extra power gets dissipated in the motor as extra heat and can cause a shortened lifespan to the motor with some blowing out in a short timespan. also, some chargers like for some power tools(but not limited to power tools) and other wall wart devices have been known to blowout too. this type of an inverter may do fine on lights, radios, and even most tvs. if you want to run a sweeper i suggest a sinewave inverter and one that has plenty of room for the surge power such devices can draw. running multiple devices with motors at the same time may not work well for you without going even larger on the inverter and battery capacities. it is my opinion those 2 concorde batteries should handle the sweeper.
    btw, if it's a "dooms day scenario" nobody will be around to use it even if it should survive whatever caused the doomsday scenario. i think you mean an emergency situation.

    Yea I mean emergency situation :) Yea I don't want the know that I could be damaging something every time I plug something into the inverter. My original plan was to get the $750 True Wave inverter with 1500watt capacity, not sure what surge wattage is on it.

    I also have a 175watt xantrex inverter also as a backup but I do agree a 300watt Morningstar True Wave inverter would at least allow me to think that I would be no possible harm to any device powered by it vs. the Modwave inverter.

    Its a tuff decision. I want as least equipment as possible, but I don't want a inverter to die on me and not have another one ya know.

    I like the morning star 300w unit and agree it would power just about everything I would want to run. But when it comes time to power the big loads I want to have the ability to run them for short periods of time.

    I guess its just something I will have to figure out :)
    PS: I would still highly recommend (if your budget can justify) a "small" true sine wave (TSW) inverter for the smaller loads, and get the cheap, big, MSW inverter for large loads/backup... 300 watts is more than enough to power a laptop and (smallish) TV/Sat system (perhaps one at a time). Bigger inverters have much more losses when running small equipment and are less efficient in many applications (because of the MSW behaviour in many appliances). Plus, you will have a backup inverter.

    yes your right BB. Having a backup is a very good idea indeed :)
    Regarding the whole 3 day rule, 50% max discharge, whether it is better to only cycle a battery by 10% and using a generator to recharge in bad weather vs letting the battery discharge 50% and at that point, decide whether to use the generator to recharge the bank.

    In the end, when I went through a few of the senarios in the "3 day rule thread"--it appeared that within a margin of error of +/-20% (there is probably no way we could predict typical battery life any closer than that), it turned out that turning on the generator after the first day of no sun would give a longer cycle life; ~3x longer, but letting the battery go 3 days and then recharging used 1/3x the number of charging cycles--pretty much becoming a wash in battery life (charging every day life gave only marginally longer battery life vs charging every three days). When you add the price for fuel (vs the "free power" that may be available from the sun to recharge your bank in day 2 or 3; the cost of the fuel/generator maintenance may have well equaled the costs vs a buying a new battery bank marginally sooner because of the deeper cycling).

    The other thing to look at... Designing a battery bank to cycle an average of 10% Depth of Discharge (DOD) vs designing a battery bank for an average of 50% DOD---the 10% bank is 5x larger (and 5x more costly) than the 50% DOD designed bank.

    If the 10% bank lasts 5+x longer, but costs 5x as much--have you really saved any money. Add to that the cost of money (if a loan) vs positive of the ever upwards price pressures on buying ever more expensive batteries vs the "cheap" batteries you have been using for 10+ years...

    In the end, from what I have seen, just take care of your bank (properly charged: Keeping batteries above 75% SOC (state of charge) for long term storage, don't overcharge/boil batteries--especially for AGM/Sealed batteries, and keep the water up--in flooded cell, and keep the installation clean, etc...

    Don't over think the system design and usage, and you can easily move the "3 day rule" around by 1/2x to 2x (for battery capacity) and still have a very usable system that does not (typically) violate any basic system no-no's...

    Thanks for explaining that better, it does make perfect sense to me now. Exactly why I want to run with 2 batteries and drain them down farther yet still get 2 to 3 years of life out of them or more. I'm just looking for the smallest setup with most amount of power generation. I do not need a battery bank to last me many many years with this setup. All that being said I still will be as good to the batteries as the situation allows.

    Plus I am buying the best equipment so if I ever want to grow with it and use it for home use only all I would need is a new bigger set of batteries, add more panels if wanted, and larger inverter possibly then I'm good to go at home also later down the road.

  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Does This System Make Sense?

    addressing the 3 day rule again? ok. anyway it is advisable to have some extra in your battery bank over what you think you'll need for each day so as to have a state of charge over 50% each day. crewzer had picked 3 days of autonomy and made it a rule of thumb, but anybody should've been able to figure that between the base needed power per day that depletes to 50% of capacity (dod) and one that allows going 3 days to 50% dod is at the discreation of those designing the system. i didn't make it a rule, but only refer to what jim had said and i never disagreed about the idea of extra power for ones needs meaning i favor dods less than 50% in the design. going 2 days in ones design (the one i favor) would mean of the initial ah used that would've taken the percentage to 50% (half the capacity used) is now representing 1/4 of the overall ah capacity and would appear to be 75% soc or 25% dod on the daily basis which would allow being able to go 2 days until 50% dod is reached if need be. this seems like an expensive waste, but it really is a good idea to have that extra powere whatever you can afford. face it, half of it is a waste from the get go so unless somebody comes up with something better in the way of batteries then this we deal with.
    many do not have generators or don't wish to turn them on everyday. now i'm not totally following how you figured what to be better than what as i skimmed your post bill, but going to 50% dod on day 1 and recharging will seemingly extend the life of the battery as opposed to going to 3 days and reaching that same 50% dod because of a bit of sulphation creaping in that may reduce the cycles by a few with most likely a slight decrease in ah capacity for not reaching full charge every day(small amount of sulphation to be sure and not readily noticable unless side-by-side tests done). at the same time the battery being depleted and charged every day wil have 3 times as many recharge cycles used than compared to the the one cycle that is sized for 3 days autonomy. i should note that this is a design criteria and there isn't anybody saying you must use that power to the 3rd day and then recharge for the basic idea is still to try and get the batteries charged up every day. this won't always happen with solar being there are cloudy days and shorter ones in winter for the northern hemishere. i like the idea of an extra day over what one would need per day and this would be a 2 day design. this is a cushion to any expansions on loads and the aging of a battery in addition to the lowered sunlight periods that would also lower the capacity in a battery, but this is no rule either. imho, designing for 1 day at 50% dod is not going to last as long as another that is upped in its ah capacity so as to have dods lower than 50%. to take away some confusion here for some of you, the idea is to always have at least half of your capacity in the batteries as a goal to never be used excepting in an emergency. you just extend the operational period that can go to 50% by upping the capacity. emergencies are better handled by the batteries if there's more capacity in them than needed and this takes some aging factors away from the system design too, but odds are this will be the cushion for low insolation periods. note: if a battery suffers a loss in capacity due to age or whatever then you may be exceeding 50% dod when still drawing the designed draw of the system loads and will further lessen the life of the batteries in this manner too.
  • BB.BB. Super Moderators, Administrators Posts: 32,814 admin
    Re: Does This System Make Sense?

    Part of the whole solar / battery design issue is looking at the needs and the loads...

    If you are running a home 24/7--a large battery bank with backup generator (and sufficient solar panels) makes sense.

    If you are designing an emergency system... The battery bank is going to last X years. You can buy enough batteries for a "3 day/50% system" or a "1 day/80% DOD system"... In one case, you will be running your system like a "normal home system"--the other, as a subsistence system where if there is insufficient sun, you are going to leave things turned off until the sun comes back.

    One system will "cost" you 6x daily load worth of batteries--the other will cost you 1.25x daily load of batteries... And if the system is virtually never used (hopefully, "doomsday" is well off in the future), in X years, you will again be forced to make the purchase decision--a factor of 4.8x between the "nice" vs the "subsistence" system.

    When you look at battery life (I search around, and I did not find a "standby" life for the AGM)--the Sun-Xtender has a 1 year replacement warranty. A very good quality "5000 series" Surrette comes with a 3 year warranty plus a 10 year prorated warranty from date of first service...

    ~424 amphours of Sun-Extender $960; Surrette (not sure which warranty applies for 546 AH of 12 volts is around $1,740... (prices from our host's store, tax and shipping not included). And just for interest, a 20-25 year life Crown Forklift battery 24 volts at 935 amphours (equivalent to 1,870AH at 12 volts) is $5,000.

    The "fork lift" battery is 5x the capacity at 5x the cost of the Sun-Extender--but possibly some ~4x the service life (5 years vs 20+ years--note, life is a flat out guess on my part for the AGM's).

    While I think the AGM's are about "perfect" as batteries go (good life, efficient, little out gassing, freeze tolerant, etc.) vs the Fork Lift having more internal losses (needing constant maintenance charging, even in storage), the need for distilled water, cleaning, etc... The overall service cost of the Forklift battery can be much less because of the longer service life...

    Which is better? That is a decision that only "you" can make--there is no "optimum" solution here (I will argue, that if/when "dooms day" comes, there probably will not be any satellite TV to watch, or much free time to watch DVD's).

    Your thoughts?

    -Bill

    Please note, I do not work for Wind-Sun / NAWS, and I do not work for any battery company either--above is just information supplied from various websites.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • RWBRWB Solar Expert Posts: 168 ✭✭✭✭✭
    Re: Does This System Make Sense?

    For me as far as batteries go I am limited by weight. If I needed to move this system to a new location I think that 130 pounds batteries is about all I am gonna be able to lift myself. Maybe the 160 pound 8D AMG is max weight I am wanting to go, but not sure since I have not tried to move either the 130# battery or the 160# battery, its something I am gonna have to test out.

    The forklift battery is out of the question probably due to there weight. I'm not really sure how much they weigh actually.

    If I knew for a fact that I would never need to move the system then I would be building a different system and be looking at much larger batteries considering I would probably never need to move them.

    As far as emergency goes I'm just not very sure how the US is gonna adjust to the coming financial banking collapse, I'm not sure how its gonna play out but alot of people who know whats going on are all saying its not looking very good. I personally see alot of things changing here in the US and it doesn't make me feel very good so I'm gonna prepare to be self sufficient rather than not.

    I'm gonna need to power 2 way ham radios for communication, Scanners, Short Wave Radios, sat or local TV if they are still transmitting, basically I'm preparing for a loss of power, Cellular phones, and the internet. So I will be prepared to communicate and tune in via other options than the web.

    I'm getting years of Storable Foods, and a few guns and ammo for protection if its ever needed.

    Looking for a good country property out in the boondocks with a well so I can get a DC well pump and be able to have water.

    I don't know whats gonna happen but all I do know is I want to be prepared :) I've heard enough to know that being prepared is a good idea right now even though I'd rather spend the money on other things.

    Considering the above I think that the system I want to build would provide for those circumstances just fine. What do you guys think?
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Does This System Make Sense?

    i have no problem with those wishes, but do realize that many of the ham items are 12v and not needing 120vac and that's a good thing because you lose some power in inverting to 120vac. the bad part is many of those items will go 24/7 and you must plan for them. conserving power is paramount when dealing with radios so it isn't advisable to run items with high power even if you can cut back on the rf power levels because they will draw more dc power than a radio made to run at those lower power levels. you could add a linear amplifier to the works if need be for short duartion. choose your antennas wisely too. omni is nice, but a directional beam can up your signal at times when you don't want to use the extra dc power for the linear. hf transmit operations will dry up your dc power fast with ssb as the best general voice method to conserve power with digital operations as a good option.

    do plan out your power needs and you'll find that in an emergency there's never enough. agms do last longer than 5yrs, but battery manufacturers tend to be cautious because they can't control somebody overcharging them. agms are your best bet as they have a higher efficiency in charging (up to around 10% less current to fully chargecompared to standard batteries) and being sealed you won't have need of gassing worries if proper regulation from a good charge controller is utilized. if they gas it won't be more than a standard battery would, but these have no way to put the gas back in. sounds scarey, but it isn't as i use a concorde 1040t to use with my ham stuff. i admit i could use more ah capacity for when i get into a good long mood to chew the fat as my ts2000x does draw it out of it pretty well and i don't use a power supply.:cry: i currently supplement with an auto battery charger when i get in the mood to go long term so i can keep it from going under 50% soc and i can get a good jump on the next day's bulk charge. i do not try to fully charge it with the auto charger as this is unregulated and i keep a good eye on the voltage when doing this.
    enough for now i guess as you've got some figuring to do.
  • RWBRWB Solar Expert Posts: 168 ✭✭✭✭✭
    Re: Does This System Make Sense?
    agms do last longer than 5yrs, but battery manufacturers tend to be cautious because they can't control somebody overcharging them.

    That's good news!
    do realize that many of the ham items are 12v and not needing 120vac and that's a good thing because you lose some power in inverting to 120vac.

    Yes I do realize they are 12v and no inverter needed and I will not be dealing with inverter losses.
    conserving power is paramount when dealing with radios so it isn't advisable to run items with high power even if you can cut back on the rf power levels because they will draw more dc power than a radio made to run at those lower power levels. you could add a linear amplifier to the works if need be for short duartion. choose your antennas wisely too. omni is nice, but a directional beam can up your signal at times when you don't want to use the extra dc power for the linear. hf transmit operations will dry up your dc power fast with ssb as the best general voice method to conserve power with digital operations as a good option.

    There are some options I haven't though about. I was looking at a YAESU - FT-8800R or one of there other mobile radios that put out 75watts. What kind of range do you think I could reasonbaly get with a 75watt YAESU radio on the 140 band in flatland area with a magnetic mount antenna with a matched antenna for that band witout the help of a repeater? I'm guessing 20 to 50 miles.

    I can monitor all the bands via my Uniden scanner then if I ever have the need to speak up or want to communicate I will have the option to fire up the radio.

    I have a local friend who will also have on that lives about 15 miles away or less and we just want to be able to communicate if other avenues go down for some reason.I also like that there is alot of other people out there with Ham radios too so there will be network of people out there to network with.
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Does This System Make Sense?

    we will discuss some particulars via pm. i sent you a private message on the subject.
  • RWBRWB Solar Expert Posts: 168 ✭✭✭✭✭
    Re: Does This System Make Sense?

    I am looking at batterys and was wondering if I went with 2 of the new High Capacity Trojan T-16's if I wired 2 so I had 12 volts would the Amp Hour Capicity double to 840 (420x2=840)?

    Or does it not work like that? Just wanting to make sure?

    Also how hard is it to keep the Flooded batteries maintained? What would I be looking at doing regularly with just 2 of these batteries using 25 to 50% DOD regularly?
  • BB.BB. Super Moderators, Administrators Posts: 32,814 admin
    Re: Does This System Make Sense?

    "Capacity is Volts*Amps*Hours=Watt*Hours" for batteries...

    If you add two batteries in parallel, they will double in capacity...

    However, voltage adds when batteries are put together in series.

    Amp*Hours add together when added in parallel...

    So, from the equation, if you double voltage (two 6 volt batteries added together in series), you get double the Watt*Hours.

    If you add two batteries in parallel, you double the current (AmpHours), but not the voltage... But you will still get double the Watt*Hours (because amphours doubled in this example).

    So, for your example:
    I am looking at batterys and was wondering if I went with 2 of the new High Capacity Trojan T-16's if I wired 2 so I had 12 volts would the Amp Hour Capicity double to 840 (420x2=840)?

    You would now have 420 Amp*Hours at 12 volts (assuming two 6 volt batteries at 420 AH each).

    Make sense?

    AGM are very nice batteries--no maintenance or cleaning required...

    Maintaining two flooded cell batteries is not bad--provided you have the time and access to distilled water (may need a few cups to a gallon per month)...

    AGMs are easier to damage from overcharging (you cannot add water if you overcharge and vent AGMs). AGMs are, roughly, 90% efficient. You almost have to get a battery monitor to watch their state of charge/system usage.

    Flooded cell batteries are (probably) easier to kill if over discharged (down to 20% state of charge)--especially if not recharged right away. With Flooded Cell batteries, you can get a good glass hydrometer to monitor their state of charge once a month or so--once you have your system dialed in (a battery monitor is still not a bad idea though).

    AGMs cost 2-3x the amount of similar flooded cell batteries.

    Generally, it is recommended here that you start out with "cheap" golf cart batteries--which will last ~3-7 years (if taken care of)... Once those have worn out/been abused--you can make your AGM/Flooded Cell battery purchase based on your experience.

    A few batteries with easy access--it is not a big pain to keep them filled and clean... If you have a rack of a dozen+ batteries--not a lot of fun.

    On the other hand, you can get "LARGE" flooded cell batteries (forklift type), and have some very long lasting batteries, 10-20+ years (heavy--so you have to have plans how to move/install them). But probably less than 80% efficient.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • RWBRWB Solar Expert Posts: 168 ✭✭✭✭✭
    Re: Does This System Make Sense?

    Thanks so much Bill for the advice.

    Guess the AGM are still the best. From what I read the AGM Gel batteries are best if you plan on deep discharging. Do you agree that the Gel's would be better if I was going to do 50% DOD regularly? Thats what it shows in the Home Power Mag Battery Article for a month or 2 ago.
  • BB.BB. Super Moderators, Administrators Posts: 32,814 admin
    Re: Does This System Make Sense?

    Oh gosh NO!

    Stay away from "GEL" batteries... AGM is not the same as GEL.

    From the Battery FAQ:
    Gelled electrolyte

    Gelled batteries, or "Gel Cells" contain acid that has been "gelled" by the addition of Silica Gel, turning the acid into a solid mass that looks like gooey Jell-O. The advantage of these batteries is that it is impossible to spill acid even if they are broken. However, there are several disadvantages. One is that they must be charged at a slower rate (C/20) to prevent excess gas from damaging the cells. They cannot be fast charged on a conventional automotive charger or they may be permanently damaged. This is not usually a problem with solar electric systems, but if an auxiliary generator or inverter bulk charger is used, current must be limited to the manufacturers specifications. Most better inverters commonly used in solar electric systems can be set to limit charging current to the batteries.

    Some other disadvantages of gel cells is that they must be charged at a lower voltage (2/10th's less) than flooded or AGM batteries. If overcharged, voids can develop in the gel which will never heal, causing a loss in battery capacity. In hot climates, water loss can be enough over 2-4 years to cause premature battery death. It is for this and other reasons that we no longer sell any of the gelled cells except for replacement use. The newer AGM (absorbed glass mat) batteries have all the advantages (and then some) of gelled, with none of the disadvantages.
    AGM, or Absorbed Glass Mat Batteries

    A newer type of sealed battery uses "Absorbed Glass Mats", or AGM between the plates. This is a very fine fiber Boron-Silicate glass mat. These type of batteries have all the advantages of gelled, but can take much more abuse. We sell the Concorde (and Lifeline, made by Concorde) AGM batteries. These are also called "starved electrolyte", as the mat is about 95% saturated rather than fully soaked. That also means that they will not leak acid even if broken.

    AGM batteries have several advantages over both gelled and flooded, at about the same cost as gelled:

    Since all the electrolyte (acid) is contained in the glass mats, they cannot spill, even if broken. This also means that since they are non-hazardous, the shipping costs are lower. In addition, since there is no liquid to freeze and expand, they are practically immune from freezing damage.

    Nearly all AGM batteries are "recombinant" - what that means is that the Oxygen and Hydrogen recombine INSIDE the battery. These use gas phase transfer of oxygen to the negative plates to recombine them back into water while charging and prevent the loss of water through electrolysis. The recombining is typically 99+% efficient, so almost no water is lost.

    The charging voltages are the same as for any standard battery - no need for any special adjustments or problems with incompatible chargers or charge controls. And, since the internal resistance is extremely low, there is almost no heating of the battery even under heavy charge and discharge currents. The Concorde (and most AGM) batteries have no charge or discharge current limits.

    AGM's have a very low self-discharge - from 1% to 3% per month is usual. This means that they can sit in storage for much longer periods without charging than standard batteries. The Concorde batteries can be almost fully recharged (95% or better) even after 30 days of being totally discharged.

    AGM's do not have any liquid to spill, and even under severe overcharge conditions hydrogen emission is far below the 4% max specified for aircraft and enclosed spaces. The plates in AGM's are tightly packed and rigidly mounted, and will withstand shock and vibration better than any standard battery.

    Even with all the advantages listed above, there is still a place for the standard flooded deep cycle battery. AGM's will cost 2 to 3 times as much as flooded batteries of the same capacity. In many installations, where the batteries are set in an area where you don't have to worry about fumes or leakage, a standard or industrial deep cycle is a better economic choice. AGM batteries main advantages are no maintenance, completely sealed against fumes, Hydrogen, or leakage, non-spilling even if they are broken, and can survive most freezes. Not everyone needs these features.
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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