Help with new battery bank setup

Hi,
first, please bear with my ignorance, as i know some of these questions are stupid. i'm trying my best to learn and I want to be sure i set this up the correct and *safe* way. i've asked two experts so far and gotten 2 different answers! i'm confused :)

What I have so far: a honda 2000i generator and 8 golf-cart [lead acid] batteries (6-volt), roughly 105 amp-hours each
What I want to do:
1) wire up the batteries into a bank and keep them charged via A/C outlet until a power outage
2) In the event of a power outage, run the generator in the mornings to charge the battery bank and power any other larger wattage equipment i need (hot water kettle, hair dryer, hot plate)...not at the same time of course. then in the afternoon, turn off the generator and run the rest of the evening off the battery bank...powering only a few lights, a small TV or computer, a fan.
a) Important scenario: if power outage + heavy rain, i need batteries to run my sump pump during at least a few overnight hours. I have exchanged sump pump for a 1/3 HP with 4.5 running amps and 13 startup amps (115V)

This is for my house. Everything i need to run will be off a normal A/C plug. So my questions
a) i read this post (http://forum.solar-electric.com/showthread.php?15989-Battery-System-Voltages-and-equivalent-power) about wiring up 12V/24V/48V. I understand how to wire (serial vs parallel). It seems 48V would be most efficient. but i'm confused. if i wire it to 48V, can i hook up an inverter to it that will give me 110-115V A/C ? Is 48V the best way to go?

b) I was looking into what brand and size of charger and inverter to get. It seems like the Iota might be the best choice. I was looking at the "Charger Converter Power Supply" model. But i'm a little confused again. It seems to say it will 3-stage, smart charge the batteries and also serve as an inverter. but i don't see any outlets on the pictures of the unit...and i cannot tell what size inverter it is. Do you have any suggestions on size/brand of inverter or charger? Should i get them separately or as 1 unit (charger + inverter together)?

c) I plan to keep the batteries checked and maintained. how often should i plan to check the water/acid levels in them...once per week, once per month?

d) i will have the battery bank in my basement, which is roughly 1000 sq feet, all unfinished. there is not any specific air flow, just the opening of a dog door on occasion. one expert says that the battery off-gassing is nothing to worry about, another says i will blow my house up. What is your feedback? Do i need to build a box for the batteries and vent them? Do i need to get some sort of meter to test for the gas?

thanks for any help you can provide!

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Help with new battery bank setup

    Welcome to the forum ITSki...

    I will attempt to answer the questions--But we should try to keep the mix of wide ranging questions and answers from going everywhere.... I.e., take a path through each major step/component--It should be a little easier to understand.
    itrickski wrote: »
    Hi,
    first, please bear with my ignorance, as i know some of these questions are stupid. i'm trying my best to learn and I want to be sure i set this up the correct and *safe* way. i've asked two experts so far and gotten 2 different answers! i'm confused :)

    I will be interested to hear what your other answers were--Many times, the answers are different because you (perhaps unknowingly) asked slightly different questions of each. Also, different people will approach a problem from different angles--Which can result in somewhat different system designs.
    What I have so far: a honda 2000i generator and 8 golf-cart [lead acid] batteries (6-volt), roughly 105 amp-hours each
    What I want to do:

    The Honda 2000i is a very good pick for a smaller genset that is both reliable and pretty fuel efficient (especially if operated at partial power). If taken care of, you can get 2,000 to even 6,000 hours of use out of one with good maintenance (and scheduled oil changes). But, once they wear out/break, they usually don't seem to be worth overhauling.

    And, can you confirm your "golf cart" batteries are 6 volt @ 105 Amp*Hours (at what C/XX discharge rate)? They should probably have higher AH capacity (we use the C/20 Hour discharge rate for our rules of thumbs designs). Nominally, I would have expected closer to 200 AH or so for a 6 volt "golf cart" sized battery.
    1) wire up the batteries into a bank and keep them charged via A/C outlet until a power outage

    If we do the design correctly, you should be able to use the same AC Charger on the grid and with your Honda. But knowing your battery bank actual voltage and AH capacity is important.
    2) In the event of a power outage, run the generator in the mornings to charge the battery bank and power any other larger wattage equipment i need (hot water kettle, hair dryer, hot plate)...not at the same time of course. then in the afternoon, turn off the generator and run the rest of the evening off the battery bank...powering only a few lights, a small TV or computer, a fan.

    Loads are the first stop in Wind-Sun's design guideTM.;)

    I would suggest you look at getting a Kill-a-Watt type meter. Very handy to understand the basic requirements of your AC loads (voltage, current, Watt*Hour, etc.). Besides planning/running from your emergency power system, it is very handy for use around the home when looking at energy conservation projects... And, believe me, an off grid power system is firstly an energy conservation project.

    For example, Hot water, hair dryer, hot plates are all "energy hogs". They use a lot of power (i.e., upwards of 1,800 watts, which forces you to use a "large battery bank" and a "large" AC inverter just to turn on.

    Then there is the Watts*Hours of use... Use a microwave at 1,500 watts * 1/6th of hour (10 minutes) = 250 Watt*Hours... That is not a "lot of stored energy to use", so the battery does not have to be "large" for that reason--Just because of the peak power.

    On the other and, a desktop computer that may run at 250 watts * 10 hours per day = 2,500 WH per day--That does not need a large inverter, but the computer may use 10x as much energy over the course of a day (vs the microwave).

    Then we look at a laptop instead that may use only 25 watts, or 1/10th that of a desktop system (see how the conservation works?).

    For heating, I use multi-fuel camp stoves that can run from gasoline/kerosene/diesel/alcohol... Usually much more efficient than resistance heating/cooking powered by a genset/battery bank/ AC inverter (although, we can size a system to do electric heating, if needed--it just pushes the power requirements up dramatically).

    a) Important scenario: if power outage + heavy rain, i need batteries to run my sump pump during at least a few overnight hours. I have exchanged sump pump for a 1/3 HP with 4.5 running amps and 13 startup amps (115V)

    Pumps can be real power hogs... But using a kill-a-watt meter and understanding the loads can save you a lot of money--For example the pump may only run 10 minutes out of every hour... Much different than one that runs for hours on end. Also, there are DC pumps (and other types of pumps) that may be much more energy efficient. We can look at your options and see were things work out (pulse a little kill-a-watt meter usage).
    This is for my house. Everything i need to run will be off a normal A/C plug. So my questions
    a) i read this post (http://forum.solar-electric.com/showthread.php?15989-Battery-System-Voltages-and-equivalent-power) about wiring up 12V/24V/48V. I understand how to wire (serial vs parallel). It seems 48V would be most efficient. but i'm confused. if i wire it to 48V, can i hook up an inverter to it that will give me 110-115V A/C ? Is 48V the best way to go?

    Again, goes back to loads--A small system is easy to run off a Honda eu2000i and a 12 or 24 volt battery bank. A larger system, they tend to range more at 24 or 48 volt battery bank+inverter+charger controller(s) (and keeps the DC wiring from getting too thick/expensive/difficult to work with).
    b) I was looking into what brand and size of charger and inverter to get. It seems like the Iota might be the best choice. I was looking at the "Charger Converter Power Supply" model. But i'm a little confused again. It seems to say it will 3-stage, smart charge the batteries and also serve as an inverter. but i don't see any outlets on the pictures of the unit...and i cannot tell what size inverter it is. Do you have any suggestions on size/brand of inverter or charger? Should i get them separately or as 1 unit (charger + inverter together)?

    I would put this off until you size the system... Large AC inverters have lots of neat options--But if you can keep the system size small, 2-4 golf cart batteries plus a 300-600 watt inverter may be all you need (small system keeps your costs way down, and you will have to replace the batteries every 3-5 years or so--so ongoing maintenance costs are a factor too).
    c) I plan to keep the batteries checked and maintained. how often should i plan to check the water/acid levels in them...once per week, once per month?

    When you first get started--You may be checking specific gravity a few times a day. After the system is commissioned and stable--You should be checking electrolyte levels about once a month, and needing to add electrolyte every couple of months (lots of "it depends here").
    d) i will have the battery bank in my basement, which is roughly 1000 sq feet, all unfinished. there is not any specific air flow, just the opening of a dog door on occasion. one expert says that the battery off-gassing is nothing to worry about, another says i will blow my house up. What is your feedback? Do i need to build a box for the batteries and vent them? Do i need to get some sort of meter to test for the gas?

    You should box and vent the battery bank for two reasons... One is hydrogen gas is generated during charging (and charge controllers have been "known to run-away")--So safety is one reason. (as well as to protect the wiring/battery terminals so somebody does not drop a piece of metal on top of the battery bank (all around, a very bad idea). Hydrogen gas will probably not collect and blow up your basement/house--But if there were some sparks into the battery caps, you could have a nice little H&O explosion and spray chunks of batteries and sulfuric acid around (also not a good idea).

    The second is flooded cell batteries will generate some acid mist. You can reduce it to a degree with "water miser" battery caps (if you use them)--But both the sulfur smell and the acid mist can be irritating to some people (and cause rust/corrosion/deterioration of nearby equipment/articles in the basement).

    So--We can either design a system around your loads--Or, in your case, you can give us your battery bank spec., and then we can define the system's capabilities (see if it meets your needs) and design the balance of the hardware to support the bank.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Help with new battery bank setup
    itrickski wrote: »
    What I have so far: a honda 2000i generator and 8 golf-cart [lead acid] batteries (6-volt), roughly 105 amp-hours each

    Welcome to the forum... normally in a situation like yours my first advice would be "Stop spending money until you/we figure the whole system out". But now you've already purchased the batteries and they must be properly commissioned and maintained or they will be ruined within a few weeks.

    Therefore, time is of the essence in getting this figured out. As BB said, system design starts with an evaluation of your loads.

    Now, back to the batteries... exactly what batteries are these? I am suspicious that at 105 amphours these are not real deep cycle batteries. All of the deep cycle golfcart batteries that I know about are about double that amphour rating.

    Also, since you are on the grid, these batteries will spend most of their life fully charged. I suspect the batteries you purchased are not optimal for that type of service.

    Finally, the iota charger is fine for grid use. However, it is not power factor corrected which means that it is not an optimal solution for a small generator system. Most of the inverter-chargers have efficient chargers and make very good backup systems for grid failures.. they also have transfer switches built in.

    One more question... how often and for how long do you lose grid service? If the outages are brief, you will not need to worry about the generator charging the batteries... the grid can do it. Perhaps use the batteries for lights and small loads and run the generator for the coffee maker, hair drier, etc.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • itrickski
    itrickski Registered Users Posts: 4
    Re: Help with new battery bank setup
    BB. wrote: »
    Welcome to the forum ITSki...
    Thanks, and thank you for taking the time to reply.
    BB. wrote: »

    I will attempt to answer the questions--But we should try to keep the mix of wide ranging questions and answers from going everywhere.... I.e., take a path through each major step/component--It should be a little easier to understand.
    Understand that, sounds good.
    BB. wrote: »
    I will be interested to hear what your other answers were--Many times, the answers are different because you (perhaps unknowingly) asked slightly different questions of each. Also, different people will approach a problem from different angles--Which can result in somewhat different system designs.
    yes, I think there were two problems: my questions were too broad in scope and I did not properly clarify exactly what my ultimate goals were.
    BB. wrote: »
    The Honda 2000i is a very good pick for a smaller genset that is both reliable and pretty fuel efficient (especially if operated at partial power). If taken care of, you can get 2,000 to even 6,000 hours of use out of one with good maintenance (and scheduled oil changes). But, once they wear out/break, they usually don't seem to be worth overhauling.
    Thanks, that makes me feel better, and is good to know on the repair piece. Honda generally makes good engines, so i was hoping that carried over into their generator line.
    BB. wrote: »
    And, can you confirm your "golf cart" batteries are 6 volt @ 105 Amp*Hours (at what C/XX discharge rate)? They should probably have higher AH capacity (we use the C/20 Hour discharge rate for our rules of thumbs designs). Nominally, I would have expected closer to 200 AH or so for a 6 volt "golf cart" sized battery.
    Sure. I may have calculated wrong. The batteries came from Sam's club. They are Duracell GC2 6-volt. Instead of exact amp-hour, they come rated as "75 Amp rating 105 Min." So to get actual amp-hours, I calculated as (Amps * min)/60. So in this case, (75*105)/60 = 131 amp-hours. Sorry, it should have been 131 instead of 105....if this calculation is correct.
    BB. wrote: »
    If we do the design correctly, you should be able to use the same AC Charger on the grid and with your Honda. But knowing your battery bank actual voltage and AH capacity is important.
    Yes, that's what I would like to do. 1 charger either plugged into regular outlet, or into generator if power is out.
    BB. wrote: »
    Loads are the first stop in Wind-Sun's design guideTM.;)

    I would suggest you look at getting a Kill-a-Watt type meter. Very handy to understand the basic requirements of your AC loads (voltage, current, Watt*Hour, etc.). Besides planning/running from your emergency power system, it is very handy for use around the home when looking at energy conservation projects... And, believe me, an off grid power system is firstly an energy conservation project.
    Thanks, yes I've seen that meter. Will order it today. So far, I've just been trying to estimate power needs based on the watts or amps stamped on the various items that might be needed.
    BB. wrote: »
    For example, Hot water, hair dryer, hot plates are all "energy hogs". They use a lot of power (i.e., upwards of 1,800 watts, which forces you to use a "large battery bank" and a "large" AC inverter just to turn on.

    Then there is the Watts*Hours of use... Use a microwave at 1,500 watts * 1/6th of hour (10 minutes) = 250 Watt*Hours... That is not a "lot of stored energy to use", so the battery does not have to be "large" for that reason--Just because of the peak power.

    On the other and, a desktop computer that may run at 250 watts * 10 hours per day = 2,500 WH per day--That does not need a large inverter, but the computer may use 10x as much energy over the course of a day (vs the microwave).

    Then we look at a laptop instead that may use only 25 watts, or 1/10th that of a desktop system (see how the conservation works?).

    For heating, I use multi-fuel camp stoves that can run from gasoline/kerosene/diesel/alcohol... Usually much more efficient than resistance heating/cooking powered by a genset/battery bank/ AC inverter (although, we can size a system to do electric heating, if needed--it just pushes the power requirements up dramatically).
    Makes perfect sense. I setup a spreadsheet to calculate watt-hours for various appliances, guesstimating time used. this has been eye-opening. I will get the kill-a-watt meter and make more accurate measurements of energy needed. I have other fuel sources...some propane and kerosene that i hope to use for most of the heating and cooking.
    BB. wrote: »
    Pumps can be real power hogs... But using a kill-a-watt meter and understanding the loads can save you a lot of money--For example the pump may only run 10 minutes out of every hour... Much different than one that runs for hours on end. Also, there are DC pumps (and other types of pumps) that may be much more energy efficient. We can look at your options and see were things work out (pulse a little kill-a-watt meter usage).

    Yes, the pump was a big concern. It's a permanent installation. Originally, I had a 1/2 HP pump. When I began thinking about running essential systems without power, I realized that had to be changed. So I swapped the 1/2 HP for a 1/3 HP model that has the lowest start-up amps. Additionally, I bought a 1/4 HP Thermoplastic Submersible Utility Pump that I can hook a water hose to...this would be a backup for the permanently installed pump.
    BB. wrote: »
    Again, goes back to loads--A small system is easy to run off a Honda eu2000i and a 12 or 24 volt battery bank. A larger system, they tend to range more at 24 or 48 volt battery bank+inverter+charger controller(s) (and keeps the DC wiring from getting too thick/expensive/difficult to work with).

    I would put this off until you size the system... Large AC inverters have lots of neat options--But if you can keep the system size small, 2-4 golf cart batteries plus a 300-600 watt inverter may be all you need (small system keeps your costs way down, and you will have to replace the batteries every 3-5 years or so--so ongoing maintenance costs are a factor too).

    Yes, perhaps my process and goals should be better defined here. In some ways, I think I've put the cart before the horse. Like everyone else, what it boils down to is "what i would like" vs "what i can afford". If I had infinite resources, my objective would be to be able to live off-grid indefinitely. I'd have solar panels, a large battery bank, some generators, a big garden, etc. But that's not my reality, and with the idea of "you have to start somewhere," i set a more reasonable objective for our current situation.

    My objective: "provide food, water and power for essentials so that our family could be decently comfortable during an extended power outage of 4-6 weeks". A 4-6 week power outage is not especially typical in this day and time. But I'm a good scout, and I'd like to have this ability..."just in case". Bad winter storms, natural disaster, etc.

    What I'm NOT doing: connecting my generator or battery bank to the grid.
    i'm also not expecting to power my entire house off the generator/battery bank. When i created the spreadsheet to calculate watt-hours for appliances, it opened my eyes to how much stored energy would be required for all the "comforts of home." Allowing for only 50% battery drain, my initial battery bank size was something like 30 batteries. YIKES! Hence my objective of only providing power for "essentials" during an outage.

    My essentials are:
    - sump pump (if it's raining). in a recent 6-day continuous rain, the pump cut on about every 5 min 24/7 for the entire 6 days plus about 2 days after the rain stopped. each cycle of the pump was about 5 seconds. BUT, that was on the 1/2 HP pump. i have not had opportunity to test the 1/3 HP pump yet. i will do that with the kill-a-watt meter next rain....or fill the basin with water from a garden hose to test.
    - charge communication devices like telephones, ipads, small TV/radio
    - power some low watt LED lights ( have some LED xmas type string lights and a few lamps with 4 watt LED bulbs)
    - plug in a small chest freezer 2-3 times/day to keep food cold.
    - run a laptop computer, modem and router (assuming internet is available)
    - perhaps run the microwave for a few minutes 3 or 4 times a day

    i plan to take a weekend very soon and simulate a power outage, to find out exactly what all we would need/miss. This should help cement the list of essential items and how much energy we would use.

    To meet my objective, I tried to figure out what setup would give me to most power for my $$. That eliminated solar, as it was too expensive for my wallet and too complicated for me as a DIY at my current knowledge level. I wanted the battery bank so as not to waste fuel running the generator when i only need to power smaller loads. This will stretch the fuel supply and the life of the generator.
    - After evaluating generators, I landed on the honda. from your feedback, looks like that's a decent choice. thankful!
    - after evaluating all the different kinds of batteries, i landed on the lead/acid golf cart style. They were easy for me to buy locally and seemed cheapest for the power they put out.

    I had a plan, then, to setup a battery bank, consisting of 8 GC2 batteries (because that was how many i could afford) and wire them up 12-volt. I bought the generator and the batteries, then started having doubts about how to charge them and how to wire them. So i stopped and started digging more. as vtmaps noted "stop spending money until this is figured out". :) So this landed me here for more help.

    Sorry for the novel, but maybe this will help explain where I am and where I need to be.
    BB. wrote: »
    When you first get started--You may be checking specific gravity a few times a day. After the system is commissioned and stable--You should be checking electrolyte levels about once a month, and needing to add electrolyte every couple of months (lots of "it depends here").
    thanks, that helps.
    BB. wrote: »
    You should box and vent the battery bank for two reasons... One is hydrogen gas is generated during charging (and charge controllers have been "known to run-away")--So safety is one reason. (as well as to protect the wiring/battery terminals so somebody does not drop a piece of metal on top of the battery bank (all around, a very bad idea). Hydrogen gas will probably not collect and blow up your basement/house--But if there were some sparks into the battery caps, you could have a nice little H&O explosion and spray chunks of batteries and sulfuric acid around (also not a good idea).

    The second is flooded cell batteries will generate some acid mist. You can reduce it to a degree with "water miser" battery caps (if you use them)--But both the sulfur smell and the acid mist can be irritating to some people (and cause rust/corrosion/deterioration of nearby equipment/articles in the basement).
    ok, makes sense. i will start working on that.
    BB. wrote: »
    So--We can either design a system around your loads--Or, in your case, you can give us your battery bank spec., and then we can define the system's capabilities (see if it meets your needs) and design the balance of the hardware to support the bank.
    I think in this case, i've already go the batteries, so let's design the hardware to support the bank. And I will be sure to run within the limits of this system if/when the power is out.
  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Help with new battery bank setup

    What your trying to setup pretty much mirrors what I Install in most Marine setups. 8-10 GC-2's pulled to 50 % will give you a reasonable amount power and Generator run time to put back. If you subscribe to a regimen of pulling the batteries to 50 % and charging back to 85 % on a daily basis and then doing a full charge once a week, you'll do fine. The net amp hours on 8 GC-2's is about 350 for 50-85% putback. A Honda EU2000 will pull a 60 amp charger easy and still have some ECO throttle left, 75 amp is full throttle and a strain. It would take you a good 6+ hrs to put back 350 amps hrs, you could break it up and do it twice a day. I guess I don't have to tell you that the power you don't use, is the power you have to spare and don't have to put back. 6-7 hrs is about a gallon of fuel, so that has to be in your plan. I usually install a 2500-3000 watt inverter / charger, you don't need that much all the time, but you need the surge capability of that size to start your pumps.

    If your sticking with 12 V , you'll have to oversize all your battery cables to 4/0 to the Inverter and at least 2/0 for interconnects.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Help with new battery bank setup

    OK--We have a place to start.

    First, the batteries... With the mix/match of large retailers (like Walmart) and their house branding the same batteries from different vendors depending on where the store is located--getting answers is not easy. Here is a thread from another forum about these specific batteries:

    http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/25515901.cfm

    I am not sure I understand/trust entirely the information given (fog of retail marketing). But 105 minute discharge (100% to dead) is about 1.75 hour discharge rate. For our rules of thumbs here, we use the 20 hour rate--Closer to how we use batteries in off grid systems. And they are probably around 215 AH capacity (use this number for now).

    I will use a 24 volt battery bank--But that may not be the best choice--The AC Inverter is the "wild card" here... For smaller power needs, the MorningStar 12 volt 300 watt TSW AC Inverter has no equal in 12/24/48 volt systems. But if you need more than 300-600 watts, then you are shoved into the larger inverter range--Costs a lot more, more inverter/system losses, etc., which drives other stuff larger (like solar array, battery chargers, etc.).

    If you want to run a standard refrigerator or freezer, you are pretty much sent into the 1,200-1,500 watt minimum inverter range (which should run your sump pump find too).

    OK... 8 x 6 volt @ 215 AH batteries. Will make a 4 battery in series * 2 parallel string 24 volt @ 430 AH battery bank. The rate of charge for such a bank would be ~5% to 13% cost (you can go to 25% rate of charge--but that does have cost and thermal management issues).

    Solar charging wise, that would be:
    • 29 volt * 430 AH * 1/0.77 panel+controller losses * 0.05 rate of charge = 810 watt array minimum
    • 29 volt * 430 AH * 1/0.77 panel+controller losses * 0.10 rate of charge = 1,609 watt array nominal
    • 29 volt * 430 AH * 1/0.77 panel+controller losses * 0.13 rate of charge = 2,105 watt array "max cost effective"

    A 1,609 Watt nominal solar array running off grid with an AC inverter on 4 hours of sun (noon time equivalent) per day (for ~9 months a year in much of the sunnier side of the US) would generate:
    • 1,609 Watt array * 0.52 system efficiency * 4 hours of sun minimum = 3,347 Watt*Hours per day

    A 3.3 kWH per day (100 kWH per month) system is about the minimum power needed to run a very efficient off grid home (lights, computer, well pump, fridge, TV)... So that is not bad. Of course, during winter/poor weather, you will either need to cut back on power usage and/or use a generator.

    Your 24 volt @ 430 AH batter bank with two days of storage and 50% maximum discharge would support an over night (no sun) load per day of:
    • 24 volts * 430 AH * 1/2 days of storage * 0.50 maximum discharge * 0.85 inverter eff = 2,193 WH per day of usable storage

    So, in poor weather, use the battery bank for 1-2 days, then start the backup genset.

    For charging, we are looking at again at the 5/10/13/25% rate of charge with 10-13% being the aim point for an of grid system (a stand by system, perhaps you can get away with 5%).
    • 430 AH * 0.05 rate of charge = 21.5 amp minimum
    • 430 AH * 0.10 rate of charge = 43 amp nominal
    • 430 AH * 0.13 rate of charge = 56 amp cost effective max
    • 430 AH * 0.25 rate of charge = 107.5 not to exceed with thermal management

    A Honda eu2000i should be able to manage any ~20 amp @ 24 volt battery charger without problem. And for more efficient battery chargers even a larger one. Here is an example between a typical and very efficient charger on a 1,600 Watt (really VA) maximum genset:
    • 1,600 VA * 1/29 volts charging * 0.80 charger eff * 0.67 PF = 29.5 amps @ 24 volt bank max
    • 1,600 VA * 1/29 volts charging * 0.90 charger eff * 0.95 PF = 47 amps @ 24 volt bank max

    If you want the details behind picking a battery charger for use with a smaller genset, this thread has all of the ugly information (almost identical battery bank setup as you):

    Question about battery charger selection with EU2000 generator.


    For a 120 volt 2kW TSW Inverter/Charger, look at the features of this unit:

    Magnum MS2024 2000 Watt Sine Wave Inverter w/Charger

    For a 120/240 volt 4000 watt inverter/charger:

    Magnum Energy MS4024PAE 4000 Watt Sine Wave inverter 120/240 Volt

    If you need 120/240 VAC split phase power (either 240 VAC appliances/water pumps) and/or have "common neutral" circuits (120 AC Black and Red circuits sharing a common neutral back to the main panel)--The 120/240 units are nice for an existing home.

    If you have the choice to rewire some circuit (do not share black/read hot circuits with common neutral) and don't need 240 VAC for well pump, then a 120 VAC unit is probably the better choice.

    I will stop here--Lots of reading a head for you.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Help with new battery bank setup

    Note that my Honda eu2000i battery charger calculations are based on a 24 volt battery bank. BC04's are based on a 12 volt bank (2x current factor between the two).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Help with new battery bank setup
    BB. wrote: »

    A Honda eu2000i should be able to manage any ~20 amp @ 24 volt battery charger without problem. And for more efficient battery chargers even a larger one. Here is an example between a typical and very efficient charger on a 1,600 Watt (really VA) maximum genset:
    • 1,600 VA * 1/29 volts charging * 0.80 charger eff * 0.67 PF = 29.5 amps @ 24 volt bank max
    • 1,600 VA * 1/29 volts charging * 0.90 charger eff * 0.95 PF = 47 amps @ 24 volt bank max


    -Bill
    If it only worked out this way in the real world. Test it, it won't.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Help with new battery bank setup
    If it only worked out this way in the real world. Test it, it won't.
    A Honda EU2000 will pull a 60 amp charger easy and still have some ECO throttle left, 75 amp is full throttle and a strain.

    Me:
    1,600 VA * 1/29 volts charging * 0.80 charger eff * 0.67 PF = 29.5 amps @ 24 volt bank max

    BC04,

    Where are we disagreeing? Me 59.5 amp "typical" worst case 12 volt AC charger... You 60 amps minimum 12 volt (I assume) charger?

    I am factoring in the 0.67 Power Factor and using 1,600 VA as the maximum sustained output--Which would leave some engine capacity to generate more Watts--But could overheat the breaker/generator-inverter circuitry due to poor power factor.

    The above numbers were estimates and Kill-a-Watt numbers (PF) supplied by another poster here on their system... Should be pretty accurate (within 10%).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Help with new battery bank setup

    I guess I should add that the high efficiency numbers are those from other manufacturers.

    And I would not suggest running at 1,600 watt light weight/portable genset at 1,600 watts for hours on end (industrial which may be spec'ed at 0.8 or even 0.7 PF, and over designed gensets such as the Honda EM4000SX that Chris Olson is using is a different matter).

    For powering a battery charger with a large battery bank, I would suggest the genset should probably be operated at ~75% or so of rated power, or 1,200 Watts in this case, which would drop the 47 amp @ 24 volt to ~35 amp @ 24 (or 70 amps @ 12 volt).\

    Anyway--Was trying to show the concept and suggested the other thread if details were needed....

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Help with new battery bank setup

    A lot more figures into the figures. Temperature for one. I am Bulk charging a bank right now. I have a IOTA dls -75 amp charger. It's pulling 8.83 amps @120 VAC and putting out 73.26 amps DC @13.8 V. That sure doesn't square with your PF numbers. There must be some kind of a overlap between the efficiency and the PF.

    I going to buy a Meanwell PB-1000 just to prove it 's not any better with the claim of a great PF. It sure won't be 29.5 amps to 47 amps because of a PF. I'll be glad to ship it to anyone that wants to test it after I do. The Meanwell I have is a Inverter / Charger and supposedly it's PF corrected, that would be mixing and the circuity would be different.

    Another thing, it's has to be able to put out it's rated output, hour after hour, not put out 60 amps for 15 minutes then drop to 40 amps, I'v got a box full of those.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Help with new battery bank setup

    Hmm...

    13.8 volts * 73.26 amps / (8.83 amps * 120 VAC) = 0.954 = 95.4% overall efficiency

    That would be great if you are getting those types of numbers (assuming that Amps is RMS and not just the real vector with respect to voltage phase angle... But given that past questions from Iota (as I recall) confirmed they were not power factor corrected--I wonder if there are some measurement errors in the system.

    And don't get me wrong--I would be very happy to be proved wrong. The overall VA efficiency of 0.67pf*0.80eff=0.54 is really sad.

    We have other posts over that last couple years that seemed to support the math. But--I will give you that Kill-a-Watt meters are not lab grade instruments and are at best "sort of close" to what the real numbers are (as in +/- 10% close). Feed them nonlinear current wave forms (such as non-PFC rectifier front ends for a power supply/converter) and they probably are not much more accurate than a guess.

    That is why Fluke can charge >$300 for just for a plastic box with their name molded in.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Help with new battery bank setup

    Some other Iota related links FYI:

    Power Factor Correcting power supplies on MSW Inverters

    choosing the right charger, help?
    Power Factor correction with CFL bulb question?
    Can Iota chargers run with less power?

    Anyway, the PF for a typical Iota seem to be in the 0.65 to the 0.75 range (PF can frequently be very load dependent too).

    If there are new Iotas that have PFC--Happy days!

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Help with new battery bank setup

    Don't get me wrong. I just don't see where it translates from a 13.5 amp output on a Honda EU2000 to where the rock hit's the road. If I can get 73.26 DC amp output @ 12V nominal from a $200 IOTA and consume 8.83 amps of the Honda's capability, I am happy.

    I will order a Meanwell PB-1000 and let the chips fall where they may.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Help with new battery bank setup

    But I have never seen a 95.4% VA efficient AC Battery Charger... It may be possible, but I don't think the Iota's are them.

    From:

    http://iotaengineering.com/dls75.htm
    Efficiency >80%
    18.2 amps @ 108 VAC max AC Current
    75 amp max @13.6 DC current (?)

    75 amps * 13.6 volts * 1/108 volts * 1/18.2 amps = 0.52 overall VA efficiency (probably worse case)
    0.52 est VA eff / 0.80 Watt Eff = 0.65 PF

    I don't see anywhere I could expect 95.4% VA (or Power) efficiency.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Help with new battery bank setup

    I should probably stay out of this but...

    BC04 is measuring real watts being delivered by his honda and real watts going into the battery:
    It's pulling 8.83 amps @120 VAC and putting out 73.26 amps DC @13.8 V.

    Iota claims efficiency of greater than 80% and BC04 is seeing greater than 80% efficiency.

    In my opinion, power factor is a red herring here. The PF issue just means that the Honda needs to be rated 1600 watts in order to deliver the 1000 watts that BC04 is drawing. The Meanwell may not be any more efficient than the Iota, but it could put out its 1000 watts with a smaller generator than the Honda eu2000.

    To see the difference between a Meanwell and an Iota, try running the chargers off the Honda while also powering a 500 watt resistive load. I predict the Honda will be overloaded by the Iota and not by the Meanwell.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Help with new battery bank setup
    BB. wrote: »
    But I have never seen a 95.4% VA efficient AC Battery Charger... It may be possible, but I don't think the Iota's are them.

    From:

    http://iotaengineering.com/dls75.htm



    75 amps * 13.6 volts * 1/108 volts * 1/18.2 amps = 0.52 overall VA efficiency (probably worse case)
    0.52 est VA eff / 0.80 Watt Eff = 0.65 PF

    I don't see anywhere I could expect 95.4% VA (or Power) efficiency.

    -Bill
    Let's make sure were on the same page.

    Iota DLS-75 using 8.83 amps 120v Input and 73.26 output. That means to be equal the Meanwell would require 7.2 amps @120v to have a 60 amp Output. By your number's the Meanwell PB-1000-60 requires 23% less input amperage to give the same 60 amps. So your saying the The Meanwell will require 5.54 @120 V to produce 60 amps DC output ??

    The Meanwell is $100 more, I want to see what I am getting. Thats a huge difference on a Honda EU2000 and you justify the cost.
    .
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Help with new battery bank setup

    I was using the Iota DLS-75 specifications... And they are (relatively) self consistent with my math (80% efficiency and 0.65 PF if you back it out from their VA rating of 108v*18.2a).

    I agree that 0.65 PF may be the "worst case" number--But it is not going to be (on average at full power) much better than 0.67 to 0.75 PF.

    Which gets me back to BC04's measured numbers... At this point, I have never seen a 95.4% commercial AC to DC Power supply. Let alone a (not disparaging) "low tech" power supply.

    What vtMaps is asking/implying (I think) is that even if you have a 100% efficient power supply, there is still the PF issues.

    PF is not a "red herring" but more of a "confounding factor" with AC power...

    You can have power power factor because the current phase and voltage phase are not aligned (i.e., the current lags the voltage between zero and 90 degrees for a motor/inductor) and the PF=invCos(phase-angle).

    These types of PF require a power meter that can measure both voltage and current at the same time to measure both the phase angle between the two wave forms, and also to perform the RMS (Root Mean Square) of the voltage and current wave forms (if they are not pure 60 Hz sine wave).

    InvCos(0 degrees)=1.00; and InvCos(90 degrees=0.00 = Power Factor

    And then there is the "nonlinear" spiky current. For example current stays at zero amps until the voltage sine wave exceeds 100 volts, then as the sine wave voltage rises to (srt(2)*120VAC)=~170volts DC peak... And that is (roughly) where the current will peak, then the current falls very quickly as the sine wave falls towards zero (and repeat on negative cycle).

    This type of PF can be estimated with a pure voltage wave form and measuring the RMS value of the current (assuming there are no inductors in the AC circuitry).

    So--If not using an RMS meter with something like 50kHz sample rate (to estimate the areas under the nonlinear curves), a standard (my cheap DMM) would tend to over estimate the RMS current because it assumes a sine wave and does not do RMS calculations.

    With BC04's measurements--I would have guessed if his meters are calibrated, that he would have over estimated the AC RMS current and came up with too low of over all efficiency--Or that the DC voltage/current measurements are too high.

    So, at this point, I do not have a good idea of where (I think) systematic measurement could come into play--And I am left wondering if there is a calibration issue with the meter(s).

    As I think about it--vtMaps is probably commenting on the issue of engine loading... High/overloading of the Watts (power) will cause the engine to sound loaded (use more fuel).

    But VA overloading is "silent". VA overloading will only be seen with an RMS meter and/or overheating of windings/wirings or popping a breaker.

    Anyway--My thoughts.

    Very Respectfully,
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Help with new battery bank setup
    BB. wrote: »
    These types of PF require a power meter that can measure both voltage and current at the same time to measure both the phase angle between the two wave forms, and also to perform the RMS (Root Mean Square) of the voltage and current wave forms (if they are not pure 60 Hz sine wave).
    So--If not using an RMS meter with something like 50kHz sample rate (to estimate the areas under the nonlinear curves), a standard (my cheap DMM) would tend to over estimate the RMS current because it assumes a sine wave and does not do RMS calculations.

    With BC04's measurements--I would have guessed if his meters are calibrated, that he would have over estimated the AC RMS current and came up with too low of over all efficiency--Or that the DC voltage/current measurements are too high.

    Actually, I think that you have found the explanation and do not realize it. When you have a current waveform which is more or less in phase with the voltage but is zero except for a small area around the positive and negative peaks of the waveform, the RMS voltage will be higher by comparison to the average current than it would be for a sine wave. So a true RMS meter would give you a reasonable number to use when combined with the power factor and efficiency to get the output power, but the average value, as measured by the meter, will be too low.
    You can either do the math to convince yourself of this or look at the case of a pure symmetric square wave of peak voltage Vp (peak-to-peak voltage = 2Vp)
    Then Vav = Vp = Vrms.
    For a very narrow pulse, with duty cycle t/T, the average voltage is (t/T) times Vp. But the RMS voltage is sqrt(t/T) times Vp.

    That means that the average voltage decreases faster as function of duty cycle than the RMS voltage does.
    A simple averaging AC meter which assumes a sine wave will give you a "corrected" reading which is too low once you reach the point where sqrt(t/T) is less than .636/.707 (the correction factor between Vav and Vrms for a sine wave, which is built into the meter.)

    (in the above description, please substitute I for V, since the measurement we are interested in is the current, not the voltage which is still sinusoidal.)
    SMA SB 3000, old BP panels.
  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Help with new battery bank setup

    Let me tell you what I go by, AC amps in and DC amps out. Here is the following. One in at 120 V and what ever the division gives me out in DC amps.

    1 / 8.2 Iota
    1 / 7.5 Outback
    1 / 7.9 Magnum

    For the Meanwell to do what you say it has to be 1 /10.9 and it'll never do it. The Magnum and the Outback are both PF corrected and they can't even beat the Iota. I know you'all have chargers, do the math.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Help with new battery bank setup

    I don't think the IOTA is doing the 95.4% VA efficiency.

    And for meters, the cheap versions tend to be just peak reading, then divide the AC reading by sqrt(2) -- which mathematically what the integration of the area under a sine squared wave conversion works out to be (sqrt(2) conversion factor). Different wave forms have different conversion factors (a perfect square wave would be 1.0 conversion--I think).

    So, in the case of a "simple" peak reading meter, the narrow/high peak would be divided by the sqrt(2) which would "over estimate" the sine squared area under the curve by a lot--So, that is why I would not understand how come a non-RMS reading meter would read "low" on a rectifier+capacitor type current profile.

    With your AC input voltage/current of 120 VAC and 8.83 amps, the output should be (at a maximum with PF = 1):

    120 * 8.83 amps * 0.80 energy efficiency * `1/13.8 volts battery = 61 amps DC at 13.8 volts

    And if my PF estimate of 0.67 is correct, and your 8.83 amps is measured with an RMS reading meter:

    61 amps * 0.67 PF = 41 amps DC...

    I believe that one of the current readings are wrong--But I don't know which one is--And why it would be wrong.

    At this point, I am not even worried about the high efficiency estimate (Meanwell, Xantrex, Outback, etc.).... Just trying to understand the Iota measurements.

    If we want to continue this discussion, I probably should move it to its own thread... This is probably getting beyond the original questions.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Help with new battery bank setup
    BB. wrote: »
    I don't think the IOTA is doing the 95.4% VA efficiency.

    And for meters, the cheap versions tend to be just peak reading, then divide the AC reading by sqrt(2) -- which mathematically what the integration of the area under a sine squared wave conversion works out to be (sqrt(2) conversion factor). Different wave forms have different conversion factors (a perfect square wave would be 1.0 conversion--I think).

    So, in the case of a "simple" peak reading meter, the narrow/high peak would be divided by the sqrt(2) which would "over estimate" the sine squared area under the curve by a lot--So, that is why I would not understand how come a non-RMS reading meter would read "low" on a rectifier+capacitor type current profile.

    With your AC input voltage/current of 120 VAC and 8.83 amps, the output should be (at a maximum with PF = 1):

    120 * 8.83 amps * 0.80 energy efficiency * `1/13.8 volts battery = 61 amps DC at 13.8 volts

    And if my PF estimate of 0.67 is correct, and your 8.83 amps is measured with an RMS reading meter:

    61 amps * 0.67 PF = 41 amps DC...

    I believe that one of the current readings are wrong--But I don't know which one is--And why it would be wrong.

    At this point, I am not even worried about the high efficiency estimate (Meanwell, Xantrex, Outback, etc.).... Just trying to understand the Iota measurements.

    If we want to continue this discussion, I probably should move it to its own thread... This is probably getting beyond the original questions.

    -Bill
    Bill, it's a 75 amp charger, if it was putting out 61 amps I'd throw it in the lake. As I said, I worry more about what I get out rather than what I put in, but there is a scale to it. When this thread came up, I just happened to be charging a bank of 10 GC-2's. so I put my amp meter on it and I posted the readings.

    I am done.
  • itrickski
    itrickski Registered Users Posts: 4
    Re: Help with new battery bank setup
    What your trying to setup pretty much mirrors what I Install in most Marine setups. 8-10 GC-2's pulled to 50 % will give you a reasonable amount power and Generator run time to put back. If you subscribe to a regimen of pulling the batteries to 50 % and charging back to 85 % on a daily basis and then doing a full charge once a week, you'll do fine. The net amp hours on 8 GC-2's is about 350 for 50-85% putback. A Honda EU2000 will pull a 60 amp charger easy and still have some ECO throttle left, 75 amp is full throttle and a strain. It would take you a good 6+ hrs to put back 350 amps hrs, you could break it up and do it twice a day. I guess I don't have to tell you that the power you don't use, is the power you have to spare and don't have to put back. 6-7 hrs is about a gallon of fuel, so that has to be in your plan. I usually install a 2500-3000 watt inverter / charger, you don't need that much all the time, but you need the surge capability of that size to start your pumps.

    If your sticking with 12 V , you'll have to oversize all your battery cables to 4/0 to the Inverter and at least 2/0 for interconnects.

    Thank you, this is very helpful. Do you normally use 12 V or 24V? Do you have any recommendations on chargers and inverters?
  • itrickski
    itrickski Registered Users Posts: 4
    Re: Help with new battery bank setup

    Thanks for the information and good resources. I'll keep studying.
  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Help with new battery bank setup
    itrickski wrote: »
    Thank you, this is very helpful. Do you normally use 12 V or 24V? Do you have any recommendations on chargers and inverters?
    Well, usually do 12v but only because thats how most come wired from the Factory and there so many things that run on 12 v in a boat. If I was going to change, I'd have to have a separate battery bank to flush the toilet's ( 12 v @ 50 amps DC ). By sticking to 12 v I can do it all on one bank and all I have to charge is one bank. 24 V has a lot of advantages, In my personal boat I have both. They do create a charging issue though, but I have a Bow Thruster that is a 24 V, 5 hp DC motor ( 320 amps ), so I don't have much of a choice.

    I wouldn't waste my money on anything under 2500 W , Xanterx SW 3012 , Magnum MS2812M , Outback VFX 2812M. all are also available in 24 V versions. Those are the big 3 , There are others. Magnum is coming out with a new version that has true Generator support ( MSH2812M ) in the next few months, it could be a big winner for a Honda EU2000, where they support each other, instead of either / or.

    All the inverters above have built in chargers. The only problem is with a small generator you cannot split the generator output well through the inverter. Your better off having the stand alone charger, if you have big loads and feeding you Battery Bank with DC from the charger. I like IOTA's because they have been consistent with their output. I think you read the posts below. I have a Meanwell on the way, as soon as I set it up, I'll let you know how it does ( My opinion is it'll be a waste of time, but we'll see if the PF helps it, you have to love the 13.8 float voltage locked into the firmware ). I have been doing this long time. I know what works and what doesn't. I have tried 20 chargers that didn't work right the way I use them. IOTA is really NOT a battery charger, It's a power supply. It just happens that it has a option to be able to 3 stage charge.

    We are just now going into the 3 generation of Inverter evolution. In some features, sometimes it's a old feature that can be re-born with new understanding and control. Stand alone chargers may not be the way to go as certain things mature. The Remotes now have many more programmable perimeters and a whole lot less defaults you couldn't get to before. I just got the New SW3012 today and have it on my test stand at home. I'll see how it adapts to the way I want it to work.

    It's not my goal to find fault with the engineer types in here. There is so much more than things like PFC. It's the algorithm and the logic that these manufacturers employ that makes their equipment usable. Example : Xantrex employs a full cycle recharge Bulk, Absorb, Float once the float voltage drops below re-float, OutBack just re-floats. Xantrex's will do 50 full re-charges a day if there is a parasitic load on the system, how's that on your battery cycle life ??, and it runs through every charging system they make. There 100's of quirks in all of them, some you ignore and some you can't.
    .