New Off Grid System - Please help me make a battery decision!

whitestrabbit

We have been living off grid with a Honda 3300EX generator and XW6048 inverter for over a year now. Designed (with alot of help from this forum) and plan to install the following next week: 15 Evergreen 205W panels (3075W Watts Total expandable to 20 panels), Xantrex XW6048, XW-MPPT60 charge controller, Bogart Pentametric. However no matter how much research I do, I cannot seem to make a concrete decision on what batteries to buy - there is no real solid manufacturer data to go on - much anecdotal evidence. Please help or comment if you can.

I have measured about 10kW*Hrs a day usage (which could spike to 15kW depending on usage - we'll see - family of 5), with about 6kW*Hrs after the sun is down. I've read to incorporate 2-3 days of battery capacity at 50% AH capacity for winter rainy days. Even if I have that kind of battery capacity, wouldn't the solar panel output also have to be sized significantly larger than the daily 10kW*Hr usage to catch up and refill the batteries with 3 days of output ? Our winter weather patterns (Northern CA) often include rain with no sun a week or weeks at a time. It seems like a better and cheaper short and long term solution is to size the battery bank for only 1 night capacity, and spend the money saved on a really efficient diesel generator (10kW diesel @ 0.7gals/hr) as backup rather than extra battery capacity, extra solar panels, an extra charge controller, etc. Comments?

Question for L16 users - Deka 8L16 specs say 1150 cycles at 20% DOD, or 900 cycles at 50% DOD - 1150/365=3 years max, so why do I consistently read off grid users indicating L16 life is 7-10 years? I know it depends on system specifics and usage, but according to Deka's specs even assuming best case scenario their specs indicate only ~3 years life @ 1150 cycles. Is real world 2-3 years or 7-10 years or am I missing something?

Here are the batteries under consideration:
1. Deka 8L16 - 6V, 370AH, 1150 cycles @ 20% DOD, 900 cycles @ 50% DOD, found for $150 blemished (1 yr warranty), or $199 new (full factory warranty)
http://www.eastpenn-deka.com/assets/base/0919b.pdf (cycle specs)

2. Northstar NSB-125 VRLA AGM - telecom/USP batteries - 12V, 130AH, 2000 cycles @ 20% DOD, 10000 cycles @ float, 4000 cycles @ 10% DOD, 800 cycles @ 50% DOD, $125 each new (this seems like a good deal so leaning towards these)
http://www.northstarsitetel.com/1/1.0.1.0/110/SES-544-01.pdf (cycle specs)

3. Surrette S-530 flooded - 6V, 400AH, 1000 cycles, $299 - seems like Deka 8L16s are a better deal - warranties are the same - was planning to purchase these a few months ago

4. Fullriver DC400-6 AGM, 6V, 400AH, $379 - my neighbor has had these for 2 years, no water/SG maintenance, no problems - was initially going to purchase these based on my neighbors good experience, but the cost is almost 2x the Dekas or Northstars

5. Been reading posts about Lithium Iron Phosphate Batteries, LFP, LiFePO4 batteries but haven't seen any real usable solutions... anybody using these ?

So, as of today I'm thinking either the Deka 8L16 or the NSB-125 VRLA/AGM. They are very similar in price for a similarly sized bank. I've read VRLA telecom batteries like the NSB-125s aren't good for deep cycle applications such as off grid. But comparing the manufacturer specs the NSB-125 nearly matches the L16s at 50% DOD, and is double the cycles at 20%DOD. So, I am thinking to target 20% DOD daily use. And of course the AGM batteries don't require maintenance which is a huge advantage.

So much money to spend on batteries, and seems like little really reliable information from manufacturers....

thanks for any suggestions or information!

whitestrabbit

Re: New Off Grid System - Please help me make a battery decision!

To clarify my point/question on the generator and battery capacity, I'm figuring about 60 days of cloudy/rainy weather for our area (and ~300 days near full sun) which would require generator usage, let's just figure 100% of our usage or 10kW hr per day to be conservative.
That's 1 hr runtime for a 10kW diesel generator.
1hr * 60 days * 0.7 gals/hr * $3.2/gal = $134/year on diesel

This seems better than spending thousands extra on 3 day battery capacity, and extra solar panels to recharge the batteries, extra charge controller, etc.

halfcrazy

Re: New Off Grid System - Please help me make a battery decision!

With the size of your daily usage I would look at 2 volt cells to make a larger Amp hour bank. The thing You want to do is keep 2 parallel strings or less. 3 is the absolute max but 2 is a lot better. I have a couple friends that bought the Hup Solar One battery and love them they are supposed to be very long life.

I personally have 2 strings of Trojan L16's wired for 48vdc and can go 2-3 days but we only use 4-5kwh a day max So maybe a string of Trojan's new 2 volt cells would be a good place for you. But call the people at Hup Solar One they are very friendly and helpful with sizing etc.

Ralph Day

Re: New Off Grid System - Please help me make a battery decision!

Whites
If you really want your off-grid living to be sucessful and comfortable you need to bring down the loads. Things as simple as power strips, turning lights off, dumping the extra fridge (if there's one), that kind of stuff to get the daily loads down...and the nightly loads especially.

The generator sounds like the way to go. I have a 10kw diesel that will more than supply my needs, but when you're charging batteries you don't usually get to use the full 10kw , and you should really only use 70% or so (7kw) of capacity for charging. The charging cycle only uses the "top"of the sine wave, the rest being lost as heat in the windings of the alternator...I've had mine shut down due to overheat when using over 8kw of charging power. A big barn fan on a thermostat venting the generator shed helps reduce that happening, as does reducing the charging rate.

When you're charging batteries the XW will reduce the amps required as your SOC rises, further reducing your 10kw of available power to the system. My recommendation is for robust battery set, either Surrette or a new fork lift type of large amp hours capacity. And watch them closely for SOC and depth of discharge, avoid sulfation etc etc.

Best of luck

Ralph

audredger

Re: New Off Grid System - Please help me make a battery decision!

I agree with Halfcrazy; 2 strings of Trojan L16RE-2v cells would give you 2220 amp hrs @ 48 v. Just a little over what you would need for 3 days of 10 KWh / day.

That's 1 hr runtime for a 10kW diesel generator.

Sorry, for every amp you take out of a battery you need to put in 1.2 amps +. In order to put 10 KW worth of power into the batteries you will need a whole raft of battery chargers.

Not knowing where you are; I don't think 15 panels are going to cut it and, 20 may still not be enough.

Cariboocoot

Re: New Off Grid System - Please help me make a battery decision!

For the size of your daily usage I would look at the size of your daily usage. 10kW/hrs is massive for off-grid. Sounds like some people need to learn that switches have two positions, and one of them is "OFF".

Trying to supply that much power with solar is daunting ... and expensive. I agree with audredger; 15 panels won't do. You've got to get that 10kW into the bank in about 4 hours of good sun. That's 2500 Watts per hour, and with the usual panel de-rating that means roughly 3200 Watts of panel minimum - and that on a good day.

As for battery capacity, that is dependent on loads and time between re-charging. If you can be sure of a daily recharge via the generator if necessary, then you need (roughly): 10,000 W/hrs / 48 Volts = 208 Amp/hrs * 2 (maximum DOD 50%) = 416 Amp/hrs. Your giant-sized bank would either allow for two days with zero charging or keep the DOD down to 25%, either of which is good but not strictly necessary.

If I were building a bank that big, I go for the 2V cells.
But then I wouldn't build a bank that big.

BB.

Re: New Off Grid System - Please help me make a battery decision!

Also remember that only the "Bulk" phase of recharging can you put 100% of the current into the battery bank... After the battery reaches ~80-90% of capacity, then the charger will be cutting back on the charging current--such that you will now be charging on time (roughly 2-3 hours) more to top off the battery bank... Now, if you are running the genset daily, that is 3 hours of run time per day, not 1 hour.

And there is a limit to how much current you can put into a flooded cell battery bank... For the most part, without special cooling/temperature monitoring (a remote battery temperature sensor is always high recommended anyway)--The fastest you can charge a battery bank is about C/8. So, for a smaller battery bank, you will also be limited to how fast you can replace the energy.

Using 10kWH per day, 20% cycling, C/8 charging, 80% charger efficiency, 80% battery efficiency:

• 10kWhrs * 1/48 volts * 1/0.80 inverter eff * 1/0.20 discharge = 1,300 AH @ 48 volts
• 1,300 AH * 59 volts charging * 1/0.80 charger eff * 1/8 max charge rate = 12,000 Watts maximum charge watts from generator

Run time for your setup (assuming near zero solar power days):

• 10kWHrs per day * 1/0.80 batt eff * 1/0.80 charger eff * 1/10kW gen * 1/0.70 max gen loading = 2.2 hours assuming 100% charging current
• Absorb Time of ~2 hours
• Daily run time ~3-4 hours

Of course, fuel flow will be somewhat lower for final 1-2 hours of that run time as the current reduces because the battery is becoming > 80-90% charged. But it is not out of the question that you will be using ~3x as much fuel as you expected for your setup based on the longer generator run times and battery charging cycle.

Realistically, you will be, on average, recharging your battery bank to roughly 90% or a bit more per day... Recharging to 100% capacity every day is fuel inefficient and relatively hard on the battery bank if done every day (high voltage/equalization causes lots of electrolysis which increases water use, cell shedding, and oxygen formation/corrosion at the positive plate/grid).

Lastly, regarding cycle life of a battery bank--using the generic battery life vs discharge level graph from the Battery FAQ, you will see that the batteries will last ~2.7x as many cycles when discharged by 20% vs by 50%:



Battery FAQs:
Deep Cycle Battery FAQ
www.batteryfaq.org

-Bill

audredger

Re: New Off Grid System - Please help me make a battery decision!

I would like to propose that we work at reducing you loads, I'm sure you have but maybe you have overlooked something.

Are all the TV's, satellite receivers & VCR's on switched plug strips or switched outlets? Those devices can continue to use up to 80% of their rated power if only turned off with the remote! Do the girls stand there with the blow dryer in there hand for hours? Are your appliances the most efficient money can buy? A new rang or water heater is cheaper than panel & batteries to support them.

whitestrabbit

Re: New Off Grid System - Please help me make a battery decision!

audredger: "I would like to propose that we work at reducing you loads, I'm sure you have but maybe you have overlooked something."

Interesting the consensus is we're using too much power. I've included details on "calculated" usage below. I should give some more perspective on the design. This is a 4,000 sf house with a family of 5. It's a new house we just built ourselves. The local power company quoted us ~$40,000 for extending powerlines (to be split between us and a neighbor) and has been jerking us around for several years (keep upping the price and no power in sight) which is why we finally opted for off grid. We are still trying to get a grid tie by doing a meter set at the existing pole and taking 30A 240VAC4/0 from there underground 900' shortest route to the inverter, but the economics will need to make sense vs battery maintenance or we won't bother with grid tie. Even if we had grid tie, the grid typically goes down for a few weeks every winter here during storms so we still will want to have battery/generator backup. Also, hydro may be a possibility as we also have a small stream running through our property that runs in the winter with especially high volumes for days after a rain. 98% of the time our weather is either sunny or it has rained within a few days so this should provide a fairly consistent winter power source, at least in theory. I am not sure exactly how much it would cost to make hydro a viable winter power source (800' from inverter is a main concern) but I am hoping in the future I can hook a hydro turbine up here so that more than 1 day of battery capacity is not necessary even without the generator most of the time. So, both because of potential for grid tie and for hydro, I don't want to spend too much up front for our battery bank. I figure I can always add another parallel string within a year if the grid tie/hydro doesn't work out. Your suggestions to use 2V rather than 6V are something to think about but investing in a 2V system requires a minimum 24 batteries which is probably more than I want to spend at this point. Also, as I said I have found a source for $150 blemished Deka L16s. My source does not have 2V, so I'd likely need to spend at least twice the amount for normal retail cost.

We do want to conserve but also want to live a somewhat "normal" lifestyle. I did get bids from professionals. Interestingly, they indicated 10kW*Hrs/day was lower than what they thought was typical usage. The professional installers recommended around 3-4kW panels and between 8-24 Fullriver DC400 AGMs for our design which is 19,200-57,600 W*Hrs or 1-3 days usage @ 50%DOD. Also, our neighbor has a nearly identical off grid system with 16 DC400 battery bank, and he lives alone so I guess "huge" is relative.

Also, this is only estimated usage at this point as we don't yet have a trimetric installed. We have CFLs throughout the house. Each room has both CFLs and incandescents on dimmers for mood lighting - we use one or the other and incandescents are never dimmed up and I always make sure lights are off in not used. Both CFLs and dimmed incandescents use about the same power which I've measured on the inverter. All plugged in appliances are on power strips which are switched off when not in use. We have a new energy efficient fridge. Propane dryer, stove/oven, and on demand water heater. Furnace is propane but uses 600W for blower. But we heat 90% primarily with a wood stove which uses only a 60W blower. No AC. Actual calculated daily usage is 7.3kW summer and 8.8kW winter sunny days, and 7.2kW winter rainy days. I figured 10kW to build in some buffer. As I indicated our system is sized/designed/wired for 20 205 W panels which is 4100 W (STC) and 3748W(PTC). We are just starting with 15 panels and will see how that goes. If we need 5 more we'll add those.

Daily 8.8kW*Hr usage is (all instantaneous values were measure on inverter except the fridge):

• 1233 Fridge (not measured) - kill-a-watt is on order to check
• 473 Microwave
• 2075 Lights Night
• 330 Coffee Pot, Lights Day, phone chargers, misc
• 807 Well Pump
• 180 Laptop
• 540 LCD TV
• 400 Washer
• 400 Dryer
• 500 Dishwasher
• 1200 Furnace (2 hrs blower)
• 720 Wood Stove (60W * 12 Hrs)

We can take out the well pump, washer, and dryer on rainy days to get to 7250W*Hrs.

Generator:
"Of course, fuel flow will be somewhat lower for final 1-2 hours of that run time as the current reduces because the battery is becoming > 80-90% charged. But it is not out of the question that you will be using ~3x as much fuel as you expected for your setup based on the longer generator run times and battery charging cycle."
Yes, I forgot about this and also the max charge rate of my inverter is 6kW, not 10kW so I will use more fuel than indicated, but still I'm not sure it's enough to justify spending so much more on the battery bank especially since I hope I can make hydro viable at some point. Isn't one solution to this to run the generator early in the morning during bulk charge, and then let the solar take care of the absorption/float top off. I have the Xantrex AGS (automatic generator start). Also the Pentametric has an output relay that can start the generator based on AH DOD.

halfcrazy: "The thing You want to do is keep 2 parallel strings or less. 3 is the absolute max but 2 is a lot better." I have read this with regards to off grid solar. Telecom backup systems commonly use many parallel strings with buss bars. Seems like it should work but maybe I am underestimating issues with parallel strings. Any comments on using Telecom batteries like the NSB-125 - these seem to be a very good deal I found. Please refer to the DOD graphs I linked for the NSB125 and for Deka 8L16. The NSB125 seems to match the 8L16 at 50% DOD and outperform it at lower depth of discharge.


BB: "Lastly, regarding cycle life of a battery bank-- using the generic battery life vs discharge level graph from the Battery FAQ, you will see that the batteries will last ~2.7x as many cycles when discharged by 20% vs by 50%"
Although this generic graph shows 3,000 cycles at 20% DOD, the Deka graph I linked specifies only 1150 cycles at 20% DOD. Trying to figure out what to believe. The Deka 8L16 also seems to be more efficient/economical at 60% DOD than 20% DOD so if buying the 8L16 it would actually make more sense to buy 8 L16s than 16 and plan for deeper discharge cycles. This was discussed in detail here:

http://forum.solar-electric.com/showthread.php?t=4939&highlight=8L16
Patrick Brown: "When I crunch the numbers it tells me the 8L16 is more efficient/economical at a 60% DOD (as opposed to 20%) while the DC27 is more efficient/economical at the opposite end, 20% DOD. "

halfcrazy: "I have a couple friends that bought the Hup Solar One battery and love them they are supposed to be very long life."
Online list prices seem more than what I want to pay. Any idea what your friends paid?

I think 2V is going to be more than I want to spend since I'll need 24 and I don't have a source of 2V's at a discounted price. So probably the 6V L16s since I have a deal for $150 each which is half the cost of anything else I have found. I guess my main question at this point is what is real world life from L16s. Why does the Deka 8L16 indicate 1150 cycles max (~3 yrs)? Is this realistic or do Dekas last longer? Are other brands of L16 (Trojan/Surrette) lasting longer on average than Dekas and if so how much?


thanks!

icarus

Re: New Off Grid System - Please help me make a battery decision!

It looks like you have looked pretty seriously at this, but a couple of quick obsrvations,

Can you reduce the dishwasher by either not using it, or disconnecting the water heater/dyer cycle?

Can you live without a dryer except for emergencies? (I assume gas/propane dryer)

Your 2 kwh of night lighting seems high. That would translate to 6 hours @ 333 watts. That in turn would be 22 cfls going for those entire 6 hours. Can you reduce the number of bulbs, the times they are on, the wattages of some. I noticed you mentioned incandescent dimmers. Why not use dimmable cfls? Or leds?

New generation energy star fridge should get down to .5-1kwh/day Consider a different blower set up for the stove. Sterling Engine or TED powered stove top fans work fairly well, and no power cost. A 60 watt paddle fan will move way more air than the stove blower,, even cheaper if you run it at 1/4 or 1/2 speed.

Consider oversizing your water tank so that you only have to pump water ~ once a week, maybe to coincide with battery charging and run the pump on the gennie. Stove top, Coleman MR Coffee uses no electricity, works just as well, and then you store hot coffee in a carafe or thermos, reducing that use.

Lap tops, phone chargers etc can usually be set up to charge when you have excess solar capacity (after batteries have gone to absorb or float). (Time shifting loads)
Consider the net value of the Micro wave and see if it makes better sense not to use one.

As we say, every dollar spend on conservation saves ~ $10 in PV costs. There are lifestyle trades to give up off grid, but you can live a pretty comfortable live, (with some considerable expense up front I should mention) but small changes around the margins have a pretty considerable effect on the cost as well as the life style.

Good luck and keep in touch,

Tony

solarvic

Re: New Off Grid System - Please help me make a battery decision!

White rabbit, Did you look at the blem batterys? I looked at some New Castle blems once and didn,t get them. They had melted plastic around terminals and bulges in the cases. Told me that was caused by the test they run them thru when they short out the post. The ones that end up like that are blems. I would surely think that the life of those batterys would be suspect. S:Dlarvic

whitestrabbit

Re: New Off Grid System - Please help me make a battery decision!

Can you reduce the dishwasher by either not using it, or disconnecting the water heater/dyer cycle? Can you live without a dryer except for emergencies? (I assume gas/propane dryer). ....Consider the net value of the Micro wave and see if it makes better sense not to use one.
I asked my wife just now about these. She laughed at me. I think that means no.

Your 2 kwh of night lighting seems high. That would translate to 6 hours @ 333 watts. That in turn would be 22 cfls going for those entire 6 hours. Can you reduce the number of bulbs, the times they are on, the wattages of some. I noticed you mentioned incandescent dimmers. Why not use dimmable cfls? Or leds?
I think our actual usage may be less but I want to be somewhat conservative in the design. Hard to say for sure since these are estimated values. We do have alot of bulbs as it is a new house. For instance in the living room where we mostly live there are 6 CFLs (main task lighting) and 12 dimmable INCs (permiter mood lighting). We use one or the other (CFLs for full light or dimmed INCs for mood) and either way that's about 120W with about the right amount of light. We have some dimmable CFLs in the kitchen per our code. They really don't work very well at all compared to dimmable INCs. Calling them dimmable is an overstatement. I'd call them 2 state (full power and medium power) CFLs. Maybe there are some better dimmable CFLs available. But we enjoy the mood of the dimmed INCs and the energy usage is the same as CFLs as long as they are dimmed. You are right I should look into some dimmable LEDs at some point but these cost about $50 each. I think we have something like 100 INC bulbs in the house on dimmers so it would be about $5,000 so we'll probably have to wait until that cost comes down.

As we say, every dollar spend on conservation saves ~ $10 in PV costs. There are lifestyle trades to give up off grid, but you can live a pretty comfortable live, (with some considerable expense up front I should mention) but small changes around the margins have a pretty considerable effect on the cost as well as the life style.
Yes, I agree we'll have to see where we can conserve, but it's hard to say for sure until we get it up and running, and see where we're at on actual usage. For now, trying to figure out which batteries to get.

thanks for your input!

halfcrazy

Re: New Off Grid System - Please help me make a battery decision!

I do not recall prices but at the time figuring the life of all the different battery's they where the cheapest.

whitestrabbit

Re: New Off Grid System - Please help me make a battery decision!

White rabbit, Did you look at the blem batterys? I looked at some New Castle blems once and didn,t get them. They had melted plastic around terminals and bulges in the cases. Told me that was caused by the test they run them thru when they short out the post. The ones that end up like that are blems. I would surely think that the life of those batterys would be suspect. Slarvic

Yes, I did. Looked ok. Tested the SG of each and voltage which looked acceptable. All cells ok. No bulges. No 7 yr factory warranty either. 1 year warranty from the supplier so it's a definite risk. I also wonder why does Deka give a 7 year warranty on an L16 battery labeled "Solar" and their cycle discharge graph (linked below) shows only 1150 cycles max = ~3 yrs. These two don't coincide.

Deka Solar Warranty:
http://www.energy-alternatives.ca/mmEA2005/Others/EPC%20Deka%20Solar%20Warranty%20June09..pdf

BilljustBill

Re: New Off Grid System - Please help me make a battery decision!

whitestrabbit wrote: »

White rabbit, Did you look at the blem batterys? I looked at some New Castle blems once and didn,t get them. They had melted plastic around terminals and bulges in the cases. Told me that was caused by the test they run them thru when they short out the post. The ones that end up like that are blems. I would surely think that the life of those batterys would be suspect. Slarvic

Yes, I did. Looked ok. Tested the SG of each and voltage which looked acceptable. All cells ok. No bulges. No 7 yr factory warranty either. 1 year warranty from the supplier so it's a definite risk. I also wonder why does Deka give a 7 year warranty on an L16 battery labeled "Solar" and their cycle discharge graph (linked below) shows only 1150 cycles max = ~3 yrs. These two don't coincide.

Deka Solar Warranty:
http://www.energy-alternatives.ca/mmEA2005/Others/EPC%20Deka%20Solar%20Warranty%20June09..pdf

The warranty is most likely prorated... Those last "years" won't be worth much more that the value of a trade-in core.... ;>)

What I'd like is a warranty that is said to be on the battery for the Toyota Prius. It's said that if the battery fails within 8 years, it's replaced for free... That "warranty" may be like Dell computers' extended warranty.... What they do, for instance, is they replace a bad hard drive with one stamped: "Refurbished"...

Bill

audredger

Re: New Off Grid System - Please help me make a battery decision!

Can you reduce the dishwasher by either not using it, or disconnecting the water heater/dyer cycle? Can you live without a dryer except for emergencies? (I assume gas/propane dryer). ....Consider the net value of the Micro wave and see if it makes better sense not to use one.
I asked my wife just now about these. She laughed at me. I think that means no.

Yes that means no .... I believe you missed half the point. I won't do without my dishwasher either but, I only run it when the batteries are full. That may be a challenge with 5 in the household but, I run the hot water in the sink until its HOT before starting the dishwasher and run it on "economy" so it doesn't heat the water. My dishwasher does not have an air dry setting so, we open the door when starts the dry cycle.

I think we have something like 100 INC bulbs in the house

Loose the incandescents ... mood lights? .... There is only one incandescent bulb in my house and it's in the flashlight. I think you are fooling yourself with the dimers .... put in switches and CFL's

westbranch

Re: New Off Grid System - Please help me make a battery decision!

here is some detail on CFL's...they are not all created equal...

http://forum.solar-electric.com/showthread.php?t=5461&highlight=power+factor+correction+corrected+cfl

HTH

Eric

whitestrabbit

Re: New Off Grid System - Please help me make a battery decision!

I believe you missed half the point. I won't do without my dishwasher either but, I only run it when the batteries are full. That may be a challenge with 5 in the household but, I run the hot water in the sink until its HOT before starting the dishwasher and run it on "economy" so it doesn't heat the water. My dishwasher does not have an air dry setting so, we open the door when starts the dry cycle.

Agreed. Once we have solar up and running, we'll ony run dishwasher/washer/dryer during the day. Also need to turn off the dry cycle.

Loose the incandescents ... mood lights? .... There is only one incandescent bulb in my house and it's in the flashlight. I think you are fooling yourself with the dimers .... put in switches and CFL's

Actually, the INC work great - wouldn't have it any other way - they actually save energy believe it or not over using 100% CFLs. Key is you have to have both in the same room. The lighting was designed this way with off grid in mind since it's a new house. Eventually the INC will be replaced with LEDs once bulb prices drop. Sitting here now watching tv with very dim perimeter INC lighting. It's using only ~60W for 12 lights. If I had the CFLs on in the same room, they would be burning twice as much power, and the room would be too bright to comfortably watch tv. With all the light off it is too dark to watch tv. Also, the quality and color of light from dimmed INCs is far above that of CFLs in my opinion. If you think I'm bad I have a neighbor who is off grid and his house is 100% INC bulbs - no CFLs. He works for a company that makes LEDs and he is very particular about the quality of light.

jeffkruse

Re: New Off Grid System - Please help me make a battery decision!

I have 8 8L16 370AH Deka’s and 10 205W panels. I use 60 – 100AH a night (3-5KWH). So I think that’s about 70-75%SOC give or take. IMO these batteries are hard to get to 100%SOC :roll: so I probably get them to 90 – 95%SOC most every day. We also use about 2-3KWH during the day. That’s 5 – 8KWH total each day.

My XW bulk and absorb voltage is set to 60.5V, the trimetric shows battery voltage of 49.5 with these settings. I have measured .3V drop @20Amps from all the cables combined. What I am getting at is that I have the voltage set high so my SG gets close to full.

Some people are starting to use the LiFePos. If they can truly deliver the stated life expectancy with 80%DOD then they could change everything.

audredger

Re: New Off Grid System - Please help me make a battery decision!

Light color is a very subjective. Are you aware that CFL's come in various spectrum's?

stephendv

Re: New Off Grid System - Please help me make a battery decision!

I'm not off-grid yet and have no real world experience with batteries, but after comparing specs and prices, I'd go with new flooded forklift batteries with an air-pumping system. These are built with the same technology used in stationary flooded lead acid batteries that are supposedly designed for renewable energy/telecom use - but cost about 40% less. Market forces at play me thinks: more forklift batts around than renewable energy installations.

The air lift/air pumping system is basically a simple air pump that is integrated into the battery system so that charging is more efficient and you can help avoid stratification without having to do an EQ charge as often.

In europe forklift batts life expectancy is rated according to a standard and most are rated at 1500 cycles at 80% DoD. I'm sure they'll be similarly rated in the US.

Cariboocoot

Re: New Off Grid System - Please help me make a battery decision!

It should be said that there's absolutely nothing wrong with Deka brand batteries. I've never heard a word against them on this forum or in 'real life; and would say they are as good as Trojans. If they're going to warrant these 'blemished' units and you're happy with the price there's no reason to not buy them.

As far as lifespan goes, there's a big difference between how long a manufacturer feels their unit will last under 'reasonable' or 'average' use and how much time you can actually get from it with judicious care. I've had batteries last (as in still reasonably functional) up to twelve years. I've had others fail in ONE. :grr

whitestrabbit

Re: New Off Grid System - Please help me make a battery decision!

I have 8 8L16 370AH Deka’s and 10 205W panels. I use 60 – 100AH a night (3-5KWH). So I think that’s about 70-75%SOC give or take. IMO these batteries are hard to get to 100%SOC so I probably get them to 90 – 95%SOC most every day. We also use about 2-3KWH during the day. That’s 5 – 8KWH total each day.

We have very similar systems (Evergreen 205, Xantrex XW) and daily kW*Hr usage. Sounds like the 8 Dekas are working well for you. Do you have a generator that charges batteries on rainy/cloudy days ? How often, how much do you have to run the generator ?

Other ideas:

Hydro:
We had a medium rain yesterday probably around an inch. On non-sunny days in winter, we usually will get similar amounts of rain or more with max daily rainfall around 10 inches. I measured stream flow at ~90GPM after the rain stopped which is more than I thought it would be. Not sure what our available head is but I am guessing somewhere between 50-120 feet. Need to measure that. Based on the turbine chart linked below it's not unlikely we could get 200-500W usable output or 4.8-12kW*Hrs/Day from Hydro at least if it's rainy weather. Need to keep checking this. Assuming I can make this work I think 8 Deka 8L16s would be plenty. Need to figure out how to get this power 800' and into the batteries. Looks like I need to use a Xantrex C-Series charge controller but voltage inputs look pretty low <55VDC so 800' could be a problem.
http://www.nooutage.com/powerspout.htm

Pumped Hydro:
http://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity
Another interesting storage option I considered is pumped reservoir storage. This is what power plants sometimes use. When it's sunny excess solar capacity could be used to pump water up a hill to an upper reservoir. When it's cloudy run water downhill to lower reservoir and use a turbine to generate electricity. It can work out well (much cheaper than any battery solution in long run) if your property is such that you can dig a couple of ponds cheaply at different elevations. The cost of plastic/metal storage containers for me I think kills the cost. Our property is pretty steep and mudslides are a concern so I'm thinking ponds are likely not an option. But if they were, I think this is the most cost effective energy storage solution. 100% DOD, lasts forever.

jeffkruse

Re: New Off Grid System - Please help me make a battery decision!

whitestrabbit wrote: »

We have very similar systems (Evergreen 205, Xantrex XW) and daily kW*Hr usage. Sounds like the 8 Dekas are working well for you. Do you have a generator that charges batteries on rainy/cloudy days ? How often, how much do you have to run the generator ?

No generator but we have the grid available if needed. I have to switch to it about once a month just for a night or two because of weather (and unwillingness to reduce TV watching)

whitestrabbit

Re: New Off Grid System - Please help me make a battery decision!

Ground Trac mounting rails and components arrived yesterday. Solar panels are sitting at the local shipping yard - arrived today! Still waiting on UPS to deliver the charge controller, XW distribution box, etc. Now for the real fun. Inverter shed (which is not yet built) is 165' from the house. Solar array is 285' from the inverter shed. Had to go this far to get good sun since house is blocked by mountain and trees to the south. Have to trench 285', run conduit, pull 4/0 cable, build the shed. After running off the generator/inverter/cheap batteries full time for almost two years, I WILL NOT miss hauling gasoline, filling the generator EVERY DAY, and losing power every time the battery voltage drops or we trip the 3kW generator breaker. Looking forward to 9 months of sun!

icarus

Re: New Off Grid System - Please help me make a battery decision!

Possibly a dumb question,

Why didn't you build the inverter shed closer to the PV? The shorter the low voltage run the lower the loss. 285' seem like a long way to send PV voltage. Where are the batteries?

Tony

whitestrabbit

Re: New Off Grid System - Please help me make a battery decision!

Three reasons:
1. The solar array is 100'+ in elevation higher than the house up a very steep hill. The panels sit on the other (South facing) side of the hill and it's the only place we can get good sun. Didn't want to have to climb up there to do battery maintenance, for inverter issues etc. The batteries and inverter are in the same shed with a dividing wall between. The inverter shed is about 30' higher in elevation than the house but right near the road for easy access.
2. Xantrex indicates I should not try to go farther than 200' with the inverter System Control Panel and I want to have the System Control Panel in the house. The Xantrex manual states 130' max but I spoke to engineering and they said they've gone 200' in the lab, so hopefully it works. The Parametric can go much farther.
3. It's actually cheaper by about $300 for wiring to locate the inverter/batteries in the middle than at the panels. The 450' 240VAC run @100A (oversized for expansion & surge current) to the house costs more than the 285' 75VDC run @50A and 165' 240VAC@100A run.

PV Vmp is 91VDC Vmp. Adjusting for PV record low temp min Vmp is 75VDC which is what the DC wires are sized for.

whitestrabbit

Re: New Off Grid System - Please help me make a battery decision!

BTW - has anyone tried to run Xantrex cat 5 for SCP in the same conduit with 240VAC ? I know you're not supposed to run low and high voltage together but I already ran the conduit from the shed location to the house 165' long before the details of this system were worked out. The conduit is 3' deep and runs under an asphalt road 12' wide.

Guess I'll try it and see if it works. Cat 5 is cheap. If not have to run another conduit.

audredger

Re: New Off Grid System - Please help me make a battery decision!

Note: My large array is ~135' from the "Bat Shack". That array is wired for 106v to lessen the line loss. Would run higher if I could find a controller that would handle it.

285' of 4/0 cable ... Wow, you must be rich ... corection; have been rich ... poor now

Edit: 285' x 2 = broke

Cariboocoot

Re: New Off Grid System - Please help me make a battery decision!

I think I might have considered moving the house. Might be cheaper than all that wire!

You have our sympathies.

whitestrabbit

Re: New Off Grid System - Please help me make a battery decision!

I think I might have considered moving the house. Might be cheaper than all that wire.

I would have liked to have moved the house up there. Best views on the property are at the solar panels. Driveway would have been a bit steep though - fire chief wouldn't have like it! Don't get me started on how much the county and fire dept reamed me on my driveway/retaining wall costs on the "flatter" part of my property.... that's where I really went broke. :grr

Edit: 285' x 2 = broke

4/0 Aluminum = $1.25/lf = nearly broke
vs 2/0 Copper = $2.50/lf = broke
paying power company $40k to run powerlines = really broke and stupid!

wish me luck pulling 4/0 Al through conduit - never tried that before.