Wanting to replace my battery array

SolarJohn · November 2007

My PV system has been in place for almost two years, and I'm still on my "learner" set of batteries. I'm using sealed Marine Deep Cycle batteries that are rated at 105ah each. I've taken good care of them, and so far have noticed no decrease in their capacity, but it's time to start thinking about a more appropriate battery type for my system. Still, money is an issue, and for that reason I'm considering 220ah, 6v, golf cart batteries. Because they're not sealed, I'll be able to apply equalization, something I don't do with my current battery array. My system will stay at 12-volts, since I don't want to have to replace my charge controller and inverter. I understand how to wire the 6-volt batteries, and I'm thinking of buying 6 of them which will give me 660ah of capacity at 12-volts. I can buy the 6 batteries for less than $400.00, which seems like a bargain to me. Any comments/advice will be appreciated.

John

mike95490 · November 2007

Re: Wanting to replace my battery array

Series connections are easy - when you get into parallel connections, then you get troubles with current shareing, and vaporizing things. I'd maybe consider 2 parallel strings, wired diagonally (there is a sketch somewhere here how to do that) and if you need more power, you SHOULD reconsider going to 24V.
As you scale up your bank, you need to increase your charge current, if you want to equalize. I don't know what you use to generate your 12V now, but just adding batterys will only add "on time" till the batterys run down, then you have to pay the piper and charge them all back up.

paulstamser · November 2007

Re: Wanting to replace my battery array

SolarJohn wrote: »

My PV system has been in place for almost two years, and I'm still on my "learner" set of batteries. I'm using sealed Marine Deep Cycle batteries that are rated at 105ah each. I've taken good care of them, and so far have noticed no decrease in their capacity, but it's time to start thinking about a more appropriate battery type for my system. Still, money is an issue, and for that reason I'm considering 220ah, 6v, golf cart batteries. Because they're not sealed, I'll be able to apply equalization, something I don't do with my current battery array. My system will stay at 12-volts, since I don't want to have to replace my charge controller and inverter. I understand how to wire the 6-volt batteries, and I'm thinking of buying 6 of them which will give me 660ah of capacity at 12-volts. I can buy the 6 batteries for less than $400.00, which seems like a bargain to me. Any comments/advice will be appreciated.

John

I've had good luck with 220 AH golf car batteries. My first set of four (two pairs for 12v/440 AH system) lasted about 10 years on my stand alone PV/generator system. They were from Batteries Plus.

My current set is from NAPA (Exide brand) and I've been running them since 2003.

I noticed that when buying batteries the prices varied greatly when I called around. NAPA's prices were the best in my local area.

crewzer · November 2007

Re: Wanting to replace my battery array

Any comments/advice will be appreciated.

Flooded-cell batteries tend to vent explosive/flammable hydrogen gas when they are being charged (absorb stage) or maintained (EQ stage). Accordingly, you’ll need to consider a battery box with a hood, vent, and probably a fan to properly vent the batteries to the outdoors.

Vent fan info: http://www.solarseller.com/battery_box_power_vent_by_zephyr_industries.htm

Lowe’s sells the big Contico Pro Tuff structural foam tool box for ~$50. It might be big enough to hold six GC2 batteries (“golf cart”, 6 V X ~220 Ah each, i.e., Trojan T-105, plus others from Exide, NAPA, etc.)

AGM (sealed VRLA) batteries are worth considering. For example, a pair of big 8A8D AGM batteries wired in parallel would be rated at 12 V x ~500 Ah. Alternately, three 8A4D AGM batteries wired in parallel would be rated at 12 V x ~600 Ah. AGM’s are more efficiency during recharge, and, unless abused, they don’t vent during charging.

Check local battery warehouses for prices. I found my 8A4D’s for $220 each, and the same place had 8A8D’s for $260 each. My batteries are in an unvented box in my garage.

HTH, and good luck!
Jim / crewzer

System2 · November 2007

Re: Wanting to replace my battery array

I see your in my neck of the woods....

I found some 134AH AGM batteries from wholesale batteries in O'fallon MO
They were less than 1 year old, and came off a short term UPS lease. They couldn't sell them new, and no company would invest the labor to use used batteries. Got $300 batteries for $40 each about a year ago, picked up 8 of them.

You might want to check with them from time to time to see what they have, they do everything from UPS to forklifts.

niel · November 2007

Re: Wanting to replace my battery array

jim,
from you "I found my 8A4D’s for $220 each, and the same place had 8A8D’s for $260 each."
i'll bet those prices changed and went way up.

crewzer · November 2007

Re: Wanting to replace my battery array

Could be. The real point is to look around.

Regards,
Jim / crewzer

niel · November 2007

Re: Wanting to replace my battery array

quite true with the way the prices are going nowadays.
also noting the first snow flurries of the season here on this day.

Wanting to replace my battery array

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