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Battery data Flood Lead Acid

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lighthunter:
One recurring question that comes up often when considering the cost of a battery for an RE system is "what about a used forklift battery?
After several years of use i thought it might be useful to some
if i share data from a typical used traction battery to give an idea what to expect.

The speciman, a 510AH 48v 2000lb lead antimony made by enersys. 5 years ago it was sitting in a warehouse with a charge level of near zero less than 43v if i remember correct. I dont think i even had a way to measure specific gravity but by voltage im sure it was slightly above water. Pretty severe sulfation. It took weeks of slow charging but it came around.

It gets cycled daily from 1.250sg to 1.150sg
It has about 64.3% round trip efficiency which means if you discharge 9kwh (180AH) then you put back 14kwh.

Each day, provided sun is out, the bulk charge rate is from 40-60amps which terminates at 57.5V at around 2 pm, then absorb continues at 12-15 amps 53-56v which brings it to a moderate gassing level by 5pm.

After 180AH of discharge the resting voltage was 48.3
usable capacity is around 220AH

So these batteries are not terribly efficient some are better than this but it does a ton of work every day and i think these numbers would be typical for an end of life lead antimony. I think this chemistry always has a higher self discharge than other types though.

Certainly lithium is a better performer but they also cost more. The efficiency is a pretty good hit when its cloudy but when sun shines an  extra 5kwh is no big deal.

Our average continuous usage is 850w and the array size is 4500w on a sunny day, production can hit 30kwh.

LH
(no clue why photo upside down,  ha! I even uploaded 2 identical images one upside down and one right side up, they both show up inverted. Oh well not a big deal.

noneyabussiness:
+1 for traction battery,  mine is 2nd hand ceil battery,  i don't have the numbers like above but mine is in better condition I think, 660ah at c5 rate , i use between 200 and 300ah every night ( I also have 200ah of vla LA as well , that Ive cracked and filled a bit with extra water and resealed) . Minimum watering ( bout once a month) , by the ah gauge they hit full usually just after lunchtime as long as sun out...cost 3.5 grand with a 12 month warranty.. love it

Pete:
Sounds pretty good for a badly treated battery bank. I have used flooded batteries for decades now, but recently I changed over to SLA, one thing I found when running a 12 volt system with them was that they did not like to take a very high current. I have a 2500 watt panel setup but the best charge I ever saw going into the 12 volt bank was only around 1kw.
Since changing over to 24 volt we regularly see upwards of 1500 watts going in.
Our problem ( if it is a problem) is that we use very little from the batteries, usually only around 5% capacity each night, so our batteries are fully charge by around 10:30am. We use power in the afternoons to pump water, etc.
Still where we live we get a lot of foggy days and plenty of rainy ones, so it is good to have plenty of storage (660AH , 24 volt now)
We are in the process of dumping Gas usage, at the moment we have a gas stove and a backup Instant Gas hot water system.
We will be going to a small  2400 watt oven and an induction cooktop. As most of our cooking is done in the day time we should get free of gas with no problems. Our wood heater has a wetback and also the solar hot water system has a backup electric element too.
Pete

noneyabussiness:
Mine is 48v, so not that badly treated, would never bother with 12v unless low load,  currents just get to high... regularly over 6kw going into batteries before we moved, beauty of 48v.. thought of going " lithium " but just way too expensive for my requirements..

Pete:
Yes I agree, Lithium is pretty expensive, even going 48 volt with AGM or Gel is too expensive for me. New 24 volt bank was pricey enough. We don't plan on drawing more than 2400 watts at any one time and even then only for short time cooking.
Good to hear that your system is working well.
I would have thought that fork lift batteries would be pretty heavily cycled, but then maybe some only get used a few hours a day. Nice to hear how they perform
pete

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