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New Forklift Battery Care

CoolWill

Solar Addict
Joined
Sep 21, 2022
Messages
540
Hello! First post and relatively new to DIY solar. I've installed solar in the field but all grid-tied. Off grid battery systems I have only every done small >1 kW. So this is new territory for me.

Through a job, I have acquired a new 24-125-13 FLA forklift battery and 6 kW of PV. This is for my own personal off-grid cabin in the woods. It will replace my 24 volt 210 AH system, currently fed by 420 watts of PV.

My question is about taking care of this big expensive battery. I'm concerned that I don't have enough solar to charge it the way this battery would normally be charged in the wild: high current for a long time. I'm no battery expert, but I understand that it should be charged at or above 0.1C, which is more than 100 amps. In the best sun conditions I have, I'm not confident the array can supply what is needed for long enough. I haven't bought (or built) a charge controller yet, so I am feeling this out and looking forward to everyone's advice.

Thanks,
Will
 
If that is 24v battery, 3000w of actual power would give you about 120 amps at the battery. You could get 3000w for maybe 3 or 4 hours per day, on a good day. Day to day, how much power would you draw down from the battery?
 
Looking up the specs on your battery it shows a 750ah rating at 6 hours. Charging at .1C rate would be 125 amps for 6 hours. 125a by 48v = 6000w
 
My question is about taking care of this big expensive battery. I'm concerned that I don't have enough solar to charge it the way this battery would normally be charged in the wild: high current for a long time.
Your concerns are validated. Find the manufacturers published use and care document and do your best to follow it.

In my experience with a few sets of big flooded batteries on solar, sulphation will likely be your #1 enemy. Don't be afraid to take the bulk charge settings up much higher than the presets of your inverter/charger & SCC. I wouldn't be surprised if the manufacturer wants you to take them to 2.55 VPC every charge cycle.

Keeping a close on specific gravity and equalizing as needed with a generator will likely be your main line of defense. Pick up a refractometer on Amazon for measuring specific gravity. Plenty to be had for less than $25.
 
Great replies all! This is a 48 volt battery rated 1182 AH at the 20 hour rate. In my head, I have a DIY control system that will limit the DoD to 50%. I can't image actually using even that much in the short times I'm at the cabin, but also I may someday live there. Hopefully sooner rather than later. As far as utilizing 6 kW for charging, I figure that would never be realized in real life. Under effect laboratory conditions I might get 6 kW, but I want to be realistic.

Another question I have is does the rated charge current apply to a partial discharge? What I mean is, if I only drain the battery to 50%, is it required to still blast it at 0.1C? If I can get the voltage back up in a reasonable time, 4-6 hours, does it matter what the charge rate is?
 
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