Trying to Determine if Battery is Dying

mjp24coho

I’m trying to figure out of my forklift battery in my offgrid system is dying. I have ~4 years on my 800 A/hr 24v forklift battery - it’s been working great over the years, but suffered a hard winter a year ago when my panels were covered with snow and I couldn’t get there to my cabin for a few weeks to clean the panels off. The battery can handle minor loads fine now, but seems to be struggling when running my washing machine (washer kept restarting). I tested the battery under heavy loads (input power off and no other loads running) I ran the system with a blow dryer and space heater both going on full for a minute. Resting voltage before was 24.4v, but after loads applied it went to 23.25V and held steady. When loads turned off, it went back to ~24.4V. Not sure how to read that - what does it tell me about the life left in the battery?

Photowhit

is this a standard flooded lead acid type forklift battery?

Did you check the specific gravity, after the hard winter, and do corrective equalizing? Do you do monthly equalizing (or 2x a month equalizing if manufacturer suggests it)? Forklift batteries require a regular maintenance equalizing, and if chronically under charged over a period, likely need corrective equalizing.

I've found my forklift battery to be amazingly resilient. You should know better than anyone the state of your battery. The heavy likely 2500+ watt load should drop the battery voltage. That's a bit more than I would suspect, but recovering after is a good sign.

BTW- If you have a GB battery, they over rate the capacity of their batteries in the 20 hour rate. Their 12-85-13 which is 510 amp hour at a 6 hour rate is more like 660 amp hour in a 20 hour rate.

mcgivor

If I were in the predicament explained my first course of action would be to eliminate all loads and charge the hell out of the battery, with everything available, then equalization after equalization at ~32v  until the SG is where it's supposed to be, sounds like capacity is lost due to chronic undercharging. 

Estragon

FWIW - I've had a similar problem, though with L16s not forklift.

The good news is if the battery was cool/cold and reasonably well charged before the panels got covered, and the only load was charge controller(s), sulfation will be slow to form and harden. If too far discharged, hard freezing is a risk. Mine got as far as sort of slushy electrolyte, but not a hard freeze, and recovered well.

I'd second (third?) the EQ suggestion. As well as checking SG, you may want to use an IR thermometer to monitor battery temp in various spots. If the freeze was fairly hard, there's the possibility of expansion having created a cracked plate or internal connection, which might result in intermittent problems under load.

BB.

Check electrical connections (and voltage drop) to the battery bank... It is possible loose/dirty connections to the cells, cell jumpers, etc. could be an issue too.

With many fork lift batteries, you can check the voltage of each cell (under load, under charge, resting). Also, confirm the SG of each cell.

-Bill