Storage battery questions

A really flat deepcycle battery can exhibit considerably less than

1.98 volts per cell. Sometimes it takes a pretty healthy shot of current to "get their attention".

To test: just measure the voltage on each battery. Those that are more than 1.5 volts or so (per cell) are probably OK. Those that are lower than that may still be OK, maybe not.

To keep alive: charge with a good charger, keep on trickle charge by a good charger. The worst thing you can do to a battery is overcharge it but a good charger won't do that.

Here's a really good article

I think you'll want to fully charge, test SG, and probably then equalize, perhaps multiple times. Odds of anything close to full capacity recovery probably aren't great.

"Flooded battery life can be extended if an equalizing charge is applied every 10 to 40 days. This is a charge that is about 10% higher than normal full charge voltage, and is applied for about 2 to 16 hours. This makes sure that all the cells are equally charged, and the gas bubbles mix the electrolyte. If the liquid in standard wet cells is not mixed, the electrolyte becomes "stratified". You can have very strong solution at the top, and very weak at the bottom of the cell. With stratification, you can test a battery with a hydrometer and get readings that are quite a ways off. If you cannot equalize for some reason, you should let the battery sit for at least 24 hours and then use the hydrometer. AGM and gelled should be equalized 2-4 times a year at most - check the manufacturers recommendations, especially on gelled."

I'll add - the equalization process will hopefully blast off some the scaling that's inevitably formed.

Are you sure they're not AGM? Regardless, I'd contact the maker for some specific advice. They may need equalizing as well, but you have to be very careful doing it.

Wayne

IMO, any type of LA lead/acid battery that's neglected for years is unrecoverable. The plate surfaces are likely to start to become sulfated as soon as a battery is left at a low voltage level/dead. From what I've read, LA batteries with liquid electrolyte can sometimes be desulfated, but batteries with gel electrolyte can not.

Desulfating consists of high frequency (10 kHz, maybe higher) current pulses that are said to remove the sulfated coating, which is then held in suspension, or removed by replacing the liquid electrolyte.

If the batteries were left in a low state/dead for only weeks (or possibly a month), but wouldn't take a charge, there is a variac and rectifier improvised technique that often works to get a LA batterys' condition to a point where it can be properly charged.

If some liquid electrolyte batteries were an exceptionally high grade of batteries, they may be recoverable by desulfating if they had been left at a low voltage level/dead for a couple of months, but I highly doubt that any that have been completely dead in excess of 6 months would be recoverable.

There is a lot of battery info online, some of it factual and some related to fluke situations. Fluke being a battery that was assumed to be fully recovered, performs badly within a short time, like the car battery that starts the engine fine, but suddenly won't on a cold day. The serious non-professional battery users are the folks that live off-the-grid. These folks strive to use and maintain batteries as effectively as possible.

I'm not aware of any quick, easy evaluation methods that will accurately indicate a battery's watt-hour capacity or potential reliability, unless the battery is in very good condition, and properly maintained. I suspect that when a LA battery (and most other types) has been left in dead condition for any amount of time, it's performance capability and reliability are greatly diminished.

What Wayne suggests about being careful is wise. Many improvised/hack methods aren't particularly safe, and many methods probably shouldn't be left unattended.

Use a 12 Volt charger, charge in pairs. May need to sit on charge for hours or even days before they begin to charge. Totally dead there is no acid, only water. Water does not conduct electricity well, so as the hours pass and the water slowly becomes acid the batteries will start to charge. After charge check for full voltage. then add a load like a headlight bulb and see if they can hold voltage with a load on them. If they go from 12.6 - 13 volts to around 10 quickly then there is a dead cell somewhere in there.

All above is with the batts in pairs because 12 volt loads and chargers are much more common and what I use.

If you use a DC supply make sure it is current limited to 5 or 10 amps max if you leave it on without constant supervision, when they do decide to start charging current can go up high.

A single 6V batt with a dead cell just might read 6V+ with a meter, the dead cell will show itself when a load is applied. A 6V+ reading is very likely when checked fresh off a charger.

Above but with each battery separate from the rest.

Thank You, Randy

Remove 333 from email address to reply.

You have received a lot of good information and the only thing I can add is to be sure to watch the electrolyte level carefully. If the batteries start to take a charge and/or warm up, the level can rise quite a bit and this can result in overflow. It is best to start with the level just at the top of the plates.

Don Young

Check the date codes on the SLA batteries. With proper maintenance they only last 5-8 years. Much less if abused. After that they're a recycling nuisance.

Survival of the 6V batteries after 4 years uncharged is pretty unlikely. They are likely to be deeply sulphated and refuse to accept a charge at anything like the usual max of

2.5v/cell. Less severe cases can sometimes be partially rescued by prolonged low current overvoltage charging until it starts to accept charge at less than 2.5V/cell but the results are seldom worth the hassle.

Chances are much better with the gel pack batteries. Dependent on local ambient temperature these happily hold their charge for a year or more and just need a freshening charge before putting into service. In normal use as backup batteries on permanent float charge they seem to last about 5 years but many organisation routinely replace them at 3 years or less. Stored, charged, at reasonably low temperatures the life can be very long indeeed. I keep a few 12v Yuasa batteries in a domestic fridge when I am not using them. These were rescued after their 3 year float charge stint and and are still going strong after nearly 10 years.

Yuasa recommendation for freshening charge after long storage is either 10 hours constant current at 0.1C or 24 hours constant voltage at 2.4V/cell

Jim

Had a go at the 6 volt cells this afternoon. Put two of them in series so I could use a 12 volt charger. Started with a voltage of 1.4 volts. Put a small charger on the 50 amp boost setting with a Fluke DVM to monitor actual voltage at the terminal, it started at 11.4 volts and 4 amps. Voltage gradually crept up to 13.8 volts with no change in amperage after an hour. Every few minutes I'd turn off the charger, see what the battery would do. First time it went to about 8 volts and dropped rapidly. Each time it would stabilize at a higher voltage and drop off more slowly. After an hour or so it would start at 11.8 volts and drop off to about 8 volts after a minute or so.

I also found some more data on the machine. I'd guess at a 1997 +/- 2 years mfg date, last time anyone dealt with it was 2001. An olde.

So...... sounds like it is not shorted but is highly sulphated. Could possibly be brought back to life but not to full strength. And bringing it back would take a bit of fussing, especially since I'd need to do it

3 times for the full set of 6 batteries. I do have a big industrial strength charger but it is polarity protected, needs to read the battery voltage to assure it has the polarity correct. This whole thing sounds fairly marginal unless I have a project that is "shovel ready" ( I don't)

I also dug > I've got a couple of battery packs in the storeroom that need some