Dry Gel batteries - old/completely discharged

The Mrs is having some mobility problems at the moment, so we've dusted the power wheelchair out of storage. It's been stored for 8 years, with the batteries disconnected. They're the dry gel type. They were put away after about 2 days use, so were effectively brand new.

Have reassembled chair, dropped batteries into holder and connected up. Have plugged charger in, and currently it's just showing "on" - none of the "charge lights" is showing. The charger is a super-duper microprocessor controlled one (well that's what it says).

My gut instinct is we have 2 new paperweights on our hands. However I thought I would seek the wisdom of crowds ...

I recall with old *car* batteries, that when they were completely discharged, they wouldn't take charge either. My Dad used to connect the dead battery in parallel with a charged one, with the charger going to both, and that seemed to "catch" things. I'm guessing the lower the charge, the higher the resistance until the charger just can't work. Connecting another battery reduced the resistance, and tricked the charger into working. I'm also guessing that being "microprocessor controlled" this charger could work out such things by itself, and deliver the appropriate charge as required ?

Reply to
Jethro
Loading thread data ...

I've always understood that if left discharged for a year or so, you were pretty well guaranteed paperweight status. And that's been my experience (limited though it is).

Get new ones, and as a DIY project remodel the old ones into doorstops! .-)

Reply to
Bob Eager

Most such chargers will not attempt to charge a totally discharged battery. They look for volts on the charge line and if there are none don't do anything. It is a feature designed to prevent a damaged charge lead overheating as DC plugs getting ripped off isn't uncommon if the wheelchair is moved with the charger connected.

You need to connect each battery in turn to a 12V charger (normal car battery charger is fine for a short time) and leave them on charge for

10 mins each. Reconnect the "intelligent" charger and all should work.

(Obviously if you have access to a 28VDC supply you can put that across both batteries).

The same characteristic is exhibited by some APC UPS's If the internal battery discharges completely the UPS will not charge it.

Reply to
Peter Parry

I'm not so sure if this works with SLA types - but with wet ones a long slow charge may recover it somewhat. To do this you need a basic charger which will push some current in - regardless of how little. Many modern chargers won't even switch on if they see no battery volts at all. Within reason the higher the voltage the quicker it may start taking a normal charge. If you have access to a current limiting bench top supply, set it to about 20 volts and half an amp max. But it may take a few days before anything happens.

Reply to
Dave Plowman (News)

Sulphation causes 2 problems: the plates get insulated, and the acid gets used up. Its oftne possible to break through sulphation by connecting the batteries to rectified mains, via a suitable appliance as curent limit, but:

- its easy to kill yourself so doing

- its easy to set fire to the battery case too

- the end result might work, but capacity will be so down that the usable chair range will be pants.

So... buy new. Or if you want, you could rebuild the old ones.

NT

Reply to
Tabby

HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.