Older battery chargers

[Norm Olt]

Boy, I don't think I've ever posted on THIS forum..

Anyway, have a couple old Schumacher 6v/12v chargers: 2 & 6 amp, Manual or "automatic" settings, amp meter, full metal cases, etc.

They have always worked fine for me over the decades, ever since I bought my 1st Battery Tender, Jr. I've usually only used them to bring back a partially discharged battery (occasionally one that sat for months, unused) or to "top off" a brand new battery overnight prior to installation.

My batteries typically last 8-13 years with few exceptions: have had a couple fail under warranty, but usually they were found to be defective from the get-go and replaced FREE.

So... How long should it take to fully charge a less than two year-old Group 24F Interstate battery that "someone" parked in a garage with the parking lights on for a month(?) that was down to 3.7v with a 6 amp flow outside in 40° temps? The durn amp meter gave up the ghost a decade ago on this one, the voltmeter is showing 15v across the positive and negative terminals with the charger attached... I know it is working.

How many hours, approximately at 6v, and is there really any danger of damaging/overcharging the battery in 24-36 hours outside?

Thanks in advance for your kind consideration of this old man's question!

Cheers!

 

[eljefino]

12 hours at 6 amps will get you somewhere above half-full, and "good enough". Car batteries are rated at around 90-ish Amp-Hours. The charge rate lessens as a battery fills up so it's impossible to predict this with scientific accuracy.

The ammeter is how you do it, but the transformer will sound a little quieter when you're done, if you have a good ear for that sort of thing.

I would cut it off after 12 hours, and, if paranoid, throw a battery tender on it for "the rest".

 

[alcyon]

Nowadays with a 12V power supply and a B6 RC car charger in lead acid mode you can charge full size car batteries.

 

[ragtoplvr]

First of all that battery has almost pure water in it, all the acid is tied up. It can take days of trickle charging to recover enough acid to to take current.

Then battery may then recover to some extent. And it will be sulfated. You need a desulfate mode in the charger.

Even then, for a starting battery you would be lucky to get much over half capacity.

Good luck.

or buy a battery

Rod

 

[Linctex]

Originally Posted by Norm Olt
"someone" parked in a garage with the parking lights on for a month(?)


If the battery was shorted out (yes, a bulb filament is a "short") for a whole MONTH - then it's likely toast.

 

[Dave9]

If it's really only two years old, take it back to the place of purchase to get a new one under warranty. That solution might rub some the wrong way but it rubs me the wrong way when a vehicle gets stranded if their battery doesn't last long when everything is right, too.

If the battery didn't even have a two year warranty it was low end to start with and whatever capacity you manage to recover now, won't be worth bothering to do.

I too have one of those old metal cased 6V/12V chargers but mine lacks any automatic mode, is just a transformer, diode, and short circuit fuse. I figure keeping it simple, kept it working so long, but still because of its age I don't leave it unattended for hours on end let alone days. I check on it every half hour or so and note whether the ammeter is continuing to drop like it should.

You can replace the ammeter, just measure the panel size, buy a new one and toss it in... might need a couple rivets drilled out, can't recall. Then again it's just a sheet metal shell it's mounted on, you could cut it larger, or put a plate with a smaller hole over the original, or even get all fancy-smantzy and put in a digital one instead of analog, just make sure if it uses a separate power supply lead that you throw a regulator between the rectified output and the supply input. IIRC you can get a little digital one for about $2 delivered on eBay if you're not in a hurry (month long shipping wait). Some even have a voltmeter in them too.

 

[Donald]

I have an old Century charger/starter. In a box, waiting for retirement to have time to fix it.

I have newer chargers, but this is a challenge to o fix it.