Battery Charger Issue

[JHZR2]

I have a bunch of cars, so I have a bunch of battery chargers. My most expensive is a battery minder 12248, then I have a few 2A maintainers/float chargers (all smart), and also a Schumacher 2/4/12A charger from Wal-Mart (bought maybe 2 years ago).

Tonight I was going to go get my truck, which I was thinking would have a flat battery. Before dinner I went out and put the schumacher onto my BMW (which has a group 49 Deka VRLA) and onto the wife's VW (which has a group 94 or so Varta battery).

I set the schumacher on 4A, as I did on the battery minder. Let them go a while on fairly "full" batteries. After a while I found that on each, the charger was putting out between 14.7-14.8V. This was verified by my fluke 179.

On my wife's car, I actually heard what sounded to me like gassing or boiling, it was notable though not very loud, and I could recognize it as I put my ear near the battery.

So what gives? These battery chargers all seem to overcharge. Ive always heard that one should charge to 14.1-14.4V and cut out when the current drops to something like 50mA. IIRC, 14.4V is the onset of gassing...

Seems to me that something is not right. Didnt leave them on long enough to see what they drop voltage to long-term.

I only use the schumacher as a quick charger (though I prefer very slow charge), but the battery minder Ill leave on batteries for a LONG time. Never checked... Now Im concerned.

Thoughts?

 

[Quest]

some gassing is normal when the battery enters full-charge state.

I wouldn't be too worried if I were you.Afterall: you are dealing with wet cells and not "dry" cells to begin with.

Q.

 

[bmwtechguy]

The battery minder will bulk charge until it pulls the battery up to about 14 or 14.1 volts, then it will drop to 13 or 13.1 volts, at least on the one I have.

We charge up to 14.8 volts on the bulk charge, then drop back to 13.1 or 13.2 volts on our programmable deutronic battery charger for BMW's. this helps to condition the battery and boil/blast a bit of the sulfation off the plates.

 

[JHZR2]

Im seeing 13.7-8 float charge on the battery minders at steady-state maintenance/float. That is 2.295ish V, which isnt bad.

Just want to be sure that I wasnt destroying batteries or creating a scenario where damage is possible. Seems even the 14.8 is ok for limited time...

 

[Schmoe]

My battery minder does the same thing in my boat batteries. Kind of freaked me out at first with it pulling more than 13 volts and it's a 12 volt battery. Some of the minders also to that, at least I think that is there intent, to "de-sulfurnize" the battery.

 

[brianl703]

I have a couple of deep-cycle batteries that have been floating at about 13.9-14V for a couple of years.

No problem.