Reusing old batteries?

[vpoppv]

I've never disconnected the cables when charging a battery and haven't run in to problems.

[Xringer]

Originally Posted by johnlvs2run

This thread seems the closest to my question, so here goes. I have charged my chevy batteries for many years, without disconnecting any cables from the car - however found this in the 1999 honda owner's manual.



Is this really necessary?

Do you disconnect the cables when charging a car battery?

Because the battery presents a large load to the charger, the charge voltage
will normally never climb above what's used to charge the battery as you drive.
(Alternator charging).

But, some (Dumb) high current chargers will apply a lot of voltage to the battery,at the end of the charge.
It could be up around 15v or more.

The worse case scenario is connecting a dumb charger to a battery that has an open cell.
That's when the charger could put extra high voltage on the battery, and the electronics in your car.
The stuff that stays on all the time.

[rmay635703]

Originally Posted by Xringer

But, some (Dumb) high current chargers will apply a lot of voltage to the battery,at the end of the charge.
It could be up around 15v or more.

The worse case scenario is connecting a dumb charger to a battery that has an open cell.
That's when the charger could put extra high voltage on the battery, and the electronics in your car.
The stuff that stays on all the time.

??? Generally the absolute max voltage limit for 12v electronics is rather high in the 18-24v area before anything actually becomes damaged. I have owned many many dumb chargers and none has ever been able to exceed
16v, even open terminal no load.

So, Unless you are running a strip of bailing wire out of a 220v wall socket to charge your 12v battery it is nearly impossible for you to get a battery that high. (I say nearly because I have seen some pretty amazing things done but in reality it may as well be impossible)

Cheers
Ryan

[Xringer]

I wouldn't put 18-24 volts on any of my 12vdc ham gear. But, that's just me..
Hey, maybe my 150 watt VHF amp will put out 300w at 24v..?.

I have smoked some small 12vdc electronics using "12" vdc wall-warts.
The last one turned out the 12vdc wall-wart was actually putting out over 18vdc (no load).
Toasted a real nice cable TV amplifier..

I'm not sure what my dumb Sears 6 & 12 volt battery charger/starter supply puts out when open..
I'll have to check it sometimes. You've got me curious now.

[rmay635703]

Originally Posted by Xringer

I have smoked some small 12vdc electronics using "12" vdc wall-warts.
The last one turned out the 12vdc wall-wart was actually putting out over 18vdc (no load).
Toasted a real nice cable TV amplifier..

I'm not sure what my dumb Sears 6 & 12 volt battery charger/starter supply puts out when open..
I'll have to check it sometimes. You've got me curious now.

I would guess that wall wort was for something else in a higher load and not really a charger or it was failing.

I guess once something fails all bets are off.