Can a battery charger kill an alternator? Answer inside...

[wht67]

Mustang had been parked for a week and i had left my old phone plugged in to a charger in the center console. Tried to start and of course the battery was dead. Throw charger on it for a bit, enough to start the car to move it out of the garage. This is where I may have f'd up. I unplugged the charger while it was still connected to the battery. The made a couple of beeps and lit up the display like it does when first powered up but immediately went dark the a second later does it again. I then moved the car out and that's when I noticed the "Check Charging System" message. After I finish my work on the garage, I move the car back in and hook it up and fully charge the battery. Tonight I go out and take the alternator off (nice Denso model I got from DOB) and put my original alternator on and everything works. So yes, you can kill an alternator with a battery charger if you screw the pooch like I did.

Backstory: the original alternator had died a few years ago, so I thought hey, let's get one of the PA alternators. Well that thing died within a week, burning the battery cable in the process. So I took my original alternator to a local shop for a rebuild (one year warranty). I was working great for 3+ years until I bought the Denso from DOB (higher output that my stock one).

The Denso would probably still be going strong if I didn't kill it with my stupidity. I think I will take it to the shop that did my original one for repair.

Lesson learned...

 

[slackinoff]

Is the lesson "don't unplug the charger"?

 

[rjyote]

I don't know what killed your alternator, but it wasn't unplugging the charger.

 

[01yellerCobra]

I don't know what killed your alternator, but it wasn't unplugging the charger.

+1

It's probably just coincidence.

 

[Shok]

I almost always unplug my charger before disconnecting it from my car.

 

[05stroker]

^^^ I have to agree with these guys. I have never seen a charger kill an alternator.

 

[06 T-RED S/C GT]

Same here !

 

[Norm Peterson]

So what make/store battery charger was involved? Was it connected in some testing mode or other and not done with its testing?

I'd never heard of this happening either.


Norm

 

[Sky Render]

Battery Tenders are supposed to be unplugged from the wall outlet before being unplugged from the battery.

 

[05stroker]

Battery Tenders are supposed to be unplugged from the wall outlet before being unplugged from the battery.

That's how I always use my chargers and Tenders.

 

[wht67]

My old Sears charger that I had for 25+ years I always unplugged it before disconnecting the battery leads. I lost that one in the garage fire I had the summer of 2014. That one was old school, mechanical switches and analog gauges . The new one is digital display and controls:

Stanley 25A Battery Charger with 75A Engine Start

I can only go by the evidence I observed. This is not the first time the battery had been drained since I had installed the Denso alternator (My intercooler pump runs with the key in the on position and it drains the battery past starting voltage quicker than expected, which is why I had to buy a new charger...) therefore draining the battery didn't kill the alternator.
The was the first time with this charger that I had unplugged it from the wall while connected to the battery. The power on beeps and display light ups then power down repeatedly until I disconnected the battery cables was the only difference from the previous 4 or 5 times using this charger. Every other time I had used this charger I had disconnected the leads from the battery terminals after pushing the "Charge" button that suspended the charging, only unplugging the charger after disconnecting it from the battery.. There were zero symptoms of alternator issues before my leaving the charger connected and unplugging it.

I have never seen this before but I have never owned a digitally controlled charger. If I had not seen it I would not believe it either, so you guys can think what you want but I will not have this charger connected to a vehicle after charging the battery while unplugging it from the wall 120vac.

 

[Norm Peterson]

So I dug out the manual for my 'DieHard' digital-style charger that has multiple charging rates, multiple battery type applicability, testing options, and a 50A start, all selected by pushbuttons.

It specifically instructs the user to disconnect the 120V AC cord first. Followed by the ground clamp and finally the hot side battery clamp.

I'd always done it that way anyway, just to avoid all possibility of a spark occurring in a locally flammable hydrogen-air atmosphere. Saw what happens when hydrogen blows up once already, up close, when a wrench fell on the +terminal and shorted it to ground. Got the stained jacket, don't need to see the replay.


Norm

 

[wht67]

So I dug out the manual for my 'DieHard' digital-style charger that has multiple charging rates, multiple battery type applicability, testing options, and a 50A start, all selected by pushbuttons.

It specifically instructs the user to disconnect the 120V AC cord first. Followed by the ground clamp and finally the hot side battery clamp.

I'd always done it that way anyway, just to avoid all possibility of a spark occurring in a locally flammable hydrogen-air atmosphere. Saw what happens when hydrogen blows up once already, up close, when a wrench fell on the +terminal and shorted it to ground. Got the stained jacket, don't need to see the replay.


Norm

Sounds like I will just disconnect the battery from the car before using this charger again....