Disconnected car battery sparking violently when charging?
Discussion
As above have a car battery that used to be in my car but was starting to become unreliable nearly dead if left for a few weeks, which I replaced.
This weak battery was then kept and charged regularly in my kitchen as a quick spare for a car I keep in a lock-up, my usual routine is to check its still holding charge every month or so.
Today when connecting my battery charger there are mad sparks as if its shorted, at first I thought I connected the -+ the wrong way around but they were not, did try other way but sparked the same similar to a short I put voltmeter on battery its holding 12.58 volts.
To me there is only two explanations the charger has a short circuit or the battery has shorted internally will try the charger tomorrow on another battery. Do you think my summation is correct?
This weak battery was then kept and charged regularly in my kitchen as a quick spare for a car I keep in a lock-up, my usual routine is to check its still holding charge every month or so.
Today when connecting my battery charger there are mad sparks as if its shorted, at first I thought I connected the -+ the wrong way around but they were not, did try other way but sparked the same similar to a short I put voltmeter on battery its holding 12.58 volts.
To me there is only two explanations the charger has a short circuit or the battery has shorted internally will try the charger tomorrow on another battery. Do you think my summation is correct?
Fort Jefferson said:
69 coupe said:
and charged regularly in my kitchen

release hydrogen gas which is explosive and the kitchen is probably
the place with the most ignition sources in an average house.
i have been victim to a car battery explosion due to a wonky
connector in my shed and it wasn't pretty but it was painful!
telecat said:
Could be but it does sound like one of the "cells" is bad. Usual problem is that it will start OK unless you wait and run the radio/cd and you'll find it has drained the battery. I'd just get rid as there is usually no way to recover it.
But I'm still getting 12.58v with VM, wouldn't connecting a VM with a suspect battery cause the meter to spark fail?blondini said:
It shouldn't spark if the charger is switched off but if it does it sounds like the charger itself is faulty and shorting the battery.
I always ensure a charger is switched off when connecting or disconnecting a battery. Learned that the hard way.
^^^^^^ThisI always ensure a charger is switched off when connecting or disconnecting a battery. Learned that the hard way.
Connect the battery before the mains. Disconnect the mains before the battery.
Theres only 2 volts per cell so if youre getting 12.58v its not the fault of the battery, more likely the charger is at fault.
Ref battery explosions, ive seen one of the REMI guys drop test a battery literally as its come off charge,it was one battery off an APC so truck size, the resulting explosion was like a grenade going off, the battery literally being blown apart! Luckliy there were two of us nearby to drag the poor sod to dunk his head in running water outside. Ever since then ive been VERY wary of taking risks with batteries. Always make sure the charger is off before connecting/disconnecting and avoid the old type drop testes which invariably result in sparking.
The kitchen really is the worst place to charge a battery. Outside in the garage /shed with an open door/window being far better..
Ref battery explosions, ive seen one of the REMI guys drop test a battery literally as its come off charge,it was one battery off an APC so truck size, the resulting explosion was like a grenade going off, the battery literally being blown apart! Luckliy there were two of us nearby to drag the poor sod to dunk his head in running water outside. Ever since then ive been VERY wary of taking risks with batteries. Always make sure the charger is off before connecting/disconnecting and avoid the old type drop testes which invariably result in sparking.
The kitchen really is the worst place to charge a battery. Outside in the garage /shed with an open door/window being far better..
blondini said:
It shouldn't spark if the charger is switched off but if it does it sounds like the charger itself is faulty and shorting the battery.
I always ensure a charger is switched off when connecting or disconnecting a battery. Learned that the hard way.
Yea it was switched off when connecting that's why my feeling is the charger has an internal short, i'll try the charger on another battery in a few days time; its the one stored by the main consumer unit which sparks every now & then especially since we spliced and sellotaped the electric shower directly to the 415v electric board supply. Only joking I always ensure a charger is switched off when connecting or disconnecting a battery. Learned that the hard way.

69 coupe said:
blondini said:
It shouldn't spark if the charger is switched off but if it does it sounds like the charger itself is faulty and shorting the battery.
I always ensure a charger is switched off when connecting or disconnecting a battery. Learned that the hard way.
Yea it was switched off when connecting that's why my feeling is the charger has an internal short, i'll try the charger on another battery in a few days time; its the one stored by the main consumer unit which sparks every now & then especially since we spliced and sellotaped the electric shower directly to the 415v electric board supply. Only joking I always ensure a charger is switched off when connecting or disconnecting a battery. Learned that the hard way.


If your voltmeter has a resistance range you could check the resistance both ways across the chargers 12v terminals, with it switched off of course. In simple terms it should be low resistance connected one way round but very high the other way.
blondini said:
Bellwire for that shower? 
If your voltmeter has a resistance range you could check the resistance both ways across the chargers 12v terminals, with it switched off of course. In simple terms it should be low resistance connected one way round but very high the other way.
Just checked resistance on charger it reads 1 same as if leads are not connected to the charger which is open circuit looks like the charger is fubar'ed..
If your voltmeter has a resistance range you could check the resistance both ways across the chargers 12v terminals, with it switched off of course. In simple terms it should be low resistance connected one way round but very high the other way.
blondini said:
It shouldn't spark if the charger is switched off but if it does it sounds like the charger itself is faulty and shorting the battery.
I always ensure a charger is switched off when connecting or disconnecting a battery. Learned that the hard way.
I don't believe that a charger can "short a battery". That's nonsense.I always ensure a charger is switched off when connecting or disconnecting a battery. Learned that the hard way.
However, the advice to connect the terminals with the power OFF is correct.
69 coupe said:
Just checked resistance on charger it reads 1 same as if leads are not connected to the charger which is open circuit looks like the charger is fubar'ed..
If it was open circuit it shouldn't cause sparks when connecting to the battery so that reading is a bit puzzling and inconclusive. mrmr96 said:
I don't believe that a charger can "short a battery". That's nonsense.
Why?Wire into box.
Wire out of box.
You don't know what's going on inside the box.
Nonsense?
Very possible and likely from the description of a large spark when the terminals are connected.
All it takes is some insulation burning off the windings. Classic transformer failure mode.
996TT02 said:
mrmr96 said:
I don't believe that a charger can "short a battery". That's nonsense.
Why?Wire into box.
Wire out of box.
You don't know what's going on inside the box.
Nonsense?
Very possible and likely from the description of a large spark when the terminals are connected.
All it takes is some insulation burning off the windings. Classic transformer failure mode.
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