The battery or the battery charger is faulty when a battery gets hot and melts?

When a battery becomes hot and melts when being charged, is it the battery or the battery charger that is faulty?

Both units are several years old but the battery was showing signs of maintaining its power poorly.

Are there any way of testing if the charger is faulty?

baker said:

When a battery becomes hot and melts when being charged, is it the battery or the battery charger that is faulty?

Both units are several years old but the battery was showing signs of maintaining its power poorly.

Are there any way of testing if the charger is faulty?

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It could be both. A battery with say one shorted cell will never reach fully charged voltage so will get overcharged.

A battery charger will generally taper down the current delivered as the battery voltage increases to fully charged.

I would connect a known good battery to the charger and monitor how it behaves. I had a charger on my bench a couple months ago and when I tried to look at it with a scope and resistive load the waveform was impossible to interpret. It needs a proper battery load on it. 

A broken charger could be stuck on full output from a shorted pass element so look for overcharging.

JR

JohnRoberts said:

A broken charger could be stuck on full output from a shorted pass element so look for overcharging.

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How do you know when the charger is overcharging?

Do you mean get a good battery that is drained for example and charge it and if the charger supposedly states it takes 8 hours to fully charge, then what? Do I measure the difference in current from the first hour to the tenth hour?

Not sure what you mean?

baker said:

JohnRoberts said:

A broken charger could be stuck on full output from a shorted pass element so look for overcharging.

Click to expand...

How do you know when the charger is overcharging?

Do you mean get a good battery that is drained for example and charge it and if the charger supposedly states it takes 8 hours to fully charge, then what? Do I measure the difference in current from the first hour to the tenth hour?

Not sure what you mean?

Click to expand...

No you can start with battery that isn't discharged. We want to observe the behavior of the charger in response to battery voltage. The battery voltage will increase as the cells charge up and the charger "should" taper off the current it is pumping into the battery.  If the charger has an ammeter on it (many do) look at how it behaves on a good battery, the current should taper  off dramatically as the battery gets topped off.

My VOM has a 10A current scale but there is a different probe connection for that high current scale. If the battery charger puts out more than 10A I can't measure it .    I don't even know if you are talking about car battery charger that might put out tens of amps, or a small AA charger.

If a good battery gets hot you probably have a charger problem .

JR