Nasty short circuit blanks my batteries...?

[AceOfHearts]

Hi,

I think I have a short circuit somewhere on my robot which makes the battery overheat over a few minutes, and then eventually it shuts off.

Its the second time it happened. First time it happened, I could not find any faults, but one of the battery terminals became really hot. With the Voltmeter, it was indicating zero. After it cooled down, it was back up normal again.

I connected everything up, it ran for a while and then stopped and a battery terminal was really hot again.

I would appreciate a scientific explenation as to why this happens (possibly on a short circuit), for my own knowledge and where the likely fault may be.

Many thanks.

 

[Nigel Goodwin]

It could be anywhere that has high current potential.

 

[xxxxxxxxxxxxxx]

Motors? Does your bot move when this happens (or before?)

 

[AceOfHearts]

Thanks for the replies.

Motors? Does your bot move when this happens (or before?)

Ok, I think its fixed now. First time it happened, motors didnt didnt move. So a short circuit was most likely. Second time it happened after about a minute of the motors working.

And it has not happened again. So its all good now. It was a strange phenomenon though, battery potential dropping down to zero...and then back normal again!

 

[RadioRon]

Batteries have some equivalent internal resistance, so even if you short the output, the current does not shoot to infinity. In your case, with a dead short across the battery you would measure 0 volts (ohm's law: if your short is nearly zero ohms, you would read nearly zero volts across it even if there is a lot of current flowing). The amount of current flowing would be very high, depending on the type of battery. This would cause your terminals to heat up. It is possible there were many amps flowing and it is possible that the battery heated up inside. If the internal guts of the battery heat up enough, and quickly enough there may be gases generated inside that can cause the battery case to blow open. This sort of explosion can be dangerous and obviously hard on the battery!

 

[Hero999]

Add a fuse, circuit breaker or PTC resistor to cut off the circuit when the current reaches an unsafe level.

 

[AceOfHearts]

Batteries have some equivalent internal resistance, so even if you short the output, the current does not shoot to infinity. In your case, with a dead short across the battery you would measure 0 volts (ohm's law: if your short is nearly zero ohms, you would read nearly zero volts across it even if there is a lot of current flowing). The amount of current flowing would be very high, depending on the type of battery. This would cause your terminals to heat up. It is possible there were many amps flowing and it is possible that the battery heated up inside. If the internal guts of the battery heat up enough, and quickly enough there may be gases generated inside that can cause the battery case to blow open. This sort of explosion can be dangerous and obviously hard on the battery!

Thanks for this explenations.

Thanks to Hero999 for the adivse.