Battery replacement for auxiliary battery

[tenere Lurker Find all posts View Profile Close tenere]

Hi Guys, i replaced the cranking battery in my 150 Prado it was old, and the second battery i have started to cook. It is old also. I was lucky enough to notice it before i think it would have caught fire. Do you think it is just an old battery and a new one would be fine or could there be some other problem.

[ptommo59 Senior Member Find all posts View Profile Close ptommo59]

At a guess a fault (failed cell/s or sulfation) in your aux battery was probably the original problem and was stopping the main from charging fully.

The new crank battery if fully charged when installed would have pumped a lot of its charge into the faulty aux which is why it got hot.

I would disconnect and then replace the aux battery.

Once you have done that recheck your charging system is still OK by monitoring voltage at the crank and aux is reaching the 13.8 to 14 V mark when the engine is running.

[tenere Lurker Find all posts View Profile Close tenere]

Thanks 59 i will try the new battery and check the voltage .