dual battery set up problems

[bigdon1000 10+ year member]

I had two batteries in my car for two year's and everything was great. Than one began to heat up crazy. I took it to get tested and it was bad, but the one in my trunk was good. If I had not checked on it that day it would have blown.I don't know why it went bad but different places tell me different things. Some say its my voltage regulator. Others say alternateor and also could be because batteries were not the same exact specs. Put in another battery and everything's normal........I know people here on this forum will probably have more experience then autozone workers with dual battery set ups so feel free to give some advice.

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[keep_hope_alive Premium Member]

batteries fail. it happens. you lose a cell and the battery is toast. main reason for battery failure is heat.

batteries that want to float at different voltages will both suffer. the lower one will be forced higher by the other. and the higher one is pulled down by the lower one. this constant exchange of energy also causes heat.

run the car with the system low for a while to fully charge both batteries, then disconnect the batteries for a while (an hour) then measure them separately. if they are a different voltage, then you now they will fight each other.

 

[goingdef 10+ year member]

I had two batteries in my car for two year's and everything was great. Than one began to heat up crazy. I took it to get tested and it was bad, but the one in my trunk was good. If I had not checked on it that day it would have blown.I don't know why it went bad but different places tell me different things. Some say its my voltage regulator. Others say alternateor and also could be because batteries were not the same exact specs. Put in another battery and everything's normal........I know people here on this forum will probably have more experience then autozone workers with dual battery set ups so feel free to give some advice.

I had a voltage regulator go out once and it almost blew the battery so I would have my alt looked at, I have also seen them go in and out causing the headlights to get excessively bright as voltage would rise then drop back to normal.

 

[CAT MAN 5,000+ posts]

batteries fail. it happens. you lose a cell and the battery is toast. main reason for battery failure is heat.
batteries that want to float at different voltages will both suffer. the lower one will be forced higher by the other. and the higher one is pulled down by the lower one. this constant exchange of energy also causes heat.

run the car with the system low for a while to fully charge both batteries, then disconnect the batteries for a while (an hour) then measure them separately. if they are a different voltage, then you now they will fight each other.

i always try to keep mine within .2 volts