voltage drop from front to back

[tjjohnson91 10+ year member]

alright i have a DC 250amp alt and all that ...... my front battery was reading 14.1 and my back battery was reading 9.... what the **** .... this was at idle and radio on low volume

amp ddz1....... could the amp be messed up?

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[YoungBloodM50 10+ year member]

Could be your battery. What ga power wire you running?

What does your batt read when the car is off?

 

[tjjohnson91 10+ year member]

0/1 ............ you know i was thinking that too.... that would be gay ....

 

[YoungBloodM50 10+ year member]

The battery should be reading 12.4 with no power running to it.

 

[tjjohnson91 10+ year member]

its 12.5 i think just sitting but thats also with anoter battery to balance it so ill un hook them and just read the one alone tomrrow

 

[schackel 10+ year member]

it could be the size of your battery difference

 

[ahole-ic]

It's usually a REALLY high resistance ground...

Even with a couple cells bad on the back batt, it really doesn't matter. In a parallel circuit the voltage stays constant throughout. This means that there has to be high resistance in series with the back batt.... which is usually caused by a bad ground.

 

[audiolife 5,000+ posts]

Check/change your fuses in the power line, check grounds, pull back battery out of the system measure its voltage. If it is low charge it then load test it.

 

[maxxguy1 10+ year member]

I have seen this happen with a bad fuse gets power just not enough to do anything check grounds like audiolife said also don't use the alt to charge the back batt up if it is at 9 volt take it out and charge on a charger if not you could fry your alt

 

[audiolife 5,000+ posts]

I have seen this happen with a bad fuse gets power just not enough to do anything check grounds like audiolife said also don't use the alt to charge the back batt up if it is at 9 volt take it out and charge on a charger if not you could fry your alt

A low charged sulphated battery could fry your alt or the alt could make the battery vent or swell or worse.

 

[CRXBMPN 5,000+ posts]

my first thought is the fuse is toast... its just not getting any juice to the back and that thing has slowly been discharging... but if you are running the z1 off the back batt alone and its that low I'd be hard pressed to see it not going up in smoke.

 

[Bobby322 10+ year member]

How do you know if a fuse is bad? I have a 250anl I suspect it could be a problem but it looks fine. Sorry to thread jack.

 

[maxxguy1 10+ year member]

i know just giving one example, as far as checking the fuse try putting another one in there

 

[The HACKER 10+ year member]

How do you know if a fuse is bad? I have a 250anl I suspect it could be a problem but it looks fine. Sorry to thread jack.

Disconnect second batt, check either side of fuse for voltage with DMM..

 

[ahole-ic]

A low charged sulphated battery could fry your alt or the alt could make the battery vent or swell or worse.

While those statements are true and it should be checked to prevent problems in the future, the alt cannot be the problem right now as the voltage at the front is 14v.