Why is my alternator not charging my second batt??

[quickgreen 10+ year member]

I have 4 guage wire(all that was available) running from the pos terminal in the front to the positive terminal in the back, with 2 inline fuses. Then I have the second batt grounded to the chasis. Both of my amps are also grounded to the chasis. Then wired up the amps' power cables also to the second batts positive terminal(same terminal that first batt is connected to). Im not sure where i went wrong. I tested the second batts charge with the car on and off and it stayed the same, while the first batt had a 0.6v increase. So I know my alt is good. And the system hits lovely until the second batt loses juice. Im just looking for some help before my second batt loses life from dying and recharging(done this like twice). Any help is greatly appreciated, been looking for an answer for about a week now.

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[Phoenix Risen 10+ year member]

did you check the fuses on your power wire, also depending on the amps your running could easily be pulling more current than the 4 gauge can get to the back batt.

 

[quickgreen 10+ year member]

At any given time 2500 max.. Is the wire sufficient?

And I always checked my second fuse but not the first. Feel real stupid for not checking the first fuse... I'll check first thing in the morning. Also I have 80amp fuses, is that enough?

 

[MANTI5 10+ year member]

What amps do you have? How many amps is your alt putting out?

 

[subzero 5,000+ posts]

double up runs from pos bat to pos bat and even add a neg run from bat to bat. alt to 1st bat should be 1/0 for maximum current transfer. I would even do 1/0 from pos bat to post bat. Biger wire = less resistance = more cureent transfer to charge bats. Now, lets look at what the amp is pulling... how many amphers is that amp drawing? how many amps? How much chargin amps are you replenishing?

 

[quickgreen 10+ year member]

The first fuse did blow. Before i replace the fuse, Im gonna do the big 3 and replace the 4 gauge wire from in between the batts, all with 1/0 gauge wire. Thanks for the idea subzero. Where should I get the 1-0 at? Whats a good brand?

My amps are a hifonics 2400w and a power acoustik 1500w. I was wrong about how much juice my system was drinking. My alt puts out 90 amps though.

Also both batteries are very similar. Both duralast with just about same specs.

 

[snoopdan 5,000+ posts]

The first fuse did blow. Before i replace the fuse, Im gonna do the big 3 and replace the 4 gauge wire from in between the batts, all with 1/0 gauge wire. Thanks for the idea subzero. Where should I get the 1-0 at? Whats a good brand?
My amps are a hifonics 2400w and a power acoustik 1500w. I was wrong about how much juice my system was drinking. My alt puts out 90 amps though.

Also both batteries are very similar. Both duralast with just about same specs.

Have you checked the water in the 2nd battery? It might just have a bad cell too.

 

[groundpound4200 5,000+ posts]

Stinger, KnuKonceptz, Kicker are all good brands with wire that will meet/exceed 1/0 spec. I usually get mine from eBay or from the classifieds here. Don't use 80 amps fuses in there either. If you stick with 4 gauge get 100-120 amp fuse and if you step up to 1/0 use a 250-300 amp fuse

 

[snoopdan 5,000+ posts]

Or just go to your local welding supply house and get 1/0 there. It's ugly, but it works.

 

[groundpound4200 5,000+ posts]

true, definitely not as flexible but if you don't need it to be welding cable can save some $$$

 

[quickgreen 10+ year member]

Have you checked the water in the 2nd battery? It might just have a bad cell too.

How do I check the water for a bad cell?

 

[groundpound4200 5,000+ posts]

There should be removable plugs on the top of a wet-cell/ flooded battery that allow you to check the water level in each cell.

 

[quickgreen 10+ year member]

The water levels are all about full. Not coming out of the hole but just reaching the bottom of the hole. Is that good or bad?

 

[groundpound4200 5,000+ posts]

Sounds good to me. If you blew the main fuse from your front battery that's definitely why the rear battery was going dead.

 

[quickgreen 10+ year member]

Sounds good to me. If you blew the main fuse from your front battery that's definitely why the rear battery was going dead.

Yeah i figured that. Thanks for the help bro.