whats the problem with my voltage?

[Loud01Blazer 10+ year member]

well for starters i have a 2001 chevy blazer. The electrical consists of a 200 amp H-O alt, the big 3 done in 1/0, optima yellow top under the hood and 2 HC2200's in the back. When i first hooked up the batteries in the back my voltage "cold" would be around 15.1v and stayed around 14.6-14.8v after warming up consistently for about a month. Now on a cold start i'm lucky to see 14.5 and it'll rest at 13.9-14.1v after warming up...what happend here? I have a 3rd hc2200 waiting to be wired up but i wanna get this problem figured out first. I was thinking of getting a mla module but not sure if this will help, or if it's just my alt starting to crap out. Someone please give me some feedback

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[cj407]

how many runs of 0ga do you have going from front to back?

 

[Loud01Blazer 10+ year member]

just one for now

 

[cj407]

thats why...trying to charge 2 batteries thru one run is like trying to throw a block sprinkler party with only one hose....you need to add more runs of 0 gauge....try 2 per battery...(1 + and 1 -)

 

[MakeshiftAudio 10+ year member]

Any form of isolation?

 

[Loud01Blazer 10+ year member]

i will definitely give that a try

 

[Loud01Blazer 10+ year member]

Any form of isolation?

No, i was looking into that but was told awhile back by a few people it was not necessary..

 

[MakeshiftAudio 10+ year member]

Well, I'm not really sure on the subject, since to me it makes sense when it comes to the "one battery will drain the other until voltage equilibrium, then the ESR of one will drain them" logic. I would say keep them from being parallel as short as possible via a solenoid, since SCR isolators have a voltage drop. Just my personal opinion, but not sure.

 

[SicAudio 5,000+ posts]

yeah, I would have to partially agree on that, sounds like the alt may be working overtime. try this as a test:

disconnect the run to the rear batts and test it at the front battery see what you get. if the voltage is less than with them connected you have an issue with wiring or the batteries. but if it is doing this without anything on i would suspect the alternator itself. extra batteries only take about 10 amps for a short period until they are charged, then they run off about 1 amp after that, as long as they are not being used.

I had 1 run of 2 guage ran to 4 hc1400 batteries and never got more than .1 volts difference from the front to the rear,with nothing going but the motor, so it is questionable, and I only have a stock 135 amp alternator.

 

[cj407]

wow....4 batteries and only 1 run of 2 gauge....guess thats why you have so many batteries....if you had more runs of thicker wire than you would only need possibly 2....most likely only 1. even these crx's only need 2 batteries(1 stock and 1 in back) and they can run over 4k off those 2....

 

[rocky 59 5,000+ posts]

thats why...trying to charge 2 batteries thru one run is like trying to throw a block sprinkler party with only one hose....you need to add more runs of 0 gauge....try 2 per battery...(1 + and 1 -)

Not trying to be a d!ck but do you have any test showing that multiple runs of wire will help a relativity small battery bank charge or retain better voltage?

 

[MakeshiftAudio 10+ year member]

Not trying to be a d!ck but do you have any test showing that multiple runs of wire will help a relativity small battery bank charge or retain better voltage?

That's what I was thinking. :\

 

[cj407]

yea seeing as my voltage dips to about 11.5 before the upgrade from 1 run to 4 runs (2- and 2+)....now its stable at 12.8

 

[MakeshiftAudio 10+ year member]

Hit post twice during lag. See post below.

 

[MakeshiftAudio 10+ year member]

Well that's confusing, being that charging current to batteries is minimal. Sure, the wire has resistance, but since you're having a significant voltage drop on a (assumed) 15' run with a mere voltage test..... Something isn't right.

12.8-11.5=1.3V, and that's at idle. In other words, per every amp, you have 1.3W dissipating in that wire, so assume 100A, 130W of dissipation, AKA 130J per second in that wire. That's gonna get toasty. I don't believe you for some reason, and this is just an extremely rough estimate of how much is dissipated.

I would understand if there was a current draw, but idle doesn't make any sense.

I'm also assuming idle because the voltages are not anywhere near 14V.

xD

I do not believe the wire is the problem here Blazer, especially since it was over time. You first put the other battery in, the alternator did not have to work as much since the battery was topped off already. After time, that charge equalizes with the front, then the amp has to work a lot more to keep your whole system up. This really isn't something you can fix at this point, it is going to drain down to it's proper voltage eventually, now if it was any lower than these voltages above, I would start to say you have a draining conflict. In short, you HC(s) is(are) charging your front battery when they are put in parallel when the HC's voltage is above the front's, while the car is off. A 1/2 solution, or something to elongate it is to put an isolator in the system, so that the batteries are not connected while it is not needed. When you turn the car on, you charge them/top them off. When it's off, they sit there and eventually go down to their standing/floating voltage naturally, not charging anything to meet an equilibrium of voltage.

The wire is primarily being used to charge the battery bank, correct? Even then, 1/0 can supply 100A at 15V on a 17.35' run with .45V drop. It is not the wire.