Dual battery setup

Macallan12 · 05-04-2006, 10:49 PM

I know there's quite a bit of information about dual battery setups, and I have read them all! One thing that I haven't totally figured out is this... If I use the Painless Wiring Dual Battery Controller, will I be able to hook up, say, an Optima Group 31 and an Odyssey 1200 without them killing each other?

Many have posted that the batteries should be IDENTICAL (type, usage history, birthday, etc), but I have seen some with different models but not necessarily using the painless wiring kit.

Also, will this controller unit prevent overcharging the batteries?

Any help would be appreciated. Thanks.

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Macallan12 · 05-06-2006, 05:21 PM

OK. I think I'm starting to figure things out. I'm going to get the Hellroaring isolator/combiner and set it up in either the backup or auxillary configuration. This way, the batteries can be of any type and they'll be completely isolated. As far as the concern of overcharging, my readings have led me to believe that car batteries can withstand some extreme charges without problem, and an undercharged battery is what I should be concerned about.

4Crawler · 05-07-2006, 09:45 AM

I use that system on my dual battery system, I do have identical AGM batteries but it has worked flawlessly for the last 8 years:
http://www.4crawler.com/4x4/CheapTri...atteries.shtml

Macallan12 · 05-09-2006, 06:03 PM

Thanks for the reply. I take it you've never overcharged a battery, or heard of this happening? Also, can I use a billet box in place of the stock clamp to hold a battery in the stock location? I'm close to buying all my parts, and when I do, I'll write up my installation... good or bad

4Crawler · 05-09-2006, 06:21 PM

Self-discharge is the more common problem, that is if beatteries are left connected w/o any charging going on. If one battery is a fraction of a volt lower than the other, current will flow from high to low and kill the high battery. That is why you want matched batteries. But if disconnected while off, no problem with discharge.

dz · 05-10-2006, 02:12 AM

Quote:

Originally Posted by Macallan12

As far as the concern of overcharging, my readings have led me to believe that car batteries can withstand some extreme charges without problem, and an undercharged battery is what I should be concerned about.

ever seen an exploded battery? I can take some pictures if you'd like, I know there's at least one sitting on the pile at the shop

**waskillywabbit** · 05-10-2006, 04:47 AM

The Painless dual battery wiring setup disconnects the batteries when the vehicle is off...and/or you can use a manual marine switch to do the same thing...like w/ the triple batteries I have. I would think different batteries would be fine.

AH64ID · 05-10-2006, 05:58 AM

Both of my dads chevys have dual batteris in them. The are tied together by a heavy duty continous duty solenoid hooked up to an oil pressure switch. He now runs like batteries in both, he had a starting and a deep cycle in the P/U and it kept overcharging the deep cycle, boil over, battery acid everywhere. Now that he is running the like batteries no issues. Also no need for rewiring the alternator when you wire them this way, the second battery will charge when the solenoid is closed.

Also, it would be a good idea to rewire aux lights, stereo, etc. to the aux battery so that both batteries get used at the same time.

Macallan12 · 05-10-2006, 08:54 PM

Thanks for all the input

The way I understand the dual battery controller's function is as follows:

1. When the truck is off, the batteries are isolated and any draw from the aux will not affect the starter.
2. When the engine is running, the batteries are combined (kind of like having a single battery -- but it's now a system), causing the flow of power from high to low concentrations, with the alternator charging the battery system.
3. If the starter battery goes dead, the batteries can be combined while the engine is off to flow enough juice to start the truck.

If this is correct, then the stock charging system will ensure that neither battery is overcharged since it monitors the voltage of the system while combined (it should balance out between the two batteries, right?), and regulates the flow accordingly? If so, as long as I have two 12V batteries, I shouldn't worry about size differences (CCAs, reserve cap, etc)

4Crawler · 05-10-2006, 09:05 PM

Yep, that is the way the Painless controller (all it is is a 3 way switch and a solenoid) works. And yes, normally not too big a problem mixing batteries, they are only combined under charge. Only thing that might be an issue is to not mix wildy different battery designs, just to be safe.

Macallan12 · 06-18-2006, 01:38 PM

Making slow progress. I'm going with a Odyssey PC1200 for my starter and a PC1500 for my auxiliary. I can fit the 1200 on the passenger side, by the firewall. This is what I'm thinking...

I added some brackets on the fender to give support to the tray since the fender walls are very uneven over here...

I srewed them in with self-tapping metal screws. Next I added the tray that will hold the battery in place...

This will be held in place with 4 carriage bolts. Washers will be stacked between the bottom of the tray all the way to the fender for support. Next I put the battery in the tray, and here's my new starter...

Do you see any problems with this setup?

05-07-2006, 09:45 AM	#3 (permalink)
4Crawler Contributing Member Join Date: Jun 2002 Location: SF Bay Area, CA Posts: 7,836	I use that system on my dual battery system, I do have identical AGM batteries but it has worked flawlessly for the last 8 years: http://www.4crawler.com/4x4/CheapTri...atteries.shtml __________________ 1985 Toyota 4Runner SR-5, 22REC engine, dual t-cases, 4.88 gears, dual ARBs, 33x10.50 BFGs or 35x12.50 MTRs r.c.brown@ieee.org TruckEditor@tlca.org Project: 4Crawler 4Crawler OffRoad Gettin'Off 4WD Club

05-09-2006, 06:03 PM	#4 (permalink)
Macallan12 Registered User Join Date: Apr 2005 Location: SoCal Posts: 30	getting close Thanks for the reply. I take it you've never overcharged a battery, or heard of this happening? Also, can I use a billet box in place of the stock clamp to hold a battery in the stock location? I'm close to buying all my parts, and when I do, I'll write up my installation... good or bad

05-09-2006, 06:21 PM	#5 (permalink)
4Crawler Contributing Member Join Date: Jun 2002 Location: SF Bay Area, CA Posts: 7,836	Self-discharge is the more common problem, that is if beatteries are left connected w/o any charging going on. If one battery is a fraction of a volt lower than the other, current will flow from high to low and kill the high battery. That is why you want matched batteries. But if disconnected while off, no problem with discharge. __________________ 1985 Toyota 4Runner SR-5, 22REC engine, dual t-cases, 4.88 gears, dual ARBs, 33x10.50 BFGs or 35x12.50 MTRs r.c.brown@ieee.org TruckEditor@tlca.org Project: 4Crawler 4Crawler OffRoad Gettin'Off 4WD Club

05-10-2006, 04:47 AM	#7 (permalink)
waskillywabbit Super Moderator-Sponsoring Member Staff Join Date: Jul 2003 Location: Tuscaloosa, AL Posts: 14,555	The Painless dual battery wiring setup disconnects the batteries when the vehicle is off...and/or you can use a manual marine switch to do the same thing...like w/ the triple batteries I have. I would think different batteries would be fine. __________________ WabFab Off-Road, LLC MySpace Twitter Facebook 7th Annual South East 4Runner Jamboree, 2010 The toughest part of a Jeep is the chick driving it. WabFab Off-Road 4th Anniversary Sale

05-10-2006, 05:58 AM	#8 (permalink)
AH64ID Contributing Member Join Date: Dec 2002 Location: Idaho Posts: 4,638	Both of my dads chevys have dual batteris in them. The are tied together by a heavy duty continous duty solenoid hooked up to an oil pressure switch. He now runs like batteries in both, he had a starting and a deep cycle in the P/U and it kept overcharging the deep cycle, boil over, battery acid everywhere. Now that he is running the like batteries no issues. Also no need for rewiring the alternator when you wire them this way, the second battery will charge when the solenoid is closed. Also, it would be a good idea to rewire aux lights, stereo, etc. to the aux battery so that both batteries get used at the same time. __________________ -John '05 Dodge 3500 SRW 4x4 SLT 5.9 Cummins QC LB NV5600 2003 SR5 4Runner, V6 4WD. 1" cornfed lift Previous Toyota's '92 Red Truck NALA Speed doesn't kill, its the sudden stop that hurts.

05-06-2006, 05:21 PM	#2 (permalink)
Macallan12 Registered User Join Date: Apr 2005 Location: SoCal Posts: 30	OK. I think I'm starting to figure things out. I'm going to get the Hellroaring isolator/combiner and set it up in either the backup or auxillary configuration. This way, the batteries can be of any type and they'll be completely isolated. As far as the concern of overcharging, my readings have led me to believe that car batteries can withstand some extreme charges without problem, and an undercharged battery is what I should be concerned about.

05-10-2006, 08:54 PM	#9 (permalink)
Macallan12 Registered User Join Date: Apr 2005 Location: SoCal Posts: 30	getting there Thanks for all the input The way I understand the dual battery controller's function is as follows: 1. When the truck is off, the batteries are isolated and any draw from the aux will not affect the starter. 2. When the engine is running, the batteries are combined (kind of like having a single battery -- but it's now a system), causing the flow of power from high to low concentrations, with the alternator charging the battery system. 3. If the starter battery goes dead, the batteries can be combined while the engine is off to flow enough juice to start the truck. If this is correct, then the stock charging system will ensure that neither battery is overcharged since it monitors the voltage of the system while combined (it should balance out between the two batteries, right?), and regulates the flow accordingly? If so, as long as I have two 12V batteries, I shouldn't worry about size differences (CCAs, reserve cap, etc)

05-10-2006, 09:05 PM	#10 (permalink)
4Crawler Contributing Member Join Date: Jun 2002 Location: SF Bay Area, CA Posts: 7,836	Yep, that is the way the Painless controller (all it is is a 3 way switch and a solenoid) works. And yes, normally not too big a problem mixing batteries, they are only combined under charge. Only thing that might be an issue is to not mix wildy different battery designs, just to be safe. __________________ 1985 Toyota 4Runner SR-5, 22REC engine, dual t-cases, 4.88 gears, dual ARBs, 33x10.50 BFGs or 35x12.50 MTRs r.c.brown@ieee.org TruckEditor@tlca.org Project: 4Crawler 4Crawler OffRoad Gettin'Off 4WD Club

06-18-2006, 01:38 PM	#11 (permalink)
Macallan12 Registered User Join Date: Apr 2005 Location: SoCal Posts: 30	how about this? Making slow progress. I'm going with a Odyssey PC1200 for my starter and a PC1500 for my auxiliary. I can fit the 1200 on the passenger side, by the firewall. This is what I'm thinking... I added some brackets on the fender to give support to the tray since the fender walls are very uneven over here... I srewed them in with self-tapping metal screws. Next I added the tray that will hold the battery in place... This will be held in place with 4 carriage bolts. Washers will be stacked between the bottom of the tray all the way to the fender for support. Next I put the battery in the tray, and here's my new starter... Do you see any problems with this setup?

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