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Old 12-14-2011, 08:38 AM
vintage steel vintage steel is offline
Join Date: Nov 2011
Location: Post Falls, ID
Posts: 94
Isolate or not?

I know there are sticky's on dual battery installs, i have read them. I have also done research on the subject. But, that's why there's a newbie page, right?
I just installed dual batteries in my '75 Jimmy with an 8 1/2 Meyer. I separated the "plow battery" from the rest of the trucks electrical system. The reasons I did this were:
  • I had an isolator
  • I have installed isolators on boats with multiple batteries and had good results.
  • I have 2 old mismatched batteries that would kill each other if I let them play together.
This is apparently an old debate but I can't seem to find a definitive answer.

Some people say "Use an isolator to separate the batteries so the plow can't drain your starting battery. Also you can use one battery to jump the other"

Some people say "Avoid isolators like the plague. just run the batteries in parallel and get twice the amps and half the problems."

I have never ran a plow truck so this is all just theory to me. I would like to hear good or bad experiences from both setups so I can make an informed decision. I don't have a problem rewiring it if it's a better way. The isolator seems like the way to go but, I could be missing something.

I don't want to clutter this post with pics but here are links to my install.
I also added a volt meter so I could keep tabs on the plow battery.
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Old 12-14-2011, 07:36 PM
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maverjohn maverjohn is offline
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Location: Duluth, MN
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Looks good, I also run two batteries but did not run a isolator and have had no problems, but if I did have a isolator I would use it.
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Old 12-14-2011, 10:31 PM
vintage steel vintage steel is offline
Join Date: Nov 2011
Location: Post Falls, ID
Posts: 94
Okay after further research I have found that not only do isolators have a 1/4 to 1 amp voltage drop (not good when power is at a premium already). They are also drastically underrated so, for my 105 amp alternator I would need something like a 250 or 300 amp isolator. This is according to a very good boat mechanic with 25 years experience, he also runs a plow truck in the winter, I trust his opinion. So, I ditched the isolator, did a quick rewire and hooked up my batteries in parallel now it will have all the volts and twice the amps.
...Anybody want a good deal on an almost new battery isolator?
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Old 12-15-2011, 07:17 PM
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maverjohn maverjohn is offline
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Sounds like a good plan.
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Old 12-16-2011, 12:36 PM
dieselss dieselss is online now
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Location: N.w. Indiana
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The only thing I would add would be to try and get the closest match batteries you can. You mentioned that your batts are gunna kill each other if they play together. Since you ditched the isolator there now playing together.
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Old 12-16-2011, 02:24 PM
superdog1 superdog1 is offline
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Join Date: Oct 2011
Location: Middle of PA
Posts: 255
I also just installed dual batteries on my 94 GMC dually dump. I did go out and buy 2 brand new matching batteries and I didn't use an isolator. After reading all the stickies on this site and getting just as confused as you are, I skipped the isolator. IMHO, on a boat, it is critical that the batteries that start the motor and run it always work, because if you are 100 miles out to sea and your boat doesn't start, it is a LOT of paddling to get home.

With a plow truck, you do need it to work, but, you are always on land and can get a jump or tow, whatever. It is worth the risk to have the extra reserve capacity of both batteries to keep the plow going up and down, left and right. I have a Meyer E60 pump on a 9" Western Pro plow. While it was pretty fast before, it is lightning now when it comes to plow movement.

Some guys have never installed an extra battery and they have never had an issue. Others have to do it right away in order for the plow to work all day and night. I just wasn't taking the chance!
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Old 12-07-2012, 10:12 AM
Mackfire68 Mackfire68 is offline
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Join Date: Jan 2010
Location: ENOLA, PA
Posts: 4
I already have dual batteries and an isolator. What if I hooked my plow up to the main battery and leave the auxiliary battery for other accessories and the ability to jump myself?
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Old 12-09-2012, 07:57 PM
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thelettuceman thelettuceman is offline Addict
Join Date: Nov 2010
Location: Lutherville, MD 21093
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I do not know anything about this subject but I would say this: Pickup trucks from GM, Ford, & Chrysler are available with two batteries. Find out how they are wired and do as they do. These manufacturers do not want any warranty claims.
My 2011 F250 has dual batteries and I have know idea how they are wired.
2015 Ford F350 6.2L Gas
8' Western Pro Plow Ultra Mount
Lettuce Help You
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Old 12-11-2012, 11:34 AM
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Moose's Mowing Moose's Mowing is offline
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Join Date: Oct 2012
Location: SE PA
Posts: 198
I wouldnt waste time with an isolator. I never installed one on my boats either. Never felt the need to. On a plow truck, I'd just hook two fresh and new batteries in parallel and be done with it. Parallel would be + to + and - to -. DON"T hook in series. Parallel will remain at 12 volts but double the amperage. Series will double the voltage but keep the amps the same.

With a plow truck, you need to stay at 12 volts and it's very desirable to have a lot of amps available. This will give you all kinds of juice to crank the engine, run the plow, extra lights, a radio, the heater, and all the other crap you'll have running while plowing.

Typically, on a boat, you don't need gobs of cranking power, but you'd have lots of accessories running while the engine is not running. Things like stereos, VHF radios, gps units, fish finders and nav lights are usually on while fishing but you shut the engine off. The isolator will keep one battery for cranking the engine and the other for running all the other crap but will charge them both while the engine runs. So that's why boats usually have one installed.
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