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Discussion Starter #1
Here are one of many ways to run a dual battery set up.
Yes I know about the isolators but I am cheap. So I got a Cole-Hersee Cont. duty solenoid rated at over 100 amps cont. It only cost me 20.00 for the solenoid as well. Follow link.

http://www.tjsperformance.com/dualbattery.htm
 

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I have a question for the pros on here.

I am about to get setup with dual batteries. I was planning on hooking them up in parallel (positive to positive, neg to neg). Is there anything wrong with this? What exactly do battery isolators do? TJS: what exactly does your setup enable you to do or why is it beneficial to do it this way instead of in parallel?
 

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Ryan- That's how mine is setup. The advantage to an isolator is that you can run the aux battery alone on a separate circut, say to power your car stereo, but it will not draw down the other battery if it goes dead. The way I have mine, and you described, run them both on the primary vehicle circut, and are both charged by the alternator, but will both discharge each other if there is a problem, or if one of them dies. I bought two new batteries when I installed my auxillary, so they are both the same age, and carry the same load.

I noticed much less dimming last year, even with a fauly diode in my alternator, still charged enough to keep up tho, amazingly. After I played with my plow a little this evening, with two batteries, a good alternator, and the engine held up to about 2000rpms, I noticed veryy little dimming of the lights. I am very pleased.

I used the same welding cable that TJS used.
 

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Discussion Starter #4
Well said Snowybowtie. Actually the batteries are in parallel just with the solenoid in the middle. I was going to run pos to pos and neg to neg. as Oryano is going to do, but for the price of the cont. duty solenoid and some free welding cable (shhh don't tell).
I could not pass it up. Plus this may sound wierd, but I love to wire stuff.

T.J.
 

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What is the switch used for?

Chuck B.
 

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Discussion Starter #6
The switch energizes the coil in the cont. duty solenoid when I want to charge the other battery. I could hook it up to a feed from the ign. in the run state so it would be automatic, but I want to be able to control it.
T.J.
 

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The solenoid will not replace a good quality isolator,and may damage the batteries and\or alternator if used incorrectly.

If you wire it to ignition power,then it will work OK,but the only purpose it will serve is to isolate the two batteries when the truck is shut off.Even then,you would have to rewire anything that could psssibly create a draw off the aux battery,so that the main battery is isolated.It does nothing when the truck is on except connect the two.No isolation or control of charge rates.

If you wire it to a switch,your asking for trouble.The batteries will charge and discharge at different rates,depending on the switch position.This can lead to battery overcharging,sulphation,and even alternator damage.

Just connect them in parallel,it so much easier.Skip the solenoid.
 

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When you say Parallel, is that with or without an Isolator? What is a Isolator?

Chuck B.
 

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Snoworks said:
When you say Parallel, is that with or without an Isolator? What is a Isolator?

Chuck B.
wireing them in parallel is connecting the batterys + to + and - to - withing nothing inbetween on the lines going between the batterys. an Isolator allows the batteries to be seprate IE if you wanted to run a high powered stereo off the one battery but you dont want the stereo to be able to drain down the main battery (Starting Batt) the isolator will regulate charge to the 2 diff batterys to keep them charged but it wont overcharge one of the batteries while charging the other one if they have a diff ammount of charge in them.
 

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Parallel with no isolator\solenoid.

Positive to positive,and negative to negative.Both negatives can be grounded to the engine\chassis,they don't have to be connected together,as long as it's a good ground.This is what you want for a plow setup,as it gives you double the reserve capacity.

An isolator serves two purposes.

1- It separates the two batteries,so that a heavy draw on one battery will not discharge the other.This is better suited to a camper or motorhome,where you may run one battery dead powering the fridge\lights,etc,but still need the other battery to start the vehicle.While this would be good on a plow truck to prevent the starting battery from going dead,it gives you no increase in reserve capacity,so the plow will run the aux battery down faster,just like running the truck with one battery.

2- It also regulates charge rate to each battery based on the individual state of each battery.So if one battery is dead,and one is fully charged,it will only charge the dead one,and not overcharge the fully charged battery.It will usually charge the starting battery first,then the aux battery.This is again suited to an application where the batteries are discharged at different rates.If you did this with a plow truck,your aux battery for the plow wouldn't see enough charge rate to keep it fully charged.

That's where the problem arises with the above mentioned solenoid,and using a switch to selectivly activate it.The batteries could be discharged at differrent rates (switch off),but will be charged at the same rate (switch on),resulting in possible damage.We used to see this setup on a lot of older motorhomes and campers.It would allow you to park,and disconnect the starting battery so you wouldn't run it dead,yet still be able to power the rest of the camper with the other battery.It usually resulted in very short alt and battery life,and even a few blown up batteries.

I have tried many different setups with my plow trucks,and two BIG batteries in parallel,with a big alternator is the way to go.No switches,no relays,no isolators to break down.

Changing the batteries out every few years is a big help too,as the tend to get weak from the constant heavy discharge\charge rates created when plowing.Leaving them in too long will damage the alternator over time.Don't use a deep cycle battery either,as this is not really a deep cycle application.
 

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dual batt

i have been using 2 batts hooked up in parallel 850 amps each and 140 amp alt for 2 yrs. now , works great!! used to have problems with lights dimming, before, i pretty much run every thing every one else does, except big light bar , i agree with wyldman, about the isolator, just my opinion!! Campi !!!!
 

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Adam and Wyldman - Thanks for the explanation.

What should be the limit on distance for the second batteries cables?

Chuck B.
 

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The shorter the better,but there is no limit on length.If you have to make a long run of cable,like for a rear mounted battery,step up on the cable size,to offset for the added length.

If you going to do it,get the biggest cables you can,like a 0 gauge or bigger.Welding cable works well too,and is sometimes cheaper.Get a truck shop to put some good ends on it for you.
 

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dual batterys

hey guys... ditch the isolaters and switches and all that stuff. wire it up just like the factory does for millions of light duty diesel truck owners...two batterys in paralel. Just go to your local dealer and get the oem parts for your truck and your done. I did it for my chevy and it has worked great. just make sure the two batterys are identicle and always replace them in pairs
 

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Discussion Starter #15
Wyaldman,
I understand what you mean by having a manual switch. I have not wired this thing yet and I might let an ign. feed energize the
coil on the solenoid.
T.J
www.tjsperformance.com
 
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