Dual Batteries: Things to consider?

[kbremn71]

I've read a couple of posts concerning the installation of two batteries for plowing and I was wondering if this is something I should consider. Before I get to that point however, there are a few things about the alternator and batteries that I'd like to get cleared up.

First off, lets assume that I have a standard duty alternator and a good strong battery, I'm running plowlights, 4 hideaway strobes, two tractor lights as aux. backup lights and of course the plow itself. How much juice does this take out of the battery and how fast does the alternator recharge it (generally speaking)?

Second, if I set up two batteries, how close do they need to be? The truck has an empty battery tray on the opposite side of the engine compartment. Will running a cable across be ok? And also, will it make a difference what type of battery I install?

[John DiMartino]

You should have a 100amp alt in your chevy at the minimum.You can put the 2nd batt in the other tray on the opposite side.It will work just fine.You canget custom cables or make your own.If you have a slavage yard close sometimes you can get a cable out of a diesel truck that had 2 batts,along with the rest of the hardware so it looks factory.If its in your budget a 140amp+ alt would be best with dual batterys.You put your existing batt in something else and put a new set of identical batterys,the biggest you can fit in the trays.

[wyldman]

John pretty much summed it up.

I would keep your 100 amp alt for now,and see how it holds up.If your route isn't too long,and you don't go nuts angling the plow all the time,you should be fine.If you find the voltmeter slowly going down the more you plow,then you need a bigger alternator.

[CPSS]

As John noted, the 2 batteries should be the same type, size and most importantly, SAME AGE. Don't just add a second battery unless the original one is new.

[kbremn71]

Originally posted by CPSS
As John noted, the 2 batteries should be the same type, size and most importantly, SAME AGE. Don't just add a second battery unless the original one is new.
I plan to replace both since the one I have now is getting tired, but why should they be the same type, size and age? (for cusiosity sake)
Originally posted by John DiMartino
You canget custom cables or make your own.
What would making my own entail? Is it simply a heavy gauge wire (#2??) and should I worry about a coating of some sort?

[JCurtis]

They don't draw off each other.

If you install two identical batteries, the same age and size, same manufacturer you can be pretty much assured that they are the same quality, cold cranking amps etc.

Different batteries of different size and age will without a doubt try to draw power from the stronger, newer, bigger battery.

[CPSS]

Jeff's right on the money. 2 batteries in parallel, (pos to pos, and neg to neg) will effectively double the available current and keep the voltage the same. The alternator sees it as one large battery.

[kbremn71]

Originally posted by CPSS
2 batteries in parallel, (pos to pos, and neg to neg)

I read somewhere (perhaps another post here?) that the connections should be pos to pos with one neg to engine block and one neg to vehicle frame. Any thoughts?

[wyldman]

The ground can go anywhere there is a good ground.

I usually ground the second battery to the block,but still use a heavy ground cable to the original battery.It adds some redundancy,so if you develop a bad ground from one of the batteries to the block,the second battery can still be utilized.

[John DiMartino]

I almost always ground to the engine block.If there isnt a factory strap thats real big, i run a strap from the truck frame to the engine block as well.