Battery Tenders and Dual Batteries

Lew Ledyard · #1 (**permalink**) 01-22-2007, 07:47 PM

How do you hook up a Battery Tender for a dual 12 volt battery set-up? Since they are wired parallel, do you put the positive on the positive terminal of one battery and the negative lead on the negative terminal of the other battery?

Jim Werth · #2 (**permalink**) 01-23-2007, 04:58 AM

Doesn't matter! Parallel batteries are hooked up + to+ and - to - . Hook up the positive to the battery post and negative to any grounded part on the vehicle. Jim

Ron61 · #3 (**permalink**) 01-23-2007, 06:51 AM

Jim is correct. I don't know but since you have doubled the capacity of the batteries you may want to get a tender with a little more output. The $39.95 ones that I use on my cars don't put out as lot but do keep the batteries charged and they will kick on every so often just to stir the electrolyte up.

Ron

CSX 4027 · #4 (**permalink**) 01-23-2007, 08:32 AM

Do not hook up one tender for 2 batteries in line.
If you do you will burn up one.
A battery tender jolts a battery losing power until it comes back up. If one battery is good and the other one loses power it will jolt the good one as well and overcharge it.
Get 2 battery tenders.
Unhook your parallel connections and hook them up seperately.

Burgs · #5 (**permalink**) 01-23-2007, 10:44 AM

I was told, by the Batteries Plus store,... (well I guess they could sell me a new battery if I fry one), yes you can use the Tender on two parallel batteries, of the SAME type, AND age. So there sit my two, one year old marine batteries, staying warm for the winter with the Tender. I guess we'll see how they do this spring.

CSX 4027 · #6 (**permalink**) 01-23-2007, 12:29 PM

If one battery is weak and can't get to full charge and the other is healthy at full charge, you will be unnecessarily hurting the good one.
Battery tenders are cheap. Just get 2.

Burgs · #7 (**permalink**) 01-23-2007, 12:32 PM

Quote:

Originally Posted by CSX 4027

Battery tenders are cheap. Just get 2.

You're right about that, probably good advise.

STCinc · #8 (**permalink**) 01-23-2007, 12:49 PM

Guys, Check your local marine supply store (or marina). Ebay is also a good place to watch, but make sure its not crappy one from China.

Guest makes some great battery chargers that can be mounted just about anywhere and the best part is that they are ment for a boat, so they are waterproof!

I'm running a Guest 2608A for my Cobra, the same for my ATV and a Guest 2611A for the dual battery set-up in my trailer.

Go to www.guestco.com for more information.

http://www.guestco.com/scpt/ProdPage...20Recreational

The 2608a is discontinued, but it was the same charger as the 2611a but with a single output in a smaller hsg.

Hope this info helps.

any4xx · #9 (**permalink**) 01-23-2007, 04:56 PM

If you're looking for a good price pick up any motorcycle magazine. All the major vendors have them on full-time sale for around $35.00.

Trueoo7 · #10 (**permalink**) 01-23-2007, 08:05 PM

I have been maintaining 2 batteries with 1 tender on a bulldozer that sits outside in the weather for 3 years with no problems.

Rwillia4 · #11 (**permalink**) 01-24-2007, 01:40 AM

A well thought dual batery system will have a battery isolator, this will keep the two batteries from effecting each other when charging. If you have an isolator this is also where you want to attach a tender.

CSX 4027 · #12 (**permalink**) 01-24-2007, 06:50 AM

Quote:

Originally Posted by Rwillia4

A well thought dual batery system will have a battery isolator, this will keep the two batteries from effecting each other when charging. If you have an isolator this is also where you want to attach a tender.

Then you can't charge both at the same time which is really want all seem to want to do.