How to charge Dual (Parallel) 12 Volt Batteries

jctangney

I don't have my T@B S yet but right from the start working with dealer to get dual batteries on it as we like to camp in National Parks and they do not have hookups. Also do not want to carry generator and gas. My questions relates to how to maintain the charge in the two batteries with some sort of Battery Tender when at home. Would prefer not to remove the batteries or disconnect them unless that is the only way. I assume others have already tackled this so comments on what Battery Tender model would be needed and how to connect/disconnect things as needed.

jkjenn

I use solar. You actually want to wire in series as parallel will only produce 6v. Series produces 12v. If you use the Zamp port with solar, you don't need to do anything else.


https://www.youtube.com/watch?v=QQAG9NupRYo

jcfaber1

If the batteries are 12V they are wired in parallel, if 2 6Volt batteries they are wired in series.  For wired in series, attach the charger at the outer positive and negative terminals.  I have not dealt with 12v in parallel.  In either case, make sure the two batteries are identical and of the same age.  My personnel preference is 2 6V golf cart batteries wired in series.  Google handy bob's solar for some good advice on solar and batteries.

John

Photomom

Yes, if you put two 12 volt batteries in series they will produce 24 volts, and fry the electronics in your T@B. 

jctangney

Mine will be 12 volt batteries, so parallel is the way I need to go. Looking to see how others maintain batteries connected like this.

jkjenn

Sorry, I misread original pits. Selective reading.

Keltdubh

John, if you are charging with a battery tender then you should connect the positive contact from the tender to the positive post on one battery and the negative contact from the tender to the negative post on the other battery. 

mash2

Depends where the batteries are....

If they are in close proximity, just connect positive on one battery and negative on the other battery.   

If the distance between batteries is larger, you may need to connect an extension to have charger end on the negative extended (W1 in the diagram).  Mine are close enough that I just hook the + clamp on one battery and the - clamp on the other battery.  

The battery tender indicated that ... the purpose of this wire (W1) is to balance the voltage drop evenly across both batteries and each wire during charging. This is not critical for lower current chargers, but when you start to get into the 10 amp and above range, the voltage differential can be significant. The blue wire W1 must be connected to the opposite end of the battery pack as the black wire at the top of the battery pack. 


I use the battery tender plus (1.25 A) so am fine (no W1 wire).   

jctangney

I got email back form Battery Tender this morning. They said that as long as the batteries are fully charged the their 022-0185G-DL-WH model (1.25 A, Oregon, California model) will maintain both. In fact, the image they sent is identical to the one above! I can plug into shore power to make sure the two batteries are fully charged and then will switch over to the Battery Tender! Thanks for the replies and glad to see they match up with what I got from Battery Tender.

BTW: I also asked Black & Decker about their battery maintainers and they said they are specifically designed for a single battery and would not work properly with two batteries.