Batter tender for 2 batteries?

[FB400]

Hi - was wondering if anyone ever tried maintaining 2 batteries at once using a single battery tender?

I have 2 car batteries each with at least 2 to 3 years of life left. I want to keep them sharp in case I need them for my generator.

Could I hook up jumper wires from one battery to the other and connect the tender to 1 battery?
I would prefer not to ruin the tender or the batteries or burn down my garage, haha..

Thanks,
Tom

 

[Motogiro]

If the tender you have limits it's own current there should not be a problem using it to charge both batteries. This is with the expectation that each battery is equal. If the batteries are different which they will be at some point there will be a compromise at some level of requirement from the charger. If the difference in battery health and chemistry is small and the charger limits it output then it will be okay and will charge each battery by dividing the current and then topping off and maintaining with a minute or non amount of output to the batteries. If the unit has a de-sulfate mode it may interfere with the discharge/charge rate that it is designed to match as in a motorcycle battery. Since you have the ability to generate very high amounts current from any of those automotive type batteries you'll want to limit the ability of the units to short circuit by at least fusing the positive leads and insulating the positive posts from possible exposure to any loose metal object that may drop on them and create a path to the negative posts. As you said, you don't want burn anything up so fuse and insulate!

 

[FB400]

Hey Cliff - yeah for sure it is a smart tender and I have used them exclusively for 5 years on the bike battery. I use the deltran JR.

It sounds as if it would be ok to do this. These are old batteries with some life still left in them.

Thanks,
Tom

 

[Red Wazp]

Why not cycle the tender every two weeks between the batteries. It's not good to leave a tender on a battery 24/7 for long periods of time. Batteries need to "rest" at least 1 week a month according to a really long in depth article I read once that make me an expert.

 

[FinalImpact]

Why not cycle the tender every two weeks between the batteries. It's not good to leave a tender on a battery 24/7 for long periods of time. Batteries need to "rest" at least 1 week a month according to a really long in depth article I read once that make me an expert.

^^ Agreed!
Unless there they are being drained, no reason to charge 24/7. Let them rest 2 - 3weeks. And to the point of any two batteries having the same chemistry at the same time is rare. Its better to service them as individuals IMO...
Are they being used to do something or just sitting around?

 

[patrickb37]

Best way to do it:

 

[Red Wazp]

Best way to do it:
View attachment 65771

Holy Bat charger Batman!

 

[FB400]

So yeah.. basically I went ahead and linked the 2 batteries together. The garage didn't burn down. It's been reading steady green for 2 days and shows 13.12 on the volt meter. I will unplug and let rest for awhile.