Will a Battery Tender Charge both Batteries?

[DontSlamMyRam]

'19 CTD, I like to put all my vehicles on the Tender once in awhile to keep the batteries happy. I'm a noob when it comes to the dual batteries and charging. If I hard wire a plug in to one battery, will it back fill the other as well? Or do the batteries need topped off independently?

 

[Deleted member 80]

As long as you don't isolate them, yes they will charge together.

 

[DontSlamMyRam]

So they are married together from the factory I assume? Some form of MOD is required to isolate them if that was your preference?

 

[flan]

As your truck sits from the factory they will both charge if you hook a tender up to one of them. It does not matter which one you hook up to either, whichever is more convenient for your garage setup.

 

[DontSlamMyRam]

Thanks for info!

 

[Burn'n Oil]

So they are married together from the factory I assume? Some form of MOD is required to isolate them if that was your preference?

Ya really, really don't want to isolate them if you hang your hat where winter can be vicious cold.

 

[John Jensen]

According to Battery Tender you should connect the positive clip to one battery and the ground clip to the other battery. That way, depending on what BT you have, the BT sees two batteries and can give you a readout for each battery. If you put both clips on one battery the BT sees both as one battery.

Also, to work properly you need a BT of sufficient amperage. Too low amperage rating and the BT cannot keep batteries at full charge. Been there, done that!

 

[Deleted member 80]

So they are married together from the factory I assume? Some form of MOD is required to isolate them if that was your preference?

You would isolate them to load test them, and/or troubleshoot an issue.

 

[Burn'n Oil]

Also, to work properly you need a BT of sufficient amperage. Too low amperage rating and the BT cannot keep batteries at full charge. Been there, done that!

And that "sufficient amperage" would be... ? Asking for a friend.

 

[John Jensen]

That's a tough question. It depends on the battery CCA and whether you are using one battery or two in parallel.
I suggest you go by the manufacturer's recommendations. For a charger/maintainer, I personally wouldn't go below 5 amps. I am using 10amp units.

 

[Deleted member 80]

That's interesting. Other than Odyssey batteries, which need a higher charge voltage to reach full charge, I have activated, charged, and maintained literally hundreds of batteries with a few Battery Tender Plus units that are 1.25(?)Amp. Some batteries as big as 8D, 4D, and Group 31. Never had an issue with conventional flooded, or AGM.

 

[John Jensen]

That's interesting. Other than Odyssey batteries, which need a higher charge voltage to reach full charge, I have activated, charged, and maintained literally hundreds of batteries with a few Battery Tender Plus units that are 1.25(?)Amp. Some batteries as big as 8D, 4D, and Group 31. Never had an issue with conventional flooded, or AGM.

Low amp maintainers did not keep my Ford diesel regular or AGM batteries maintained. In fact, allowed them to go flat over time. Same with my boat batteries and my son's Ford Excursion diesel batteries. I thought had other problems until we proved that the low amp maintainers were not up to it. Was using maintainers designed for regular or AGM batteries

 

[carlrx7]

The CTEK MXS 10 states it will charge lead acid batteries up to 200ah and maintain up to 300ah. Our batteries are anywhere between 80-100ah each (don't sue me). If you use a charger too small the constant current might not be able to reach the desired voltage to top off the battery. Some chargers will just give up and automatically switch to float after 24 hours, some will error out.

That being said, I purchased a Stanley 25-amp charger for $50 bucks at walmart online.

 

[John Jensen]

That being said, I purchased a Stanley 25-amp charger for $50 bucks at walmart online.

That's a good deal.
Do you have a link? When I look at Walmart I cannot find a Stanley 25-amp charger for $50 bucks

 

[carlrx7]

That's a good deal.
Do you have a link? When I look at Walmart I cannot find a Stanley 25-amp charger for $50 bucks

Best i can find right now is here: https://www.menards.com/main/tools/...eg-battery-charger/bc25bs/p-1458270034898.htm 69.99

Looks like its random. follow the price here: https://camelcamelcamel.com/product/B01BYFSUJW

 

[John Jensen]

Thanks. Specs are vague, doesn't say it is programmed to do AGM, etc batteries so I assume it's only for regular batteries.
I guess that's why it's a good price. I'll pass

 

[carlrx7]

I don't own any AGM batteries but It should work for those as well, as it doesn't run an equalization stage automatically, which is the main thing to avoid. I'll monitor the charging profile and see where its constant voltage is set at tomorrow.

Check out Minn Kota Precision Chargers: https://minnkotamotors.johnsonoutdoors.com/battery-chargers/board-precision-chargers?id=13951

I run the 2-bank on my boat. Takes good care of mine.

 

[John Jensen]

That's also what I run on my boat.
Here's what I'm using on my 2020 Ram HO Cummins:
Minn Kota, 20 amp, 2-Bank On-Board Battery Charger - # MK-220PC

 

[bas4241]

Here's the one I got.....10 amps, and has a 14.4/14.7 volt choice to properly charge AGM batteries.

Amazon.com: OptiMATE 7 SELECT, TM-251, 9-step 12V 10A sealed battery saving charger & maintainer: Automotive

Buy OptiMATE 7 SELECT, TM-251, 9-step 12V 10A sealed battery saving charger & maintainer: Battery Chargers - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

smile.amazon.com

 

[John Jensen]

^^^^^ Nice unit