Has Anyone Put a Battery Tender on their Auxiliary Battery?

[Hawkeyes3312]

Found out today that my Aux battery is failing. I live in the Midwest and the Gladiator doesn't get driven but once or twice a week and, likely, less now that winter is upon us. I didn't know if anyone has done this or if it's even physically possible given the location of the aux battery. I am trying to come up with solution(s) to avoid batteries going bad, etc. Also, any suggestions on what to replace it with other than the Mopar battery? There's got to be better available aftermarket. Thanks!

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[sharpsicle]

Found out today that my Aux battery is failing. I live in the Midwest and the Gladiator doesn't get driven but once or twice a week and, likely, less now that winter is upon us. I didn't know if anyone has done this or if it's even physically possible given the location of the aux battery. I am trying to come up with solution(s) to avoid batteries going bad, etc. Also, any suggestions on what to replace it with other than the Mopar battery? There's got to be batter available aftermarket. Thanks!

Main and aux battery are wired together and can be put on a battery tender together. No real reason to try and maintain the aux by itself. So long as your charging current goes through the IBS, I'd just hook the battery tender up as usual to the main and carry on, it will maintain the aux as well.

 

[abe57]

Main and aux battery are wired together and can be put on a battery tender together. No real reason to try and maintain the aux by itself. So long as your charging current goes through the IBS, I'd just hook the battery tender up as usual to the main and carry on, it will maintain the aux as well.

I do this and it works just fine .

 

[Gelo]

Hi, I use a battery tender to charge the auxiliary. I put the positive clamp on the "N1" and the negative on the main battery's negative. This seems to charge the auxiliary. After the tender shows that it is fully charged, I move the positive clamp from "N1" to the positive on the main battery to charge that until it shows fully charged.

 

[punk'n]

Main and aux battery are wired together and can be put on a battery tender together. No real reason to try and maintain the aux by itself. So long as your charging current goes through the IBS, I'd just hook the battery tender up as usual to the main and carry on, it will maintain the aux as well.

I do this too. (Pigtail exits by grille -I tuck it out of sight behind plastic trim until neded.) I plug it in once a week if I have not taken it on a long drive.

 

[Oil_Burner]

Hi, I use a battery tender to charge the auxiliary. I put the positive clamp on the "N1" and the negative on the main battery's negative. This seems to charge the auxiliary. After the tender shows that it is fully charged, I move the positive clamp from "N1" to the positive on the main battery to charge that until it shows fully charged.

Do you think the JTRD (diesel) is configured the same way?

 

[ShadowsPapa]

Hi, I use a battery tender to charge the auxiliary. I put the positive clamp on the "N1" and the negative on the main battery's negative. This seems to charge the auxiliary. After the tender shows that it is fully charged, I move the positive clamp from "N1" to the positive on the main battery to charge that until it shows fully charged.

Doesn't matter, you are not charging the aux only. They are connected in parallel.
They are connected together via the PCR.
You are actually charging both.

 

[ShadowsPapa]

Do you think the JTRD (diesel) is configured the same way?

Yes. There is no reason for them to be different at all. It's a ESS system, not a diesel system or a gas system.

I've covered this ad nauseam in several threads - they are CONNECTED in parallel. That means any charger is touching both batteries.
The voltage that touches one touches the other.
Basic electricity.

Hi, I use a battery tender to charge the auxiliary. I put the positive clamp on the "N1" and the negative on the main battery's negative. This seems to charge the auxiliary. After the tender shows that it is fully charged, I move the positive clamp from "N1" to the positive on the main battery to charge that until it shows fully charged.

Take a look at the orange wires in that image - I can't recall if I did that one or Jerry, but somewhere I have one like it showing the path from crank battery positive to aux battery positive.
Note the orange looking path - when you connect to the crank battery positive post, it's got a path through N2, fuse N3, and the PCR to the aux battery.
Tenders reset and will see almost any battery as needing charged if you disconnect them then reconnect. It doesn't mean that your second battery didn't get charged, only that the logic inside is starting over. If you checked with a real charger, you'd likely see the voltage and SoC numbers.
Iv'e got pics of my charger charging both, and each apart.
The reason you can jump start these with a dead battery is because they are connected together.

Hopefully you've been charging correctly and putting the negative clamp on TOP of the IBS and not below it on the crank battery negative terminal.
That can cause you trouble.

 

[Oil_Burner]

Yes. There is no reason for them to be different at all. It's a ESS system, not a diesel system or a gas system.

I've covered this ad nauseam in several threads - they are CONNECTED in parallel. That means any charger is touching both batteries.
The voltage that touches one touches the other.
Basic electricity.


Take a look at the orange wires in that image - I can't recall if I did that one or Jerry, but somewhere I have one like it showing the path from crank battery positive to aux battery positive.
Note the orange looking path - when you connect to the crank battery positive post, it's got a path through N2, fuse N3, and the PCR to the aux battery.
Tenders reset and will see almost any battery as needing charged if you disconnect them then reconnect. It doesn't mean that your second battery didn't get charged, only that the logic inside is starting over. If you checked with a real charger, you'd likely see the voltage and SoC numbers.
Iv'e got pics of my charger charging both, and each apart.
The reason you can jump start these with a dead battery is because they are connected together.

Hopefully you've been charging correctly and putting the negative clamp on TOP of the IBS and not below it on the crank battery negative terminal.
That can cause you trouble.

I'm a bit confused... you say they are connected in parallel; however, that is only the case when the PCR is closed. If the PCR is not closed, they are not effectively in parallel.

We know the PCR opens when the ESS is active and the engine is off. Unless we know all the conditions when the PCR closes to put the batteries in parallel or conditions which open the relay, should we be assuming that the PCR is closed putting the battery in parallel? I saw the relay and my assumption, which could be incorrect, is that the relay is not a Normally Closed relay.

 

[Gelo]

Hi Bill (ShawdowsPapa), I believe I got that pic from your past posts. Like many forum members, thank you for posts! I've learned and am still learning from you!

 

[Mr._Bill]

I'm a bit confused... you say they are connected in parallel; however, that is only the case when the PCR is closed. If the PCR is not closed, they are not effectively in parallel.

We know the PCR opens when the ESS is active and the engine is off. Unless we know all the conditions when the PCR closes to put the batteries in parallel or conditions which open the relay, should we be assuming that the PCR is closed putting the battery in parallel? I saw the relay and my assumption, which could be incorrect, is that the relay is not a Normally Closed relay.

They are always paralleled together except during ESS events (when ESS stops the engine) and when the ESS battery is tested at startup.

 

[ShadowsPapa]

I'm a bit confused... you say they are connected in parallel; however, that is only the case when the PCR is closed. If the PCR is not closed, they are not effectively in parallel.

We know the PCR opens when the ESS is active and the engine is off. Unless we know all the conditions when the PCR closes to put the batteries in parallel or conditions which open the relay, should we be assuming that the PCR is closed putting the battery in parallel? I saw the relay and my assumption, which could be incorrect, is that the relay is not a Normally Closed relay.

We do know - been researching and experimenting for a long time on it -
There are only TWO times the PCR is open -
A. ESS stop event. It opens to isolate the crank battery from the rest of the truck,
B. During a big button start, the PCM opens the PCR for a split second to check the status of the aux battery - it closes again quickly. Open/test/close. Takes almost no time at all.

So:
when it's sitting in your garage, running - PCR is closed.
when it's sitting in your garage not running - PCR is closed.
when you are driving - PCR is closed.

It is a N/C relay.

 

[rbryant76]

I tried connecting my tender to N1 and negative of main battery. Tender thinks it’s charged. Reading voltage of 13.40 main battery is around the same and if I move tender to that it tops it off in seconds. N1 I know goes to aux battery per the fuse panel. Something still doesn’t seem quite right. If I drive it will charge up pretty quickly. I know the batteries are good. Something doesn’t seem quite right. This should be easy to charge this thing when not running.

 

[ShadowsPapa]

I tried connecting my tender to N1 and negative of main battery. Tender thinks it’s charged. Reading voltage of 13.40 main battery is around the same and if I move tender to that it tops it off in seconds. N1 I know goes to aux battery per the fuse panel. Something still doesn’t seem quite right. If I drive it will charge up pretty quickly. I know the batteries are good. Something doesn’t seem quite right. This should be easy to charge this thing when not running.

The two batteries are connected in parallel. You cant charge just the aux battery alone unless you take the ground cables apart.
13.4 sounds like the surface charge not the true voltage.
They measure tbe same be ause they are connected together as one

 

[rbryant76]

Conflicting info I am seeing. Some say you can’t tend just the main battery as it won’t charge the aux. which is what I have been seeing since I started using a fender. Mine is wired to the main batteries positive and negative posts.

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