Aux battery replacement

[LouDog]

Replaced my main 12v battery a few weeks ago and was wondering about replacing the aux 12v battery. Is there a benefit to them being about the same age because they are wired in parallel?

I have a 21’ powerboost lariat.

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[Snakebitten]

A good question.
I think I would test it myself similar to the AGM.
Or put another way, I'd take it out of the truck and see if it has a decent resting state SOC. It's a 12V battery and should be considered one similarly to any other 12V battery.

However, it serves a very specific mission, according to the documentation. It's job is to momentarily provide 12V current to the entire electronics side of the truck, while the AGM is isolated from that portion of the truck. (for the heavy work of turning over the starter)

So in that context, I personally would like to see the battery rest with some nice headroom above 12V. And it'd be nice to see how well it could handle a few seconds of a 20-30amp hit? Can it stay above 12V getting slapped?

 

[LouDog]

A good question.
I think I would test it myself similar to the AGM.
Or put another way, I'd take it out of the truck and see if it has a decent resting state SOC. It's a 12V battery and should be considered one similarly to any other 12V battery.

However, it serves a very specific mission, according to the documentation. It's job is to momentarily provide 12V current to the entire electronics side of the truck, while the AGM is isolated from that portion of the truck. (for the heavy work of turning over the starter)

So in that context, I personally would like to see the battery rest with some nice headroom above 12V. And it'd be nice to see how well it could handle a few seconds of a 20-30amp hit? Can it stay above 12V getting slapped?

appreciate the response. I’ll pull it out and see what voltages I get.

 

[Kodiak]

appreciate the response. I’ll pull it out and see what voltages I get.

Come back and let us know. That is a good question and would be great to see your results. The OCD in me tells me to just change them both at the same time but that may be totally unnecessary.

 

[Samson16]

The OCD in me tells me to just change them both at the same time but that may be totally unnecessary.

Your inner OCD and mine think alike.

 

[Samson16]

Remember the 12V air compressors that got as hot as a gun barrel that we used before the PB changed everything? That would make a good load bank for testing.

 

[Gros Ventre]

The issue is that batteries don't like to just sit... And that's what the Aux battery does. I suspect the current draw on it when starting the engine isolates the main battery is relatively low, a few amps intended to keep the memory and a few key circuits alive. There is no reason a battery cannot go some 8 years, but for most that's a real reach. What I intend to do is alternate replacing one and then the other. Likely on a 4 or 5 year cycle.

 

[dmarkjohn]

I have a 22 XLT Powerboost. I replaced the main battery in January after having several "low state of charge" messages. I went with the Batteries Plus X2 AGM. Everything was good until the other day I started to get low state of charge messages again. I had Batteries Plus check it and they said it was bad so they replaced under warranty. The question I have is could the auxiliary battery cause those Low SOC messages if it was going out? I have not replaced it yet so it's original. Thanks for any input or guidance.

 

[Snakebitten]

It's possible for a bad auxiliary battery to drag on the primary battery.
It's also possible for the auxiliary battery to prop up the primary battery.

 

[Double-A]

I posted in some other threads about this, but I personally swapped both because the last OTA update I had gotten [on the old batteries] was for the BMS, and since it seemed like the original charging strategy was kinda crappy I wasn't sure if prior to that update it was affecting both or not?

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