Charging batteries of two different temperatures - a problem? Or not?

[chorky]

I know there has been some mild talk on this topic so let me give some backstory.

2022 JTR gasser

I have, not yet installed, the Genesis system
I am considering purchasing their battery tie down that Is used on the diesel version and putting a second Group 31 aux battery (so 3 batteries in total) under the right rear seat - https://www.genesisoffroad.com/gen3-diesel-jt-dual-battery-kit


Now, they use this for they diesel setup. But what I am wondering, is based on past discussions in other threads of issues charging batteries of different temperatures, how much of a problem, if any, will this actually create.

Obviously in the winter the in cab battery would be warmer (maybe?? not sure how hot the underwood batteries actually get) and in summer the cab battery would be cooler. And this would of course cause some weird charging probably - however, is it enough to really worry about if battery life expectancy is only 3-5 years anyway???

Also - granted it is an AGM - but has anyone experienced an AGM blowing up? Just curious of the potential safety concern of having a battery in the cab. I know a lot of people have lithium in the cab, and I never hear of anyone having a problem, but it is something to consider IMO

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[TroutFishingInAmerica]

Use a quality DC to DC charger or a quality battery management controller on the 3rd battery. Camper and trailer people do this all the time. Tons of info on the Google machine.
Good luck.

 

[chorky]

Use a quality DC to DC charger or a quality battery management controller on the 3rd battery. Camper and trailer people do this all the time. Tons of info on the Google machine.
Good luck.

I have covered this in other threads but for this particular setup, I am not interested in a DC/DC. However, I am making the whole setup with the ability to be modular and change things up in the future for DC/DC with lithium. But for now I want to stick with AGM. I do know very well the pros's and cons's of DC/DC - and they are excellent systems! It's just not something that fits my current situation and lifestyle.

 

[TroutFishingInAmerica]

I have covered this in other threads but for this particular setup, I am not interested in a DC/DC. However, I am making the whole setup with the ability to be modular and change things up in the future for DC/DC with lithium. But for now I want to stick with AGM. I do know very well the pros's and cons's of DC/DC - and they are excellent systems! It's just not something that fits my current situation and lifestyle.

You sparked my interest, can't wait to see what you come up with. I hope you post it for us.

 

[chorky]

You sparked my interest, can't wait to see what you come up with. I hope you post it for us.

Oh absolutely! possibly on my build thread just to keep it all centralized. I think in the future I will still go the DC/DC route, but my current use case just doesn't warrant that need right now. I'm also rushing a bit to get it all ready for this July

 

[ShadowsPapa]

One purpose of the IBS is to tell the BCM, etc. the battery temperature. When it reaches a certain point, the charging voltage is cut to prevent over-charging or over-heating the battery.
A cold battery needs higher voltage to charge it because the chemical reaction is restricted by the cold.
It's one reason legacy voltage regulators upped the regulated voltage when the temperature dropped.
So - a cold battery requires more voltage to charge, where a warm battery should have the voltage cut to prevent damage and over-charging.
My battery charger adjusts the charging based on the ambient temperature.
If we are talking a few degrees, not much of a problem, but if one is 10 degrees and another at 80 - the cold battery won't charge as quickly.

(Wrangler 4xe is equipped with both a dedicated battery heater and a battery chiller)

 

[chorky]

One purpose of the IBS is to tell the BCM, etc. the battery temperature. When it reaches a certain point, the charging voltage is cut to prevent over-charging or over-heating the battery.
A cold battery needs higher voltage to charge it because the chemical reaction is restricted by the cold.
It's one reason legacy voltage regulators upped the regulated voltage when the temperature dropped.
So - a cold battery requires more voltage to charge, where a warm battery should have the voltage cut to prevent damage and over-charging.
My battery charger adjusts the charging based on the ambient temperature.
If we are talking a few degrees, not much of a problem, but if one is 10 degrees and another at 80 - the cold battery won't charge as quickly.

(Wrangler 4xe is equipped with both a dedicated battery heater and a battery chiller)

Hmm. So then in theory, the IBS gauging temperature of the battery under the hood, in winter, will ramp up voltage, while the battery in the cabin under the seat being warmer would thus be over-charging.

So it begs the question, at what point does it go 'boom'. Or is that an excessive worry - if the outside ambient temp is, say, -15 (no clue what under hood temp would be) but cabin ambient temp is 70......

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