Yes, another aux battery question..

[K9WG]

To the best of my knowledge my '21 JL is stock from the factory, aux battery included. When I am running the radio etc. in acc mode it this pulling off the aux battery?
Thanks
Rich - K9WG

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[AndySpill]

To the best of my knowledge my '21 JL is stock from the factory, aux battery included. When I am running the radio etc. in acc mode it this pulling off the aux battery?
Thanks
Rich - K9WG

Yes.

A dual AGM battery JL that is factory configured always taps the Aux battery.

The only question is if the main battery is also tapped, which tends to not be the case in engine start stop events until the end, in which the main battery seems to effect the engine crank.

In all other cases, whether parked or in accessory mode both batteries provide power, including to your radio.

 

[THAW]

The amount of time the AUX (ESS) battery powers Jeep electronics on its own is measured in milliseconds, and it never happens without the ignition in the RUN position.

So, both batteries power the radio while the ignition is in the ACC position.

 

[andy29847]

There are 2 starting regimes on the JL Jeeps with 2 batteries. A cold start is when you have to press the start button. An ESS start is when your engine starts (after a stop) when you release the brake.

In the case of the cold start, the 2 batteries function as 1. The 2 batteries are separated for ~40 milliseconds before the start so that the aux battery can be tested to determine suitability for an ESS stop. The batteries are rejoined before the start.

In the case of an ESS Stop/start, the 2 batteries remain together while stopped. When the brake is released, the batteries are separated. The main battery starts the vehicle. The aux battery keeps the electronic systems in the vehicle powered up. The batteries remain separated until the vehicle starts and then they are rejoined.

 

[AndySpill]

To the best of my knowledge my '21 JL is stock from the factory, aux battery included. When I am running the radio etc. in acc mode it this pulling off the aux battery?
Thanks
Rich - K9WG

In your perfectly harmless question Richard lies some irony (I'll explain.)

By good authority the Aux battery was an afterthought in dual AGM battery JLs that arose from issues testing the vehicle prior to its 2018 release, where drops in voltage as the main (at the time of this testing the "only") battery would crank the engine at the end of an engine start stop (ESS) event, and the somewhat sensitive electronics of the entertainment system, would result in that entertainment system giving off a crackling sound. Some owners running ESS events having bypassed the Aux battery report this.

Of course you asked about accessory mode when the engine is off. And since at all times but an instant and cold crank to test the Aux battery, and at parts of an engine start stop event, the batteries are connected together in parallel, so indeed your Aux battery plays role in powering the radio, if not an exclusive one.

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