Which battery for aux switches?

[FL Handle Guy]

I have the aux switch group and am running a 12v socket of the constant hot wire and am wondering which battery the wires in the aux group run off of?

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[Mr._Bill]

I have the aux switch group and am running a 12v socket of the constant hot wire and am wondering which battery the wires in the aux group run off of?

Everything runs off the Main battery. The ESS battery is primarily for keeping the computers stable during ESS events. The Main and ESS batteries are separated from each other when ESS turns the engine off, the rest of the time they are paralleled together.

 

[FL Handle Guy]

Thank you for your prompt response.

 

[biodiesel]

Everything runs off the Main battery. The ESS battery is primarily for keeping the computers stable during ESS events. The Main and ESS batteries are separated from each other when ESS turns the engine off, the rest of the time they are paralleled together.

@Mr._Bill, can you think of a benefit for keeping the ESS battery?

I read this on the Wrangler Forum: "The main battery starts the Jeep; the auxiliary battery keeps everything else, lights, wipers, head unit, HVAC, seat and steering wheel heaters, etc., running. When you turn off ESS, the engine won’t shut off when you come to a stop, but every other feature will continue to draw power from the auxiliary battery."

If the above is true, I would think there would be a potential benefit to keep the extra battery onboard. Thoughts?

 

[Radio Guy]

@Mr._Bill, can you think of a benefit for keeping the ESS battery?

I read this on the Wrangler Forum: "The main battery starts the Jeep; the auxiliary battery keeps everything else, lights, wipers, head unit, HVAC, seat and steering wheel heaters, etc., running. When you turn off ESS, the engine won’t shut off when you come to a stop, but every other feature will continue to draw power from the auxiliary battery."

If the above is true, I would think there would be a potential benefit to keep the extra battery onboard. Thoughts?

That doesn’t sound right because when the engine is running and ESS is not in effect, both batteries are in parallel and charging and sharing the load for lights, wipers, head unit, HVAC, seat and steering wheel heaters, etc.

 

[Mr._Bill]

Since they are paralleled together, keeping the Aux battery provides a little more reserve capacity. With the high parasitic draw, the OEM batteries need all the help they can get. Keeping it also eliminates potential warranty hassles with the dealer. Replacing the OEM Main with a good quality 94R provides a large increase in reserve capacity.

The system is wired so that each battery powers specific components during ESS events. The separation is done primarily to keep low voltage issues from rebooting the computers while the truck is running. The system will operate normally on just one battery. There is the potential for issues at ESS restart, with just one battery as it ages, which is one reason for the two battery system.

The ESS system cannot be turned off or disabled. The only control we have is to prevent the engine from turning off when ESS calls for it. The ESS system is quite complex. It is integrated into all the areas of the truck and does extensive monitoring. It started with a Mercedes (remember when they owned Chrysler) two battery design and has evolved from there.

I think the ESS system works quite well, for what it is. I always press the button on the dash because I live in a hot climate and don't like the cabin cooling interrupted.

 

[Zachanadandy]

Since they are paralleled together, keeping the Aux battery provides a little more reserve capacity. With the high parasitic draw, the OEM batteries need all the help they can get. Keeping it also eliminates potential warranty hassles with the dealer. Replacing the OEM Main with a good quality 94R provides a large increase in reserve capacity.

The system is wired so that each battery powers specific components during ESS events. The separation is done primarily to keep low voltage issues from rebooting the computers while the truck is running. The system will operate normally on just one battery. There is the potential for issues at ESS restart, with just one battery as it ages, which is one reason for the two battery system.

The ESS system cannot be turned off or disabled. The only control we have is to prevent the engine from turning off when ESS calls for it. The ESS system is quite complex. It is integrated into all the areas of the truck and does extensive monitoring. It started with a Mercedes (remember when they owned Chrysler) two battery design and has evolved from there.

I think the ESS system works quite well, for what it is. I always press the button on the dash because I live in a hot climate and don't like the cabin cooling interrupted.

The problem is paralleling 2 batteries of very different size. They don't charge or discharge at the same rate because of this. Neither charging nor discharging can be optimized because of this. If you want extra capacity, go with a true dual battery setup with 2 identical batteries. The aux battery will kill the main battery when it dies because of the parallel configuration. It's not enough of an issue that I've removed mine yet, but there's 0 reason to replace it when it goes, at that point put in a new quality main and delete the aux.

 

[biodiesel]

It's not enough of an issue that I've removed mine yet, but there's 0 reason to replace it when it goes, at that point put in a new quality main and delete the aux.

The extra battery does offer some reserve capacity, though.

I still think I can get 5+ years out of the main and auxiliary battery just by charging/maintaining/desulfalting the batteries. I only drive the Jeep maybe two - three times each month. But when they do fail, I plan to replace both with the Odyssey to see if that improves longevity.

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