The aux battery is the only source of power for the computers during an ESS event. The aux battery is not monitored, but it's tested prior to a cold start. If it fails the test, ESS is disabled and the error light is lit. The main battery is monitored by the battery sensor and ESS will not activate if the main battery is not sufficiently charged.
When the aux battery is tested prior to a cold start, if it can't sufficiently power the system electronics, the electronics shutdown. On the 2018 JLs, the test was repeated every starting attempt so a bad aux battery would strand you. Starting with 2019, once the aux battery fails the test ESS is disabled and not tested anymore until the error is reset.
This feature must have been designed by the Italians. Pure idiocy. And I'm Italian American. ha.
I'm getting confused reading the 1st part and last part of that. On a 2019+ from a cold start, will a dead aux battery let you start?
No. It doesn't matter what year it is. If the Aux is dead the vehicle will not start.
Yes, but rarely is it just the aux bad, most of the time both batteries are drained. Or as described in this post https://www.jeepgladiatorforum.com/...l-battery-system-operation.44028/#post-729742 , sometimes a fuse gets blown and you need a jumper to the N1 terminal to bypass the blown fuse and get power to the system electronics.
I will disagree with you from personal experience of my JT as well as two friends' JTs and multiple JL's. Main battery was fine but aux was dead (tested both batteries every time). My Aux died 4 times in three months but the stock battery had more than enough juice to start up.
So what would happen if a guy eliminated the Aux negative cable entirely, and then transferred the Aux positive wires over to Main positive? So, N1 and N2 (and maybe N3) are all going to Main battery positive?Be aware that the negative cables were changed at some point. At the negative battery terminal, what used to be the aux battery cable is now the body ground cable. Disconnecting that cable used to just disconnect the aux battery, now it disconnects both.
With a properly operating system, both batteries are in parallel all the time except during an ESS event, so batteries tend to go dead together. It's still possible for the aux battery to fail internally in a way that it has low power output and won't discharge the main battery, but that is not typical.
That's probably the most common way people eliminate the aux battery. That's how the Genesis dual battery system eliminates the small aux battery - moving the aux battery positive cables to the main battery.
No fuses were blown/popped in the 6+ vehicles where this occurred from my personal experience. The aux battery had an extremely low voltage yet the main battery was fine (lower than normal but not low enough to not start). For my JT, each aux battery failed internally.
That's what I'm thinking. So does N3 need to be in the equation? Send it to main positive also, right?
If the Genesis kit was the fix for yours, it could still have been a bad N3 fuse or a bad ESS relay (PCR). The Genesis kit bypasses those. What was the fix for the other vehicles?
Couldn't say about the PCR personally, although my trusted mechanic and my dealership confirmed the PCR was good. N3 is/was fine.If the Genesis kit was the fix for yours, it could still have been a bad N3 fuse or a bad ESS relay (PCR). The Genesis kit bypasses those. What was the fix for the other vehicles?
Here's a diagram that show's the battery connections. The main battery is connected to the aux battery and system electronics through the PCR and N3 high capacity fuse. As long as that circuit and ground cables are intact, the batteries are in parallel and will maintain the same voltage.
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