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Pro tip: Leaving it in ACC mode for 4 days will kill both batteries

PsyRN

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Bone head move: In a rush last week I parked my truck, forgot to put it in park and just hit the "off" button (I blame it on the prius I was driving for work all day), and was out of town for the next 4 days. When I came back, totally dead. Both batteries read about 3v. ugh!

I replaced the main battery to get it going again, but the Aux battery i'm sure won't be charging. Of course the ESS isn't working, but not concerned about that. I know I should also replace the Aux battery, it's just a pain to get under there and deal with it. what would happen if I don't replace it? how long till I have problems for not replacing it?

I'm still not totally sure why we need the Aux battery, and have everything run off the main battery.
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Mr._Bill

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Bone head move: In a rush last week I parked my truck, forgot to put it in park and just hit the "off" button (I blame it on the prius I was driving for work all day), and was out of town for the next 4 days. When I came back, totally dead. Both batteries read about 3v. ugh!

I replaced the main battery to get it going again, but the Aux battery i'm sure won't be charging. Of course the ESS isn't working, but not concerned about that. I know I should also replace the Aux battery, it's just a pain to get under there and deal with it. what would happen if I don't replace it? how long till I have problems for not replacing it?

I'm still not totally sure why we need the Aux battery, and have everything run off the main battery.
The secondary battery is required for the ESS system. It should eventually recharge, but if the cells are damaged it will just keep draining the primary battery and causing issues. There have been reports of a dead ESS battery preventing the truck from starting. The method to get rid of the ESS battery, and maintain full function, is to install a Genesis Dual Battery Kit.
 

jebiruph

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Bone head move: In a rush last week I parked my truck, forgot to put it in park and just hit the "off" button (I blame it on the prius I was driving for work all day), and was out of town for the next 4 days. When I came back, totally dead. Both batteries read about 3v. ugh!

I replaced the main battery to get it going again, but the Aux battery i'm sure won't be charging. Of course the ESS isn't working, but not concerned about that. I know I should also replace the Aux battery, it's just a pain to get under there and deal with it. what would happen if I don't replace it? how long till I have problems for not replacing it?

I'm still not totally sure why we need the Aux battery, and have everything run off the main battery.
When they aren't being charged by the alternator or a battery charger, the depleted aux battery will drain power from the replaced main battery until the batteries equalize. You may not have any issues after everything gets fully charged.
 
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PsyRN

PsyRN

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I'm going to guess that if the Aux battery doesn't "equalize" and charge by the end of the week of driving it every day, I'll need to replace it. I wish the that battery was easier to reach. Any tips on getting to it?
 

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I'm going to guess that if the Aux battery doesn't "equalize" and charge by the end of the week of driving it every day, I'll need to replace it. I wish the that battery was easier to reach. Any tips on getting to it?
Watch the Genesis installation video. It shows how to remove the ESS battery.

 

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Deadeye

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I'm like 97% sure that the vehicle starts exclusively from the ESS battery, and the ESS battery does not power anything else in the vehicle, nor will the main battery draw off and deplete your ESS battery. The ESS/Main battery relationship is a one way street. Your truck's electrical system prioritizes keeping the ESS battery at full charge, and it can pull from the main, but the main can't pull from it.. If either the ESS or main battery is too low, the truck won't even attempt to turnover.

That ESS battery charges pretty quickly too. More than likely you will be fine.
 
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PsyRN

PsyRN

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I'm like 97% sure that the vehicle starts exclusively from the ESS battery, and the ESS battery does not power anything else in the vehicle, nor will the main battery draw off and deplete your ESS battery. The ESS/Main battery relationship is a one way street. Your truck's electrical system prioritizes keeping the ESS battery at full charge, and it can pull from the main, but the main can't pull from it.. If either the ESS or main battery is too low, the truck won't even attempt to turnover.

That ESS battery charges pretty quickly too. More than likely you will be fine.
I'm not so sure about that. My Aux battery came in at a whopping 3v when I tested it, same for the main, and nothing worked. As soon as I replaced the main, everything worked except the ESS. I had an issue where my TIPM board wasn't working had to be replaced and the only way to get the car started and running was to disconnect the Aux battery and run a jumper from the main to the fuses. My understanding of the ESS battery also runs all the accessories when in "Stop" and the engine shuts off.

I"m not an electrical engineer, so there's a good chance I don't know what I"m talking about here. Also the reason why I don't see why something like this Aux battery even needed. Seems like 1 more thing to go wrong/replace.
 

Mjolnir

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Many people, myself included, have been unable to start our JT's due to the Aux battery being too low of a voltage, even though the main battery is the cranking battery.

How the system is wired is dumb. The aux does help power the cabin (supposedly, still not sure on this). So do not be surprised if you can't start the truck even if the main battery is fine. I have the genesis dual kit so that never happens again (4 times to me by simply sitting overnight with nothing on or plugged in because those aux batteries are absolute shit.)
 

jebiruph

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I'm going to guess that if the Aux battery doesn't "equalize" and charge by the end of the week of driving it every day, I'll need to replace it. I wish the that battery was easier to reach. Any tips on getting to it?
Your batteries would have equalized right away. If your not having any more issues, it looks like your aux battery is good. I don't think the ESS error condition will clear by itself, it can be cleared with a code scanner or I think you can disconnect both batteries to clear it.
 
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Delhux

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I had my truck at the dealership for some work about 3-weeks ago. It sat there for about 5-days and when I got it back the secondary battery was too low for ESS to work.

Thing is, with ongoing COVID stuff (I just don’t drive much) and the fact I have a parking mode hardwired dashcam always running, that secondary battery has only once had enough charging time to re-enable the ESS system—and even then, just for a short time before sitting and draining again.

Prior to the dealership visit, the truck could sit equally as unused and still always have the ESS battery work just fine.

I just wish I had a better way to charge the batteries than driving around for hours (I have a 1500amp jump pack, but that seems to be insufficient to fully charge the batteries).
 

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I'm not so sure about that. My Aux battery came in at a whopping 3v when I tested it, same for the main, and nothing worked. As soon as I replaced the main, everything worked except the ESS. I had an issue where my TIPM board wasn't working had to be replaced and the only way to get the car started and running was to disconnect the Aux battery and run a jumper from the main to the fuses. My understanding of the ESS battery also runs all the accessories when in "Stop" and the engine shuts off.

I"m not an electrical engineer, so there's a good chance I don't know what I"m talking about here. Also the reason why I don't see why something like this Aux battery even needed. Seems like 1 more thing to go wrong/replace.
I agree, on several occasions after first starting the vehicle, I have had an annunciation stating ESS is not ready, so the aux battery is not the only thing that is used for starting, but some how does not always have a full charge for use with ESS. ESS will also not work until your engine reaches a certain temperature.
 

jebiruph

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I believe the ESS not ready, battery charging message means the IBS (battery sensor) is reporting that the status of the main battery does meet the threshold to auto stop.
 
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PsyRN

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Your batteries would have equalized right away. If your not having any more issues, it looks like your aux battery is good. I don't think the ESS error condition will clear by itself, it can be cleared with a code scanner or I think you can disconnect both batteries to clear it.
This looks like what happened. I disconnected both batteries, the aux came in at about 12.6v, same for the main. This also cleared the ESS error and it all works fine now.
 
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PsyRN

PsyRN

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Welp! So much for it running fine. All electrics just went out! Not even hazards working. Thank god for HF blinking lights. Waiting for a tow. Last time this happened the TIPM board had to be replaced. Ugh!
 

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I'm doing the Genesis system day one. Too many issues have been reported on that smaller OEM battery. Dual Odyssey batteries will take care of that. Plus, I have a fridge that I only run off the secondary.
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