4xe 12v Battery Charging behavior and testing with Odyssey H7 Performance Battery

Tyler-98-W68

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I’m getting closer to understanding how the 12v battery gets charged with the DC/DC charger and potentially uncovering a reason for why the 12v batteries are failing. I recently got a Odyssey Performance H7 Battery installed in my 2022 4xe and wanted to test out how well it would charge/discharge with the 4xe.

Test parameters as following. I set an approximately 7 amp discharge on the rear 12v socket and left that for almost 12 hours (overnight). During this time the vehicle was plugged in to a Morec 32a EVSE charger.

In the morning I used J-Scan to connect to the vehicle without unlocking it or doing anything (amazing feature of J-scan for this type of testing!)
The battery voltage was at 11.18v and a state of charge of 15% pretty low.


At 00:24 seconds I touch the door handle and unlock the doors – the current spikes up to 164amps before stopping charging.

At 00:45 I put the vehicle to run without “starting” it, the current spikes up and for 2 minutes is charging the battery at well over 100 amps, after 2 minutes the current drops and the voltage drops off

At 04:15 I start the vehicle fully and unplug the EVSE, once again the current spikes up over 100 amps for 2 minutes then stops.

I then keep the vehicle stationary but running until 09:15 when I put it in drive and go driving.

At 17:59 I pull over turn the vehicle off and restart it and continue driving, it charges at a high rate for 2 minutes then stops

At 22:09 I pull over and restart the vehicle, same charging behavior.

At 26:12 I pull over and restart the vehicle, same charging behavior again.

It would appear there is some sort of 2 minute timer for providing a lot of charging current to a deeply discharged battery. I fully understand recharging a battery long time at high amperage isn’t healthy for it, but with this scenario if you deeply discharged your battery and went only for a short drive, its possible your battery isn’t going to get fully or close to fully charged. Leaving a battery discharged for an extended period of time is also not healthy for it either.
From this test I can determine. If you have a draw on the 12v battery and the vehicle is plugged in, the HV battery is not going to top up or charge the 12v battery at all. This is puzzling because I’ve observed some 12v battery charge happening while plugged in charging the HV battery. I’ve come back to a 12v SOC in the 90s when it wasn’t that high before I plugged the vehicle in.

I can somewhat understand the reasoning for not having the HV battery top up the 12v if there is a continuous draw, because IF the 12v has a draw and the HV battery is in a low SOC if It was going to keep topping up the 12v battery it could create it’s own problem of not being able to “start” itself with a low HV battery state of charge, causing potentially a low 12v and low HV battery. This could be why there is this 2 minute BOOST of high current when the 12v battery is low in order to give it just enough power to engage the HV battery and “start” the vehicle.

I’m going to review the smart alternator charging parameters and see why the vehicle is dropping to a very slow charge after the 2 minute timer is up. This high amperage for 2 minute charging behavior is really only apparent when the 12v is in a low state of charge, normally this charging behavior isn’t really that noticeable when the battery Is “charged” and by charged I mean 80%+ SOC.
Why do I go OCD over this stuff. It’s for figuring out how to make the 4xe a great overlanding vehicle without having to worry about adding additional hardware if it’s not needed.

 

kelvin.teller

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This is really good info. Thanks for running the test. Please let us know as you gain more understanding of the relationships between batteries and batteries and accessories.

I’m installing 200W of solar panels on top of my jeep-top camper soon. Initially I’ll use that to charge a separate battery system, but if I can replace the one 12v with a better battery as you did and use an mppt charge controller to charge that up, I’m a happy camper.
 
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Tyler-98-W68

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I honestly would not really bother with solar(unless you mean not on the jeep) I mean if you are really set on it use it, but lets say under perfect conditions you get 150w for a few hours, that's 12 or so amps. The onboard DC/DC charger can provide that amount of power to the battery in about 15 minutes. I guess the only time solar would be a good option is if you are drawing the 12v battery down and leaving the vehicle for an extended period of time (say 12 hours) I can run my 12v battery flat in about 12 hours if I have my fridge/freezer set to the freeze mode. But since i'm going in every few hours to grab something when I unlock and open the door it sends a charge to the 12v battery.

One interesting thing is that for whatever reason there doesn't seem to be battery rundown protection on the vehicle because I absolutely killed my 12v battery a few weeks ago and required a boost.

 

kelvin.teller

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Oof, odd there is no rundown protection. My interest in solar is being able to camp for four days, a week and keep recharging the jeep’s 12v battery as i use it for fridge, lights, etc. Yes, we do essentially have a 17. megawatt “house battery” to use if I don’t use it up on the way into the woods, but with gas prices as they are… Anyhow, having a battery continuously topping up for camp use would be shiny.
 

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Oh wow, yeah this is great info. I put a genesis dual battery in mine a few months ago and am about to install an Ursa this week. I have been wondering why it will drain the 12v down if I leave the fridge on for several days even when the Jeep is plugged in. It's always seemed perfectly fine if I go anywhere but when the jeep sits for a few days (esp when its hot out) it drains the accessory battery down. Seems like I could just fix that with a solar panel.
 


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Tyler-98-W68

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The 12v battery will be recharged when the vehicle is plugged in and ACTIVELY charging, meaning as long as the HV is getting a charge the 12v battery charges. Now he's the interesting part. If you use a level 2 charger the 12v battery if drained down a fair amount won't recharge much as it's only going to get 2 hours of charge time. If you use a level 1 charger since that takes much longer to charge the HV battery the 12v battery will also get more of a charge
 

kelvin.teller

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Oh, ha, hadn’t thought of that. Good point.
 

Obi.Wan.Shawnobi

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I honestly would not really bother with solar(unless you mean not on the jeep) I mean if you are really set on it use it... The onboard DC/DC charger can provide that amount of power to the battery in about 15 minutes.
It's a good point. The DC/DC charged my 17kw battery from 1< % to 49% in 40 minutes or so while descending back down to the valley from the Sequoias.

However, what do you think might be the best solution long term solution for overlanding/ camping? I have remote start and I fire that up every hour if need be. the run cycle on that is what? 10 minutes?
 
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Tyler-98-W68

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Remote start cycle is 10 mins, now I haven't tested the remote start and battery charging (which gives me something to do now).
You will get the 2 minute high amperage "boost" and then a lower but still decent charge for the remainder of the remote start. Another option, just hop in and put the vehicle to run (without starting it) then use the FOB and lock the vehicle up, it will run for 30 minutes and then turn off.
 

kelvin.teller

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Oh wow, yeah this is great info. I put a genesis dual battery in mine a few months ago and am about to install an Ursa this week. I have been wondering why it will drain the 12v down if I leave the fridge on for several days even when the Jeep is plugged in. It's always seemed perfectly fine if I go anywhere but when the jeep sits for a few days (esp when its hot out) it drains the accessory battery down. Seems like I could just fix that with a solar panel.
Is your intent to charge the 4xe’s 12v with your solar or an auxiliary battery/solar generator?
 


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Is your intent to charge the 4xe’s 12v with your solar or an auxiliary battery/solar generator?
The intent would be to set it up as Shane describes here in this Genesis Q&A video, where the MPPT charge control would be hooked up to the bus bar on the dual battery kit, which would flow power into the Acc battery first then the cranking battery when charge was high enough that they were connected (which is most of the time when the vehicle isnt just sitting there running the fridge for days in the heat without being started) The point of doing this would be to allow me to just leave my fridge on all the time so I dont have to spend a day cooling it off ahead of a quick weekend trip.

 
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Tyler-98-W68

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Here's what I do. I have a few Ecoflow Lithium battery packs, built in MPPT solar controller AC inverter ect. They real selling feature though is they will fully recharge in less than 2 hours from an AC power source.
What I normally do is use my R600 Pro in my 4xe. I run my 12v Fridge/freezer off the 12v output of the R600 Pro, and plug the unit into the 12v socket in the rear which recharges the unit at up to 10amps. At night or when i'm going to be away from the vehicle for more than 10-12 hours I unplug the R600 Pro from the 12v socket so the 12v battery doesn't completely drain. In the morning or whenever I plug the R600 Pro back into the 12v socket in the rear. Should it get depleted far enough where the 12v charging at 10a isn't going to suffice, I just plug it in to my 1000W inverter and put the 4xe on run without starting it, and if the R600 Pro is around 60-70% 30 minutes later it's back to full charge again. Yes its not totally automated but it works without any solar or additional wiring.
As a backup I also carry a lithium boost pack incase I do manage to kill the 12v battery (which I have done once)
 

kelvin.teller

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Thank you for all the great info and discussion. I think I have what I need for a set up similar to what Tyler-98-W68 outlines but for the addition of the solar panels as an alternate method for charging the lithium battery in the cargo area.
 

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Here's what I do. I have a few Ecoflow Lithium battery packs, built in MPPT solar controller AC inverter ect. They real selling feature though is they will fully recharge in less than 2 hours from an AC power source.
What I normally do is use my R600 Pro in my 4xe. I run my 12v Fridge/freezer off the 12v output of the R600 Pro, and plug the unit into the 12v socket in the rear which recharges the unit at up to 10amps. At night or when i'm going to be away from the vehicle for more than 10-12 hours I unplug the R600 Pro from the 12v socket so the 12v battery doesn't completely drain. In the morning or whenever I plug the R600 Pro back into the 12v socket in the rear. Should it get depleted far enough where the 12v charging at 10a isn't going to suffice, I just plug it in to my 1000W inverter and put the 4xe on run without starting it, and if the R600 Pro is around 60-70% 30 minutes later it's back to full charge again. Yes its not totally automated but it works without any solar or additional wiring.
As a backup I also carry a lithium boost pack incase I do manage to kill the 12v battery (which I have done once)

I used to do something similar in my tacoma with my fridge and a 500wh bluetti battery. I went with the dual battery setup this time since I wanted plenty of power to the Ursa without having to worry about my 12v "starter" battery, and to save space in the cab (its all under the hood).

I dont NEED solar. I have only run into an issue when I've left the Jeep completely untouched in the heat for more than a couple days with the fridge running, and even then the only thing that happened is that the fridge cut itself off. Solar should just let me leave it on all the time.

 

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