Tyler-98-W68
Well-Known Member
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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.
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.
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