Considering charger module upgrade from 3.6kwh to 7.2kwh

1633 Views 8 Replies 5 Participants Last post by hellsop, Feb 17, 2022

bfoster3413

Discussion Starter · Feb 16, 2022

Hi All,

I have a 2019 Volt LT that currently has a 3.6kwh charging module. I am wondering if upgrading to 7.2kwh will not only increase the charging amperage from 16A to 32A but will it ALSO double up the energy regeneration when driving?

I am shopping for a Level 2 charging unit and been looking at many different options out there. Before I decide on one, I am going to price out the charging module upgrade to see if it's worth it. As far as I know, I can say it's definitely worth it as far as charging go. But if it doesn't increase the regeneration while driving, I don't think it would make it worth the cost.

Thanks,
Brad

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Steverino

· #2 · Feb 16, 2022

The car controls the draw. Unless the 2019 Volt LT was bought with the 7.2kwH option it won't matter that you have a 7.2kwH capable EVSE, the car will only charge at 3.6kwH. the 2019 Premier has the higher rate standard, the LT is 3.6 unless the 7.2 was purchased as an upgrade.

Regen rate is unaffected either way, this option only affects charging time from the wall.

Regardless, get an EVSE with that capability, it'll come in handy for your next EV.

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bfoster3413

Discussion Starter · #3 · Feb 16, 2022

Thank you Steverino!

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obermd

· #4 · Feb 16, 2022

Regeneration is DC from the motors to the battery. Wall charging is AC. The on-board charging unit is fundamentally an AC to DC converter (rectifier).

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bfoster3413

Discussion Starter · #5 · Feb 16, 2022

Ah that makes sense thank you obermd....... so I am curious, what is the MAX kwh that comes from regeneration back to the battery? I mean, I see -25 to -35 when actively braking. How much of that is actually restored to battery? 3.6kw in a given hour and obviously we don't brake for a whole hour so instant regeneration only restores very little if any energy back, correct?

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hellsop

· #6 · Feb 16, 2022

bfoster3413 said:
Ah that makes sense thank you obermd....... so I am curious, what is the MAX kwh that comes from regeneration back to the battery? I mean, I see -25 to -35 when actively braking. How much of that is actually restored to battery? 3.6kw in a given hour and obviously we don't brake for a whole hour so instant regeneration only restores very little if any energy back, correct?

Round trip from "momentum" to regen to battery then back through the motor to momentum again has been quoted at various efficiencies, but the lowest ones seem to be about 70% goes back round trip. We've also had people report up to -60kw under peak braking. But you're right that it doesn't amount to much compared to actually running wall power through a charger because of the huge amount of TIME available while plugged into a wall.

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Kato659

· #7 · Feb 17, 2022

bfoster3413 said:
Ah that makes sense thank you obermd....... so I am curious, what is the MAX kwh that comes from regeneration back to the battery? I mean, I see -25 to -35 when actively braking. How much of that is actually restored to battery? 3.6kw in a given hour and obviously we don't brake for a whole hour so instant regeneration only restores very little if any energy back, correct?

I might be misreading, but it looks like you're saying the charger limits regen, but regen charges the battery using the electric motor and not the charger.

If you are high up a mountain with an empty battery you can "charge" much more than 3.6 kWh in an hour regenerating to the bottom.

On the flat during normal driving, regen doesn't amount to much at all. I do still like it on long declines (shift to L and set cruise control to maintain set speed).

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obermd

· #8 · Feb 17, 2022

Kato659 said:
I might be misreading, but it looks like you're saying the charger limits regen, but regen charges the battery using the electric motor and not the charger.

If you are high up a mountain with an empty battery you can "charge" much more than 3.6 kWh in an hour regenerating to the bottom.

On the flat during normal driving, regen doesn't amount to much at all. I do still like it on long declines (shift to L and set cruise control to maintain set speed).

Correct, regen bypasses the AC to DC rectifier and feeds directly to the battery. Max regen is somewhere around 50 KW. As for descending a mountain, I filled half my battery between the parking lot on top of Independence Pass and Aspen, CO, just by using cruise control, L and the regen paddles to maintain speed or slow down during the descent.

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hellsop

· #9 · Feb 17, 2022

obermd said:
Correct, regen bypasses the AC to DC rectifier and feeds directly to the battery. Max regen is somewhere around 50 KW. As for descending a mountain, I filled half my battery between the parking lot on top of Independence Pass and Aspen, CO, just by using cruise control, L and the regen paddles to maintain speed or slow down during the descent.

Sort of. The power control electronics (the big flat thing under the hood that DOESN'T have fill caps on it) are still involved. But that's designed to handle the full working load of the car, so it can handle a LOT more than even 50KW. It's just that the paddle won't command that level of draw and the wide pedal system will start blending in friction above that in order to keep wheels turning and to start using the rear to slow as well.

But that has little to do with the actual charger module behind the bumper.

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