[Shivetya]

I am having a not so fun time trying to search it out on the forum so apologies as it has to have been answered before.

When braking you get to see how much power is regenerated. I wanted to understand just how high that number can be before it exceeds the systems ability to absorb it and does it absorb it on a 1:1? Is it a wholly separate system from the 3.3 charger?

 

[llninja]

In my tests on a G1 I was able to make something like 111 or 114 kw. The test is easy, drive the car up to 80-101 MPH then brake hard to see how high you can get regen to go.

Of course it's a separate system than the 3.3 charger. The electricity can flow from both electric motors into the batteries bypassing the on-board charger.. But you cannot sustain this high charge level for long periods of time, so don't get any ideas about modifying your charging system to charge at that level for hours. That would likely overheat the batteries and fry them.

 

[Sean-a-Tron]

Most EV's can do a lot of regen, though the harder you brake, the more friction brakes are used. On Gen 2, it's best to use the regen on demand button, as that will only use regen. Nothing will be 1:1 on any car. There will always be inefficiencies. I'm assuming regen wastes 20% of the kinetic energy.

I don't believe the regen system uses the normal 3.3kw charger as the power produced wouldn't be very consistent.

 

[Ziv]

I think regen recovers around 50-75% of the energy it takes to accelerate to the speed the vehicle is moving at. So if you accelerate from a dead stop using 25 kW, accelerating for 30 seconds to get to approximately 40 mph and then brake to a stop, you will get back 50-75% of 25 * 0.5 kW minutes, depending on how fast or gently you brake. This was discussed at length 5 or 6 years ago, and I don't think we ever got a definitive answer from Chevy. But this is just my memory of a discussion we had here several years ago.

On the "how fast can you recharge" issue, I believe someone once said he had set the daily distance record for a Volt by having his Volt towed with the front wheels on the ground and used regen to recharge the battery much faster than normal. This memory is so bizarre I wouldn't be surprised if it is completely wrong.

 

[Qinsp]

The highest I've seen is 60kW regen, 120kW discharge

 

[telveer]

In Gen 1, the max regen you can get is equal to the rating of MGA (generator) motor, which is 55kW. This rating also pairs nicely with the ICE, which is rated at 63kW. I have seen regen go over 50 kW on a regular basis. Even though Gen 1 Volt has two motors, only one of them (MGA) is used for regen.

MGA in Gen 2 Volt is rated lower, at about 48kW. But the ICE is rated at 75kW. For Gen 2 Volt, I am thinking MGB is also for regen. If not, max regen would be limited to 47kW.

 

[llninja]

The highest I've seen is 60kW regen, 120kW discharge

You might be right. The 114 might have been me flooring it from 0-to 101 mph

 

[Joiner]

For the gen2 cars it is definitely 60kw max regen. I've seen it many times.

 

[ClarksonCote]

Yes, 60kW is the max regen. Easy to achieve coming off a freeway and using the regen paddle to slow quickly.

With the Bolt EV, it's even higher, i.e. 70kW or more.

 

[viking79]

I am having a not so fun time trying to search it out on the forum so apologies as it has to have been answered before.

When braking you get to see how much power is regenerated. I wanted to understand just how high that number can be before it exceeds the systems ability to absorb it and does it absorb it on a 1:1? Is it a wholly separate system from the 3.3 charger?

The generated voltage potential is going to be across the battery terminals so you are basically DC quick charging the battery. There are losses in each of those processes, so it is not 1:1. You have conversion loss in the power inverter, chemical losses in the battery, etc.

The AC charger is separate and converts 120/240V to DC to charge the battery.

Whenever you have an electric vehicle, the designer has the option to have a charger internal and/or external to the car, the internal charger for the Volt is the 3.3kw charger you mention. Vehicles with DC chargers basically bring the battery terminals externally so that it can be charged via an external charger (Low or even no cost option in most cars). This is why regen is disabled when the battery is fully charged, this is more noticeable on the Bolt EV since it can actually charge to full, whereas the Volt doesn't ever charge to full with the AC charger.

 

[Raymondjram]

Any attempt to do a DC charge of the Volt's battery can void its 8-year warranty. So, for anyone who wishes to experiment with DC charging, get a salvaged Volt which lost its warranty to work with. Up to now, I see the first Dc opportunity at the output of the onboard 3.3 (or 3.6) kW AC charger as a test point for DC input, bypassing that charger. If the battery is monitored, maybe it can accept over 7 kW of a DC charge at that point. Since I have no Volt, I am guessing here. And maybe another point would be where the A/C compressor gets its power from the battery. I doubt there can be any free point to do a DC charge other than those two.

 

[Arcanox]

Any attempt to do a DC charge of the Volt's battery can void its 8-year warranty. So, for anyone who wishes to experiment with DC charging, get a salvaged Volt which lost its warranty to work with. Up to now, I see the first Dc opportunity at the output of the onboard 3.3 (or 3.6) kW AC charger as a test point for DC input, bypassing that charger. If the battery is monitored, maybe it can accept over 7 kW of a DC charge at that point. Since I have no Volt, I am guessing here. And maybe another point would be where the A/C compressor gets its power from the battery. I doubt there can be any free point to do a DC charge other than those two.

I believe the AC compressor is going to be hooked in through a 3-phase inverter just like the drive motors; that's how it was on my Highlander Hybrid, at least. I don't think they'd use a DC motor for that.

There may be a potential access point where the APM is connected to the HV battery, but I really wouldn't consider it safe to charge the battery through anything other than the onboard charger. I'm not sure what unit balances the cells but you wouldn't want to shove current into it without the individual cell voltages and internal resistances being monitored carefully.

 

[P_L]

I don't know about maximum regeneration but the regenerative system seems very efficient to me. We live in a valley and I drove to the top of the hillside, which is in two shelves, then I went about another 1 or two Km's beyond to get to the store. I started out at 70 km range and drove gently but at the speed limit up the hills and on the flats, getting down to 66 km range. I then used the regenerative break hand pedal as much as I could driving back home, and I got back to my starting 70 km range. I know the car cannot defy the laws of thermodynamics but it seems like I got back at least 75 percent or more of the energy.

 

[tibble]

I don't know about maximum regeneration but the regenerative system seems very efficient to me. We live in a valley and I drove to the top of the hillside, which is in two shelves, then I went about another 1 or two Km's beyond to get to the store. I started out at 70 km range and drove gently but at the speed limit up the hills and on the flats, getting down to 66 km range. I then used the regenerative break hand pedal as much as I could driving back home, and I got back to my starting 70 km range. I know the car cannot defy the laws of thermodynamics but it seems like I got back at least 75 percent or more of the energy.

Actually, the range is now taking the down hill into account and assuming you will use less power/mile. So you are back up to 70km range, but not back up to the same battery % as before.

 

[P_L]

Ah. That makes sense because it just did not seem possible. Nevertheless the regenerative breaking is quite impressive and I enjoy the game of seeing how much I can get back. It really depends on if you hit the traffic lights or manage to not have to stop at all. The amount of energy needed to keep the car going compared to restarting from a complete stop is incredible. Just that I cannot use it as much with my wife in the car because she hates the deceleration feeling.

 

[canehdian]

I'm assuming regen wastes 20% of the kinetic energy.

This is probably a reasonable number.

Gen 1 regen was measured at 78% efficiency "round trip" by a university or national lab or similar organization's study (can't find the PDF anymore, but it was posted here at one point years ago).
78% was like likely 90% motor in and 90% motor out = 81%, minus some other inefficiencies along the way.
And I can't imagine gen2 is less efficient in that manner than gen1.

Those saying <50% are seriously overestimating the losses here.

 

[namja]

The highest I've seen is 60kW regen, 120kW discharge

Yup, this is correct. On the Gen2 Volt:
Max regen is 60kW.
Max discharge is 120kW.