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Discussion Starter · #1 ·
So I was wondering. Does anyone know if the regen braking charging the battery goes through the onboard charger? The reason I ask is that, as I've said in other posts, if I drive up to the top of one of the hills where I live and use Hill 2 on the 2 mile or so drive down, usually by the end of the decline I've added about 3 or so miles to my range or what I'd estimate is roughly 1 kwh. Extrapolating this, if I were continuing to go down a much taller hill for an extended period of time, wouldn't I theoretically be able to charge all 20 kwh of the battery in, say, 20-30 minutes? Would this damage the battery? How exactly does the regen recharge the battery?
 

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I've noticed that the range estimator is highly dependent on many variables including the pitch of the car (presumably this affects gas tank estimates?) and how much braking vs coasting vs accelerating I'm doing, so I wouldn't use it to extrapolate how much effective charge the 400 V battery is getting.
 

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Regenerating is done by your electric motors in the rear, through the rear inverters just like the generetor does in the front of the car with the exception of it being driven by the ICE.
You can get some gestimate of the regen power in the power flow screen while your going down a hill.
Ive also seen a test being done on a rolling road to charge up a car, it took around 30 mins with hill 2 @ 55mph. No idea how much it damages your battery tho.
 

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Discussion Starter · #4 ·
Seems like charging that fast wouldn't be good for the battery. I wonder if that's why they removed the recharge feature in Sport mode
 

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It does not use the onboard charger as that really only converts household electricity to the 333v DC that the HV battery uses. Therefore, as Raven stated it goes from the motors thru the inverters to the battery, no charger involved.

As for damage, the battery is 20 Kwh, 333v, 60Ah battery roughly. In Hill 1 and Hill 2 without depressing the brakes regenerates about 30 and 45 kw respectively, which at 333v, is 90 and 135 amps whic would be a 1.5C and 2.25C charge rate. When the brakes are applied I see as high as 75kw, which would be a 3.75C rate charge. A123 Systems' lithium iron phosphate batteries are rated at like 10C. I think the battery will be just fine, I am more worried about the cooling fans giving up the ghost when the car is parked in a 100 plus degree garage with no ambient air flow, with the low 3.3kw charge, which is a 0.165C charge rate.
 

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Discussion Starter · #6 ·
kabalah70 said:
It does not use the onboard charger as that really only converts household electricity to the 333v DC that the HV battery uses. Therefore, as Raven stated it goes from the motors thru the inverters to the battery, no charger involved.

As for damage, the battery is 20 Kwh, 333v, 60Ah battery roughly. In Hill 1 and Hill 2 without depressing the brakes regenerates about 30 and 45 kw respectively, which at 333v, is 90 and 135 amps whic would be a 1.5C and 2.25C charge rate. When the brakes are applied I see as high as 75kw, which would be a 3.75C rate charge. A123 Systems' lithium iron phosphate batteries are rated at like 10C. I think the battery will be just fine, I am more worried about the cooling fans giving up the ghost when the car is parked in a 100 plus degree garage with no ambient air flow, with the low 3.3kw charge, which is a 0.165C charge rate.
Thanks - helpful! Now that begs the question why Fisker didn't include a faster (6.6kw or 10kw) onboard charger and why it removed the recharge feature from Sport mode (that can't possibly be emissions related and I doubt that the power generated from the battery is 100% equal to it's load, so some energy is likely wasted). Further, I thought all ICEs has optimal RPM levels which in theory is where an ICE+gen combo should operate to maximize MPG, no?
 

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Does anyone seem to get real extra miles out of regen? I drive with great attention to hill1 and 2 at every stop sign and light and I dont find it gives me that much extra mileage. Just perception?
 

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bigdaddyo811 said:
Does anyone seem to get real extra miles out of regen? I drive with great attention to hill1 and 2 at every stop sign and light and I dont find it gives me that much extra mileage. Just perception?
Stay tuned on this one....I recently drove my Karma up to Tahoe, and will be driving back later this month. Drops from 7100 ft (at the Donner Pass) to sea level in about 60 miles. Will be interesting to see what regenerative braking does. I expect to reach Auburn with close to a full battery - will report out!
 

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Skibum said:
bigdaddyo811 said:
Does anyone seem to get real extra miles out of regen? I drive with great attention to hill1 and 2 at every stop sign and light and I dont find it gives me that much extra mileage. Just perception?
Stay tuned on this one....I recently drove my Karma up to Tahoe, and will be driving back later this month. Drops from 7100 ft (at the Donner Pass) to sea level in about 60 miles. Will be interesting to see what regenerative braking does. I expect to reach Auburn with close to a full battery - will report out!
Over 650 miles on a weekend with my Karma

The day started at 7:00am in Fremont with a full tank and a full charge. We had three people in the Karma, my wife, a friend that I met in China seven years ago (this was her first trip to the US) and of course, myself along with our luggage. I arrived in Yosemite valley at about 11:30am. We had lunch at the Ahwahnee hotel and then proceeded to check out the valley. Stopped off at several locations where people were constantly asking questions about the beautiful car. Had no trouble finding parking for the car as other people wanted to see it and offered parking spaces. After visiting the valley we headed up to the high country and Tenaya Lake proceeding on to Tuolumne meadows after picking up 6 gallons of gas on the way which filled the tank (still had 9 miles on the battery).

From there we went over Tioga pass, 9,943’ elevation, and headed down to the south shore of Mono Lake off of CA-120. Coming down from Tioga Pass we picked up 9 miles on the battery with the dynamic brakes bringing the battery up to 18 miles. I had to go over a stretch of gravel road to get to the lake arriving at 4:30pm. Checked out the lake where I met my son and his dog while everyone took pictures.

We then left Mono Lake and headed up US-395 and entered Nevada., From there we caught Kingsbury Grade. At the steepest part of Kingsbury grade I tried accelerating and found the Karma to be extremely responsive with no problem accelerating up a 9% grade. When we reached the top of Kingsbury grade we took Tramway Drive to our Condo at the Ridge. We arrived at the Ridge at about 8:00pm where we checked in and starting charging the car (115V only). The next morning we pulled out at about 10:00am and headed down to Lake Tahoe. We than filled up the gas tank with 8.9 gallons of gas. We still had 48 miles on the battery from the previous charge the night before. We then headed counterclockwise around the lake stopping for pictures at Sand Harbor State Park, then on to lunch at a Casino at North Shore. After lunch we continued on around the lake with a stop at Emerald Bay. The parking lot at Emerald Bay was coned off with a sign saying the parking lot was full with no parking available. I went around the cones and drove to the ticket booth, where you are supposed to pay for parking, to ask where I could park. They gave me a spot next to the ticket booth and said there would be no charge for my Karma. The park Ranger made a number of very positive comments about the car.

After leaving Emerald Bay we continued to head south to US-50. I then got another 7.7 gallons of gas after traveling 630 miles. The battery now had 19 miles left (we gained about 12 miles on the battery using dynamic braking coming down from Lake Tahoe). After the fill-up we continued back home. We arrived back home at 7:00pm. At that point we unloaded the car and I washed it in preparation for going to work the next day.

Total trip Miles 653.6 miles
Total gas 22.636 gallons @ 629.4 miles
Total Battery charge added 81 miles
Approximate Dynamic Charge 21 miles
Final charge on Battery 9 miles
Cars recorded mpg for trip 29 mpg
Actual calculated mpg 28.9 mpg
Software Revision 615
Total Mileage on Karma 3565 miles

Obviously most of the trip was on gas with a LOT of up and down grades. The Karma performed flawlessly with no problems at all. A lot of people asked a lot of questions and took a lot of pictures while commenting how beautiful the Karma is.
 
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