Regen question

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FWIW, I recently bought an SOC meter from garygid. Initially, it just showed SOC (% remaining) but, with the latest firmware update, now shows Voltage, current (directional) and Power. I was braking downhill at 45 MPH last weekend and thought I saw 40 kW of regen Power for a brief moment. Then today, having to do a rapid deceleration at a freeway off ramp, it appeared to give 44-45 kW regen Power. So, maybe the 30 kW limit indicated by the energy display in the LEAF is fictitious and arbitrary? Just sayin.... :cool:
 
tbleakne said:
This is a very nice graph. Do you have a link to the report from which it was extracted ?

It's from a nice article from SAE on Vehicle Electrification with the chart available with the following link.

http://www.nxtbook.com/nxtbooks/sae/11EVSD0223/#/16" onclick="window.open(this.href);return false;
 
gascant said:
FWIW, I recently bought an SOC meter from garygid.
I guess I missed the memo that garygid sells his SOC meter. Can you point me to the thread that talks about this in more details? I'd like to learn more. Thanks.
 
Volusiano said:
gascant said:
FWIW, I recently bought an SOC meter from garygid.
I guess I missed the memo that garygid sells his SOC meter. Can you point me to the thread that talks about this in more details? I'd like to learn more. Thanks.
http://www.mynissanleaf.com/viewtopic.php?f=44&t=5045&start=0" onclick="window.open(this.href);return false;
 
gascant said:
So, maybe the 30 kW limit indicated by the energy display in the LEAF is fictitious and arbitrary? Just sayin.... :cool:
It's possible - gary mentioned he's seen more than 80 kW under power.

Or perhaps the two don't necessarily agree.

Or perhaps the gauges only indicate what the maximum sustained power/regen is, but lets the car go briefly over those limits in certain conditions.
 
abasile said:
tbleakne said:
If I can find a steady grade not quite so steep, with a higher safe speed, where I don't need to apply any brake pressure, I can hopefully get a higher regen efficiency reading.
The road that we use to reach our mountain town (CA-330) seems pretty good for that purpose. When there is not much traffic and the SOC is sufficiently low, it is possible to use ECO mode regen to keep one's speed down with little to no use of the brake pedal. You'll have to come visit! :D
Andrew, this sounds like an excellent plan. I will contact you to find a mutually convenient time.

I have re-edited my regen report above with some new data that now yields this estimate:
Regen efficiency = (5 clicks/7 clicks) = ~73% +- 7%.
 
tbleakne said:
I have re-edited my regen report above with some new data that now yields this estimate:
Regen efficiency = (5 clicks/7 clicks) = ~73% +- 7%.
I assume this is for a one way trip (energy back into the battery, not out again to kinetic energy)? If so, and if the efficiency on the way out is assumed to be 80% (motor alone is 87-95% efficient per Nissan), then the round trip would be 0.73 * 0.8 = 58%
 
Nekota said:
The KW loss going from the battery to the wheels is described by Nissan to have an efficiency range of 87% to 95%
The graph seems to be describing the efficiency of the electric part of the drivetrain.
 
SanDust said:
The graph seems to be describing the efficiency of the electric part of the drivetrain.

Yes, motor and inverter.. then you have the one speed gearbox. the differential and the two halfshafts with their universal joints. Probably 2% mechanical losses and 1% battery losses.
 
Herm said:
Yes, motor and inverter.. then you have the one speed gearbox. the differential and the two halfshafts with their universal joints. Probably 2% mechanical losses and 1% battery losses.
The SAE has published a composite efficiency map for the Volt and the efficiencies ranged between 70% and 88%. The Leaf's shouldn't be that different. http://papers.sae.org/2011-01-0887" onclick="window.open(this.href);return false;
 
Stoaty said:
tbleakne said:
I have re-edited my regen report above with some new data that now yields this estimate:
Regen efficiency = (5 clicks/7 clicks) = ~73% +- 7%.
I assume this is for a one way trip (energy back into the battery, not out again to kinetic energy)? If so, and if the efficiency on the way out is assumed to be 80% (motor alone is 87-95% efficient per Nissan), then the round trip would be 0.73 * 0.8 = 58%
Since this was calculated from measured data (-7 clicks driving up and +5 clicks coasting down), I think this is the full round-trip efficiency. After driving up and regening(?) back down you have recovered 5/7th of the energy required to climb the hill (consuming only 2 clicks instead of 7 had there been no regen).
 
drees said:
Depending on conditions friction brakes may engage at any time. There's a lot of things which may cause friction brakes to kick in under 30 kW. Primary culprits that I've noticed.

1. Battery over 80% full.
2. Quick application of the brakes.
3. Hard braking.
4. Bumpy road.
5. Low vehicle speed.

1. Is (IMHO) a bit over-protective.
5. Is physics.
But 2-4 I've also seen and it's really annoying. At moderate speed and SOC, the regen is frequently limited by the traction control system. This is also true with the Prius and RAV4-EV... Go ver a light bump while decelerating and the regen may cut out entirely... And not come back for a while. #2 and #3 have been annoying me in the Leaf lately.. Hit the brakes too hard or a tad harder beyond max regen and it reduces dramatically.. You'd think in this day and age, we could maximize regen without confusing the traction control system.
 
Sorry if this has been asked already, but I just read through this entire thread and didn't see anyone mention it: If regen can effectively charge the battery at a 30kw (or more) rate, then doesn't this mean that we basically have the equivalent of a quick charger on board our cars already?

Obviously, making use of the motor controller / inverter for charging would require some serious "hacking", both software and hardware, but am I right in assuming that it's theoretically possible? It seems as if the external electronics in a DC quick charger, and for that matter, the puny 3.3 kw on-board charger, are unnecessarily redundant if the on-board inverter is already capable of charging the battery at such high rates from an AC power supply like the motor provides in regen mode.

Am I completely missing something here? I've read of Rav4-EV owners doing basically the same thing, and I believe the "Long Ranger" generator trailer connected via the regen circuitry. Although of course there are some important differences with the Rav4-EV, such as the use of a DC motor rather than the Leaf's AC.
 
fooljoe said:
Sorry if this has been asked already, but I just read through this entire thread and didn't see anyone mention it: If regen can effectively charge the battery at a 30kw (or more) rate, then doesn't this mean that we basically have the equivalent of a quick charger on board our cars already?

Obviously, making use of the motor controller / inverter for charging would require some serious "hacking", both software and hardware, but am I right in assuming that it's theoretically possible? It seems as if the external electronics in a DC quick charger, and for that matter, the puny 3.3 kw on-board charger, are unnecessarily redundant if the on-board inverter is already capable of charging the battery at such high rates from an AC power supply like the motor provides in regen mode.

Am I completely missing something here? I've read of Rav4-EV owners doing basically the same thing, and I believe the "Long Ranger" generator trailer connected via the regen circuitry. Although of course there are some important differences with the Rav4-EV, such as the use of a DC motor rather than the Leaf's AC.

Sure... If you have access to 400VDC. I actually do (this is the voltage on my solar array) and have had similar thoughts of making a cheap quick(er) charger (my array can only deliver 12kW) but not seriously because 400VDC scares the $*#% out of me.
 
TickTock said:
Sure... If you have access to 400VDC. I actually do (this is the voltage on my solar array) and have had similar thoughts of making a cheap quick(er) charger (my array can only deliver 12kW) but not seriously because 400VDC scares the $*#% out of me.
No, the 400VDC is the output of a quick charger or the car's motor controller that goes straight to the battery. The input of the quick charger is 3-phase AC, which, as far as I know, is also what the Leaf's motor generates in regen mode. Since the Leaf's on-board electronics can apparently use 3-phase AC to charge the battery at 30kw or more, the question is why do we need an external quick charger to do what is essentially the same thing?
 
This is how AC Propulsion's system works on the Mini-E and others. I suspect that have patents on it and that is why Nissan did not use it...

fooljoe said:
Since the Leaf's on-board electronics can apparently use 3-phase AC to charge the battery at 30kw or more, the question is why do we need an external quick charger to do what is essentially the same thing?
 
fooljoe said:
TickTock said:
Sure... If you have access to 400VDC. I actually do (this is the voltage on my solar array) and have had similar thoughts of making a cheap quick(er) charger (my array can only deliver 12kW) but not seriously because 400VDC scares the $*#% out of me.
No, the 400VDC is the output of a quick charger or the car's motor controller that goes straight to the battery. The input of the quick charger is 3-phase AC, which, as far as I know, is also what the Leaf's motor generates in regen mode. Since the Leaf's on-board electronics can apparently use 3-phase AC to charge the battery at 30kw or more, the question is why do we need an external quick charger to do what is essentially the same thing?
Good point. Would have to intercept the stator coils and the rotor position sensor and, likely, the brake sensor to fool it into looking like a regen event. Probably be easier to build a rig to spin your wheels and put a brick on the brake. :D you'd probably get first place on CarWings... :)
 
TickTock said:
Good point. Would have to intercept the stator coils and the rotor position sensor and, likely, the brake sensor to fool it into looking like a regen event. Probably be easier to build a rig to spin your wheels and put a brick on the brake. :D you'd probably get first place on CarWings... :)
Haha I actually thought about using a machine to spin the wheels after watching the video of that Dutch guy who was charging up on regen while his Leaf was getting towed by a Tundra. Yeah, I didn't say hacking the Leaf to do this would be easy, just that it seems like it should be doable with the electronics on board, had Nissan designed it that way.
 
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