Page 1 of 2

Why a separate charging unit?

Posted: Fri Oct 14, 2011 4:53 pm
by Levenkay
I kind of asked this before, but in a reply to an old thread in another forum. So here goes again..

From a massively simplified point of view, the motor drive electronics already seem to provide not only the function that will transfer energy from an AC source (the motor being used in regenerative-braking mode) to the car's battery, but the function for converting the battery's energy into AC power (normally used to supply the motor). What would be the problem(s) in using the regenerative-power-recovery features of the motor drive to charge the battery, by disconnecting the drive electronics from the motor and connecting the drive electronics to the AC line instead? And, after you'd achieved that (probably challenging) bit of switchery, a few control setting tweaks to the driver should make it transfer battery power back into the AC line (it IS an inverter, after all; you just don't need the variable-frequency aspect of it for V2G).

The difference between L1/L2 charging and something faster might then be as simple as connecting to a 3phase power drop instead of a one or two-phase one.

Re: Why a separate charging unit?

Posted: Fri Oct 14, 2011 5:09 pm
by Smidge204
In a word: Safety.

The EVSE is a safety device that protects the wiring between the wall socket and your vehicle. It also protects the user by keeping the power in that cord off until there is a proven, proper connection to a vehicle.
=Smidge=

Re: Why a separate charging unit?

Posted: Fri Oct 14, 2011 5:25 pm
by tbleakne
The Mini-E Mini-Cooper Electric's electronics can do all this, as reported by a forum member named Matt whose handle I can't spell, who drives one. The electronics were designed by AC Propulsion in San Dimas, CA.

Re: Why a separate charging unit?

Posted: Fri Oct 14, 2011 5:26 pm
by Herm
It has been done, I believe AC Propulsion has a patent on dual use of an inverter as a high power charger and a motor controller.. there are probably some tricky safety issues and failsafes that have to be properly engineered before it sees production.. but you can be assured that in a few years the architecture of BEVs will be optimized, if its not there yet.

Re: Why a separate charging unit?

Posted: Fri Oct 14, 2011 5:36 pm
by johnr
I guess the OP's question is, is it possible to design the car's inverter - which can convert power generated by the motor during regenerative braking to the tune of 30KW - such that it can also be used as a charger. The result being, the car could potentially charge much faster - at a rate of up to 30KW versus its present limit of 7KW - and eliminating the existing bulky charger that takes up luggage space. This does not necessarily preclude the EVSE, which is simply a safety gateway between the car and the electrical outlet.

Ok, so with the right hardware and firmware combination, it seems like a plausible concept. Why Nissan's engineers didn't go this route, I have no idea. Considering there are other things about the car that make me question the judgment of its designers, I wouldn't be surprised if it simply hadn't entered their minds to consider doing it this way. But it is also certainly possible that they determined it would be unsafe, costly, or not feasible. Maybe they considered it but found a good reason not to do so.

Edit: I see a couple people already replied while I was typing. LOL. In that case, maybe AC Propulsion asked for too high a price to license the technology, and Nissan said no dice.

Re: Why a separate charging unit?

Posted: Fri Oct 14, 2011 9:49 pm
by Levenkay
Smidge204 wrote:In a word: Safety.

The EVSE is a safety device that protects the wiring between the wall socket and your vehicle. It also protects the user by keeping the power in that cord off until there is a proven, proper connection to a vehicle.
=Smidge=
I'm not talking about the EVSE; I'm talking about the separate package of charger electronics that's inside the car.

And the necessity of DISCONNECTING THE MOTOR from the car's inverter while charging or grid-leveling was underway in order to "re-use" the motor driver as a bidirectional power interface with the AC line would make for a greater degree of safety than the Leaf's charging system currently seems to have.

Re: Why a separate charging unit?

Posted: Sat Oct 15, 2011 11:29 pm
by garygid
Patents.

Re: Why a separate charging unit?

Posted: Sun Oct 16, 2011 8:00 am
by EVDRIVER
ACP has done this since day one, go to their site and read about their drive tech.

Re: Why a separate charging unit?

Posted: Sun Oct 16, 2011 3:40 pm
by Levenkay
garygid wrote:Patents.
Ironic that in institution created to foster the dissemination of technological advancements should so often have the opposite effect.

But if it was a mere matter of money, shame on ACP. If you've set so high a price on licensing your patent that a major automotive manufacturer can't swing it economically, this is a clue that your price is too high. You were waiting, maybe, for a customer with larger sales volumes than an automaker????

Re: Why a separate charging unit?

Posted: Sun Oct 16, 2011 3:54 pm
by garygid
Sometimes, two separate systems, each optimally designed for its task,
is more efficient, safer, more reliable, easier to troubleshoot and maintain,
easier to upgrade, and no more costly than one more-complex system.