My ZEV 6100
Problem is anything that will provide 30A charging current is too heavy, bulky, or too expensive. Currently looking at using the proximity signal on the J1772 standard to limit the AC current source to 32A. Then rectifing the signal and then routing through the battery at less than 30A.
The J1772 compliant charge stations don't limit the current at all, all they do is tell the charger what the maximum amount that can be drawn is.
If the charger goes above this, the charge station disconnects you.
have you seen this charger:
it's a kit, and its limited to 50A output current (which for a 72v nominal pack you would be drawing ~30A @ 240v (80v * 50A * 0.9 eff * 0.5 PF)
Thanks for your input. Yes, I've seen the emotorwerks DIY charger and it's much too expensive.
I think you were talking about the J1772 pilot signal signaling a max current via its PWM output. They use that signal to indicate to the EV the max current output of the station (many of our stations are limited to 30A) but also as a way to throttle back EV chargers during peak demand periods or rolling blackouts. So what you stated about the pilot line is true, but what I was alluding to is the EV's current control function of the proximity signal line:
The function of the Proximity Pilot PP allows the car to control the maximum charging current of the charging station by adding a resistor on the PP-PE loop. This allows adapter cables to use a resistance coding for the current. The pilot line circuitry examples show that the resistor is put in the plugs of the adapter cable itself - if the PP-PE is connected through to the car then it allows its battery management system to control the charging process by shifting additional resistors that are put in parallel with the permant 2700 Ω resistor on the loop.
total resistance PP-PE 1500 Ω 680 Ω 220 Ω 100 Ω
current capacity 13 A 20 A 32 A 63 A
wire cross section 1,5 mm² 2,5 mm² 6 mm² 16 mm²
My gameplan is to signal to the charging station to limit current to 32A max (most are already limited to 30A) via the proximity signal, full bridge rectify that AC power to
340Vdc, add HVC circuitry (thanks to Fechter) and fuses before stuffing the power into the battery pack. What I need to verify with the engineers is:
1. That the charge station will indeed limit the current to 32A max without shutting down if my Bike tries to draw more current.
2. That the charging station won't shutdown if it is already maxed out at 30A and I request via the proxminty signal 32A.
3. That the rectified DC power acts as a current source much like a 'Freddie Charger'.
4. Charge station max output is 32A at 240Vdc or 7.7KW. Rectified DC output is 340V - 80V (appox pack voltage) or 260V. 260V/7.7KW is about 29.5A avg charging current.
If the above is true then a 30A charger could be built for less than $200. Add the $120 adapter cable and you have a small, lightweight, inexpensive charger that could be very attractive to the EV marketplace.
Hmm, on the above charger idea, the avg current would only be about 22.4A as the current is only flowing when the full wave rectified voltage is above pack voltage or about 76% of the time. On the GBS 40AH cells, GBS recommends a charging current from 12A to 32A with an ideal rate of 20A. So the ~29A pulses and ~22A avg current should be a good fit for these batteries. It still would give me a 2.5 times improvement over the 9A charger that came with the bike.
This all sounds very interesting. Keep us posted! :-)
Update - over 5100 miles and still rides great.