Acmotor is the pioneer here!Hemonster wrote: 5/
My battery protection circuit will be similar to acmotor's, utilising configurable zener shunts to set voltage limits and an equalisation shunt. The voltage limits will trigger a warning line that is optically isolated back to the controller, and also a dash light so I can see when it happens.
We're also considering monitoring - basically, being able to read the voltage or temperature of any cell. That likely requires a microcontroller per BMS board, which I am not particularly in favour of. I'll actually consider a PWM-analogue solution with shift registers to implement a crude "addressing mechanism".I am also considering a voltage monitoring system per 48V block - not sure yet.
That should work, though the inrush current of 13 chargers connecting at the same instant might be a bit fearsome, depending on their input circuit. They are only ~70W output, so even 13 of them, even if not "power factor corrected", should still be OK from a 10A outlet.6/
Charging is going to be done per 48V module, utilising the gs battery charger (at this stage anyway). These are 48V 5A chargers that will be ganged up at the AC input side, so that each battery module has a dedicated charger.
Edit: oops, factor of 4 out. Each charger is about 300 W output, so up to 500 VA input; even 11 of these would be over 5 kVA, more than a 15A outlet.
I don't see a problem with say 4 chargers on board, more at home where you have a 15 A or 20 A outlet, all in parallel, with all the 48 V nominal groups in parallel (when the contactors separate the groups, of course). The multi-pin connector does this automatically. The lower voltage 48 V groups will hog the current; the higher voltage groups will mark time while the others catch up. The devil is in the low-impedance detail, of course...
Yes, some form of interlock is essential.When the ignition is turned off, I'll have the breakup relays disconnecting the pack into 48V modules. As an added safety, I will disconnect the relays if the charger voltage is detected (probably DC side), so the traction pack will not be enablable when the charger is plugged in.
I'm not so sure any more that this is the best way. I'm liking acmotor's multipin connector idea (but beware of voltage ratings), so each 48 V group can be essentially independent and floating. It probably depends most on what you do for leakage detection.Each module will have a charging fuse and protection diodes (maybe? depends if it upsets the charger or not), ustilising the traction pack return as the common -ve rail for all 48V modules.
You may have noted some lengthy arguments on that topic a month or so ago. I think it starts about here: viewtopic.php?p=8745&t=618#p8745.7/
Safety wise I plan to have two strings of 300Vdc each (about what mains voltage is in NZ), both connect up in series to create the HVDC bus. I'm not sure what to do with the middle point just yet, need advise here.
Weber and I are leaning towards fully floating, and I can't remember if the midpoint is used for the detection or not. Others seem to be adamant that connecting the centre point to chassis is a good idea.
Beware: 250 V x sqrt(2) ~= 350 VDC. If you have 13 12 V nominal batteries in series, that's 780 V at 15 V each (heavy regen or just after equalisation), or an average of 390 V. Even 265 VAC is only 375 V, so if that's the DC-DC's limit, you may have to do something (brake resistor? Controller limit parameter?) to limit the DC bus voltage.8/
There will be two DCDC converters that will go from each 300V string to 13.8V to charge the accessory pack. I plan to use off the shelf AC mains rated DCDC regulators for this - some of which are rated up to 250Vac or higher.
Ok, or you could use a 10" thermatic fan or two, to save power when the motor isn't hot, and really cool it when it is.9/
I plan to use a RPM encoder so that the VFD can operated the in close loop flux vector. For this I will take off the existing plastic fan to attach the encoder directly to the shaft. I'll replace the fan with 120mm PC fans instead which will operate at all times the ignition enables the accessory line.