Hemonster's ACIM conversion

[coulomb]

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.

Acmotor is the pioneer here!

I am also considering a voltage monitoring system per 48V block - not sure yet.

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".

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.

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.

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...

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.

Yes, some form of interlock is essential.

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.

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.

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.

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.
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.

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.

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.

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.

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.

[acmotor]

Hemonster,
Please throw your pics up on this forum so it shows a more complete record of your project. If you use outside links and they get broken then the record is lost for us on this forum.

Weber has covered most of the points
I can only add that both Mal(4x4kiwi) and I run DC-DC pairs up to 750 volts or so and so far they are fine. The main limit seems to be the input caps on the DC-DC at 400V ea. ( I have also removed the VDR out of the DC-DC input stage as this could have a problem with the higher voltage.)

[weber]

Weber has covered most of the points

Hi acmotor,
I'm afraid you're confusing me with my electrostatic analog. It was probably the flux capacitor that did it.

Just so we're clear:
A coulomb (charge) is an amp second or a farad volt or a joule per volt.
A weber   (flux)   is a volt second or a henry amp or a joule per amp.

Hemonster,
You did an awesome job of summarising that huge thread on AC motors. Now here's another one for you (not quite so long) on "To chassis-earth or not to chassis-earth?".

As a relatively low cost learning experience I think your plan is a good one. But I have briefly driven an EV (a LiteAce van) limited to 15 kW and it was not a good experience. You can feel the annoyance of drivers behind you as a palpable radiation, particularly starting off from traffic lights or going up the merest slope. However this was a 4-pole motor with no gearbox, so you may be a little ahead.

However I suspect the weight and volume of the cast-iron motor will mean that your base vehicle will need to be fairly large and heavy, negating any advantage of keeping the gearbox.

[Hemonster]

Ok, some pics here ... though picasa just make it so much easier ... a one by one uploader really can be made better... IMHO It has been an intrepid journey ...

[Hemonster]

Can you tell us a bit about the RVR? I don't think it's a model we see in Australia, at least by that name. What's the kerb weight? Is it a large 4WD?

I imagine that you probably do have such a vehicle in Oz, here is a link for the one I'm potentially interested in.
http://www.trademe.co.nz/Trade-Me-Motor ... 892180.htm

It's the turbo version, and its sort of a hybrid car/van with the back seats seated on sliders and a flat deck (like a van). I wanted to mount the batteries in the centre to rear of the vehicle so its nicely balanced, but may have to cut into the floor to do this - some issues may arise come inspection though.

From what imformation I can acquire so far, it's got a GVM of about 1750kgs and weighs in at 1500kgs. There is a non-turbo version that has a GVM of 1500kgs and 1350kgs kerb. The turbo one may be heavier because the turbo engine may need more metal in it? If that is the case I may be ok for weight - whatever it is, I'm going to find it difficult to hide 360kgs of GS batteries. My calcs place me at:

Motor: 150kgs (with flange fitted)
Controller: 40kgs (for the higher performance one, the one I have now is 30kgs)
Batteries: 360kgs
Misc: 50kgs
----
Total main parts: 600kgs (ouch!)

Estimated engine weight: 200 kgs (optimistic)
Estimated other weights: 80 kgs (optimistic?)

Total parts removed: 280 kgs
Net gain to vehicle: 320 kgs

Neither of the RVR types have a GVM to kerb difference in that region. So I don't think this is a suitable vehicle to convert unless I:
- change to a 4-pole and direct drive the drive/tail shaft only, throw the engine and gearbox out as you clever folks have done
- get a much lighter motor
- get lighter batteries! (even EVPST 12AHr cells are too dear at NZD$10K for 220 cells at the moment, --- oh why can't these be cheaper!), this really is the crux of the weight issue.

I think ideally I need something like a 7 seater and remove two seats - a chariot for instance has a GVM-kerb of 500kgs, this should be ample for 4 people and the conversion as long as I get a lighter motor.

That's some 12 kWh nominal, but with lead, that will translate to a lot less than 12 kWh usable at EV discharge rates. So range won't be fantastic, but I agree it's a good starter pack, and more in keeping with the cost of the other components.

Actually after peukert corrections, its more like 12AHr cells at 7-8kw average power requirements to push a 1500 kgs vehicle at 50-60km/hr. So at 80% DOD I'm looking at really only a 5.8kwh pack, which really is quite measly - even for one of the better rated AGMs out there. There certainly are huge advantages to getting LiFePO4 cells.

[Hemonster]

I'll actually consider a PWM-analogue solution with shift registers to implement a crude "addressing mechanism".

Hmm ... interesting, can you expand on this idea for my clarity, or point me to the thread?

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.

Can I ask how you arrive to 500VA?

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.

It certainly reduces wiring But yes I do see your point about floating each 48V module, fewer paths for runaway electrons to take.

Another thing I thought was using a DPDT (or DPST) for each of the charger's two terminals, the coils get energised by the charger voltage itself (via some voltage reduction). These only need to be 60V 8-10A rated and should be relatively cheap?


QUOTE=coulomb]
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.
[/quote]

I think you mean 26x 12V nominal cells in series?

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.

Is a thermatic fan a thermally activated fan?




[/quote]

[Hemonster]

( I have also removed the VDR out of the DC-DC input stage as this could have a problem with the higher voltage.)

What is a VDR?

[Hemonster]

Hemonster,
You did an awesome job of summarising that huge thread on AC motors. Now here's another one for you (not quite so long) on "To chassis-earth or not to chassis-earth?".

You've now committed me to more reading ... , oh well I had to do it anyway, will be reading it soon then.

As a relatively low cost learning experience I think your plan is a good one. But I have briefly driven an EV (a LiteAce van) limited to 15 kW and it was not a good experience. You can feel the annoyance of drivers behind you as a palpable radiation, particularly starting off from traffic lights or going up the merest slope. However this was a 4-pole motor with no gearbox, so you may be a little ahead.

Understood. The controller I have in variable torque mode can take up to 46A for 60s maximum, 600V bus is 27.6kw - but even this I think will still be very sluggish for direct drive, perhaps ok with gearbox. Weight is the key issue with acceleration, and I have real weight issues ... my conversion needs an atkins diet

[weber]

What is a VDR?

Voltage Dependent Resistor, more often known as a MOV or Metal Oxide Varistor.

[woody]

for reference, the 1200cc, 800kg cortina ICE is 90Nm / 36kW, it is OK in traffic, but only sounds fast because of the noise 0-100 in 26s. A 1600kg bus will be more leisurely.
Your Motor should be ~150Nm peak, probably close to original, but you'll hit your 15kW mark at around 1000 rpm, 26 at 1600, so a flat power curve from 1600 to 4000. Gear change to keep inside that range.
The cheapest lithium I've seen is Optimum (see other thread) which squeak in under AU$5k for 224 x 8 Ah cells and will do 75kW according to specs.

For a vehicle, can you get something like a datsun 1200 ute - lots of load capacity but not much weight?

Cheers,
Woody

[coulomb]

Can I ask how you arrive to 500VA?

Yes, you can.

Oh, more?

48 V nominal battery, charges to 58.something, call it 60 V. Five amps times 60 V is 300 W. About 80% efficient at full load, so that's 300/0.8 ~= 375 W going in. It probably won't be "power factor corrected", so the input current waveform will be far from a sine wave, call it an effective power factor of 0.75. So 375W / 0.75 = 500 VA.

I'm a bit hazy as to why the current rating goes up due to the shape of the current waveform; I guess the breaker might respond to average current, whereas power comes from RMS current. Feel free to shoot me down here, guys, or at least educate me. I realise it's not actually power factor, since the current is about in phase with the voltage (there is a spike of current every peak of the voltage waveform).

So that 500VA calculation is really rough, and as has been pointed out, it probably won't supply maximum current for too long... but it might.

Have a look at the specs for some cheap chargers; you may be surprised at how much current they are rated at drawing from the mains.

Another thing I thought was using a DPDT (or DPST) for each of the charger's two terminals, the coils get energised by the charger voltage itself (via some voltage reduction). These only need to be 60V 8-10A rated and should be relatively cheap?

Err, not if I understand you correctly. If the other end of the relay has pack voltage, then although it won't have to break pack voltage, it will have to withstand pack voltage while the vehicle is running, and not flash over.

I think you mean 26x 12V nominal cells in series?

Yeah, another factor of 4 again, I think. Hopefully you get the idea: you'll probably get away with it, but it's pretty close with 13 groups of 48 V.

Is a thermatic fan a thermally activated fan?

Yes, that's what I meant.

[woody]

OK, hemonster, I plugged your motor and a lenze 9327 (16kW drive with 50% boost) into my spreadsheet with Mal's Hilux as a base (1520kg).
0-60kph in 18s using the gearbox is way better than 26 seconds direct drive.

400m in 29 seconds (Gearbox) 35 (direct drive)

A 15kW controller can probably only give 48A which is only 98Nm with your motor.

Scratch what I said about the flat power curve, you don't get to 26kW with this motor.

A bigger controller will get direct drive close (1-2 secs) to the gearbox times, but not improve the gearbox times.

In a light car (Cortina) with lithium (920kg) all up, 0-60 in 12 seconds (direct drive), 8 seconds (gearbox) is looking better for the not so patient.

[acmotor]

The store of energy and the cutting force. Makes sense !

Yep, a MOV is a type of VDR that clamps voltage spikes.
The one on my DC-DCs was spec'd to clamp at 275VAC (380VDC).
If these devices turn on then they don't let go until voltage drops well down. Bad news on DC ! Fine on AC. I considered it tempting fate to leave it in.

Hemonster, I would not underestimate the 0-40kmph acceleration of your proposed setup. I would predict it to be quite satisfactory. It will be the higher speeds where performance will fall short. By then you will have the EV bug and a good stepping stone.

Keep the weight under control though.

Hey, thermally cued air mass flow turbine if you don't mind !

Re DC-DC (SMPS) power factor.
It's all about the harmonics of the load i.e. not simple 50Hz sine wave. There is power in the odd harmonics 1,3,5 etc and these are seen by the circuit breaker or fuse as more than the basic kW. A good SMPS input circuit can improve (reduce) the harmonics and improve power factor (closer to 1) so VA is closer to Watts. Input inductors in the SMPS being the simplest (passive) way.
Sorry, that probably makes it less clear !

[weber]

The store of energy and the cutting force. Makes sense !

Very clever. Actually the relationship between coulomb and weber is fairly symmetrical. For a capacitor, voltage is force-like (called electro-motive force EMF) and stored energy is volts times coulombs. For an inductor, current is force-like (called magneto-motive force MMF) and stored energy is amps times webers.

[Edit: Tried to make it clearer that I was playing along with acmotor's double meaning. Sigh.]

[acmotor]

I was summing up the MX5 duo !

The symmetry is in the electrons. However the magnetism remains unexplained, like gravity. We have formulas that's all.
As I ask people, what is the speed of a gravity wave ? Think carefully now.   

[coulomb]

[coulomb] I'll actually consider a PWM-analogue solution with shift registers to implement a crude "addressing mechanism".

Hmm ... interesting, can you expand on this idea for my clarity, or point me to the thread?

Not yet. It's still all in my head. But I have some basic ideas which I'll post in the homemade BMS thread.

[Hemonster]

Do you mean like a VCO that transmits at a different freq for each 48V module unto a single wire bus? ie. Each 48V module transmits using a different carrier frequency - using tuned LC filters on the receive side you can then decode what each of the modules is saying, even if they are all transmitting simultaneously?

[coulomb]

Intriguing idea. But no, per Weber's idea started about here:

viewtopic.php?t=900&p=11259#p11259

[Nutz]

Hi there I found a couple of similar vehicles on EV Album
http://www.evalbum.com/1949
http://www.evalbum.com/1864
http://www.evalbum.com/1166
The eagle summit is a strange creature, not quite RVR not Quite Chariot(Nimbus in AUS. Spacewagon some countries)

[Hemonster]

Hi Nuts,

Thanks for the links, these do indeed appear to be the same cars ... but as I suspected they are HEAVY beasts! averaging >1700kgs and losing the back seats ... not really my style - I've got kids after all and I want us to enjoy the car as a family.

I have since found that the Mitsi Chariot is likely a better candidate if considering AGM SLAs. This is because kerb to GVM difference is 670kgs, compared to the RVR which is 520kgs (comparing 1999 space runner/wagon equivalant UK models in the workshop manual). That's a whopping extra 150kgs it can carry, but it is a bigger vehicle and weighs in at 1500kgs (instead of the 1300 kgs the space runner weighs, non-turbo).

Being a 7 seater, you just have to remove the back seats and now you have a large station wagon, with a flat deck at the back ... the way I wanted to do it was to cut holes in the floor and sink the battery box in, externally vent it, which means it is not considered "inside" the passenger compartment (higher holding force required for certification). However cutting into the floor of the vehicle needs to be done carefully and with full blessing of the certifier - so it may complicate things. Here is an example of this car.

I'm starting to lean towards EVPST 12AHr cells like Woody, it will cost the bulk of my conversion budget, and then some But I think it is the better choice because I am then much more free to choose what vehicle I want using a cheaper/heavier motor and controller and not be too fussed. This is provided the cells don't die prematurely - that would be baaad! Optimum is cheaper but C discharge rating/AHr is less also, though only slightly. Their 10AHr cyclindrical comes close, but doesn't have nice and easy bolt on screw terminals.

Woody (or anybody), did you get some of these EVPST cells for testing?

Has anybody tried the BMI cells?

[Hemonster]

Hi Coulomb,

Thanks for the reply.

Another thing I thought was using a DPDT (or DPST) for each of the charger's two terminals, the coils get energised by the charger voltage itself (via some voltage reduction). These only need to be 60V 8-10A rated and should be relatively cheap?

Err, not if I understand you correctly. If the other end of the relay has pack voltage, then although it won't have to break pack voltage, it will have to withstand pack voltage while the vehicle is running, and not flash over.

I'm not sure I understand. As the suggested charger relay terminals will go across each 48V battery module terminals, why does it need to be rated for the entire pack voltage? Would not an 60-80V rated relay do the job? I was thinking these would be cheaper because their current rating can be much lower, say 5A DC.

[coulomb]

Sorry. As long as the chargers can withstand full pack voltage, that should be OK. Not sure what I was thinking there.

And of course you need one charger per 48 V module/group, and need to run all of them at once.

[Hemonster]

Hemonster, I would not underestimate the 0-40kmph acceleration of your proposed setup. I would predict it to be quite satisfactory. It will be the higher speeds where performance will fall short. By then you will have the EV bug and a good stepping stone.

It would seem like top end speed is the bug bear for most of the AC conversions I've seen so far - surely with a 2 pole things would improve as you only start getting a dropoff in torque at higher revs? Of course without the gearbox things would seem sluggish on the low end torque, but then again with a big enough controller, my 2-pole will give me 150Nm of torque, that's still pretty decent at low revs isn't it? (say with a 3.5:1 diff?) Isn't this around what a ICE typically gives out peak anyway?

Keep the weight under control though.

It's had one too many donuts
But a point you made earlier about dropping the motor weight being relatively insiginificant (to the weight of the car) is quite true. When you have 350kgs of battery to reckon with, even a 100kg drop in motor/gearbox setup may only just get you within GVM (with 320kgs worth of passengers), and even then only on a select few cars. The battery IS the bug bear no matter what the conversion is, DC or AC ... and more to the point, PbA is where the optimisation really needs to happen. That's why I'm coming round to the idea that I will need to spend money on the battery if I'm to get not only decent power to weight for the car, but also better pack ageing, better Wh/km and hence better range. That's a lot of plusses ...

[Electrocycle]

Of course without the gearbox things would seem sluggish on the low end torque, but then again with a big enough controller, my 2-pole will give me 150Nm of torque, that's still pretty decent at low revs isn't it? (say with a 3.5:1 diff?) Isn't this around what a ICE typically gives out peak anyway?

yep, that's close to the peak torque of a <2L 4 cylinder engine, but don't forget that'd be like taking off in 4th gear.
1st would usually give you another 3:1 reduction.

[Hemonster]

Ahh true true ...