Voltron-Evo; jonescg's new electric race bike

Post by **jonescg** » Wed, 18 Jun 2014, 00:16

This is the current setup for the High Voltage PCB. The precharge relay and the main contactor are activated by the inverter.

The idea was that as the power was shut off, all of the isolating contactors open and the NC pole would complete the discharge circuit. It relied on the precharge relay remaining on as long as the main contactor was on. On the first time I turned it off, there must have been an arc carry across, as the relay internals were vaporised, the trace was vaporised and the very expensive 200 A fuses in my battery pack blew. At least they did their job superbly. Easy fix, but expensive.

So this circuit was not going to work. I have since removed the discharge circuit (NC pole to the battery negative of the shunt) by grinding the trace off - net result is a bike that works safely and discharges fully in 2.5 minutes. Now in the exceedingly unlikely instance that the bike is crashed, the rider is pinned and the inverter's DC bus connection is doubly severed, there is a risk that the capacitors will still store a lethal jolt, for about 2 minutes anyway.

How should I safely discharge the capacitors in under 5 seconds when the E-stop is hit(cutting power to all contactors and the inverter) WITHOUT adding new and exciting failure modes involving fire and sparks?

A separate relay and resistor across the switched terminals of the main pack voltage could work, but it would rely on there being an NC pole to do this, and the relay would need to be held NO whenever the main contactor is closed. This won't help, however, as the precharge and main contactor relays are managed by the inverter. As the inverter tries to precharge, it now has a 50 W load on it, so it will never reach full charge on the caps and won't turn on.

I just don't like putting things across the terminals of a battery if they add to the risk of a short and fire. Any other ideas?

Post by **weber** » Wed, 18 Jun 2014, 02:45

This old thread may be of interest.
viewtopic.php?title=precharge-postdischarge&t=2715

and this one
viewtopic.php?title=split-pack-battery- ... 202#p40203

What happened to "software which allows the inverter to discharge itself by turning itself on while the main contactor is open"?
viewtopic.php?title=split-pack-battery- ... 202#p40227

Post by **jonescg** » Wed, 18 Jun 2014, 03:56

Yeah the DPDT high voltage relay in my original drawings was too big to fit in this application, and it too relied on the precharge relay remaining energised while the bike was on. Ian's original post was full of issues too, most of which can be dealt with using appropriately rated parts, but in the end, something needs to be done for this bike to pass electrical scrutineering. If there was a prescription for the problem, as there is for lockwiring brake parts, rounding edges and catch-trays in bellypans etc, surely there could be one for electric bikes. I'm at a loss as to how I should do this without making things needlessly dangerous for myself.

Post by **weber** » Wed, 18 Jun 2014, 04:22

According to the online manual, the precharge output from the inverter can be made to stay on while the inverter is on. You just need to set Precharge_Output to 1.
See bottom of page 38:
https://app.box.com/shared/jqr2e8x17h/1 ... 24798119/1

However, it must already be doing this, otherwise your resistors would be fried. And when I look at the parameter dump you sent me, I find this parameter doesn't exist.

But there is a far more interesting parameter in the dump, that is not in the manual: Discharge_Enable. I'm guessing if you set this to 1 your troubles will be over.

This is presumably the "software which allows the inverter to discharge itself by turning itself on while the main contactor is open", that you mentioned here:
viewtopic.php?title=split-pack-battery- ... 202#p40227

Post by **jonescg** » Wed, 18 Jun 2014, 04:33

I have set it to 1 and even tried 2, but it still only discharges during a fault state. Just turning the bike off doesn't constitute a fault state. I'd hoped that it was a more convenient option, but dissipating energy in caps can be a risky process, and understandably the manufacturer would prefer you didn't discharge them rapidly.

The precharge_output is set to 1, yes.

Indeed the inverter needs to be powered in order to do the discharge, but my e-stop cuts power to all contactors by means of interrupting the key switch supply. It also means the inverter will lose power. As the batteries would present the far greater hazard, it makes sense to use the e-stop to isolate them as a priority. Any other ideas?

Post by **weber** » Wed, 18 Jun 2014, 05:08

jonescg wrote:A separate relay and resistor across the switched terminals of the main pack voltage could work, but it would rely on there being an NC pole to do this, and the relay would need to be held NO whenever the main contactor is closed. This won't help, however, as the precharge and main contactor relays are managed by the inverter. As the inverter tries to precharge, it now has a 50 W load on it, so it will never reach full charge on the caps and won't turn on.

I can't make any sense of this. If you have a separate relay with a NC contact in series with resistor across the inverter's hazardous voltage input terminals, and you connect its coil in parallel with the coil of the precharge contactor (which has a NO contact in series with its resistor) so both are driven by the inverter, how could this ever present a load during precharge?

That's just what you have here, which would have worked fine, except using two single-pole relays instead of double-pole relay.

But if you couldn't fit a double-pole relay, how can you fit two single-pole relays?

Post by **jonescg** » Wed, 18 Jun 2014, 05:35

weber wrote:I can't make any sense of this. If you have a separate relay with a NC contact in series with resistor across the inverter's hazardous voltage input terminals, and you connect its coil in parallel with the coil of the precharge contactor (which has a NO contact in series with its resistor) so both are driven by the inverter, how could this ever present a load during precharge?

That's just what you have here, which would have worked fine, except using two single-pole relays instead of double-pole relay.

Sorry I was thinking about putting the discharge relay coil in parallel with the main contactor. It could go in parallel with the precharge relay, but you would have to set the precharge_output to 0 so that it stayed on as long as the main contactor was on. I think the only reason Rinehart suggests you don't do this is because there's a chance it might stay on. If the auxiliary battery is low, the main contactor will drop out but the rest will stay on. I assume the precharge relay would drop out too.

If the discharge relay was powered by the same supply as the main contactor, it would remain in the discharge state while the precharge relay is initially activated. This would serve to remove the charge which is supposed to be slowly charging the caps, so there's a chance it won't every fully charge the caps.

I'm mostly just throwing ideas out there, some of which may not make sense...

Post by **weber** » Wed, 18 Jun 2014, 05:36

That high voltage relay shouldn't have done that. Can you point us to a datasheet?

You could probably get by with the single relay if you just have separate resistors.

        main  
  _______/ _____
 |    |     |   |
 |   Rpre   |   |
 |    | ____|   |
bat    / pre   inv
 |    |         |
 |   Rdis       |
 |____|_________|

Post by **jonescg** » Wed, 18 Jun 2014, 05:40

Sure - it's the GH3-12 V coil from Gigavac. http://www.gigavac.com/pdf/ds/hv/gh1_3_5.pdf

Post by **weber** » Wed, 18 Jun 2014, 06:05

jonescg wrote:Sorry I was thinking about putting the discharge relay coil in parallel with the main contactor.

Ah. I agree that won't work.

It could go in parallel with the precharge relay, but you would have to set the precharge_output to 0 so that it stayed on as long as the main contactor was on.

You haven't been getting much sleep, have you?

To make precharge stay on as long as the main contactor is on, you set Precharge_Output to 1. That's what you have now. That's what you want.

I think the only reason Rinehart suggests you don't do this is because there's a chance it might stay on. If the auxiliary battery is low, the main contactor will drop out but the rest will stay on. I assume the precharge relay would drop out too.

Yes. They don't recommend it because some fault might cause the main contactor to drop out while precharge is still on. This would result in burning out your precharge resistor. But I don't see that you have any choice. I don't think it's a fire hazard, but to be sure, you could try blowing one deliberately, off the bike, with fire extinguisher and kill switch in hand, and face protection, to see what happens. It may result in charring of the polycarbonate it's mounted on, and the resistor exploding and blowing conductive bits all over the place.

OK. Maybe you do have a choice.

Take the diode-OR of both the main and precharge outputs from the inverter and use this to drive a separate discharge relay with NC contact and separate resistor. Assuming you can fit them.

Post by **weber** » Wed, 18 Jun 2014, 06:42

jonescg wrote: Sure - it's the GH3-12 V coil from Gigavac. http://www.gigavac.com/pdf/ds/hv/gh1_3_5.pdf

On reading those specs, I really don't understand why it failed in that way, in that circuit. But given your description of the failure, it must have arced over between NO and NC, and I agree we shouldn't have battery voltage directly across any terminals on the same relay. Either use a single relay with the resistors between battery and relay, or better still, separate relays and resistors for charge and discharge.

Me sleep now.

Post by **jonescg** » Wed, 18 Jun 2014, 16:35

OK so it looks like the best option would be to put the COM pole of a SPDT relay on the inverter side of the main contactor, and have the NC pole go to a 2500 ohm power resistor. The other side of the discharge power resistor would go to the shunt. This should discharge the caps to below 50 V in 4 seconds. The coil of said relay would be wired in parallel with the precharge relay output from the inverter, and the precharge relay output must be set to 1 so that the precharge relay is always on as long as the main contactor is on.

A possible failure mode is that the operator forgets to check the EEPROM setting and allows the discharge resistor to be permantnely across the high voltage terminals. There's 200 W worth of heat there. Should be set and forget, but being human, one can forget before setting.

I still don't know where I'm going to fit these components...

Post by **weber** » Wed, 18 Jun 2014, 16:41

Now that Chris Brune has directed me to the separate manual

for the Discharge Enabled parameter, I see that setting it to 2 should do what you want, with no extra discharge relay or resistor required. You just need to rewire your emergency stop switch so it does not interrupt 12 V power to the inverter. It only needs to interrupt 12 V power to the coils of your half-pack and quarter-pack contactors.

This is definitely allowed by the TTXGP rules. See rules 24 and 25.

At the end of rule 24 it explicitly states: "Low power accumulators provided for low voltage circuits, for example auxiliary circuits, do not have to be isolated by the general circuit breaker and Emergency Stops, provided that they are completely isolated from the main power accumulators."

In other words, the 12 V battery does not have to be isolated by the Emergency Stop, provided the HazV battery is floating with respect to chassis (and hence 12 V).

Turning off 12 V power to the half and quarter contactors will most definitely "interrupt ALL electrical transmission between the [HazV] accumulators and the energy consumers" and will most definitely "include isolation of pre-charge circuitry".

Problem solved.

Post by **jonescg** » Wed, 18 Jun 2014, 16:47

I thought the same thing, except this would discharge the inverter in 9 seconds. TTXGP rules want 5 seconds

Post by **Johny** » Wed, 18 Jun 2014, 16:49

jonescg wrote: I thought the same thing, except this would discharge the inverter in 9 seconds. TTXGP rules want 5 seconds

No, it reads like 9 seconds is a failsafe. If the voltage hasn't dropped below 50V in 9 seconds it shuts off the self discharge to protect itself.

[ Edited Coulomb: repaired smiley in preparation for phpBB transfer ]

Post by **weber** » Wed, 18 Jun 2014, 16:58

I agree with Johny. Try it and see how long it actually takes.

Post by **jonescg** » Wed, 18 Jun 2014, 17:00

Ah OK.

Well in any case, re-wiring the e-stop to suit the above mentioned option would not be a trivial job on my bike. The battery pack needs unswitched and switched 12 V supplied to it, so I would be needing to interrupt the switched supply to the battery, but not to the inverter...

I suspect I will have to devise a power resistor and (appropriately rated) relay. A PTC resistor could be a safer way of doing it over a regular resistor. If it does get hot it self-regulates the current so it never gets too hot.

Post by **weber** » Wed, 18 Jun 2014, 17:31

jonescg wrote: OK so it looks like the best option would be to put the COM pole of a SPDT relay on the inverter side of the main contactor, and have the NC pole go to a 2500 ohm power resistor. The other side of the discharge power resistor would go to the shunt. This should discharge the caps to below 50 V in 4 seconds.

All good so far. Except for a terminology quibble. That should be "COM terminal" and "NC terminal". All three terminals constitute one "pole".

The coil of said relay would be wired in parallel with the precharge relay output from the inverter, and the precharge relay output must be set to 1 so that the precharge relay is always on as long as the main contactor is on.

A possible failure mode is that the operator forgets to check the EEPROM setting and allows the discharge resistor to be permantnely across the high voltage terminals. There's 200 W worth of heat there. Should be set and forget, but being human, one can forget before setting.

No. If you go this route you will use two 3 amp diodes; one from the precharge drive output and one from the main drive output, so the discharge relay operates when either of those operate. That way it won't matter about the setting of the Precharge_Output parameter.

I still don't know where I'm going to fit these components...

I still think rewiring the e-stop will be simpler.

Post by **weber** » Wed, 18 Jun 2014, 17:49

I have no idea how the e-stop is presently wired, but here's a method that should be fairly quick and easy irrespective of that. It can be tidied up later when you have more time. It requires 3 crimp joiners, some cable-ties and a length of twin cable (or two singles) of the same cross-section as those that feed switched 12 V to the battery contactor box and that reach from the battery contactor box to the e-stop.

1. Disconnect the two existing wires from the e-stop and join them together with a crimp joiner, but leave them in place.
2. Cut the switched 12 V wire near where it enters the battery contactor box and join the cut ends to the wires of the new twin with crimp joiners.
3. Run this twin to the e-stop, tying it along a safe route.
4. Connect the twin to the e-stop.

Post by **weber** » Wed, 18 Jun 2014, 18:14

On another matter. Is 25 Nm really the most regen torque you can safely use? If so, I guess I haven't previously appreciated just how little weight is on the rear wheel when braking into a corner. But in that case you should probably reduce the proportion of throttle given over to regen, to more like the 10% suggested by Johny, or less. If you want it to be linear with the motoring torque (no discontinuity in slope -- constant newton-metres per degree of throttle rotation) then regen would need to occupy only about 5% of the range between Accel_Min and Accel_Max, according to the formula for Coast_Hi and Coast_Lo I gave earlier. This would also have the benefit of giving less dead zone on a standing start.

Others have suggested additional regen enabled by the rear brake pedal, but the trouble with that is that without a lot of work to add a variable pressure or position sensor, it is too sudden, either on or off. Sure it can be made to ramp slowly, but that's still outside the control of the rider. At least the throttle regen can be smoothly controlled with no extra work.

Post by **jonescg** » Wed, 18 Jun 2014, 20:05

weber wrote: I have no idea how the e-stop is presently wired, but here's a method that should be fairly quick and easy irrespective of that. It can be tidied up later when you have more time. It requires 3 crimp joiners, some cable-ties and a length of twin cable (or two singles) of the same cross-section as those that feed switched 12 V to the battery contactor box and that reach from the battery contactor box to the e-stop.

1. Disconnect the two existing wires from the e-stop and join them together with a crimp joiner, but leave them in place.
2. Cut the switched 12 V wire near where it enters the battery contactor box and join the cut ends to the wires of the new twin with crimp joiners.
3. Run this twin to the e-stop, tying it along a safe route.
4. Connect the twin to the e-stop.

Sorry in advance if this reply makes little sense - I'm a bit rushed with getting the bike packed and all... but...

Post by **Johny** » Wed, 18 Jun 2014, 20:16

So the PM150DZ already has unswitched +12VDC and is in control of when it switches off it's own 12V supply via J2-15/RLY3.

It kind of looks like it's all setup correctly for the PM150DZ to do the self discharge.

Post by **weber** » Wed, 18 Jun 2014, 21:44

Yep. I'm with Johny on that one too. No e-stop rewiring required. Discharge on e-stop should just happen, provided you have:

Key_Switch_Mode_EEPROM                ,      1  
Precharge_Bypassed_EEPROM_(0=N_1=Y)   ,      0  
Discharge_Enable_EEPROM               ,      2

But you say it only happens on faults, not on key off. And yet the Discharge manual says that when discharge is enabled, turning the key off generates a dummy fault called "Discharge Active" to cause the inverter to shut down properly.

And it's hard to see why prematurely losing HazV power should prevent discharge, since this in itself should cause a fault, either overvoltage or undervoltage.

But there's also the requirement that the motor must be turning at less than 75 r/min before discharge will occur, so if you've been testing this on the stand with some throttle applied, it may take quite some time for the back wheel to spin down before discharge can occur. Could that have made you think it wasn't working?

If not, maybe you should run this one by Chris Brune.

Post by **pottz** » Wed, 18 Jun 2014, 22:41

weber wrote: On another matter. Is 25 Nm really the most regen torque you can safely use? If so, I guess I haven't previously appreciated just how little weight is on the rear wheel when braking into a corner.

Yep, if I'm getting it right there will be very little if any at all weight on the rear, it's not uncommon for it to be off the ground. You really just want a settling affect not any actual braking.
Your also correct in making the zone as small as possible, we go straight from 100% throttle to snapping it shut and grabbing the brake as fast as possible. When we get it right we are on the brake right up to the apex where I will want to be off the brake and straight back on the power.
For longer corners having the ability to crack the throttle and controlled the small applications of power is important too.

if your interested and it helps with setup this is what my throttle hand looks like in my ICE bike, skip the first 2min......couple laps: http://youtu.be/NDcrytJtXkg

Post by **weber** » Wed, 18 Jun 2014, 23:41

I asked Chris Brune (Reinhart Motion Systems) why the parameter Precharge_Output_EEPROM_(0=OFF_1=ON) did not appear in the parameter dump [but it appears in the software manual].

Chris Brune wrote:In this version of code(and later) the parameter has been replaced with a parameter called Relay_Output_State_EEPROM_(0=OFF_1=ON), the functionality is described in the firmware release notes. Generally if the fault and OK relay functionality is desired then it should be sent to 0x000c.

The manual doesn't show the latest changes I think.

I believe we do indeed desire the OK relay functionality (so the inverter controls its own 12 V power), so you might try setting

Relay_Output_State_EEPROM_(0=OFF_1=ON),      12

as well as the other parameters and values I listed in my previous message.

If the inverter is prematurely losing 12 V because it is not turning on J2-15/RLY3, that would certainly stop discharge from working with key off or e-stop. Have you seen that relay get turned on?