Weber and Coulomb's MX-5

[7circle]

0.72kV is pumping the wheels round.!!
And what's your peak current allowed to get to???

You Whovians need a sonic screw driver to sort out you tricky problems.

Lucky you haven't got a bunch of welded kilovacs $$$$$$$ :phew:

Why wasn't he ignition sense input picking up the loss of power to the relays?

Is it a 6.5mm spade or gage clamp connection?

Such a critically and costly control signal that could be strung with tensional loss to be looked so kindly by Mr Murphy to not have occurred at high probabilities of detaching itself under coulombic transfers of more expected Murphy moments!

(That was my boy wonder replacement for many expletives that I'm sure must have passed through your minds of how lucky you you have been in this learning lesson of life. To the Bat cave in the hills the great gotham Master Weber has disappeared in his Mexy to reguvinate with his family to return one day soon for more fluxing moments.)

This thread should be a comic strip of Weber and Coulomb having adventures with there physically fitting side kicks bound by unwritten laws of the cosmos.

There great great grandchildren will find in the long missing cloud archives of the early 21st century.

7Circles of Tau tripping off to take time tensioning his tempered tantric tampers 'till next time.


:_©©____τ_τ__
: ©©©__ τ_τ_τ_
:_©©____τ_τ__

   

... spelling by poetic licsense

[coulomb]

Also, if the crash sensor opens, this affects the CRASH inputs to the EVCUs, which will drop out of drive mode and switch to OFF mode.

I got the details wrong here, not that it matters a great deal. But to set the record straight, the CRASH inputs are actually not involved here, just a lack of continuity from key on to the diodes and the IGN_RUN input. Also, if CRASH was asserted, it would go into a special crash mode, which is similar to OFF mode, but charging won't be allowed.

[offgridQLD]

Nice to see the MX5 out and about at it's full potential. Looks like you guys are having a real blast.

Me being a data freak. I'm keen to see some of the measurements when you get a chance. 0-100kph times will be very interesting.

I know it's a performance orientated build but efficiency numbers would be interesting to. Particularly the trips up to Maleny via the back roads (same path I take each week in the Imiev) though 105km trip all up for me from The gap to Reesville 12km out of Maleny. I find on the way home there is not much difference in consumption when comparing the freeway or the back roads.40% SOC vs 35% but 1/2hr faster on the freeway. So I settled on back roads up freeway home.

How do you go with motor temps? The climb up the range would be a good test of a (already warm) air cooled motor.

Kurt

[coulomb]

Why wasn't he ignition sense input picking up the loss of power to the relays?

It was; all part of my hurried and imprecise explanation, sorry.

[weber]

0.72kV is pumping the wheels round.!!
And what's your peak current allowed to get to???

We designed the battery pack and its wiring and fusing for 6C which is 240 A. The WaveSculptor DC current limit is still set to 300 A from when we had the half-packs in parallel, but we should back that off to 240 A now. But in fact the highest DC current we've logged is 205 A, with the battery voltage sagging to 632 V. This peak DC power of 130 kW occurred at 5140 r/min. That was at around 90% SoC.

We currently have the motor speed limited to 6500 r/min. We blew any warranty on the (nominally 22 kW 230 V 50 Hz) induction motor as soon as we went over 4500 r/min. But it's so well balanced, it's tempting to let it go out to the 7200 r/min fuel cutoff of the MX-5's original ICE, so MX-5 drivers feel right at home. Besides, that will let me get a 0 to 100 km/h figure without having to change to third gear. 100 km/h is right at 6500 rpm in second.

The existing 0 to 100 km/h logs shows that the optimum motor speed to change from first to second is about 6000 r/min (56 km/h) which is about what we've been doing by "feel". Immediately after such a change (assuming it was instantaneous), the motor should be doing about 3600 r/min, since the ratios of 1st and 2nd are 3.136 and 1.888.

Unfortunately, what the logs show instead is horrendous clutch-slip at about 5400 r/min for about 3 seconds after that gear change. So I'm afraid 0 to 100 km/h times will not be forthcoming until I get that clutch's diaphragm spring stiffened.

Is it a 6.5mm spade or gage clamp connection?

I assume you are asking about the connector on the crash switch. I don't know what a gage clamp connection is. It isn't a 6.5 mm spade. It is something like a 2 mm spade.

Such a critically and costly control signal that could be strung with tensional loss to be looked so kindly by Mr Murphy to not have occurred at high probabilities of detaching itself under coulombic transfers of more expected Murphy moments!

(That was my boy wonder replacement for many expletives that I'm sure must have passed through your minds of how lucky you you have been in this learning lesson of life.

So, 7-Trippy-Tau, I think you're saying we're lucky the dodgy contact on the crash switch connector didn't cause the battery contactors to drop out under maximum load, say 200 A, as Murphy's law decrees.

But when you have eleven (11) EV200 contactors in series, all dropping out at once, it's not really a problem for the contactors, even at 720 V.

[weber]

I know it's a performance orientated build but efficiency numbers would be interesting to. Particularly the trips up to Maleny via the back roads (same path I take each week in the Imiev)...

We'd need to put her on a dyno to get efficiency, but I assume you mean energy consumption. However I have already posted all the necessary info to calculate consumption, so I'm really not sure what you're asking for.

98 km trip via back roads. 720 V 40 Ah battery stores 28.8 kWh. 75% used on trip up. 60% used on trip back. So that's 220 Wh/km on the trip up and 176 Wh/km on the trip back.

How do you go with motor temps? The climb up the range would be a good test of a (already warm) air cooled motor.

That one was answered too, although admittedly it was in a cryptic SMS which Coulomb spotted as a fake from the aliens who abducted me.

The motor only went a little over 100°C. It's allowed to go to 140°C so it was totally not a problem. What limited our speed was that the cells were getting low and so sagging more under load. Our BMS signals the voltage of our lowest-sagging cell to our EVCU 15 times a second. The EVCU runs a PI loop that backs off the WaveSculptor's DC current limit (effectively a power limit) as required to prevent that cell's voltage from going below 2.6 V. Not even Tritium's own BMS does this. In fact I don't know of any other EV conversion that has this fine level of inter-operation between BMS and motor controller. This limited our speed to 74 km/h by the end of the steepest part of the climb. Not a big deal, as the posted limit is 80 km/h anyway.

I said it sends voltage, but really it sends "stress" which can also be due to cell temperature. So it will also prevent any cell from going over 48°C. Few BMS even bother measuring cell temperature, or if they do, it is only one sensor per battery box or per row of cells.

I could tell it was voltage stress because I could see it on the Stress gauge (re-purposed Oil Pressure gauge) and it responded instantly to my right foot, whereas stress due to temperature responds only slowly.

[offgridQLD]

Yes sorry total consumption. Assuming you just did the posted speed limit in each section of the trip you used almost spot on double the consumption of the Imiev. 110whr km going the same way.

Kurt

[T1 Terry]

You may need to change to a 4 puck iron clutch plate to get the grip you require, the lack of asbestos in clutch materials these days presents a real high torque v slip problem that only iron or ceramic clutch facings seem to be able to handle. As clutch slip is not required for a quick launch the higher expense of ceramic flacing is not required. You could use the the old brass button clutch, but if the slip was too much they tend to weld themselves to the flywheel/pressure plate.

T1 Terry

[weber]

Yes sorry total consumption. Assuming you just did the posted speed limit in each section of the trip you used almost spot on double the consumption of the Imiev. 110whr km going the same way.

Yes, posted speed limit, but my accelerations were probably higher.

100% is a big difference. What about the other direction?

So I have to wonder where the energy is all going, with the MX-5. The MX-5's stock drag area is 0.62 m² where the iMiev's is 0.78 m², so that explains nothing. Sure your motor will be more efficient. But my motor can't be that inefficient since the windings run at around 90°C and it is a fully-enclosed motor that is only rammed-air cooled, with lots of obstructions. The WaveSculptor runs at about 40°C, so it's just loafing most of the time.

I do need to buy new tyres and will buy lower rolling-resistance types. Yokohama BluEarth 195/60R14 86H.

MeXy is about 1500 kg with two people. I believe your iMiev would be about 1230 kg with two people.

Of course there is gearbox loss that you don't have. We both have differentials, but I worry that MeXy's may be badly worn, given the noise it makes. And I think I may have significant brake drag on the rear. I should have a play with the adjusters.

Any other ideas, anyone?

[EV2Go]

were the revs flaring to suggest clutch slip?

[weber]

were the revs flaring to suggest clutch slip?

Yes indeed. Here's the rev plot for one 0 to 100 km/h run. I've added the green line showing what I think it should be without the clutch-slip, based on taking the 1st-gear part of the curve for the same rev range and stretching it horizontally by a factor of 1.66 (the ratio between 1st and 2nd).

The horizontal axis numbers are sample numbers. Samples are 0.2 seconds apart. So the green line predicts a 0 to 100 km/h time of 7.5 seconds. Hopefully it will be a little less if I raise the rev limit to 7000. With the limit set at 6500 as it is now, presumably the WaveSculptor has to begin cutting back the torque before it gets to 6500, so by the time it gets there the torque is zero.

[offgridQLD]

Perhaps a combination of factors resulting in comparitavly more consumption. Weight, transmission drag, larger tyres, perhaps driving style ( taking off fast). How about regerative braking (I'm sure the mx5 has it to) the imiev has strong regen that can add up to a reduction in consumption by 10% or so. Perhaps the power steering (clutching at straws with that one)

My trip back (freeway) is usually 95/100whr/km.

Trip up (back roads) is 109 - 115 whr/km .

Based on 40+ trips where I ran data logging.

Kurt

[7circle]

Thanks for the response on the contactors.
If the contactors chattered under high load currents that would be worst for contactors allowing heat and possible melting and fusing. But with SF6 Gas in the KiloVACs the arcing would be suppressed and minimal.
And the battery circuit should not be confused (by me) with the higher inductive path of the motor.
So I can understand that the 720V pack will release less current for same power and with such an accumulated gap of 11 (x2 per Kilovac) contacts the voltage would have hard time jumping those hurdles.

Glad to read the wear is minimal. And chance of having to replace 11 contactors is minor.

So also you have implemented motor power shutdown when "Crash" blocks the pilot relay of the engaging of the battery packs.
I wondered if the connections at the CRASH output may have allowed feedback but not power to the pilot Relay. I've seen some dodgy daisy chained 6.2mm Quick Connects linked up for wire interconects. Sorry "Gage" was meant to be "CAGE CLAMP" style terminals with spring pressure... like in the solar panel thread. But you wrote they are 2mm male/female spade style. So there seems to be two wires twisted and joined into the female crimp terminal side. I wondered if there were two connections.

Also makes me wonder if further protection of the contactors and pre-charge circuit would be a valuable investment with further monitoring of the actual voltage supply to the contactors.

But you have Bus Voltage monitoring by Wavesculpter Controller on Can-Bus and IMU measuring battery half segments and the CMU's adding up to full Cell Voltage.

Monitoring and Alarms can sometimes blow out and cost more than the core functionality. So suggesting even more is worrying.. [:{]

Sometimes just relying on rugged construction is all that is warranted.

Interesting energy consumption rates.

176Wh/km * 85km/hr = 14.96 kW (Mexy down )
220Wh/km * 85km/hr = 18.70 kW (Mexy up )
110Wh/km * 85km/hr = 9.35 kW (ImEIV Up hill )

What else contributes..........
"Any other ideas, anyone"

Charger - (Charger and Cell efficiency is important but not included in the above numbers, so "wall to wheel" would be another comparison to consider"

Battery - Does the Battery segment above the motor get warmer than the others?

Wiring/Contactors -

Heating/AirConPump/Lights/etc - Cosy warm toes are need some times in cool convertible cruising...

Inverter - Water cooled so how do you know if losses are significant. In/Out coolant temps?

Wiring3Phase - When low speed and high torque pushes high currents.

Motor - (100°C may push alot of heatsink power out such a large connected metal area. But clutch may be source nearby missleading thermal status)

Clutch - (There maybe more slip/heat than expected in MeXY)

Gear Box - (not sure of how many shafts are between motor and diff in iMIEV)

Diff/90Spur - Mexy is 90° and iMIEV is //

Wheels -

Brake - Drag ... are they hot?

Cornering/Camber/Toe-In - Handling can prioritize over straight line efficiency for 'fun'

Mass - Up Hill (M.G.H) and Kinetic(M.V²/2) and contribution for Regen
Aero -

Regen -
( Wheels/Diff/GearBox/Clutch/Motor/Inverter/Wiring/Battery)
( These can each have different factors when power flow is in the other direction)

Long list....

Would be interesting to know what the motor draws when on a dyno.
- So when speed is 85km/hr and Motor and Battery currents are as per driving on flat ground the torque can be measured by dyno and mechanical losses determined.

I hope the worn Diff and Clutch (and tyres) are big contributors to the Consumption Figures and can be eliminated with new replacements. For an "easy" fix.

Then you could line up against these three moded MX5's, I wonder what there fuel consumption is ???
http://www.youtube.com/watch?v=lt39DhYBaA0#t=379

Makes me think of Bullets Dyno Setup.
Shown in the Youtube clip is bolts to the wheel axles not to the rubber via flywheel.

7C

[offgridQLD]

85 kph ?

I'm sure the avarage going the back road would be way less than that.

Kurt

[7circle]

The up hill run makes me ponder on the benifits of lighter cars.
176Wh/km * 85km/hr = 14.96 kW (Mexy down )
220Wh/km * 85km/hr = 18.70 kW (Mexy up )
110Wh/km * 85km/hr = 9.35 kW (ImEIV Up hill )
90Wh/km * 85km/hr = 7.65 kW (iMIEV down)

"MeXy is about 1500 kg with two people.
I believe your iMiev would be about 1230 kg with two people."

So at 85km/hr up 350m at 5% grade (rise/slope) = sin(road_angle_to_horizontal)

P = M.g.H / t
or = M.(grade%).g.v for v (m/s) = km/h / 3.6
= 1500kg x 0.05 x 9.8 x 85/3.6
= 17.4kW

for 1230kg P = 14.23kW

The 5% grade looks like a poor guesses for Melany ascent.
appears 3% might be more in line
or my formula is faulty.... most likely.

7c

[offgridQLD]

The Imiev is 1080kg. typically we load it with two adults 75kg - 50kg one child 25kg and luggage on average 25kg. 175kg load + 1080kg = 1255kg.

From just out of Landsborough at the point where the steep climb actually starts to the top of hill (bald knob lookout) is 4.5km total. Broken up into two steep sections of just over 2km each. The sign on the side of the road shows a 12% grade.

The Imiev can do about 100kph up the hill with just 50kw (don't ask me how I know) and it takes 22kw to do a steady 70kph up the steep sections.

EDIT: sorry its actually 32kw to hold a steady 70kph in the steepest sections.

I took a video of the climb. Steady 70kph then nailed it. Though a old ute struggling at 50kph on a blind corner in front of me so that spoiled the fun.

Imiev climb up to hinterland


What tyre pressure do you run? I use 40psi all round for low rolling resistance.

Is there much more wind drag with the soft top down?

Kurt

[coulomb]

Is there much more wind drag with the soft top down?

I have a suspicion that it would add 50% to the load.

Was the top down much of the way?

I think some tests are in order.

[offgridQLD]

I found some data on a cycling forum that listed the Climb from landsborough to bald knob at 4.83km with a average gradient over that distance 7.1%.

Kurt

[weber]

Is there much more wind drag with the soft top down?

I have a suspicion that it would add 50% to the load.

Was the top down much of the way?

I think some tests are in order.

Yes, we went topless all the way to Maleny and had the top up almost all the way home.

But given that it doesn't blow your hat off, and you can carry on a conversation, even at 100 km/h, I don't see how it could add anything like 50% to the drag. The windscreen apparently deflects the air over and around the cabin quite well. But it would add some.

[EV2Go]

Removed due to relevancy.

      

[EV2Go]

removed due to relevancy.

[weber]

Thanks 7circle and offgridQLD for all those suggestions for where the energy is going. Quite a few I hadn't thought of. We'll try to improve this where we can.

Thanks T1 Terry and EV2Go for your clutch suggestions. We already have a 4 puck ceramic that you can see here, from about a year ago:
viewtopic.php?title=weber-and-coulombs- ... 879#p46879

In fact, EV2Go, you helped us decide to get the version with the solid centre.

BTW, there is an in-thread search at the end of the first post of the first page of this thread.

The supplier, 949Racing in the US, claimed it was good for 350 Nm, but it seems it's good for less than 2/3 of that. I notice they don't sell it any more.

EV2Go, your post before-last, while interesting, seems way off-topic to me, not only for this thread, but for this forum, unless you post it in "The Lounge".

[Edit: Changed "your last post" to "your post before-last".]

[EV2Go]

I have a terrible memory so please forgive anything I may say and later forget I posted.

I used the link on the first page and it took me to page 29. I really am crap at searching...

The point of the previous post was to show the point of failure / power level at which time the organic clutch became useless, but since you have moved on from the stocker the point is mute, and I have deleted it.

Back to troubleshooting:
Fortunately being electric you wont be suffering from lack of grip from engine oil dripping onto the clutch plate so we can rule that out completely.

A 4 puck should have sufficient grabbing force to stop any slip, so I can only see it coming down to three possible causes. 1) the pressure plate has insufficient clamping force and 2) the clutch plate is not bedding in properly due lack of scuffing 3) combination of 1 and 2.

If I had to take an educated guess I would probably say the clutch plate hasn't bedded in properly due to the lack of slip i.e. no slipping of the clutch to take off.

While you can take off with it in gear, my suggestion would be to try drive it like a regular car for a while so the pressure plate / clutch plate / flywheel friction surface can properly mate with each other.

[Adverse Effects]

my suggestion would be to try drive it like a regular car for a while so the pressure plate / clutch plate / flywheel friction surface can properly mate with each other.

i agree with that

[weber]

OK. I'll leave the clutch for a while and see if it improves by slipping.

We've just started a new thread for our BMS development, with the latest CMU schematic.

viewtopic.php?title=weber-coulombs-litefyba-bms&t=4302