# too many amps



## Rob_of_Waterloo (Nov 2, 2011)

Hi Folks

I recently finished converting a Miata which includes a Soliton controller, WarP11 motor and 64 100AH GBS batteries. The performance is gutless and does not match my calculations. For example. I drawing *150A @ 200V *while driving about 25mph This is about 40hp, when it should be significantly less than 10HP.

I attached a log file from the Soliton. As you can see the Soliton is cutting out; as it should, due to a low pack voltage error. 

https://docs.google.com/spreadsheet/ccc?key=0ArhRFzfrJakRdHZnaHNMYmdXRVFPWjU1cDVTODFaYWc

It is a brand new motor , but I did replace the brushes. The motor was mistakenly shipped with racing brushes.

Any suggests or has anyone experience something similar.

Rob


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## Yabert (Feb 7, 2010)

150A on motor side and 200v on battery side. Pretty commun.
At 25% PWM it's right 10hp

But the low voltage error at only 100-250 battery Amp isn't normal.
Cold temperature?


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## Ziggythewiz (May 16, 2010)

What's the car's weight, and are you in the same gear the whole time?


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## dougingraham (Jul 26, 2011)

Rob_of_Waterloo said:


> I attached a log file from the Soliton. As you can see the Soliton is cutting out; as it should, due to a low pack voltage error


It looks like you have the low voltage limit set to 189v. That would be 2.95 volts per cell. Cells under reasonable load will sag 25% and your initial voltage of 209 sagged to 189 is only 10%. I would set the under load voltage to at least 2.5 volts and possibly as low as 2 volts per cell. This would be what, 160 volts or 128 volts. The way you have it set you are limiting the motor current horribly because of pack voltage sag. And it gets worse when it is colder because the cells sag more. I have 33 cells of the GBS 100 AH cells in my car and it is a pleasure to drive when the cells are 60 degrees F or higher. When it is around freezing the pack voltage sags and the car is gutless. I have decided I need to put in a heater pad under the cells because of this. I will be putting in another 19 cells in a second battery box which will mask my low voltage issue but I still need to do the heater to warm the pack for charging.

Anyway, change your low voltage limit and the car will wake up. Don't worry about the voltage sag. Under load sag will not hurt the cells unless you pull current for so long that they overheat. I've tried to warm the pack when it is cold by pulling 1000 amps and it just doesn't work because I see too much sag and the controller limits the current.

40HP to go at 25mph does seem like quite a lot. Are you sure you were calculating this based on battery volts and battery amps and not mixing the battery volts times motor current?


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## Rob_of_Waterloo (Nov 2, 2011)

Thanks everyone. I received a lot of good points.


Set the low voltage limit lower...maybe around 2.0 v per cell.
Yes the battery are cold, around 40 °F
The weight of the car is not bad, 2680 lbs, only 418 lbs over stock. 
looking at the pack voltage not the motor voltage to calculate HP.
The HP still seems a bit high for the speed I was going. I will take another run with constant speed.

Thanks again.


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## major (Apr 4, 2008)

Rob_of_Waterloo said:


> Thanks everyone. I received a lot of good points.
> 
> 
> Set the low voltage limit lower...maybe around 2.0 v per cell.
> ...


Hey Rob,

I think it is always good to get a baseline. Jack the drive wheels up and power up to the same speedometer mph as you do on the road. See what your motor power is for that no-load test. Also,


> drawing *150A @ 200V *while driving about 25mph


 Is that battery current or motor current? And what gear were you running?

major


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## Tesseract (Sep 27, 2008)

major said:


> ... Also, Is that battery current or motor current? And what gear were you running?
> ...


Here's a random line from the logfile:


```
752600    57.13    362    361    21.6    193    30.4    382    0.24    0.2    0.08    13.32    5    Running
```
Which says that motor current is 361A, duty cycle is 21.6% and battery voltage is 193V. Thus, 15kW.


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## Rob_of_Waterloo (Nov 2, 2011)

Good suggestion on comparing load and no load. I am running in third gear. It is motor current. As Yabert and Doug point out it was Battery voltage not motor voltage. Even after this correction I am still close to 3x off of my predicted power.


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## Tesseract (Sep 27, 2008)

Rob_of_Waterloo said:


> G...Even after this correction I am still close to 3x off of my predicted power.


No you aren't. See my post above. 15kW is entirely reasonable for maintaining 65mph/100kph on a level highway with most cars.

EDIT - sorry, I see you were referring to 25mph, not highway speed. Yes, this is too much power. Perhaps the reason is the transmission oil is too thick because it is cold? Bad alignment? Low tire pressure?


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## jeremyjs (Sep 22, 2010)

Yeah. Have you checked the car out mechanically? The first thing I'd check would be the brakes, the alignment, and tire pressure. All should be easy to check. If a brake pad is dragging it's obvious when the car is in the air and you try and turn it by hand. If it's alignment, depending on how many miles they have you will see uneven wear. You can actually look up the wear pattern online and see more or less which way the alignment is off. Or just take it to a shop. The tire pressure is pretty obvious.


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## Batterypoweredtoad (Feb 5, 2008)

I am not sure how knowledgeable you are with Miatae  so please forgive me if this is stuff you know. Check the rear calipers, they are prone to gumming up the rods they slide on and dragging. Check your bushings, there are something like 24 in the suspension and if it is an early Miata they are likely shot and your tires are all pointing in different directions.


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## dtbaker (Jan 5, 2008)

I am a little curious about what you had to do to get an 11" in there. thinking that possible significant alignment issues in transmission/drivetrain are costing you... If the drivetrain is at a significantly different angle than stock, that might be part of it?

also... amazed you fit 60 x 100ah cells in this wee beasty? where? did you fill the trunk?


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## njloof (Nov 21, 2011)

From having test fit a Warp 11 mockup in a Miata engine compartment, the fit actually isn't too bad, not even the transmission. Not much clearance though...


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## dtbaker (Jan 5, 2008)

njloof said:


> From having test fit a Warp 11 mockup in a Miata engine compartment, the fit actually isn't too bad, not even the transmission. Not much clearance though...



huh, I am a little surprised.... there's not a lot of radial clearance between motor housing and motor mounts, or motor tailshaft and front torsion bar using a 9" motor.

do you have a picture of motor mount? did you cut off tailshaft of motor, or change torsion bar?


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## Rob_of_Waterloo (Nov 2, 2011)

I did some more test today with the car jacked up. The weather prevent any road tests today. 

Yesterday at 25mph I was measuring appox 20HP, which is too high. It should be closer to 5 to 7 hp. Alignment, tire pressure, brakes could account for some loss of power but not the difference between 5 and 20 HP.

Today with no load or the car jack up I was measuring the following at 12 mph
1st gear = 3hp
2 gear = 2.5 hp
3 gear = 1.8 hp
4 gear = 1.4 hp
5 gear = 1.5 hp
neutral = 0.5 hp is 370 w reasonable for no load on the motor ?

It does not *sound *right to me and I think the problem might be between the motor and the transmission. I am using a Rebirth Premium adapter plate and a racing clutch. I am wondering if I could have misaligned something, I can't see how though. I know when I attached the adapter plate to the motor, I had to draw it on via the bolts. Yes I tighten alternating bolts slowly.


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## Ziggythewiz (May 16, 2010)

Rob_of_Waterloo said:


> I know when I attached the adapter plate to the motor, I had to draw it on via the bolts. Yes I tighten alternating bolts slowly.


Bad sign. I started trying to do that on mine, then crunched the numbers and realized the trans shaft + coupler + motor shaft was 1/4" > than bell housing + adapter plate + motor.


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## Rob_of_Waterloo (Nov 2, 2011)

I not sure that is the same issue. When attaching the adapter plate to the motor the bell housing, trans shaft is not in the picture. The rebirth adapter plate has the coupler built in. I think drawing in the adapter plate is ok since you are putting the coupler onto the motor shaft and it is a good fit.


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## Batterypoweredtoad (Feb 5, 2008)

I'm not sure I am describing this right but it seems like drawing the coupler onto the motor shaft using the adapter would end up with a lot of thrust forces on the bearings when you are done.


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## Rob_of_Waterloo (Nov 2, 2011)

If you look at the Premium Rebirth adapter plate, I am not sure there is another way.


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## dtbaker (Jan 5, 2008)

Rob_of_Waterloo said:


> I did some more test today with the car jacked up. The weather prevent any road tests today.
> 
> Yesterday at 25mph I was measuring appox 20HP, which is too high. It should be closer to 5 to 7 hp. Alignment, tire pressure, brakes could account for some loss of power but not the difference between 5 and 20 HP.
> 
> ...



this amount of drag just sounds bad... there MUST be interference, misalignment, or bad bearings somewhere.

In neutral, then load on the motor is just the fan, which would go up with rpm. rather than post the load in hp.... how about if you post the kW showing on your meter at a specific rpm. perhaps someone ele w/ an 11" motor can do the same and that would tell you the MOTOR is 'ok'. Does your metering display kW?

in a specific gear, at the same specific rpm you should see the fan load , plus a *little* from turning all the gears in oil, but really not very much more if the car is up on stands. transmissions are very efficient, so it should hardly be more than when in neutral. I would expect the resistance to go up slightly with each gear as the speed thru the rear diff increase if you bring each up to the same MOTOR rpm (not wheel speed), but again, not much.


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## rwaudio (May 22, 2008)

How are you measuring the power?

Does the car coast well in gear?

Coast well in neutral?

Is there a difference between in gear and neutral?


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## Rob_of_Waterloo (Nov 2, 2011)

The car coast well. All the data is from the Soliton log files. I am not sure where the Soliton measures the voltage and current, so this number might have some efficiency losses. The motor voltage is the pack voltage * PWM. 

Regardless of the Soliton, the motor is still spinning a fly wheel and pressure plate which is 30lbs even when the clutch is engaged. So 300 w does not sound that bad. 

Hopefully I was successful in attaching the graph.


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## Rob_of_Waterloo (Nov 2, 2011)

It was a challenge to fit everything, but it worked out well. I am over due in posting some pictures. I have 20 cells in the spare tire wheel well, another 20 where the gas tank was, 20 in the nose of the car and a lone 4 cells above the motor. The motor was mount using a bracket from CANEV, this bracket was mount right on the cross arm( not sure if that is the correct name).

I did cut the from motor shaft, but that was to clear the front batter pack.


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## davids_rv (Jun 15, 2008)

I'm doing a 2002 Miata with Warp 9, a happy meal from Flying Miata and the Premium Rebirth adapter. I used a wood mallet to tap on the adapter with no problems. I did find that using the stock flywheel bolts, I had to add a washer to prevent the bolts from going to deep and causing interference. Did you run the motor with just the flywheel installed before installing it in the car to see of there was any unusual noise or vibration?


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## dtbaker (Jan 5, 2008)

davids_rv said:


> I'm doing a 2002 Miata with Warp 9, a happy meal from Flying Miata and the Premium Rebirth adapter. I used a wood mallet to tap on the adapter with no problems. I did find that using the stock flywheel bolts, I had to add a washer to prevent the bolts from going to deep and causing interference. Did you run the motor with just the flywheel installed before installing it in the car to see of there was any unusual noise or vibration?


david.... you've been a member since 2008, and this is your first post?! Lets see a build thread on your EV buddy! glad to see another Miata under conversion, and I'm looking for ideas.... How far along is your conversion? specs? etc.


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## davids_rv (Jun 15, 2008)

Yes, I've been lurking for a long time. Finally got started about a month ago. Details in my blog.


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## dtbaker (Jan 5, 2008)

davids_rv said:


> Yes, I've been lurking for a long time. Finally got started about a month ago. Details in my blog.


looks like a great start.... start a build thread! with pix of course. lots of people here are likely to help/comment that might not go off to a separate site/blog to comment. I have found it useful to build and maintain both a personal site/blog and a build thread here on DIY...


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## powerhouse (Apr 1, 2011)

Subscribing to see the outcome of this..


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## Rob_of_Waterloo (Nov 2, 2011)

I updated my parameter in the Soliton and that made a big difference. I collected some data on the road and it seem ok, but not great.

Base on some calculations I figure it takes about 8 hp to drive at 60kph (37 mph) I am measuring about 15 hp. If you want to see my calculations they can be found using this google doc link. 

https://docs.google.com/spreadsheet/ccc?key=0ArhRFzfrJakRdDA3REZTZFplOXplUWVxNVU4U0lodkE


The next step is to get the motor tach input working, so I can get a better graph with speed. Currently the tach input has way too much noise.


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