Watt meter connected to E-skateboard.

I connected a power analyzer, Turnigy watt meter, to my skateboard (Fiik clone). Very interesting. Since Evolve say that many manufacturers motors don't put out as much as they specify, I was not expecting so much from my 600 W motor. So I was a bit surprised that it put out more then double. Max output was 1400 W, with topped up batteries. Top current was slightly more then the 40 amp fuse in series with the batteries. The power analyzer is very fast so the top numbers was measured for a period of under a second. But if I go up a hill on fresh batteries, the motor draw around 1000 W continuously. No wonder the motor gets smoking hot. At full throttle on flat ground at top speed, 23 km/h, the motor draw about 600 W.

Unloaded the SLA battery is about 40 V fully charged to 37 V when its not funny anymore. Under max load it gets down to about 32 V breifly.

The 7 Ah batteries delivers between 3 to 4 Ah useful capacity depending on how much hills I have to climb. Pretty normal for SLA.

The battery delivers around 150 Wh of useful energy, what gets me confused is that I only get about 5 to 6 km on that when riding fairly flat roads. I read here that people use a single 6s 5000 mAh Li-Po battery, which in best case can deliver 120 Wh, and go over 10 miles or 17 km. Yes, my board weight 20 kg and I am about 90 kg. But still strange some can go 17 km on 120 Wh and I only 6 km on 150 Wh?

I consistently get 5-6 miles (~9km) on 6S 5Ah.

It sounds like your board is a little overgeared. I know mine is, and it is not good for it. You want to adjust your gearing such that the current draw is within the manufacturer's specs or you will be cooking your equipment in short order. I would suspect that the degree to which your motor is overgeared (drawing 2.5X its rated current) might contribute to your relatively poor efficiency. Maybe someone more knowledgeable can comment?

Yeah, not too sure on the distance for SLA batteries. I also use Dual motors with 6S 5000mah and get about 6-8 miles under heavy throttle/brake and without heavy throttle/brake should be able to reach 10-12 miles if not a bit more. Which turnigy watt meter did you get? I should definetly get one on my next HK order.

torqueboards said:

Yeah, not too sure on the distance for SLA batteries. I also use Dual motors with 6S 5000mah and get about 6-8 miles under heavy throttle/brake and without heavy throttle/brake should be able to reach 10-12 miles if not a bit more. Which turnigy watt meter did you get? I should definetly get one on my next HK order.

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Good point. My battery pack is LiPo, which I believe has superior discharge characteristics to SLA.

Barndom, if you are getting 3-4Ah out of your battery your 6km doesn't sound unreasonable.

kkEdlund said:

I consistently get 5-6 miles (~9km) on 6S 5Ah.

It sounds like your board is a little overgeared. I know mine is, and it is not good for it. You want to adjust your gearing such that the current draw is within the manufacturer's specs or you will be cooking your equipment in short order. I would suspect that the degree to which your motor is overgeared (drawing 2.5X its rated current) might contribute to your relatively poor efficiency. Maybe someone more knowledgeable can comment?

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It is a comercial board. Gearing, is 16/44 from fabric. The motor seams to have a temp sensor on it. It's a brushed motor but have three cables, two to the poles and one connected to the shell. The top speed is "only" 23 km/h but lower gearing probably woldn't hurt the distance. But the 2.5 x current is for a very short time.

torqueboards said:

Yeah, not too sure on the distance for SLA batteries. I also use Dual motors with 6S 5000mah and get about 6-8 miles under heavy throttle/brake and without heavy throttle/brake should be able to reach 10-12 miles if not a bit more. Which turnigy watt meter did you get? I should definetly get one on my next HK order.

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Since it measures " Wh " the kind of battery shouldn't matter in this case. Besides the weight factor.

This is the watt meter I have. Im very pleased with it. Im curios to see what numbers an E.S. style E-board could display.

kkEdlund said:

. My battery pack is LiPo, which I believe has superior discharge characteristics to SLA.

Barndom, if you are getting 3-4Ah out of your battery your 6km doesn't sound unreasonable.

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Yes, no question Li-Po is superior. But Wh/km should be a measurement for the board efficiency, regardless of battery, or am I missing something? My brushed motor is maybe a lot less efficient than your outrunners. Since it to hot to touch after a session, a lot of energy seams to go out in heat. My 110 mm rubber tyres and low quality bearings togather with the huge weight, paired with crappy pavement with gravel on top maybe have this big impact on the distance? The speed would also be a factor, my everage speed is 10 km/h or 6 mph.

your measurements show the effiency of the brushed motor - outrunners are in another category of efficiency
I would roughly guess than 50% of the power you measure helps keeping the birds warm

made_in_the_alps_legacy said:

your measurements show the effiency of the brushed motor - outrunners are in another category of efficiency
I would roughly guess than 50% of the power you measure helps keeping the birds warm

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Yes, something happens here that is hard to explain otherwise. I was in the belief that a brushed basic motor was 90 % effective and an outrunner about 95 %. Have to rethink i think.

My motor also weights 3 kg. But is 100 kV.

The controller takes aboat 4 W and doesn't get varm at all. With wheel in the air the motor pulls 100 W. Normal?

Hi,Just coming back from a test with the same powermeter as yours connected between the battery and the ESC.

With the wheel in the air :
if I press instantly the throttle from 0 to 100% (increasing speed from 0 to full speed), the peak power consumption is 240W
if I leave the wheel spinning free at 100% throttle (steady speed), the power consumption is 50W

so, your 100W seem OK to me.

Thx.

Yes, about 100 W whith wheel in the air seams ok for my e-board, not too much parasitic drag from the transmission.

On a bit of a side note: I adjust the timing on the motor a good bit of the mark either side, the motor runned smooth on both positions and seamed to rewing faster at one side and accelerating faster on low RPMms on the other. Did these tests whith wheel in the air only. But the power consumption was a whopping 1000 W whith wheel in the air So maybe I can get the no load power consumtion down a hair with fine tuning the timing. But will probably do nothing under load.

What would really be interesting is how far you get on a certain amount of Wh, say f.e. 100 Wh? Or just how many Wh did you use on a measured distace?

You did a very nice board build by the way

Barndom said:

Yes, no question Li-Po is superior. But Wh/km should be a measurement for the board efficiency, regardless of battery, or am I missing something? My brushed motor is maybe a lot less efficient than your outrunners. Since it to hot to touch after a session, a lot of energy seams to go out in heat. My 110 mm rubber tyres and low quality bearings togather with the huge weight, paired with crappy pavement with gravel on top maybe have this big impact on the distance? The speed would also be a factor, my everage speed is 10 km/h or 6 mph.

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No, you're not missing anything. I was just pointing out the obvious, that comparing a 7Ah SLA pack to a 4-5Ah LiPo is not a meaningful comparision. With you getting 3-4Ah from the SLA battery and running ~6km, vs my pulling ~5Ah from a LiPo and getting 8km range it seems like the numbers are similar enough to be believable.

6/4 = 1.5 km/Ah; 8/5 = 1.6km/Ah. Considering that both of us are ballparking numbers, varying design considerations (brushed vs brushless, gearing optimization, rider weight, etc) I don't think your range is all that unreasonable for the amount of power you have available.

However, now I reread your first post your battery is a much higher voltage than mine. So my reasoning no longer applies. I dunno, maybe brushed motors are really that inefficient? Also, my average speed at ~12mph is nearly double yours. Maybe that affects something?

Exactly, that's why I am focusing on Wh rather than Ah.

I'm planning to change to four 5S, 5000Ah Li-Po battery. Connected 2P 2S, will give me voltage just above what I have now, but hopefully double the range so I can get over the magic 10 km distance. And not at least for the weight reason.

I'll also change one ball bearing that is bad. I opened it and find hair inside cleaned and regreased it but didn't help. So that can give me a few yards more distance :wink:

Barndom said:

What would really be interesting is how far you get on a certain amount of Wh, say f.e. 100 Wh? Or just how many Wh did you use on a measured distace?You did a very nice board build by the way

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Thxs, i measured today a nice 28wh along a 2.8kms ride, means i am around 10wh/km, and eventually 50% (?) more if i ride full throttle, will check and let u know

the logging data for my single drive eboard is as follows :
3000mAh used for 8km and driven for 2x15minutes with only 1 bridge to cross. Average speed = 15km/h
So for the consumed energy this leads to 23x3x2 = 138Wh

pack = 6s 5000mAh

My board weight is only 6.7kg and my weight is 70kg

Maybe usefull for you, see more data in the graph in my thread : http://endless-sphere.com/forums/viewtopic.php?f=35&t=56568&start=75#p866439

regards
Sebastien

made_in_the_alps_legacy said:

Thxs, i measured today a nice 28wh along a 2.8kms ride, means i am around 10wh/km, and eventually 50% (?) more if i ride full throttle, will check and let u know

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Wow, three times more effective the me. I have 30wh/km...

666yeti666 said:

the logging data for my single drive eboard is as follows :
3000mAh used for 8km and driven for 2x15minutes with only 1 bridge to cross. Average speed = 15km/h
So for the consumed energy this leads to 23x3x2 = 138Wh

pack = 6s 5000mAh

My board weight is only 6.7kg and my weight is 70kg

Maybe usefull for you, see more data in the graph in my thread : http://endless-sphere.com/forums/viewtopic.php?f=35&t=56568&start=75#p866439

regards
Sebastien

Click to expand...

Read in your other post. If I understand you correct, you drive 4 km in 15 min, then go back 4 km for 15 min without recharging in between? That would be 23 (voltage) x 3 (Ah) = 69 Wh for 8 km. Wich equates to 8,6 Wh / km. Very good effeciency.

today, I measured a 34.4wh along a 2.3km ride, so 15Wh/km
...riding "quite fast" with a GPS recorded average of 35.4kph on 1km (need to check that again, but fresh battery, Timing test at 18.5°...why not )

Barndom said:

Wow, three times more effective the me. I have 30wh/km...

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seems to potentially indicate that your motor is a twice better heater than mine (the motor temperature was almost at ambiant temperature right after this test )

Yes, but it helps keep my feet warm and I can stop and warm ny hands and fry an egg if I'm hungry :wink:

as hot as swedish girls

Maybe :wink:

Time for an update:

I did changed the bad bearing and allthou the free spinning time of the wheel when spun by hand changed from crappy 5 sec to crappy 10 sec, I did easy go 7 km - about 2 km more then before.

Then I switched the cables to the motor so it now goes backwards with front wheel drive. It did feel smoother, alot more stable and also friskier. The measurements confirms it, I now easiely go 9 km, top speed increased by 4 km/h and I go up a 9 to 10 degree hill all the way wich I before only reach halfway. I suspect there is a better timing when the motor turns the other way.

It have also broken the 10 km distance on a eco driving session allthou it wasn't perfect ecodriving.

In the motor truck one of the axels are crocked, so the wheels have to-in -obviously creating rolling resistant. If this where straight and I had real skate bearings, I would probably go too long :lol:

funny to read that reversing the motordirection leads to such a increase in efficiency, I could not explain this other then that the brushes are mounted in such a way that the motor now spins in the direction it is designed for ?!
Anyway, not bad for such a heavy board + rider.
regards
Sebastien

I think the motor is symmetric in both directions. I had it torn apart some year ago, didn't remember anything that indicate a preferred direction, but I didn't look for it either. There is no arrow on the motor either, which it should have if it was designed for one direction. I still suspect the timing is better in reverse, it is on the neutral mark, which in fact isn't the best for turning in one direction most of the time, but the mark may not be the most exact and I have seen very little movement do a lot for current draw. In practice the timing will never be a perfect neutral, so one of the directions the motor turn is always better than the other. A small bit advanced timing shall be the best. Since it goes so well now I don't want to experiment with it until the season is over. I will measure the current draw at a fixed voltage before I take it apart again.

I was also able to ride to work. It's 8,5 km but uphill all the way, not steep but still uphill.

Another part of maxing the distance on this board is battery management. This means I don't charge it full, just over 37 V so it won't sulfating, until the day I will ride. Then I try to go out as soon it has being charged full and I don't disconnect the charger until I go out. The full charge from a discharged battery seams to fill it up better and also warming it up. So this means I will start charging 3 am for going to work

I while ago I tested the timing. I connected the motor cables to a bench supply with adjustable voltage and ampere. I had the voltage set to a fixed 29.0 V and the ampere set to max. When the timing on the motor is moved the A is affected. The wheel was connected but spinning in the air. The current droped a bit with time at the same timing, espacially at cold start (maybe it was the drivebelt getting softer after a while?) So I tried to do the measurement after the A droppings have settled. The rpm is also affekted by the timing, low rpm at low current values. There is very little movement involved, about +- 3 mm then the bench supply bottoms out at 3 A.

The first thing I did was to read out the A draw I have when the motor was on the factory mark, turning for FWD and proven performence as stated in the post above. This so I could go back to this value after testing. The value was 1.53 A. When the motor was running for RWD at the factory mark the value was 1.40 A.

Now loosing the screws so the timing could be adjusted, finding the lowest value (neutral point) which was 1.39 A. Both FWD and RWD. Marked that point.

I find out that at RWD with the timing at the factory mark it was on the wrong side of the neutral point, the timing was lagging the motors turning direction, something that is always a bad thing (weaker torque and draw more current) for motor use (good for generator use thou). Also confirmed the timing was on the good side (advanced timing) of the neutral point at factory mark with FWD, -hence the significant performence differenche between RWD and FWD.

Driving testing!
Set the value to 1.53A but advanced timing for RWD, the performence was like the FWD at factory mark, confirmed the rotational direction has nothing to do with performence.

Set the value to the lowest value of 1.39A: It was weak and slow.

Set the value to about 2 A: It was fastest and the torque was about the same as on 1.53A position. But at speeds under walking speed it dropped sigificant in torque.

Efficiency test: Set to lowest value of 1.39A it consumed about the same Wh as on 1.53A at a fixed distance with steep hills. But the low value trip took a lot longer time. So distance efficiency was about the same but time wise at draw less per minute in the low value setting. But it was too weak and boring in the low setting.

Conclusion:
The timing has a big impact on the performence of a DC brushed motor. The factory setting may not at all be the best one either fastest or the most effective. In my case the factory setting was lagging, bad for speed AND efficiency. I have marked out the 1.53A settings for advaced timing for RWD on the motor. It seams like 1.53 A is a sweet spot. Much advaced timing ( 2 - 3 A) gives highest top speed but the effiency and low speed grunt goes down.

In theory it could be good to have dynamic timing that adjust to the best value dependent of rpm and load, just like the timing on an ICE. Probably not practical other than big applications which is a saga for the DC brushed motors anyway.