Battery Efficiency Question 56v vs 32v

avoleoo

10 W
Joined
Feb 12, 2014
Messages
87
Location
West Palm Beach, FL
Allright having a problem here. Two bikes, two different voltage batteries, both ridden the same.

The bike with 56v system averages 18wh/m
The bike with 32v system averages 30wh/m

Am I missing something why there is such a difference?

Bike one: Mac 10T in 26" | 15A max | 56v, 8AH = averages 18wh/m @ 20mph
Bike two: Polaris Vector 26", geared and direct drive in one motor, rated at 450w | 32v, 15AH = averages 30wh/m @ 20mph
street tires on both, both roll well and no issues can be found.

Charge capacities measured with iCharger and Cycle Analyst, so very legit.

Just not getting the difference, is there anything wrong with Polaris or it is voltage that makes it so inefficient?
 
avoleoo said:
Allright having a problem here. Two bikes, two different voltage batteries, both ridden the same.

The bike with 56v system averages 18wh/m
The bike with 32v system averages 30wh/m

Am I missing something why there is such a difference?

Bike one: Mac 10T in 26" | 15A max | 56v, 8AH = averages 18wh/m @ 20mph
Bike two: Polaris Vector, geared and direct drive in one motor, rated at 450w | 32v, 15AH = averages 30wh/m @ 20mph

Charge capacities measured with iCharger and Cycle Analyst, so very legit.

Just not getting the difference, is there anything wrong with Polaris?
++subed.

The answers to this one will be very interesting to follow.

(Questions: what are the top speeds of both bikes? Is the test route very hilly? Is there a net elevation gain?)
 
Completely flat ! all pavement, both ridden at 20mph.

Top speeds:
bike 1: 35mph
bike 2: 20mph limited by factory, so I don't know the wind count of the motor, but feels like it could go way faster. Maybe around 260 - 320.
 
Sounds like the Polaris has a problem.

15wh/m to 20wh/m is a normal range for most ebikes at 20mph average. Anything higher than 20, and you probably have an issue.

try this simulator. Use thee throttle slider to set the speed, and you can see the constant wh/m used at speed on the right, labled as "Consumption". that will be lower than your average, of course, but gives a good ballpark number to work from.
http://www.ebikes.ca/tools/simulator.html?bopen=false&axis=mph&blue=Lbs&throt=99&motor=MG310_STD
 
Yup, I understand that. Let's assume the issue is within the bike, what could be wrong with it? Heck its production bike and Polaris is bragging about it being very efficient in their videos.

It is using direct drive part of the motor while going at 20mph, and if it's very high wind motor, could it be that it's that much inefficient that it's using extra power just to maintain 20mph?
 
Nope, CA is on bike one, which has MAC 10T
Bike two - Polaris, I can only measure what I have used by charging back the battery with iCharger and noting Ah.
 
avoleoo said:
Completely flat ! all pavement, both ridden at 20mph.

Top speeds:
bike 1: 35mph
bike 2: 20mph limited by factory, so I don't know the wind count of the motor, but feels like it could go way faster. Maybe around 260 - 320.

Maybe it has something to do with how you are riding the Polaris and this:
BioSync cadence sensor can detect gear shifting using an internal pulley, it uses this information to provide slow torque in low “climbing” gears and high speed in high “fast” gears


(Pure speculation based on the quote above.)

The only thing that comes to mind as a way for providing "slow torque" and "high speed" from a direct drive hub, is if they are switching between Wye and Delta.

If you aren't using the gears as intended -- eg. if you are staying in high gear all the time and letting the motor make up the difference; or maybe the sensor is broken -- then it may result in using the "wrong mode" some or all of the time and thus running it at less than best efficiency?
 
Allright, turns out my riding style and the way I use Polaris was the problem. I'm used to use throttle on MAC 10T bike, however, Polaris is just very inefficient with it having a small DD motor. If I do pedal assist only on Polaris, all the readings are good 18wh/m same route and conditions, but as soon as I start using thumb throttle to help acceleration or even pedal with pedal assist + throttle these numbers just go way up. Polaris has two full size 9 fet controllers inside, most likely one for DD and other for geared part of the motor, go figure out. So I may as well just eliminate that sucker.
 
Hello Folks.

I might be able to contribute something.

I just finished a MAC Build.

12t Motor, 24" Alex Rim, Maxxis Hookworm tyres.

Singlespeed in effect, 11t rear cog, 48t front.

16s 8Ah Multistar. So that's around 62v

6 Fet Cellman Infineon, Sensored.

There is no dragging on the brakes. The tyres are hard. I weigh 250lbs.

The stats are alarming.

This thing pulls 5000w if I go WOT.

It does around 4 Amps NO-LOAD draw on max-speed setting.

It drinks Watts for fun. I did 4 miles of hard ripping and with some pedalling at that and it took up 4Ah of juice.

The chain is set up so that I work hard with the motor. In lowest power setting, I can pedal hard and keep the watts as low as 150-250w.

But...if I give it the whip, it thinks nothing of using 3000w up a hill.

This will probably break the motor.

The system is efficient in that a blip on the throttle at low power allows for constant cruising with pedal work.

But it is inefficient as it sort of lurches in power once you move on to Medium and High settings, even with pedalling it's hard to keep it down to around 1000w.

Very impressed by el cheapo multistars. Seem happy to give me 60 Amps even though people here feel they are a 2c battery at best.
 
IMO, unless you pedal like a pro racer, 20-22 wh/mi is more typical for 20 mph cruise. Then more wh/mi, the more starts and stops you have.

First thing, your experiment has about 6 variables, instead of one. So its not science. You need to wattmeter both bikes, and if not the same watt meter, then you need to make sure they calibrate the same.

30 wh/mi IS a lot for 20 mph, but not if its a strong motor pulling hard on lots of starts and stops. I've seen motor wind affect wh/mi up to 20% with a stop every block, but yours is worse.

If possible, repeat the test with less variables. Watt meter on the charger is fine, if both charge on the same charger. Otherwise, set up the CA for stand alone, and run it on both bikes.

Eliminate all other variables, take the starts and stops out of the test for the first comparison if at all possible, and ride a square route, that means that whatever direction the wind is, the test has all 4 compass directions. Ride when the temp and the wind is the same. And best you can, ride similarly, pedaling just as hard each test, in the SAME gear ratio. Hills will matter less than you think, if you ride up and down them in the test. But the best baseline is flat and cruising no stops.

When I finally got as many varaibles as I could out of it, similar weight and areo bikes got the same wh/mi, even with huge differences in voltage and motor type and wind.

Once rolling, I was pulling a very consistent 20 mph wh/mi. For my minimal pedaling effort, around 20-22wh/mi on "regular" bikes. Much worse though for heavy cargo bikes with shitty areo.

It still could be something wrong with your polaris. One bad contact on a battery wire for example. Or a shunt dying in a controller.
 
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