How to correctly estimate range and maximum power

Hi,

Theres still two bits of a maths / logic that I haven't got my head around.

1. I have a 48v 18.4aH battery and a Q128C + 17a controller. Whats the logic to work out far roughly range I have? The LCD3 display shows current output so I know that much?

2. How do you know the max power a motor can take? Is it just a case of common knowledge or is there some logic? My Q128c is 500w and the controller can output roughly 800w. I've seen the display show nearly a thousound though when testing PAS level 5 + throttle, is this pushing the controller and motor too far?

Range is going to depend on a few factors, mainly how fast you're going. Also tire width/pressure/tread type, and rider weight/position (Upright vs recumbent).

All that being said, my consumption is about 20Wh per mile, at a touch over 20 mph. That's on 2" road tread tires at 50 psi, 180lb rider in upright position, so fairly typical I'd say.

The motor's watt rating is a continuous rating, it can handle peaks substantially higher than 500W, but running continuously over could result in it heating up.

Too much heating up and bad things happen, but as long as you're not cruising at over 500W for long periods of time don't worry about it. If you are running over 500 continuous you might still be fine, but you'll want to monitor the temperature. Some motors can handle substantially more than their rated power.

dustNbone said:

Range is going to depend on a few factors, mainly how fast you're going. Also tire width/pressure/tread type, and rider weight/position (Upright vs recumbent).

All that being said, my consumption is about 20Wh per mile, at a touch over 20 mph. That's on 2" road tread tires at 50 psi, 180lb rider in upright position, so fairly typical I'd say.

The motor's watt rating is a continuous rating, it can handle peaks substantially higher than 500W, but running continuously over could result in it heating up.

Too much heating up and bad things happen, but as long as you're not cruising at over 500W for long periods of time don't worry about it. If you are running over 500 continuous you might still be fine, but you'll want to monitor the temperature. Some motors can handle substantially more than their rated power.

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Thanks!

Im 140lb (10st) on a road bike with 23c tyres. How many Wh is there in a 18aH Battery? Or it is not that simple?

EDIT: I Found this site: https://convert-formula.com/ah-wh

I believe I could get around 40 miles minimum depending on speed etc and also not completely blitzing the battery.

Check out the Trip Simulator over on Grin Techs (ebikes.ca) website. Get the specs as close as possible to what bike you have.

For input type, you can change it to Google Maps, and then plan out a route, and it will show you how much power you will use on that route.

So much depends on your ride habits terrain, etc. My experience is that you simply have to establish some benchmarks for yourself, perhaps recording some Wh/mile figures for some rides. Once established, you can extrapolate with some simple math for the distance you intend to go. But in the end it will always be inexact due to changes in wind and changes in your pedal output. For longer trips, you'll want to see if you battery voltages or watt hours drawn are in line with estimates. That way you can slow down to extend your range if necessary.

I've established that my commute rate is about 20-21 Wh/mi - round trip. I tend to go a bit faster when I commute.
My long distance rate is less well established but is probably between 16-18 Wh/mile. I plan to do some test rides soon to better establish that for some trip planning.

When I experimented with a temperature sensor I came to the conclusion that you can overvolt and overamp the motor as much as you would like so long as you keep the motor cool (I cut off at 110 celcius).

-RC hobbyking airplane motors intended for 3s overheat and seemingly run very inefficient (inefficiency in this test defined as how hot it feels on my finger at a given wattage) during this test
-9c style e-bike motors, in my case a MXUS run overvolted seemingly perfectly efficient. Running both on 12s and 18s seems to yield the same efficiency numbers (efficiency this time being defined by wh/mi) but 24s again overheating prematurely similar to the rc airplane motor experiment. I hypothesize that in the specific brand of motor I was using there was some headroom in the "overvolt protection", both 12s and 18s working in my "48 volt" motor but not 24s.

"maximum power" is kinda weird too. My MXUS can withstand 1800watts continuous without overheating if it is running at its near maximum speed and not necessarily under a big load but can overheat with as low as 800 watts when its bogged way down, like when you are going up a long steep hill at a very slow speed with a load of camping gear on the tail.

So to answer you question "how to estimate maximum power" I would say that number would be as hard as you can push your motor before it hits ~100 Celsius.