Only 7 mile range on new BPM Ultra fat-tire bike. Am I doing something wrong?

I just took my first ride on my new BPM fat-tire (4 inch) with Ultra motor. It’s as fast as I hoped (26 mph on flat with throttle only). But the battery is draining rapidly. I rode it 7 miles on highest level assist, pedaling the whole way without throttle, on mostly flat ground and drained almost the entire battery (48v, 17a). I weigh 225 pounds. Am I doing something wrong or is this what I should expect?
 

TMH

Well-Known Member
Probably not doing anything 'wrong'. BPM seems to indicate a minimum range of ~31 miles for their fat bikes with 17 AH batteries, on highest level of assist. While you didn't really seem to use pedal assist ("throttle only"), and assuming that their range tests were done under more ideal conditions and with a lighter weight rider - and assuming that maybe they inflate the numbers a bit for marketing purposes - maybe the bike's real range with a heavier rider in non-ideal test conditions and with no pedal assist is half of what they say, or about 15.5 miles. Note also that their range tests may be done at a much lower riding speed. Anything above 20 mph really seems to cause almost exponential increases in air resistance, and will drain any bike's battery a lot faster. Maybe their range estimate is based on a 10 mph riding speed?

But it seems that you are getting only half of what is perhaps a more real world range, so a few things could be going on. First, ride the same route maybe 3-4 more times after fully charging the battery, and see if the range starts improving. Also try your route with some pedaling assist, and at speeds below 20 mph and see what range you get.

But then again your bike also could just have a bad battery or some other electrical issues going on.
 

TMH

Well-Known Member
speed plus weight plus huge tires plus max assist are going to be real battery eaters.
Yes, or to maybe make my point above in a different way... Think of yourself as a "Marketeer" for an e-bike company, who wants to paint the most favorable picture of their bike against the competition. They will optimize their testing to show the best results. Anything you are doing differently from the list below will reduce your bike's range in the real world, some items drastically.

Optimal performance test criteria:
1) Small, light rider;
2) Smooth and clean paved riding surface;
3) Flat terrain;
4) No wind;
5) Tires inflated to maximum pressure;
6) Low speed;
7) Moderate rider pedal input;
8) No accessories on bike which would cause aerodynamic drag;
9) Cherry-picked battery pack;
10) Battery pack ridden until totally empty.

And there may be other 'optimizations' used.

Also, while not specifically e-bike related, I have some extensive experience with Lithium batteries from flying drones. Some brand new packs don't perform to their greatest capacity until after (sometimes) up to 10 discharge/charge cycles.
 

fooferdoggie

Well-Known Member
yes plus you need to ride and see what happens with different settings. my bosch bike I find I cna ride at 20+ mph for about 22 miles with ups and downs at full assist. but the miles start going up with less and less assist at the same speeds.
 

Mike_V

Active Member
Dave,
You describe pedaling on level ground for about 20 minutes depleting a 17 AH battery.
That seems really bad, did you call BPM tech support?
EX: I get +20 miles riding in cold weather for hours on BPM F-35MX with Samsung 14AH & 750W Bafang hub motor.
( & Still have 'two - three bars' to spare afterwards )
Mike
 

FlatSix911

Well-Known Member
I just took my first ride on my new BPM fat-tire (4 inch) with Ultra motor. It’s as fast as I hoped (26 mph on flat with throttle only). But the battery is draining rapidly. I rode it 7 miles on highest level assist, pedaling the whole way without throttle, on mostly flat ground and drained almost the entire battery (48v, 17a). I weigh 225 pounds. Am I doing something wrong or is this what I should expect?

Congrats on your new eBike. What tire pressure are you running... I would recommend inflating your tires to the maximum PSI found on the tire sidewall.
Experiment with the pressure to achieve maximum range... you can even exceed the recommend ratings by 10% without any issues. Good luck. YMMV ;)
 

baxterblack

Member
I just took my first ride on my new BPM fat-tire (4 inch) with Ultra motor. It’s as fast as I hoped (26 mph on flat with throttle only). But the battery is draining rapidly. I rode it 7 miles on highest level assist, pedaling the whole way without throttle, on mostly flat ground and drained almost the entire battery (48v, 17a). I weigh 225 pounds. Am I doing something wrong or is this what I should expect?
I'm 225 - Haibike full fat 6 seven 4 inch tires also ,and ave 40+ miles with 20% battery remaining
 

TomD

Well-Known Member
Seems quite low. Eco or sport? From one of the reviews on the BPM site:

It allows you to switch between 5 levels of pedal assist, but there is also sport and eco modes with 5 levels each so it’s more like 10 levels. I tend to ride it around Florida (flat roads) in pedal assist 5 in eco mode and that allows me to easily cruise around 20mph without having to pedal hard while still getting good range (30+ miles). I’m sure you could get much farther in the lower pas modes
 
My second battery did better — it got 20 miles, though it slowed a LOT As the charge got low.
BPM said that I should cycle the battery a few times and that will help. My question:
When cycling the new battery these first few times should I discharge it all the way or leave some charge in it?
 

TomD

Well-Known Member
Electric bikes are not motorbikes.

^penis envy

though it slowed a LOT As the charge got low.

This may help, per the same review...

Whenever I get a small hill or want a little boost I’ll switch to sport mode and the thing just takes off, getting to 30mph plus pretty quickly. In sport mode when you get below 50% battery, it will sometimes cut the power way down to like 500w. I would assume this has to do with the lower voltage as the battery drains and what you are trying to demand. If you leave it in eco mode though (even at level 5), it will more consistently pull up to 1000w well below 50% battery level and doesn’t cut the power at all. (I’ve run it down below 20% before charging and it never cut out.
 

smorgasbord

Well-Known Member
My second battery did better — it got 20 miles, though it slowed a LOT As the charge got low.
BPM said that I should cycle the battery a few times and that will help. My question:
When cycling the new battery these first few times should I discharge it all the way or leave some charge in it?

First, charging the battery all the way and letting it sit for 30 minutes or so is good to do a few times early on, as sitting at full is when the BMS (Battery Management System) balances the cells. A balanced battery will hold more charge. After doing this, say, a half dozen times, then I recommend not charging all the way, or at least not charging all the way until you're ready to ride. This isn't always practical, I know, especially since you apparently need all the range you can get. Again, it's true that batteries will do better after a few full charges.

As for cycling the battery, do not discharge it all the way - ever. If you're at one (out of 5) bars, try to get it on the charger ASAP. Hopefully the bike has circuitry to detect and prevent the battery from being drained too low, but...