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

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Dave Ultra   1 µW

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

Post by Dave Ultra » Mar 19 2020 10:12am

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?

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Skaiwerd   100 W

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Re: 7 mile range on new fat-tire bike with Ultra. Am I doing something wrong?

Post by Skaiwerd » Mar 19 2020 10:18am

We’re you riding off road? I’m guessing so. The fat tire will create a lot of rolling resistance and at low pressures even more. Pump up your tires to 30psi and ride on road only and see what happens to your speed and range.

camdon44   1 µW

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Re: 7 mile range on new fat-tire bike with Ultra. Am I doing something wrong?

Post by camdon44 » Mar 29 2020 10:54am

Hi Ultra Dave, I assume you have the F-1000. How have you been doing with the range?? Reports on the Ultra motor seem to be all over the place. I don't understand how different companies with the same motor and similar batteries get so different range and power performances. I don't see Watt Wagons having any issues with their Ultra motors... But, they are about $4K-$5K more than BPM.

Bigwheel   100 W

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Re: 7 mile range on new fat-tire bike with Ultra. Am I doing something wrong?

Post by Bigwheel » Mar 29 2020 11:40am

My first instinct would be to blame the battery not the motor....the higher cost mentioned of the Watt Wagon is partly due to the battery they have speced which costs more to manufacture because it uses higher grade cells and BMS?

High power runs, even with active pedaling, will drain batteries pretty fast anyway but 816wh's in 7 miles is beyond bad....

Check the output of your battery hot off the charger to see if it is even getting a full charge?

Balmorhea   10 kW

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Re: 7 mile range on new fat-tire bike with Ultra. Am I doing something wrong?

Post by Balmorhea » Mar 29 2020 3:47pm

It's your motor getting really hot? If not, I think you have a weak or faulty battery.

flat tire   1 MW

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Re: 7 mile range on new fat-tire bike with Ultra. Am I doing something wrong?

Post by flat tire » Mar 29 2020 5:13pm

Apparently nobody responding to this thread can do simple math.

OP, even with some really conservative calculations on your battery you would need to be consuming almost 100Wh/mile. Now that's just not happening on a fat bike only going 26 mph.

So your battery for one reason or another is probably not offering the capacity stated. If this is not user error or misunderstanding the solution is probably a new battery.

Dave Ultra   1 µW

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Beginner needs help balancing new batteries

Post by Dave Ultra » Apr 04 2020 2:58pm

Hi friends, I have two batteries for my new bike — 48V, 17A Samsung. They don’t run in parallel, only one at a time. Both have the same problem. When they get under 50% on the display, they suddenly start to drop ten or fifteen percentage points at a time, then from 15% or so right to 0%, then, while still putting out low power, the display shows the battery jump back up to 4% or 8% ish. After that the battery might still put out low power for a long time. It might put out low power for an hour while showing 0%, or for an hour while showing 4% the whole time. The bottom line is that I can’t count on these batteries once they get under 50%.
I’ve been trying to fully cycle the batteries and let them stay on the charger for awhile when full. I’ve done that three or four times with each battery and had no improvement. I can’t find beginner’s battery balancing instructions on the web or elsewhere on this site. Can anyone help? Thanks so much!

flat tire   1 MW

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Re: Beginner needs help balancing new batteries

Post by flat tire » Apr 04 2020 3:05pm

How does someone end up with 2 batteries when they could have just gotten one better battery? Who the hell wants to change over, or lug around that spare? Absolutely terrible decision. Your batteries probably are good for scrap anyway if they're that out of balance (assuming this is a balance issue) but to answer your question most BMS balance very slowly so with your level of imbalance you would need to leave the battery plugged in for an extended period, maybe over 24 hours.

hemo   100 W

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Re: Beginner needs help balancing new batteries

Post by hemo » Apr 04 2020 5:54pm

What final voltage or cell group voltage are charging to/trying to achieve ?

john61ct   100 GW

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Re: Beginner needs help balancing new batteries

Post by john61ct » Apr 05 2020 12:23am

Ignore the gas gauge, rarely accurate, at al.

Get a wattmeter that counts coulombs (coulometer), voltmeter and ammeter for amps draw usually included.

Put a known constant load on, say 3A and time precisely how long it takes to drop from fully charged down to say 3.5V.

Get a display that shows the voltage per cell-group so you can understand any balance issues.

Likely you need a (bigger and) higher quality pack, 99% of cheap Chinese stuff is fraudlently sold crap.

But your above tools and knowledge gained will help you make the next one last longer.

Balmorhea   10 kW

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Re: Beginner needs help balancing new batteries

Post by Balmorhea » Apr 06 2020 1:02pm

flat tire wrote:
Apr 04 2020 3:05pm
How does someone end up with 2 batteries when they could have just gotten one better battery? Who the hell wants to change over, or lug around that spare?
I have used 2 frame mounted batteries wired in parallel, to feed a 24V x 30A controller. Didn’t want to build a custom pack and housing for it, and none of the cost-effective 24V options were rated for 30A. My only misgiving about it is that the packs each have their own main power switches, which leaves an opportunity for high current screwups if not used carefully.

I concur that the graphical battery gauge is not useful on most displays. I don’t know whether they’re calibrated for lead batteries, or what else might be the problem, but my usual experience with them is that all the movement in the indicator lies in the last portion of the battery’s capacity. I treat them as a low range warning rather than as state-of-charge.

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