What Is Real World Amp Draw?

[doubledipsoon]

You approach a BBSHD-driven mountain bike on a windless day in the flatlands and wonder if you'll make a 20 mile round trip to nowhereland. OK, you don't have a shunt hooked up between your 48 volt 13.5 Amp Hour storage Lithium Manganese battery and your 1000 watt finned-cooled Bafang, so you can't do a live amp draw reading. You wing it and go anyway. If I were to "CRUISE" to my destination, how many amps would be continuously drawn by a 160 lb. rider doing 20 mph in a gear that would provide optimal "sweet spot" RPM for this particular mid drive motor (2500-3000 rpm??). As you take off, you're haunted by the thought that your 13.5 Amp Hour storage bottle battery isn't quite what your journey had in mind. Should you have opted for the 17.5 Amp Hour Jumbo Shark? Blowing off the anxiety, you hit that dangerous bike path and throttle up. So, what are my chances?

 

[billvon]

Per Justin's sim, that would take about 350 watts on the flats. At 48 volts that's ~8 amps. I assume you can take it from there.

 

[motomech]

You approach a BBSHD-driven mountain bike on a windless day in the flatlands and wonder if you'll make a 20 mile round trip to nowhereland. OK, you don't have a shunt hooked up between your 48 volt 13.5 Amp Hour storage Lithium Manganese battery and your 1000 watt finned-cooled Bafang, so you can't do a live amp draw reading. You wing it and go anyway. If I were to "CRUISE" to my destination, how many amps would be continuously drawn by a 160 lb. rider doing 20 mph in a gear that would provide optimal "sweet spot" RPM for this particular mid drive motor (2500-3000 rpm??). As you take off, you're haunted by the thought that your 13.5 Amp Hour storage bottle battery isn't quite what your journey had in mind. Should you have opted for the 17.5 Amp Hour Jumbo Shark? Blowing off the anxiety, you hit that dangerous bike path and throttle up. So, what are my chances?

Who are you talking to?
When my enquiring mind needs to know, I temporarily install one of those cheap internal shunt mini-Volt/Amp meters avail. on Ebay. Don't even need to test ride, just spin the whl up(off the ground) w/ max throttle and grab the brake at the same time. The Current will spike and that is your max Amps.
If you pull more Amps than what your batt. is rated for, it will shut down.

 

[doubledipsoon]

billvon, that's great news- sounds like I can do over an hour's worth of "flatland windless cruising" with a 13.5 AH storage battery with a BBSHD. Thanks!

 

[spinningmagnets]

I have regularly gotten an hours worth of riding from a 17-Ah pack using a stock BBSHD without hitting LVC. Relatively flat land, but I am 200-lb (with a 40-lb child onboard?), my riding posture is non-aero and It's sometimes windy. YMMV

 

[doubledipsoon]

Great news, SpinningMagnets! OK, whether to fork out another $200 for a 17.5 AH Jumbo Shark or opt for the 13.5 Bottle Battery, that is the question. Anyone else out there have first hand experience with BBSHD amp burn/AH battery storage ratios?

 

[broke]

I have a
48v pf pack shark
48v ga pack shark
52v jumbo pack
I use the pf pack the most I run my hd at 25amps charge to 53v.
Pf 10 miles 45v to 46v resting
GA 10 miles to 45v to 46 resting
Jumbo shark. Is ok just heavy on my bike to only pull 30amps. And hard to mount. Both packs sag around 4v still looking for a light batt.(shark pack size) I can pull 40amps from. No lipo been there...
Most days I rip around throttle only.
Sometimes I use my right hand as my peddle assist
If I need to ride longer.