bz16
100 µW
Hi Endless Sphere, first timer poster and first time builder here. I am planning to electrify my old bike to do long commutes with mostly Grin's parts, but seeing how busy their sales teams are and how (relatively) generic my questions are, I figured asking here would be a bit faster – I plan to get this conversion done in a month so I can use the bike to commute to college! I hope I wouldn't be inundating y'all with too many text at once.
I have a Nishiki Anasazi – they call it a "hybrid bike", which is basically mountain bike frames on road wheels; it came with a front shock and 700x40C tires, and I plan to keep that unchanged. I want to ride the bike up to my local speed limit (28mph, ~45kph, with pedal assist), my one-way commute will be 12mi/21km long with about half up-and-down hilly region and half gentle (~0.5%) and mostly consistent grade. I anticipate I'll have a way to charge my battery before going home, so the battery just needs to last ~15mi or ~25km. I'm about 100kg and I plan to fit the bike with a large cargo rack, so on Grin's trip simulator, I overestimated mass and underestimated human power at 150kg/70W respectively.
At this point I am already pretty much set on the motor and drivetrain: Grin's Rear All-Axle direct-drive hub motor, 52V system, Grin's CA3 and Baserunner with regen braking (more for extra braking force than for energy recapture / ease of maintenance); with this configuration, the Grin trip simulator gives me a maximum battery consumption of ~530Wh (when going home up that gentle slope) and a maximum sustained battery draw of about 1600W – these seems to occur on steeper uphill sections for several minutes at a time, so I imagine me dropping speed and increasing human power should be able to reduce those peaks by a fair amount.
Grin sells a 52V, 14.5Ah nominal battery pack with NCR21700A in 14S3P configuration for about USD$700; using 50.4V as the actual voltage, the pack gives me about 730Wh, which means my 530Wh commute cost is about 73% of the rated capacity; I imagine the 27%, 200Wh reserve would be enough. But Grin's sales just got back with me recommending me their 52V, 20Ah pack (Samsung 35E or Panasonic GA in 14S6P) at a whopping USD$1000. That's... a lot, and also would be double the 530Wh energy expenditure I'm expecting. Granted the total energy used for a round trip is around 900Wh, so with the 20Ah pack I don't need to wait for a full charge at school, but I really don't want to fork over another $300 on top of the already expensive $700 battery budget if I don't have to.
And then I discovered EM3EV: their downtube battery with 35E in 14S5P is rated at 17Ah for only about USD$500, and they have a 14S6P triangle battery rated at 20Ah for USD$570 – still much cheaper than Grin even with the approx. USD$100 shipping added on top. The downside? I would really prefer a downtube battery if it's possible (easier to lug around and charge and less likely to be seen as a home-made bomb), and EM3EV's battery cradle does not have a controller space for Grin's Baserunner. There's also the long shipping time from China.
So, I am just not really sure why the Grin Sales rep recommended a 20Ah battery? I guess it could be concerns over either energy capacity or current draw.
Looking at energy, if my calculation above is correct, then the 14.5Ah battery should be fine in ideal situations and gives me a 27% margin of error – which I think is enough? Or is battery energy calculation not as simple as "multiply voltage by amp-hours"?
Looking at current draw, that 1600W peak translates to just under 32A at 50.4V. There's not a lot of documentations on NCR21700A, but I found some sellers stating its current capability at 10A to 15A per cell; Grin also claims their 14.5Ah pack has a 40A BMS, so it should deliver 32A with no issues. On the other hand, EM3EV claims their 17Ah downtube battery could only do 25A continuous, which would clamp my continuous power below 1260W at 50.4V. Again, the high-power situation occurs for several minutes on uphill sections, so I should be able to mitigate it by dropping the speed and increasing human power, right?
If the 14.5Ah battery will do, I'm willing to get the more expensive Grin battery since mounting the controller under the battery is really the sleekest option – or if someone can point me to some legit US sellers, that would be sweet too; if it's really not adequate, I guess I'll have to go with EM3EV. what do you guys think? Is there more details needed?
Thank you so much for reading my rambling; I hope that wasn't too much! I appreciate any help you can provide.
I have a Nishiki Anasazi – they call it a "hybrid bike", which is basically mountain bike frames on road wheels; it came with a front shock and 700x40C tires, and I plan to keep that unchanged. I want to ride the bike up to my local speed limit (28mph, ~45kph, with pedal assist), my one-way commute will be 12mi/21km long with about half up-and-down hilly region and half gentle (~0.5%) and mostly consistent grade. I anticipate I'll have a way to charge my battery before going home, so the battery just needs to last ~15mi or ~25km. I'm about 100kg and I plan to fit the bike with a large cargo rack, so on Grin's trip simulator, I overestimated mass and underestimated human power at 150kg/70W respectively.
At this point I am already pretty much set on the motor and drivetrain: Grin's Rear All-Axle direct-drive hub motor, 52V system, Grin's CA3 and Baserunner with regen braking (more for extra braking force than for energy recapture / ease of maintenance); with this configuration, the Grin trip simulator gives me a maximum battery consumption of ~530Wh (when going home up that gentle slope) and a maximum sustained battery draw of about 1600W – these seems to occur on steeper uphill sections for several minutes at a time, so I imagine me dropping speed and increasing human power should be able to reduce those peaks by a fair amount.
Grin sells a 52V, 14.5Ah nominal battery pack with NCR21700A in 14S3P configuration for about USD$700; using 50.4V as the actual voltage, the pack gives me about 730Wh, which means my 530Wh commute cost is about 73% of the rated capacity; I imagine the 27%, 200Wh reserve would be enough. But Grin's sales just got back with me recommending me their 52V, 20Ah pack (Samsung 35E or Panasonic GA in 14S6P) at a whopping USD$1000. That's... a lot, and also would be double the 530Wh energy expenditure I'm expecting. Granted the total energy used for a round trip is around 900Wh, so with the 20Ah pack I don't need to wait for a full charge at school, but I really don't want to fork over another $300 on top of the already expensive $700 battery budget if I don't have to.
And then I discovered EM3EV: their downtube battery with 35E in 14S5P is rated at 17Ah for only about USD$500, and they have a 14S6P triangle battery rated at 20Ah for USD$570 – still much cheaper than Grin even with the approx. USD$100 shipping added on top. The downside? I would really prefer a downtube battery if it's possible (easier to lug around and charge and less likely to be seen as a home-made bomb), and EM3EV's battery cradle does not have a controller space for Grin's Baserunner. There's also the long shipping time from China.
So, I am just not really sure why the Grin Sales rep recommended a 20Ah battery? I guess it could be concerns over either energy capacity or current draw.
Looking at energy, if my calculation above is correct, then the 14.5Ah battery should be fine in ideal situations and gives me a 27% margin of error – which I think is enough? Or is battery energy calculation not as simple as "multiply voltage by amp-hours"?
Looking at current draw, that 1600W peak translates to just under 32A at 50.4V. There's not a lot of documentations on NCR21700A, but I found some sellers stating its current capability at 10A to 15A per cell; Grin also claims their 14.5Ah pack has a 40A BMS, so it should deliver 32A with no issues. On the other hand, EM3EV claims their 17Ah downtube battery could only do 25A continuous, which would clamp my continuous power below 1260W at 50.4V. Again, the high-power situation occurs for several minutes on uphill sections, so I should be able to mitigate it by dropping the speed and increasing human power, right?
If the 14.5Ah battery will do, I'm willing to get the more expensive Grin battery since mounting the controller under the battery is really the sleekest option – or if someone can point me to some legit US sellers, that would be sweet too; if it's really not adequate, I guess I'll have to go with EM3EV. what do you guys think? Is there more details needed?
Thank you so much for reading my rambling; I hope that wasn't too much! I appreciate any help you can provide.