Looking for input on my first Ebike build and questions about battery range/usage

General Discussion about electric bicycles.
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pmuhob   1 µW

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Looking for input on my first Ebike build and questions about battery range/usage

Post by pmuhob » Mar 19 2020 2:46pm

Looking at the following motor/battery/bike for my build. I already own the bike:

[48v 1000w front hub motor][https://www.amazon.com/ebikeling-Waterp ... 594&sr=8-3]

[48v 14ah battery][https://www.amazon.com/dp/B082HWM883/?c ... _lig_dp_it]

[a bike][https://www.dickssportinggoods.com/p/ni ... lsrc=aw.ds]

Going with the front hub and mid mount battery since I either carry stuff on my rear mount, or have a child carrier with my cycling buddy tagging along. I chose the 1000w motor due to the extra weight (I weigh 235 lbs, not to mention the previously mentioned cargo). I am curious if I will experience any drag from the motor when pedaling unassisted. It's my understanding that gearless hub motors have no drag. Can anyone confirm?

I have also been trying to research power usage and potential range with these components. I found the formula for watt-hours and calculated 48v*14ah=672 wh. given the 20wh per mile figure [on this site][https://www.electricbike.com/watt-hours/], I am assuming potentially 33 miles on a full charge (pedal assist probably). I live in a flat area with no hills, unless you count the mississippi river levee. I also assume with a lower speed limit range is also extended (14mph vs 20mph). Can anyone comment on this math and logic?

Again any input is appreciated.

markz   100 GW

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Re: Looking for input on my first Ebike build and questions about battery range/usage

Post by markz » Mar 19 2020 3:15pm

GearLESS hub motors do have drag when no power is applied.
Its the geared motors that do not have drag.




https://www.ebikes.ca/learn/batteries.html
Motor Type Rough energy usage
Minimal Assist (using motor only on hills, slower ~30kph setup) 6-8 Wh/km
Typical Assist (~40 kph with pedaling, motor on all the time) 9-12 Wh/km
Power Hungry (either no pedaling, or hauling a load, or going really fast) 14-20 Wh/km

flat tire   1 MW

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Re: Looking for input on my first Ebike build and questions about battery range/usage

Post by flat tire » Mar 19 2020 3:39pm

Your motor will have minimal drag, just the friction from the bearings. Inertia of the spinning motor mass resists changes in speed, but not a big thing. Especially since your motor will probably be spinning under at least partial electrical power any time you're accelerating. Gearless is the way to go. Smooth and silent. Sounds like you have a good handle on the build.

Yes, going slower like you mentioned will extend range. An important note on your battery capacity calculation is that you should not use full capacity of the battery, more like 85% if you want longevity. And on top of this, the full capacity of the battery will naturally drop off with age and charge / discharge cycles.

With that in mind, it makes sense to plan for some capacity in reserve. Always get the battery you want, not one that's a compromise because a compromised battery is still expensive and only takes money away from the good battery you could have had. And it'll be with you for a while.

Finally, for pedal assist riding you want torque sensing. It is that much better than cadence-based. So keep that in mind whether for this build or a future upgrade.

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dogman dan   100 GW

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Re: Looking for input on my first Ebike build and questions about battery range/usage

Post by dogman dan » Mar 20 2020 7:29am

Just a tiny tickle of the throttle makes the drag of a direct drive motor go away. Uses so little energy, it does not reduce your range. Its just not that much drag.

However, most will choose to at least use enough throttle, to make the bike feel light again. Your kit and battery will weigh 30 pounds or so, so a 100 watts to the motor at least, to make the bike feel like it has no motor. Then it pedals like before the conversion, but it takes 100w of your battery power to feel like that again.

For a 500 watt hour battery, (48v 10 amp hours size) you could ride like that 5 hours. Or 3 hours, and have enough battery capacity left to still have assist on a big hill.

Typical use is more like 500w, to go 20 mph, and then your ride would end in one hour, for a 500 wh battery. For that reason, a 48v 15 ah battery, or even 20 ah, is good so you have as long a ride as you like. No fun to have to turn to home too soon.


Riding full speed, uses up the battery fast. But a 48v 20 ah battery will still go an hour using 1000 watts, since it has 1000 watt hours. Amp hours x voltage is watt hours.

MikeSSS   100 W

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Re: Looking for input on my first Ebike build and questions about battery range/usage

Post by MikeSSS » Mar 20 2020 3:08pm

I've been riding a front direct drive front hub motor ebike since 2014, first two years on a 36v lead acid battery, the last four years on a 48v, 14Ah, shark case Lithium battery, 13s, 4p, Panasonic GA 18650 cells. My ride is using almost the same setup you are planning.

Dog Man Dan nailed it, a little throttle overcomes direct drive drag when coasting and a bit more throttle makes the bike feel light, like a non ebike. When I ride my wife's gear drive front hub bike, it is possible to notice less drag when coasting but it's not a significant difference, mostly because I use a bit of throttle on the direct drive bike.

Battery capacity has not declined much in four years of use. But, I charge to 4.0 volts per cell, that is 52.1 volts for the battery, versus 4.2 volts per cell which would be 54.6 volts resting at the battery, for a full charge. I limit discharge resting voltage to 3.5 volts per cell, which is 45.5 volts for the battery. This shark pack battery, similar to the link you posted, is carried in a rear bag on top of the rack. The down tube mount looks way to weak for years of use, to me. Next battery will not use the shark pack, which is heavy and is not actually used. Panniers on the side of the rear rack can carry the battery much lower than atop the rear rack.

Range depends on speed, pedal effort and hills or not. Distance this year so far is 700 miles and I've been keeping pretty good voltage initial, voltage final and recharge time data. The charger is set for 3 amps charge rate and is turning off at 53.3 volts which gives 52.1 volts resting at the battery. Because the charger is not fully charging, it is not doing cell balancing, which would make the charge time vs amps data to be inaccurate, because of the amp and volt titration during cell balancing.

Yesterday I rode 29 miles at 12.5 mph average, but most riding was in the 13.5 to 14.5 mph range. Voltage initial was 52.1v, voltage final was 46.1v, so the battery was within the voltage spread I like, calculated maximum range was 31.2 miles based on Vi = 52.1v and Vf = 45.5v. Faster riding, seeing 16 to 19.5 mph on the speedometer results in a calculated maximum range of 22 miles or a bit more. Usually I limit range on this battery to 22 miles and use a second battery for the last 12 miles of a 34 mile ride.

I ride sitting upright, this gives less range than riding leaning forward or riding on the aero bars.

Front hub motor: I'm reluctant to use one on a front suspension fork, steel rigid forks have always been used. Rigid forks give harsh shocks into the handle bars, next time I'll use a rear hub motor on a full suspension bike. Suspension seatpost is a great thing. Even a little bit of suspension removes a lot of shock through the saddle.

Thumb throttle gave me a lot of pain for the first two or three years of use. A twist throttle would not do that and besides it works the same way as the scooters and motorcycle. Thumb throttle on the right and front and rear shifting on the left is my choice. A grip shift from the right side works just fine on the left. A left side thumb shifter or grip shifter, for the front, can be farther down the handlebars.

My wife and I don't use dashboard displays or voltage LEDs. They would be nice but cost extra in most cases, though I'd like to have them.

Hope this helps, keep us posted on what you are thinking, considering and what you do.

Best wishes,

Mike S

MikeSSS   100 W

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Re: Looking for input on my first Ebike build and questions about battery range/usage

Post by MikeSSS » Mar 20 2020 5:44pm

Forgot some numbers, this is for 282 miles of careful record keeping.

Average miles per 1 volt drop, dV, is 3.57 miles per volt. This is voltage for the "48" volt pack. Starting voltage is 52.1 volts, lowest comfortable voltage is 45.5 volts.

Maximum comfortable voltage drop would be 52.1v - 45.5v = 6.6v.

Maximum average miles range, based on 282 miles of data is, 3.57 mi/v * 6.6v = 23.6mi

Average recharge watt hours are 237wh. Rated battery capacity is 648wh.

Average % watt hours, from recharge data, is 237wh / 648wh * 100 = 36.6%.

Conclusion, my average battery energy use, in watt hours, is 36.6%. This includes some long rides and many 5 mile grocery rides.

And, this use fits with the general electric vehicle rule of thumb, use only 40% of total battery capacity. Use the energy stored between 40% and 80% charge.

Were bicyclists, we pedal, even when we have a motor.

markz   100 GW

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Re: Looking for input on my first Ebike build and questions about battery range/usage

Post by markz » Mar 20 2020 7:57pm

You can save money on brake pads by going Direct Drive and using e-brake/regen braking. Some posted that they hardly ever use their brake pads. I go through a ton of brake pads, need to replace mine today but both stores was closed, MEC (due to virus) and LBS (due to hours, was 6pm).

Edit: Forgot to mention too that regen can add 5-10% back into the battery. Justin LeMore got 12% back riding around Calgary AB on his cross counntry trip. I believe mountains were 30%.

bakaneko   100 W

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Re: Looking for input on my first Ebike build and questions about battery range/usage

Post by bakaneko » Mar 21 2020 8:16am

pmuhob wrote:
Mar 19 2020 2:46pm

Again any input is appreciated.
- Your kit has variable PAS so you can set it at level 1 which is like 50W I think and that will basically make the bike frictionless and remove the small resistance from the direct gearless hub

- You need to tell us your desired speed and range for battery size; its like trying to give you an estimate for a car when you just say a "fast one"

- Your terrain is perfect for an ebike though imo wind resistance is greater than a normal hilly terrain; Im in WI and its kinda hilly some places but we get a strong westerly most of the time; it saps power like no other

- Below 20mph, rolling resistance is more a factor than wind (not from actual wind) resistance so you gotta factor in your weight.

- With front hub, you need to pedal a bit more to help it off the line or I think with your weight you will spin the front tires and lose efficiency not a big deal.

- Don't smash the batteries or they will get fooked. Keep it at 50% or less max power and they will last for a long time; that also factors into your speed and range

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