Battery Voltage and Motor choices

Total noob to eBikes here, learning before spending, don't want "cheapest" but not made of money either.

I do know a bit about batteries, at least certain chemistries.

My goal is 1000+ up to 1500W, I'm a big guy and use case is pure utility, commuting and cargo, maybe tandem, occasionally (very) rough-surface usage and often big hills.

I do not want to stress the motor, reliability and longevity are key,

speed is **not** important but torque is; I assume gearing is the solution there

From a recent post:

> motors don't care about voltage - they only care about power dissipation.

I assume the first bit needs a "within reason" qualification, applying 600+V to a motor targeted for a 36V range is likely not a good idea?

Sometimes I see members talking about upping the voltage to get higher performance.

My general battery pack standard (for other purposes) is 48V nominal, but using 12V modules, so I can go to 60/72/84, (easiest) 96V or even higher as needed.

So, my 101- level questions

A. What voltage should I plan for, or should I let that be dictated by the motor choice?

I realize there are controllers in the mix, but to keep this thread streamlined, let's leave that for another.

B. Reco's please for motors, both mid and hub. Are rear hub motors different from front ones?

I will want very solid drag braking for safety, precious heavy loads going down long descents. Willing to dedicate a motor just for regen to help with that goal, at minimum the choice of rear hub motor should not compromise it.

C. I like the idea of modularity, and understand some jurisdictions impose legal limits (on voltage? power?)

Ideally I could modify the bike by removing adding / replacing motors, if I live in NYC or SF for a while, then reconfigure for off-grid boondocking on BLM land in Arizona. I do not have space for multiple bikes.

Is multiple motors a good way to accomplish this? Swapping out a front wheel to remove the more powerful one seems pretty straightforward.

Thanks in advance

I see higher voltages are needed for smaller wheels? Voltage corresponds to wheel rpm. . .

I do need a bigger wheel size for the off-road / rough ground situations.

So does that imply 48V is plenty, even for 1000W+ motors?

Have you played with the motor simulator at Grin yet? You can simulate the effects of different voltages on different motors. I went with a 52V battery and a geared GMAC 10T motor. A higher voltage on the same motor will result in a higher top end speed. A smaller diameter wheel will need a faster motor (higher voltage or lower wind) to go the same speed as a larger diameter motor as it has to spin more to cover the same ground. A smaller diameter wheel will give you more torque though.

Total watts is the voltage multiplied by the current: P=IV. So 48V with just over 20A current would be 1000W input power to the motor. If the motor were running at 90% efficiency, the output power would be 900W.

https://www.ebikes.ca/tools/simulator.html?motor=GMAC10T&batt=B5213_GA&cont=C35&axis=mph

Looks fantastic, for them that know more than I currently do, and a great tool to help me learn what I do not yet know that I don't know.

Getting a few motor reco's and seat of the pants info about the voltage question would I think help me get started playing with it.

As runforthehills said play a bit with the simulator to get an idea of what you want or need. Just keep in mind that ebike motors are usually run between 36volts and 72 volts. For the same motor if you use 72 volts it will go twice as fast as 36volt because the speed of the motor depends of the voltage. If you want to use a cargo to haul things better aim for the lowest speed that you need so that all the power is used to create torque ( power = torque x speed). Usually 48 volts or 52 volts is what people aim for in the 1000 watt range. Rear hub motors are the most reliable but mid drive a great since they use the gearing of your transmission. It is best to avoid using front hub motors if possible. If you tell us about what bike you have/want and what speed your are aiming for,it will be easier to help you out. And also what weight you want to carry.
You can have a look at EM3ev, they have nice combos of Mac motors with quite a punch with battery and all

Hope this helps a bit

You don't say anything about budget. That will factor in at some point of course.

When I read what you've said, it has me thinking longtail cargo bike with a stokemonkey or DIY stokemonkey-like setup. This is where a DD motor hub is mounted so as to drive the front crank rather than the the rear wheel. So, like a mid-drive, it can take advantage of the bike's gear system ... but it cannot act as a drag brake because it is powers the bike through the freewheel system.

The Stokemonkey works well with longtails and cargo bikes because those designs usually have space in the frame for the big motor.
[youtube]q42uGcw27Ts[/youtube]

This is a very nice DIY take on that concept. Note: longtail frame and thus space for the big motor.

https://www.electricbike.com/appel-cruiser/

Hi all,

Currently I'm using non branded rear hub motor,
The specs stated that this a 36/48v, 350-1500 watt motor, but with only 350 RPM

Previously i'm using 500 watt controller and able to reach top speed 43-44 Kph.
Then I change my controller to a 1000 watt.
But the top speed more or less still the same, the only differences is on torque/acceleration is much faster.

So my conclusion is this motor is limited by RPM, based on calculator, with 350 rpm and 26" rim will result the 43kph as well
The difference in watt is only affecting acceleration/better load.

My question is :
Is there a way to remove the rpm limiter on the motor? Maybe tricking the hall sensor?
I know that if i increase voltage or wheel size i'll get better kph, but my option is only up to 52v or 27.5" which wont affect lot on kph, more voltage or diameter will need lot of modification which not possible for my knowledge.

Think ur limited to higher voltage battery and esc or another esc with field weakening. Or rewind the motor.

kuririkura said:

My question is :
Is there a way to remove the rpm limiter on the motor? Maybe tricking the hall sensor?
I know that if i increase voltage or wheel size i'll get better kph, but my option is only up to 52v or 27.5" which wont affect lot on kph, more voltage or diameter will need lot of modification which not possible for my knowledge.

Click to expand...

There is no limit, the motor will only spin up to a certain speed with a given voltage due to the back EMF.

E-HP said:

There is no limit, the motor will only spin up to a certain speed with a given voltage due to the back EMF.

Click to expand...

Ah I see,

So the only option is to change to a motor with much higher rpm then

Thanks!

kuririkura said:

E-HP said:

There is no limit, the motor will only spin up to a certain speed with a given voltage due to the back EMF.

Click to expand...

Ah I see,

So the only option is to change to a motor with much higher rpm then

Thanks!

Click to expand...

Actually several options as stated by Hummina Shadeeba above; higher voltage battery and field weakening; larger wheel diameter can do it too.

What would be the procedure for testing how high voltage can safely go, given they're already at the "nominal" maximum?

The motor? Can go as fast as physically possible before flies apart as you increasing voltage, assuming the magnet wire insulation is good for the high voltage and won’t short which it very likely would be. But that’s extreme limits and ur limited by ur esc voltage limit and battery voltage (maybe people have put a bit more voltage in that esc and been ok)

Maybe a goofy way you could go faster increasing the motor kv by adding magnets to the outside! Good idea? Not really but maybe it would work for you. All other things being the same you could figure how many magnets in the motor and add maybe the same amount on the outside to weaken the magnetic field strength on the inside of the motor. I’ve never seen anyone with a bike hub motor that had a physical field strength adjuster. If u had all the magnets spaced nicely and could rotate them maybe you could have both the speed u want and then rotate the magnets back for probably what would be even slower speed and more torque. The stronger and bigger the magnet the more effect this would have. With bike hub motors it might be a lot of magnets but maybe it would be easy as they’d stick. No commitment. I think would look great and you could maybe store loose nails or something there, whatever your ferromagnetic fancy.

A possibly much worse way would be to put the hub on a lathe and take off some of the steel behind the magnets.

kuririkura said:

My question is :
Is there a way to remove the rpm limiter on the motor? Maybe tricking the hall sensor?
I know that if i increase voltage or wheel size i'll get better kph, but my option is only up to 52v or 27.5" which wont affect lot on kph, more voltage or diameter will need lot of modification which not possible for my knowledge.

Click to expand...

Does this controller have an LCD display associated with it? If so, which one?
What is your unloaded wheel speed? Test by elevating the motorized wheel and seeing how fast it will go.
What is the current voltage you are running?

wturber said:

Does this controller have an LCD display associated with it? If so, which one?
What is your unloaded wheel speed? Test by elevating the motorized wheel and seeing how fast it will go.
What is the current voltage you are running?

Click to expand...

Just LED the 900s type (for speed and current i use external volt/amp meter and gps)
https://www.alibaba.com/product-detail/ebike-LED-Display-Meter-KT-LED900s_60694720582.html

Unloaded wheel speed seems can reach 35-40mph (based on LED) i'm not quite sure how the LED detect the speed
but loaded will only reach 25-28mph
Currently 48V, both 500watt and 1000 watt controller have the same loaded top speed.

the speed difference between unloaded and loaded is strangely large

It’s unlikely the escs are both programmed to be speed limited but it could happen. But if the speed is dropping while riding I doubt that would be part of a program and just the normal drop in voltage likely causing to be slower

First, apologies to the OP for veering off from the original post/thread; hopefully it's still useful information.

kuririkura said:

Just LED the 900s type (for speed and current i use external volt/amp meter and gps)
https://www.alibaba.com/product-detail/ebike-LED-Display-Meter-KT-LED900s_60694720582.html

Unloaded wheel speed seems can reach 35-40mph (based on LED) i'm not quite sure how the LED detect the speed
but loaded will only reach 25-28mph
Currently 48V, both 500watt and 1000 watt controller have the same loaded top speed.

Click to expand...

Not only is it unusual to see a difference between 40 mph unloaded and 25 mph loaded, but it's also unusual to see a 5 mph range of the unloaded speed (35-40). Does it really vary that widely?

Also, what type of battery are you using? Can you provide some details on the cell type and configuration, and the capacity? What kind of voltage sag are you seeing when you're riding at full speed?

E-HP said:

First, apologies to the OP for veering off from the original post/thread; hopefully it's still useful information.

Not only is it unusual to see a difference between 40 mph unloaded and 25 mph loaded, but it's also unusual to see a 5 mph range of the unloaded speed (35-40). Does it really vary that widely?

Also, what type of battery are you using? Can you provide some details on the cell type and configuration, and the capacity? What kind of voltage sag are you seeing when you're riding at full speed?

Click to expand...

Seems I also need to apologized as well since I'm the one who start deviate from the topic

The variation of the unloaded speed depends on the battery level (at full battery will get higher speed)

I just tested it (loaded) with 50% battery level, at first boost it around 47v and 33-35A, at full speed the voltage dropped to 46.2 and 17-18A only, sometimes i see 2-3 A only.. seems something turned off after reaching top speed, and only give power again if speed getting lower

My battery is 13s4p 2900mAH 3C
I'm ordering new pack of 13s6p 2800mAH 3C and will put both pack on parallel

kuririkura said:

The specs stated that this a 36/48v, 350-1500 watt motor, but with only 350 RPM

So my conclusion is this motor is limited by RPM, based on calculator, with 350 rpm and 26" rim will result the 43kph as well

Click to expand...

I looked at the motor specs you posted again and did the calculation based on a 26" wheel rotating at 350 RPM. Based on the motor specs, your velocity at that RPM should be around 27 mph. I think you answered your own question in your original post. The motor will only go 27 mph at 48 volts, so you need to up the voltage to increase velocity.

It takes about 800 watts to maintain 27 mph on flat ground, so your numbers are consistent as well.

E-HP said:

I looked at the motor specs you posted again and did the calculation based on a 26" wheel rotating at 350 RPM. Based on the motor specs, your velocity at that RPM should be around 27 mph. I think you answered your own question in your original post. The motor will only go 27 mph at 48 volts, so you need to up the voltage to increase velocity.

It takes about 800 watts to maintain 27 mph on flat ground, so your numbers are consistent as well.

Click to expand...

Actually that's my question, is the speed/RPM limitation is because physical/hardware limitation, or it is a software limitation on the controller/motor?

what made my confuse is because I get both 27 mph on both 500 and 1000 watt controller (so wattage is not affecting top speed at all?). and I see some other person with same hub motor can go exceed 30-32 mph, and on this curve seem 1000 watt should be able to reach 35 mph?
https://www.ebikes.ca/tools/simulator.html?batt=B4823_AC

kuririkura said:

and on this curve seem 1000 watt should be able to reach 35 mph?
https://www.ebikes.ca/tools/simulator.html?batt=B4823_AC

Click to expand...

Your curve, even if your motor has the same characteristics as the Crystalite, includes 100 watts of human power and tops out at 28.8 mph. Take away the human power and it tops out at 27.6 mph, where the load curve and power curve intersect.
https://www.ebikes.ca/tools/simulator.html?batt=B4823_AC&axis=mph&hp=0

Back to the original question, as soon as you said cargo, you started wanting something different from 90% of the folks here.

Two approaches work best for cargo hauling bikes, tandems, etc. Anything with more than about 300 pounds total weight, battery, motor, bike, cargo, and the person is stressing typical hub motor kits a lot. Too much if there are long steep hills. ( long is over half a mile, steep is over 8% grade)

Mid drives, can haul huge weights up hills the same way you pedal up them heavy. The mid drive can actually put the motor into lower gears.

Hub motors are stuck in one gear. For a 400 pound bike up a mountain, simply making the motor bigger works fine, and then give it 49v 40 amps, 2000w. With more copper in the motor, and wider magnets, the motor is strong enough to pull the weight up even huge mountains, at 15 mph or more. Too slow with a hub motor overloaded, and it will melt the motor.

So go mid drive, or go big. FWIW, a front and rear hubmotor, each pulling 2000w, also works. But its just simpler to get one of the larger hub motors. My cargo hauler uses the older, crystalyte 5304. But there are still big crystalytes out there. Grin cyclery is a good place to get one.

GMAC is geared but maybe not strong enough

I don't know what it is about this thread that makes it such a bot magnet.

john61ct said:

GMAC is geared but maybe not strong enough

Click to expand...

The GMAC is plenty strong and will put out about five times more torque than a similar sized DD motor so it will climb a tree. \

BUT any geared hub motor will over heat if you push high amperage through it for a long period of time.