Running higher voltage and relation to power, amps, resistance, heat...

[theloadedquestion]

Hi,
So I've been running my leafbike 1500w at 52v and 80a batt for peaks of 4200w, but I'm wondering if going to 72v would be better? If I run higher voltage I also need to run lower amps to keep the wattage within reasonable bounds correct? This being the case I'm then wondering if that would reduce my toque at low rpm? I'm pretty clueless but it seems like ohms law would mean that at a higher voltage I can produce more power (watts) with less resistance, and therefore less heat. But if it is going to result in less torque off the line and at low rpm then it is probably not worth it for my style of riding.

Thanks all!

 

[MadRhino]

Watts are watts, no matter what. Meaning, power is equal between 100v 50A and 50v 100A.

The balance that one need to find when building an ebike, has to be in relation to components availability and cost, target performance, and reliability.

 

[markz]

Thats quite a jump in speed from 52V to 72V, why do you want to go FASTER?

 

[E-HP]

Hi,
So I've been running my leafbike 1500w at 52v and 80a batt for peaks of 4200w, but I'm wondering if going to 72v would be better? If I run higher voltage I also need to run lower amps to keep the wattage within reasonable bounds correct? This being the case I'm then wondering if that would reduce my toque at low rpm? I'm pretty clueless but it seems like ohms law would mean that at a higher voltage I can produce more power (watts) with less resistance, and therefore less heat. But if it is going to result in less torque off the line and at low rpm then it is probably not worth it for my style of riding.

Thanks all!

I switched from 52V to 72V on my cheap eBay 1000w hub, not for the speed but the huge jump in torque. It’s more than I need and I run 95% of the time in position 1 of my 3-speed switch, and still has great acceleration, up to a lower speed. As long as you monitor the motor temp, it seems you could go pretty high with the peak amps.
I tested a lot of voltage levels, up to 22S, and was ready to land at 18S, but then decided on 20S in the end since it’s more standard (if there’s such a thing with ebikes). This highest peak I’ve seen at 20S was 104A.


Sent from my iPhone using Tapatalk

 

[dogman dan]

What MR said, But if you do keep amps the same, and increase volts to 72, then you do bump up watts quite a bit.

That means more speed because of the 72v, but also more speed because you won't hit a wind resistance wall that exists at lower wattage. ( meaning more like 1500w, you got wattage now) And of course, till you over watt the motor, more watts is more torque. Once you cross the line, its just more heat. My instinct would be to lower your amps, and keep watts at least below 5000.

So do it if you want to go faster, you will. And do it if you don't mind losing some control over very low wattage, like 200w or less. At 72v, it can get a bit hard to ride 5 mph, like you need to sometimes if you ride a crowded as hell walking path, or even just the walmart parking lot. The throttle kind of goes, nothing, nothing, 1000w, as you roll it back.

Personally, I found the butter zone at about 52v, and 2000w for a street e bike. With the motor I used I had a nice 32 mph top speed, and all the power I needed to climb the rocky mountains. But when another bike burned my house, I had to live in the city center for almost a year in a rented house. Living there, I bumped up to 18s, which gave me a solid 38 mph. This worked a lot better in the big 4 lane arterial roads in a medium large city.

Dirt riding, well, you never have too much power till your motor melts, eh?

 

[theloadedquestion]

Hi,
So I've been running my leafbike 1500w at 52v and 80a batt for peaks of 4200w, but I'm wondering if going to 72v would be better? If I run higher voltage I also need to run lower amps to keep the wattage within reasonable bounds correct? This being the case I'm then wondering if that would reduce my toque at low rpm? I'm pretty clueless but it seems like ohms law would mean that at a higher voltage I can produce more power (watts) with less resistance, and therefore less heat. But if it is going to result in less torque off the line and at low rpm then it is probably not worth it for my style of riding.

Thanks all!

I switched from 52V to 72V on my cheap eBay 1000w hub, not for the speed but the huge jump in torque. It’s more than I need and I run 95% of the time in position 1 of my 3-speed switch, and still has great acceleration, up to a lower speed. As long as you monitor the motor temp, it seems you could go pretty high with the peak amps.
I tested a lot of voltage levels, up to 22S, and was ready to land at 18S, but then decided on 20S in the end since it’s more standard (if there’s such a thing with ebikes). This highest peak I’ve seen at 20S was 104A.


Sent from my iPhone using Tapatalk

This is basically what I'm trying to accomplish. I currently run 52v @ 80a for 4200w peaks, but I'm also ruining ferrofluid and hubsinks, and my cheap Chinese controller (yuyangking) has an 80a batt limit which I'm bumping up against. Even though efficiency drops off sharply over 4000w and most of those watts will simply go towards producing heat, there are still marginal gains to be had as long as temperature can be managed.
Thanks guys.

 

[E-HP]

This is basically what I'm trying to accomplish. I currently run 52v @ 80a for 4200w peaks, but I'm also ruining ferrofluid and hubsinks, and my cheap Chinese controller (yuyangking) has an 80a batt limit which I'm bumping up against. Even though efficiency drops off sharply over 4000w and most of those watts will simply go towards producing heat, there are still marginal gains to be had as long as temperature can be managed.
Thanks guys.

https://ebikes.ca/tools/simulator.html?motor=Leaf%205T&batt=B5220_GA&cont=cust_80_160_0.03_V&axis=mph&cont_b=cust_80_160_0.03_V&motor_b=Leaf%205T&batt_b=B7223_AC&bopen=true

I like having the torque/acceleration at speeds where it usually tapers off, so at 33mph on this example, you still have 50 N-M more torque.

 

[theloadedquestion]

This is basically what I'm trying to accomplish. I currently run 52v @ 80a for 4200w peaks, but I'm also ruining ferrofluid and hubsinks, and my cheap Chinese controller (yuyangking) has an 80a batt limit which I'm bumping up against. Even though efficiency drops off sharply over 4000w and most of those watts will simply go towards producing heat, there are still marginal gains to be had as long as temperature can be managed.
Thanks guys.

https://ebikes.ca/tools/simulator.html?motor=Leaf%205T&batt=B5220_GA&cont=cust_80_160_0.03_V&axis=mph&cont_b=cust_80_160_0.03_V&motor_b=Leaf%205T&batt_b=B7223_AC&bopen=true

I like having the torque/acceleration at speeds where it usually tapers off, so at 33mph on this example, you still have 50 N-M more torque.

Thanks for the responses man, helped me process my thinking and head back to the simulator. I think I'm definitely going to give 72v a shot. I run LiPO with no permanent wiring harness so it's all easily configurable for different voltages and capacities. Cheers!

 

[DogDipstick]

I do that, have for about 3000 miles.... I get 8,000w from 100A @ 72v from a 1000w motor... In the winter the hubsinks keep the temp down but in the summer I need thermal rollback.

Not much to gain once its hitting its thermal limit all the time. I can easy hold 35-40mph contin though. 50A with a 100A peak .