I would say anywhere from 20-30A but without knowing what chemistry and form factor I can’t say more
Lithium ion 18650. It’s from an AliExpress shop with excellent ratings and reviews. They called the cells “codd power” but I know that’s just a Chinese Branding
2 Likes
It would depend on the BMS, but if they’re offering a 50/100A BMS then I’d say you wouldn’t be charging at more than 10A.
https://www.amazon.com/Lithium-Battery-Electric-bicycle-Scooter/dp/B01MQ1VPLO
This similar product has harging spec listed as 3A so maybe that’s correct
1 Like
@kalebludlow That’s still pretty great. Gives me about 4hrs of charge according to my math. They can put in a xiaoxiang bms if I request it
Is there anywhere to buy a replacement motor shaft for my 6374 8mm shaft maytech motors? Do you think I can contact Maytech and ask for just a motor shaft to be sent to me?
It’s worth a shot. Poke them and see if they respond.
1 Like
I have a noob question. The noobest of the noob questions… I know you lose top speed with less groups in series (10S ledd top speed vs. 12S), but do you lose torque too? Say the difference between a 12s4p and 10s4p of the same cells, is it only top speed and range, or torque too?
You only lose torque at higher speeds. Standstill and low revs will be about the same. For example, lets say 10s top speed is 30mph. Then at 25mph, with same gearing, the 12s setup will be able to make more torque. If you run high amps, then you will see a difference in torque even at 20mph.
4 Likes
Two answers, depending on how pedantic you get.
If you have the exact same number fo cells, for example 12s5p and 10s6p (both 60 cells), then you have exactly the same power available. It’s just that one has 20% more voltage, and one has 20% more current. But watts is watts, and since math is commutative, everything works out.
However, if for example you keep the same 4p, and just add two more groups to a 10s to make a 12s, then you not only have 20% more voltage, but because the available current stayed the same, you have 20% more power overall as well.
In that latter case, the available torque may change more than with the former, because the available power from the batteries is changing, not just the voltage.
4 Likes
well first off, thank you @MysticalDork and @jkoljo! For conceptualizing’s sake, if you had the exact same setup on a board but one was 12s3p and the other 10s4p, same cells and gearing and esc and everything, would the 10s4p have less low-end torque than the 12s4p? Would the 12s3p have more high end because it is higher voltage?
2 Likes
You’ve got several different scenarios there.
12s3p vs 10s4p, the 10s actually has more cells, which means more power on tap, which means more top end torque.
12s4p vs 10s4p, 23s has more cells, thus more power, thus more torque.
Keep in mind, this is all dependent on where the bottleneck is in your system, and all this is assuming that the battery is the bottleneck. If you have a 60 amp battery and a 50 amp limit on your ESC, none of this will matter.
Same with your motors. If your motor current/power limits are the bottleneck, then changing your battery around won’t get you any significant gains, other than pure RPM from the higher voltage.
4 Likes
what does this part mean, I’m not sure I understand this part of the equation. I know there’s battery and motor amps, and your ESC is the regulator between these, and you can set the max motor amps into your VESC. So what does that mean “50 amp limit on your ESC?”
Also, there’s a big difference between top end torque and bottom end torque.
Torque is a function of current passing through the motor. So your torque will be limited by the motor current or the battery current, whichever is higher.
Generally speaking, at low speeds, your torque is usually limited by the motor current, and at high speeds, it is limited by the battery current.
Increasing your motor current will give you more low end torque.
Increasing your battery current will give you more high end torque.
Increasing the overall power without increasing the current (like by adding more cells in series) will raise the speed at which those limits switch.
4 Likes
yes yes, OK I’m getting it TY!
2 Likes
Any ESC has two limits, and if you exceed either, you will break stuff, or cause overheating, or whatever. One is the maximum amount of battery current that can go into the ESC. The other, is the maximum amount of motor current that can come out of the ESC.
You can think of the ESC as the thing that converts battery current into motor current.
If you have a battery that can give you a billion amps, but your ESC will explode if you try to draw more than 50, then your limit is 50, not a billion.
Your entire system will only be as good as the weakest/slowest/smallest component or part.
That’s why I said earlier, that all the 12s3p vs 10s4p stuff is totally irrelevant if you don’t have a motor and ESC that can take advantage of the difference in power/current.
3 Likes
OK I think I get what you’re saying. Where can I find info on the amount of motor current an ESC is capable of delivering before shit breaks? If you set the motor amps too high on your ESC, is it possible to break stuff before the temps get really high? People set their motor amps to 100+ I see sometimes for MTB’s and such; which ESC’s are generally capable of handling that much current?
PS thanks for entertaining and eductaing me @MysticalDork =)
1 Like
Big expensive ones, like the Trampa vesc6, or much bigger, even more expensive ones like the 75/300, with directfets and an aluminum case.
The vesc6 can handle 80 motor amps pretty much indefinitely with ambient cooling, if I recall Vedder’s test video correctly. And if you improve that cooling by, say, bolting it down to a big aluminum plate or something, then it only gets better.
Generally I would assume the advertised current ratings on ESCs apply to both input and output current, whichever limit you hit first.
2 Likes
Aweomse, thanks again @MysticalDork for explaining it. And this is generally monitored by ESC temp correct? I ca gauge how well an ESC is handling motor amps by monitoring the temp right?
Yes, to a certain extent. But some ESCs have other issues that rear their ugly heads beyond a certain point, that isn’t temperature related.
For example, a lot of 4.x design based ESCs will run into fried DRVs above 50 or so amps, or if you try to use FOC.
Alright, that’s enough chatter for tonight, I gotta get some sleep. Cya for now!
4 Likes