50a enough for dual motors and steep hills?

General Discussion
1

Hi guys,

I currently have a pretty weak 6s LiPo battery powering dual 5055 270kv motors and I live in a very hilly area. I want to upgrade my LiPos soon to a better Li-On pack and found the 10s5p Li-On pack from diyeboards. This is a very good price (I think) but the problem I think for me would be is that it only outputs 50a. so would 25a per motor be enough? I know 270kv is quite high so I want to change the 3:1 gearing ratio to 5:1 when I upgrade the battery.

So I’m basically asking would 25a per motor be enough and with a 5:1 gearing ration should I be able to get up steep hills?

2

Depends largely on your weight. Also depends on your definition of steep. Also depends on what your definition of “go up” is. You might get there, but not the fastest.

Some of it will just be trial and error. I always side on the side of more amps. But another big factor is the motor. I can’t speak as much on whether this will work or not, since I’m not a belt guy. If I were talking about hub motors, I would say 25 amp per motor is not that great at 10s. But belts can get a bit better efficiency, so you might be able to squeeze a bit more out of them.

3

Thanks for the reply! I only like to go at 25km/h not even. not sure how to describe the steepness, Im not that heavy im only 16.I think I will probably just have to wing it and hope for the best I would like to get higher amp battery pack but unfortunately diyeboards dont sell anything high

4

what’s your tire diameter?

5

I ran some test with an in-line watt meter on a dual drive and my weight being apx 185 lbs going up a hill that was apx 10% grade Using 12s Opto Car Esc’s and Carvon V2 direct drive motors with 90mm wheels

Both tests where at apx same speed

12s - 18a total from battery at half throttle 6s - 36a total from battery at full throttle

That should put 10s at apx 27a total But as previously mentioned, there are many variables.

2 Likes
6

83mm currently but might soon be 97mm

7

Good info to know! thanks!

I don’t think 25a per motors will be enough unfortunately :worried:

8

@Orin635 here is a chart predicting the performance you will get with 25a battery current limit and 80a motor current limit per motor (83mm tire, 3:1 gear reduction, 2 motors, 270kv, 22.8v battery)… top speed looks to be about 19mph (red line, bottom left chart - thrust pounds minus wind drag force) and peak vehicle thrust is roughly 90lbs (yellow line, bottom left chart - vehicle thrust pounds 2 motors):

1 Like
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So much information right there its very hard to understand it. Is that a website you got that information from?

10

@Orin635 here are some of the formulas involved in the prediction:

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So what sort of information does the diagram give me? I dont really understand it

12

and the load is assumed more I guess with the larger amps used

13

the yellow line on the bottom left chart shows how many pounds of thrust you have at different speeds with those settings.

14

if you want to calculate acceleration in m/s^2 then you need rider weight, but it isn’t a factor in calculating vehicle thrust or wind drag force on flat ground.

15

so at 20mp/h i’ll have 0 pounds of thrust?

16

50amps and 12s works good for me doing steep hills. enough. im 155lbs. especially with a pulley setup should be even less an issue

17

right, notice how the back emf voltage produced by the spinning magnets on the rotors (which opposes the battery voltage - red line top left chart - back emf voltage) increases with speed and surpasses the maximum pwm effective voltage of your battery/controller right below roughly ~20mph (yellow line, top left chart - effective pwm voltage).

18

There’s no 12s option from diyeboards and if I was making it myself or buying from a battery builder I would just get a higher discharge cells

19

Yes I see that

20

Is this diagram for a 10s battery? or 6s?