Over volting 36v motor to 39.6v

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Over volting 36v motor to 39.6v

Postby Sonicburn » Fri Jun 16, 2017 12:33 pm

Hi , I recently build my first ebike  and I have done some tests.

I am quite happy with the results.

I have a 15a controller with a "350"w motor and  36v  , 10350maH  10s3p  battery with a 30a BMS. the cells I am using are Samsung E35 3450maH 10A

I can run at 21mph (35 km/h) constant without use the pedals, ( just i help the motor when accelerates) and has 16miles  (26km)  range.


I just have done 2 rides , and I am thinking to buy another 10 cells to get a 10s4p to do more mileage.


1- After doing a 16miles (26km) ride, non stop...I noticed the battery got a bit warm ...is this normal? 

2- I have read there is some people over voltage the batteries to get more velocity installing another line of cells in series. As I could read, shouldn't be any problem for the controller meanwhile the capacitors on it can handle the voltage.

If for example,  I would  like to make a 11s4p battery 39.6v to increase the speed of my ebike.  It would be possible to install the same  10s BMS I already have?  

How could I wire the 10s BMS in a 11s battery? 

​​​​​​​Is there any danger or risk installing a 10s BMS to a 11s battery pack ? 

Thanks
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Re: Over volting 36v motor to 39.6v

Postby d8veh » Fri Jun 16, 2017 6:13 pm

It's normal for the battery to get warm when it's delivering 5 amps per cell. If you go up to 10S4P, the current per cell will go down to 3.75A per cell, so it'll run cooler.

You can normally go up to 12S with a 36v controller without problems, though the controller's LVC will be too low, so you need to think about how you're going to cut off the battery when the cells go below 3.1v each, which will be 37.2V for the pack instead of 31.0V. 12S gives 20% more torque and speed compared with 10S. It brings a 36v motor to life.

Motors don't really care what voltage you run them at. generally, 36v motors run fine up to 48v (13S). After that, you have to be mindful of the low-speed efficiency, which can make them run hot.
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Re: Over volting 36v motor to 39.6v

Postby Sonicburn » Sat Jun 17, 2017 5:57 am

Thanks so much for the info

As I can see its possible to change the LVC of a generic controller , changing 2 resistances (voltage divider) for different values, this ones send the amount of threshold voltage to the chip , programmed to cut off the power.
Replacing this resistors , you can cheat the chip and therefore change the cutoff voltage.

As well I could read there is people reprogram the chips!! :)

As more I read about ebikes, more interesting !! :D

Here there is a link explaining everything about how to modify this resistors , if anyone is interested:

viewtopic.php?f=2&t=26306&hilit=voltage+divider&start=25


I guess then , if I build a 12s4p I will have to replace the BMS ...and the charger as well??
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Re: Over volting 36v motor to 39.6v

Postby dogman dan » Mon Jun 19, 2017 6:42 am

What are the caps in the controller? You may be able to run 14s with no problems at all.

Should be ok with the motor itself, provided you don't weigh over 250 pounds.
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Re: Over volting 36v motor to 39.6v

Postby 999zip999 » Mon Jun 19, 2017 2:21 pm

10s - 13s - 14s are the most common for bms and chargers.14s much better than10s. Or 10 and 14 better 24s. Maybe later. More parallel less stress longer life. Plus I like a set of sense wires for a cell checker.
Last edited by 999zip999 on Mon Jun 19, 2017 2:23 pm, edited 1 time in total. View post history.
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Re: Over volting 36v motor to 39.6v

Postby fechter » Mon Jun 19, 2017 2:54 pm

Yes, you will need a whole new BMS if you want more cells. Many of them can work with fewer cells just by adding jumpers across the unused connections.
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Re: Over volting 36v motor to 39.6v

Postby Sonicburn » Tue Jun 20, 2017 5:50 am

Dogman, I did not open the controller tbh, but is a Chinese generic controller , I guess are 63v..



Ok I think understood, there are standard BMSes 10s, 13s, 14s...and its not possible to install a BMS on a battery with more groups than the BMS its made for .

But If I have got a higher BMS than my battery cell groups, I could use jumpers for unused connections...

Maybe next time I will buy a higher bms than what I really need then...And always I will have the possibility to expand my battery ..:)


Thanks for replies
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Re: Over volting 36v motor to 39.6v

Postby dogman dan » Tue Jun 20, 2017 6:13 am

Some times a 36v controller will have 50v caps. Or a voltage limiter that shuts it off above 45v.

But its less likely to have that limiter, if you see 63v caps in there. Cheaper controllers tend to be the same for 36v or 48v, with only the Low voltage limit set higher for 48v kind.

If you jack up the 36v, then its lvc will be set very low, for a 48v battery, but it may run just fine otherwise.
Last edited by dogman dan on Tue Jun 20, 2017 6:15 am, edited 1 time in total. View post history.
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