I have a Chinese electric skateboard with little to no information on it and it's recently been under performing. I opened it up and it runs on a 29 volt 2200mah battery. I happen to already have a 36 volt 4400mah battery and I would really love to swap it in but I don't want to blow it (both are battery packs composed of multiple 18650 batteries). In your opinion do you think the controller is probably under rated and i should go for it, or would it certainly fry the controller? Any tips would be awesome, thanks!

 

If you powering a 36V battery to a 29V device, maybe it could damage the device or maybe not, but you can't use a lucky chance to try, unless you know the structure of the power system, so through a LM2679 simple switcher 5A Step-Down Voltage Regulator adjust to 29V and connected to the device, that is a safe way.

 

Lithium ion cells are often considered to be nominally 3.6 or 3.7 volts, but when fully charged they will be close to 4.2 volts. Your batteries are probably 8 cell and 10 cell, making them 33.6 and 42 volts when fully charged. There are lots of common components that have an absolute maximum voltage rating between 35 and 40 volts. The chance such parts would survive at 42 volts is not zero, but pretty low. Someone designing a consumer item where cost is important probably isn't going to do the design to accommodate a power supply voltage higher than would ever happen with the specified battery pack.

 

Most chinese devices with 18650's hidden inside contain recycled cells taken from used laptop battery packs .. these are not recycled for lithium but for the good cells they contain ... trustfire and ultrafire cells I've dismantled are these .you can see the old spot welding marks from previous use when you remove the endcaps put there to hide them .... A usb power bank I recently dismantled also had the tell tale spot welding marks on the cells ...

If this is the case for your skateboard then the cells are probably old , some will have low capacity and high internal resistance and are no longer suitable for high drain ...but fine for low drain applications like powerwalls

So you probably don't want a higher voltage battery , just one with better cells .You can open up the pack , test each cell and use the good ones ... or rearrange the cells in the 36 volt pack to make a 29V pack ...

Reusing and building 18650 battery packs is very big passtime ...many youtube videos and a very active forum (secondlifestorage.com) thousands of people getting scrap laptop batteries and using the good cells.

 

if i removed 2 cells from the 36v battery do you think the BEC would give me issues or would it still work as normal assuming i completed the circuit?