4030wh Sherman battery seat mod

[Murdomeek]

I have had the OG sherman for a while with 3200wh. But sometimes I like to go on even longer rides but don't really want to hunt for outlets and sit around to charge. I decided to build a battery extender seat that attaches to the roll cage. 

The seat will add an additional 830wh connected in parallel with the main batteries totaling 4030wh.  25% increase in capacity and more battery than other 3600wh wheels   (Although the new released 4800wh Master Pro has me beat)

Here is the final result:

And here is the build process in case anyone is interested:

I originally was going to make it out of wood.

It is very bulky and ugly. I ditched that when I thought of the idea of using an ebike battery case/shell. This looks much better and actually looks comfortable to sit on. This is a mock photo using my actual ebike battery just to see how it would look:

I made the mounting base plate out of 1/8” aluminum and it will be mounted to the rollbars with the quick release clamps.

I had to make the battery from scratch because no one sells 101.8v (24s) batteries in a downtube battery case. I made these with 4800mah 21700 tesla cells in 24s2p configuration. I 3D printed cell holders from PETG reinforced with carbon fiber. And a 24s BMS with a 30a fuse. It was a tight fit but I was able to get all of that into the shell.

I installed a XT60 connector at the front next to the headlight port with a 30a inline fuse. And wired it in parallel going into the controller.  I wanted to do it in the back near the charge ports, but there was no space and it was too cramped back there.  

The battery also had a key to make it easily removable. Easier than undoing the 4 clamps at least. It can be charged separately or plugged in. I must take caution and make sure all batteries are at the same voltage levels before plugging it in or it’ll blow the fuse.

 

I hope 4030wh can satiate my fast and long range rides.  If not, the master pro might be what I need

 

Hope you enjoyed the read and here are a few more pictures of the end result:

Edited August 24, 2022 by Murdomeek

[WattsWheelhouse]

Kudos to you! This is an awesome project that you pulled off flawlessly! 

[UtahRider]

I’m impressed. Very well done!

[supercurio]

Awesome project, congrats!

[fbhb]

I love seeing quality workmanship, very well executed!

[daniel1234]

Looks awsome - you ride that long rides ?

[meepmeepmayer]

A dream mod! Awesome. One can never have enough range.

[AK euc]

But why??? Sherman has brilliant range anyway you've just created a heavier Sherman.... Well done for making it though🤙🏽

[Murdomeek]

Thanks for the kind words everyone

 

1 hour ago, AK euc said:

But why??? Sherman has brilliant range anyway you've just created a heavier Sherman.... Well done for making it though🤙🏽

I ride the sherman hard.  Most routes are suburb open roads next to farms/rivers or has a dedicated bike lane next to a road. And I cruise at 58.8kph most of the way (highest tilt back setting).  I get ~85kms range normally before it hits 20% and then I gotta ride slow due to beeps (boo).  Hopefully I'll get over 110kms of hard riding with this mod

No need to waste time waiting to charge, and hopefully it'll keep the wife happy that I'm home earlier

 

[RagingGrandpa]

Fun stuff

On 8/23/2022 at 7:48 PM, Murdomeek said:

It can be charged separately or plugged in.

Does your BMS perform a shutoff behavior? 
Or, balancing-only?

[Murdomeek]

Yes it does.

Balancing

Low voltage shutoff

Over voltage shutoff

Over current shutoff

[mhpr262]

Careful with those cells, Tesla manufactures them leaving out as many safety features as they can get away with in order to lower the price, and they rely instead on the smart pack management. There is a reason the real Tesla cells are not sold to the public and one can only get them from parted out battery packs from crashed vehicles.