Suzuki DR400 S

Putting together a EMotorcycle Build based on an old Suzuki DR400 S

The kit I'm planning on working with for the Drive train is:

QS 138 4000W 72V motor
Kelly KEB72101 180A/450A Motor controller

Battery will be
20S 24P 3.7v 18650 Battery
Daly 200A 72V BMS

Had a long debate about onboard vs off board chargers decided in the end off board would be an easier job to get going.
GTK 72V 30A lithium battery charger in the end.

Anybody able to sense check this, I've worked with smaller motors and batteries before just want to make sure I'm not missing something obvious.

As you posted this in the right category I assume you already read through some build threads of members on E-S here? If not, this is a good starting point:https://endless-sphere.com/forums/viewtopic.php?f=10&t=110633

Good luck and enjoy building your EV conversion. And please update here regularly with lots of photos :wink:

Have you picked out specifically what 18650 you plan on using? Not all are alike, some can handle the higher discharge rates than others.

The DR400 S has a dry weight of 311 pounds according to google. Lets say you can shave 50 off that by removing the engine and replacing it with batteries. 480 18650 cells will weigh 45-50 pounds, btw. Your Kelly controller is specced to pull 180 battery amps max (I think that's what the 180/450 means, btw; battery/phase amps). So the controller maxing out its 180 amps (which will happen at high speed, high acceleration) means its pulling 7.5 amps per cell. There's plenty of cells available that can handle that, btw, just make sure they can handle that amount of current and then some, for headroom.

What speed/range/acceleration are you looking for?

Looking forward to seeing it!

Yeah looking at using 25R Samsung 18650 which can do 20A continuous discharge so not too concerned with amps, worked with them before as well, they've been pretty bullet proof, also have a good supplier for them.

Having shaved weight already, I've lost about 35kg (77lbs) from the engine alone so expecting to have similar final weight as original weight of the bike. 180/450 is continuous/1 min peak should have clarified. The controller is probably over specified tbh.

Speed is 80mph, range would be good to make 60-80mph but pretty sure from calculations it'll be low end, acceleration isn't a huge concern for the build as I plan to use it for getting around town.

Sounds like you have thought out a lot of the parameters, which is the important part. In my opinion, it's less important whether those parameters are right/accurate. The fact that you considering most of the factors you need to consider is enough, and if/when you run into problems, you'll figure out what went wrong and how you might be able to adjust your build accordingly.

I will say though, 80mph might be wishful thinking off 20s/72v. I could be wrong, because you're using a mid-drive motor, so it'll be ultimately up to your gear ratio, knowing that a ratio to favor higher speed is also going to pull more amps. But you also said you plan on just driving it around town, so you may never actually need to go 80mph.

Your range is a little bit on the hopeful side as well, at 60-80 miles per charge: Samsung 25R is rated at 2500mah, at 3.7v nominal, you have 480 of them, giving you about 3.8kwh at 100% DOD. I have 5.1kwh on my bike, dry weight 350 pounds (so a bit heavier), and my range maxes out at 50 miles at 100% DOD...which I try not to do, in favor of longer cycle life.

But again, go for it. I'm already planning on making my second, with the lessons I learned from the first. And if 20S24P is what you can fit, then it's what you can fit, don't stress about it too much.