I am in the process of building a “fun” vehicle for trips to the Grocery and the like rather than dragging out the dino-eater.
I will be a 4-wheel bicycle kit with a 900W Hub motor.
Now the issue… The motor is based on 48V.
All of the interesting battery packs seem to stop at around 36Volts. Very Few Packs continue to 48v.
Some of them actually are broken into 4 x 12v for charging, and then you have to connect them in series to get your 48V. Not a BIG issue, but I am just wondering why? Do the BMS max out at some lower number of cells?
LI-poly would take 16 cells, do they max out at 12?
I am looking at 48V 25Ahr 22Lb pack, but it is enclosed in an armoured box and costs BIG $$ ($1100). There have GOT to be better options.
The larger voltage, the larger the battery. Its mostly for convenience… Its easier to put 4 batteries in series, than build one 48V. Plus, if one part of the 48V battery goes, the whole thing goes. But with 4 12’s, you can balance, and detect if one is going, and replace as needed. Plus, cost, cheaper to manufacture smaller ones, lighter. Plus, who uses a 48V battery? Most forklifts stop at 36V packs. And they’re huge.
Just because it SAYS 48V doesn’t mean it won’t run at 36V. What controller/motor package are you using? Have you calculated what HP you need to roll that weight, plus your weight? The motor might be kinda small.
I’d just use 4 motorcycle batteries. They’ll be 18Ah or near that, 12V and about 13 lbs.
I am building a “Side Kick” 4-wheel Bicycle thing…
I am planning on using the 900W Hub motor called the “Road Runner” which is probably about as much torque as the frame can take, gives me a top speed of 20+ and can use the crystalite 4840 controller. I am going with that combination for speed and range.
I was considering Motorscycle batteries for a while, but they are not deep cycle and wouldn’t last long… I am looking strongly at the new comercially available 12V car battery replacements in LiIon. They are in production, have the BMS built in, and are extreemly powerfull for the weight, just expensive. With built in BMS’s charging is no longer a problem.
I’d start simple, but plan for the better batteries in the future.
I’m converting a motorcycle, and the best calcs give me 40 miles range, at 20mph with a 450lb frame/equip, with 12 18AH motorcycle batteries running 144V to a custom controller and a DC motor thats got ~20HP. Don’t expect to get 100 miles on a charge either.
Not saying it can’t be done, but smaller decent amp hour batteries will be fine.
Also, is a bike wheel hub going to support the weight of car batteries? Maybe Lipo, but do you want to spend 80-200 bucks for 3.2V? You’d need at least 12. And at that cost, they don’t come with BMS.
You could get a dewalt pack, but I don’t know the AH would last long on your bike. Plus, lipo’s don’t like to be in parallel, so you’re stuck with that AH rating. Sure the BMS is built in…
I’d start simple … i mean, its your first project right? Prove the concept with some cheap batteries, get her running, then tweak her. Overbuild the motor/controller so you have some flexibility too…
Good luck, let us know how it goes.
Hint: I found 27 Free SLA 18Ah batteries almost no use from a guy on one of the EV listserves. They like to support their own, and freely barter/give away stuff they know someone else can use.