I've wanted to build an electric vehicle for a long time, due to cost of components i have put it off.
Recently i found a facebook marketplace ad for a children's 50CC quadbike for $150.
The seller advertised that it was only missing a fuel tank and is running. As with all online marketplaces, this was not exactly the truth.
From what i could tell, someone with no technical skill but with plenty of confidence, attempted to get the quadbike running by cutting and joining wires while blindfolded.
There was no way this was going to run without a whole lot of work. I low-balled the seller $90 and took it home.
stripped down to bare chassis.
Converting to electric
The initial plan was to try and do this project as cheap as i could. I started with a Ebay 1800W Brush-less motor kit and some lead acid batteries.
Fabricated battery mount
Dry Fit of Batteries
I was able to clear the frame when testing the suspension movement!
I attempted to use the original sprocket that the petrol motor used. This didn't turn out as there wasn't enough torque with this gearing ratio.
I ended up buying a electric bike sprocket and chain kit that had a far better ratio.
I had to drill new holes in the larger sprocket to align with the bike's driveshaft. Centering this sprocket turned out to be very hard, i wish i owned a metal lathe :-(
Charging 48v batteries with a 12 charger?
Since it was a 48V motor kit, i had this idea to use 4 relays to break up the 48V battery pack into 4 x 12V batteries in parallel for charging, saving me the need for an expensive 48V charger.
gif of the relay circuit, Note that i used DPDT (Double Pole Double Throw) relays which halved the number of relays to 4. DPDT relays aren't supported in falstad circuit simulator so its a mess of wires to get the same functionality.
This circuit worked as designed. i was able to charge these batteries with a normal 12v car charger.
As mentioned earlier these relays have multiple poles so i only need 4 (instead of 8).
Went out for a drive and it works great!!