I built my 48V charger (actually  you will need 13.8 x 4 = 55.2V) using this DC to DC boost converter.

https://www.aliexpress.com/item/32857772579.html?spm=a2g0s.9042311.0.0.6a124c4dh5BDzf

You can set your desired output voltage and maximum output current.

For the DC supply to the converter I use a PC power supply which can produce plenty amps at 12V and is cheap !

I first used 2x Meanwell 24V power supplies in series. On the Meanwell AC to DC switched mode power supplies you can adjust the output voltage by a few volts but you can cannot set the output current.

Some progress here, the motor has cleared customs and I should have it by the weekend. In the meantime I will be making sure that the brakes work and wheel bearings etc are OK.

I found a measured power curve for the  motor I have and it looks like this : 

 

Peak power is at about 3000 RPM.

The motor comes with a 11 tooth sprocket and there is a 32 tooth on the rear axle of the quad. The wheels are quite large at 50cm diameter, so at 3000 RPM at that final drive reduction the quad will be going 97 km/h, and at 4000RPM, 130km/h! That is maybe a bit quick, and I doubt the motor will have anywhere near the power to get up to that speed though. So what I will need to do is get another gearbox to reduce the motor RPM before the final drive, so I will be off to Bearing Man and see if I can get a 4:1 reduction gearbox which will give about 25kmh @ 3000RPM and a max (if it can even get there) of 32km/h. I can then fiddle with the rear sprocket sizes to adjust if necessary.

Edited November 27, 20196 yr by DeepBass9

With lots of lock down time on my hands, and a quick visit to Bearing Man beforehand, I have managed to progress on this project, almost to completion.

I have a 4:1 reduction chain onto the quad final drive which is a further 3:1 reduction. One thing that I forgot is that when you use another gear set, the rotation direction is reversed (duh!), so I need to remove the motor mounting and reverse it. So it currently has one slow forward speed and 3 fast reverse speeds.

I don't have batteries as yet, so it is running from jumper cables from my solar batteries (hence why it is standing on the paint bucket).

After the lockdown ends there is a place in Kdorp that does recon car batteries for R500 each, so I'll get 4 x 30Ah or 40 Ah and get it mobile.

 

Here's a video of it running : VIDEO. It makes a clanking noise because the back chain is loose and running over the frame. I still need to adjust that and make a rubber chain slider. Otherwise, apart from body work etc, I am quite please with the results so far.

 

 

Where the fuel tank was I'll get a plastic box to put the electronics inside. There is lots of space where the engine was to fit batteries, so I'll make a tray to hold them with some tiedowns or something to hold them in place.

On the controller there are plugs for a forward/reverse switch, a three way plug for forward slow/medium/fast speeds and another plug for a brake on the motor. I have the rear disk brake on the quad working, and I'll wire the brake light switch on the brake lever into the engine brake, so you will be able to pull the lever a bit and get engine braking and then further and the disc brake will engage.

It actually seems like it will be quite powerful, more than I expected. If you open the throttle (so to speak) it spins the wheels up very quickly. I'll still need to test that to see how it actually performs, but the gearing will be quite easy to adjust by using different sized sprockets.

How much longer is this lock down going on for??????

Edited April 16, 20206 yr by DeepBass9

I have now switched the motor around so I have 3 forward speed and one reverse. It was actually good that my wife spotted that the wheels were running backwards, otherwise I may have jumped on, twisted it's ear and ended up having a reverse crash.

A question on charging. If I get 4 x 12V car batteries, would it be possible to charge them by putting them in parallel with my solar batteries for a short time. Either when the solar batteries are at float, or early morning when the charge current is low. In that case I can just charge with jumper cables or make up a dedicated plug to do the charging.

The other option would be to use one of my solar MPPTs to charge the quad batteries. I could put a changeover switch on the MPPT output to go either to the solar batteries or to the quad batteries. 

I don't think car batteries are that particular about charging voltages?

Edited April 22, 20206 yr by DeepBass9

17 hours ago, DeepBass9 said:

If I get 4 x 12V car batteries, would it be possible to charge them by putting them in parallel with my solar batteries for a short time.

As a once or twice off, that's not too bad. But I would not consider this as a permanent solution for charging your quad.

It would be best to parallel in the early morning. I would put the 4 car batteries in series then use one set of jumper leads to parallel the string across the 48 V house battery.

Of course, car batteries are terrible for traction applications like the quad. They're designed for short term high current loads like starting a car. They won't take kindly to frequent deep discharges. Again, as a once or twice off for testing, it's not too awful.

Nice going DB9. Thanks for the video. Looking good and must be so satisfying to see the wheels turn !

I agree with Coulomb that the LA wont like frequent deep discharges but, as you said, you will only be doing this short term.

BTW Regarding your motor spinning the wrong direction, you are using a BLDC motor which has 3 (the thick wires) going from the motor controller to the motor. To reverse direction you could just have reversed any 2 of the the motor wires to change its rotation direction. Would maybe have been easier than changing the motor physically 😅

Keep up with the feedback on your progress !

I just acquired 4 x 40Ah reconditioned batteries, so this weekend I'll connect it all up and take it for a spin......

I'm thinking that for the charging I'll buy a cheap pwm solar charger and charge from one of my solar arrays. I also have a few 10w panels lying around so I can use those in series to trickle charge the batteries when not in use. 

Edited July 8, 20205 yr by DeepBass9

An update on this. I had the bike running and it got up to quite a speed on the flat ground on the slowest speed, but had no power on uphill, so I have ordered a larger reduction gear. It also turned out that one of the batteries was a dud, so I'll exchange that for a better one during the week. 

I have now changed the gearing to lower than it was before. It still goes quite fast, but is short of power on the uphills, so I am going to reduce the final drive gearing further. Currently my kids can use it, but It won't move my fat butt uphill very quickly:

 

While other people have advised different vehicles, I personally would love an electric quad.

I'm not so sure about quat bikes. This one is quite slow so you steer it like a car, but I am used to motorbikes where you lean to turn, but you can lean as much as you like on a quat, but it still goes straight. 

Hi DeepBass1 , Any update on this project ? Most interesting thread . Also , would you mind sharing your gearing details , and more details on the electric motor to wheels setup , even pics if possible. 

I'm thinking of doing a similar project for a farm , but run time is main concern.

Do you feel your 2500W motor sufficient for farm life ( torque over top speed ) , or would you go for a more powerful one , which obviously reduces run time on a charge.

Thanks

Not much has happened lately, I put a much larger rear sprocket on, but one of the cheap recycled LA batteries I have is dead and I haven't sorted out the charging system as yet, but it is there on my list of things to get to....... 

Any updates on how your quad is working?