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[Andy M]

Here is my electric bike, it uses running gear from an electric scooter and various other things. It has freewheel hub which increases range by a substantial amount. It uses the 36v 12ah sealed lead acid batteries that the scooter used. As my legs are not as good as they used to be, this is perfect for me to get out and about.

[Andy M]

Its time to get a bit more up to date with my power source, I am making the leap from lead acid to li-ion power. My lead acid power pack is 36v 12ah, now I am building a new pack of 36v 50ah, more than 4 times the capacity of my well used(probably 2000 miles on it so far) lead acid pack, and 2/3 of the weight. My friend is building a 48v 50ah pack, so we had to build a spot welder for connecting the cells, as soldering apparently heats the cells too much. It took a bit of refining but now works perfectly. It is made from a large car battery, a motorbike solenoid and some jump lead cables. A couple of solid copper wire electrodes and it was time to practice on some dead nicads. The photos show progress so far, first photois the basic layout of the pack, second photo is fully welded pack with battery management system wired in. Still to encase the pack but not decided how I am going to do this yet. I have had a problem soldering plugs onto the heavy wires from the battery management system. My biggest soldering iron is not up to the job.  I will get more photos on once the pack is finished.

[Cornishman]

  I hope you are going to put some guards on the chain drives!

[Andy M]

Hi, it has had a cover put on totally covering the motor chain and sprockets. My friend's one ate his trousers, so we both fitted guards after that.

[Unsinkable 2]

Fantastic, I love when people make stuff themselves!

[Andy M]

Well thats my bike done 600 plus miles so far since I upgraded to 18650 cells. Not really had much chance to see how much range I have available, doing the maths comparing my old lead acid 12ah batteries with my new 50ah cell block, gives me over 4 hours of full throttle. Thats a fair distance, even with my padded seat. Lol. It has been relatively reliable for a home made device, had to figure out some chain tensioning as I had run out of adjustment. My friend built one of these too then sold it and built a brushless version with a bafang mid drive motor which fits through where your pedals usually go and has its own pedals. Very compact and drives through the bikes own chain and gear system whereas my bike has 3 chains in total, with the electric drive having 2 of them. His was considerably more expensive than my version but he has had more problems, with a malfunctioning battery management system which destroyed 2 3.7v 20 cell 50ah packs. He also had a burned out speed controller and has had to pedal it home and they are not light bikes. Mine just seems to keep plodding away. So far anyway.

[Andy M]

My friend and I visited mountain bike trails in a forest beside a nearby reservoir. I was a bit worried my drive system would fail, but it performed well, all day, pretty much, popping the drive chain off once on a really bumpy bit. Its no lightweight at over 5 stone but it coped with some extremely steep drops and rocky  banked corners. It was dark before we got back to the carpark and we had done over 30 miles, mostly without pedalling. I help the old girl up the worst hills. One of the 3 battery lights had gone out. Not sure how much is left when that happens. We were trying to find that out, but I think theres good bit left.

[JimG]

What do you use as a speed restrictor? Without one if it can go over 18? mph then it is a motor vehicle and needs registered taxed and insured.

[Charlie]

Stopped by the local bike shop recently, and there was a nice looking eMTB in the window. The price was £7500

[Andy M]

Mine was definately a bit cheaper than that.


We took the bikes to the forest in a van. It only does 16-17mph depending on flatness anyway. I chose the final gearing to match the speed of the donor scooter at 14mph, the bike rolls a bit easier though, giving extra couple of mph.
I take it I am still allowed to freewheel down hills at faster than 18mph?

[Andy M]

Mine has about 3 times the battery capacity of most e bikes, they normally use 17ah packs to keep weight/cost down. Mine is a pretty heavy old beast.

[Tug Fanatic]

Another Andy M project. You are certainly never boring! 

That is a lot of 18650 cells so I am sure that you have found a good source for them. Care to share?

[Andy M]

I will have a look back through my stuff. They werent that cheap but thay are samsung 25r so a good cell judging by online reviews.

[Andy M]

https://www.fogstar.co.uk/products/samsung-25r-br-2500mah-20a

These have gone up in price since we bought them but they are good cells. They have wholesale section for larger numbers, that is the way we went to get ours.

[Tug Fanatic]

Thank you. 200 (£758) cells is a big financial commitment even with a volume discount.

[Andy M]

Covid price increases! They were down at £1.85 per cell if I remember correctly. I wouldnt have bought them if it had been as much as that. Between myself and my friend, we bought about 450 of them.

[Andy M]

After having done about 1000 miles on my ebike, the chains and sprockets had worn quite a lot, they had all been on other things before I used them on the bike.
I invested in new ones which I have still to fit, but as part of my refurbishment, I took the battery out to test it and found that one block of cells (3.7v 50ah) was down at 3.3v...not good, the battery management system had not been charging this block properly.
About a week of putting it on charge on my b6 charger whenever I was in my shed, as I dont leave batteries charging when I am not there, brought it back up but it is still a bit lower than the other blocks. They all got topped up as well.
I spent £50 (of my year's modelling budget) on a new battery management system, so hopefully this will cure the problem.
I have still to fit all the new chains and sprockets but it has been too cold for me to be biking anyway so I havent been in a rush to get it done, I will get stuck into it once the weather warms up a bit. 😁