Cas_blue_pianist said:
3) sell out 1500W engine and buy new 250W engine - in that case I would get same speed as now when uses health power option - 750W, 25Km/h, which should be good enough to run in the city or even small hills
Another thing to note, is a smaller motor running within its optimal power band and RPM is more efficient than a large motor running way below its rated power and RPM at low speeds.
Case in point, I have a 3KW Cyclone mid drive, mainly for dealing with Hilly wales. Quite efficient in America for commuting in traffic at 30MPH+
But not so efficient for cruising around the UK at the slow legal speed of 15.5MPH on the flat using only around 250w out of its 3000w capacity
So I'm considering putting the most efficient small 250w direct drive I can find on the front wheel
Plus it gives the small extra bonus of Regen braking and redundant powertrain in case of the failure of one or the other.
As for batteries, I've found building your own using genuine cells from a reputable supplier such as www.nkon.nl
Is a good option.
It's easier than you think, for an absolute newbie there's an intermediate option between buying a prebuilt pack and designing and fabricating one from the ground up.
And that is simply self assembly of a Shark style battery.
One of these with the cell layout and nickel plates already done for you ready to spotweld up: https://m.aliexpress.com/item/4001076311328.html?spm=a2g0n.order_detail.0.0.49d8f19cQVQvOL
(Only rated at 20A so I bought more nickel plates separately and double layered them https://m.aliexpress.com/item/1005003777519383.html?spm=a2g0n.order_detail.0.0.5e6bf19cJwqvTt
You might be better off buying the box with the "no nickel" option and just buying the plates separately, as the plates linked here are better because they have extra tabs that stick out for you to solder your leads onto, so there's no chance of overheating your cells by soldering directly onto them )
You will want these PET plastic insulation washers for the positive ends of the cells rather than the cheap paper ones that absorb moisture and increase the risk of corrosion
https://www.ebay.co.uk/itm/363384074940
And one of these well known and highly regarded BMS units (Battery Management System)
https://m.aliexpress.com/item/32876805034.html?spm=a2g0n.order_detail.0.0.1744f19cir8viX
(I used the 60A version for my 40A rated Cyclone, but be aware that the 60A version is too large for the case so needs to be put into a 80mm heatshrink tube with a silica gel sachet to absorb moisture, then sealed at either end with liquid tape/plastidip. Then secured on the outside of the case with black duct tape and the wires run in through a hole cut into the lower end of the battery, also sealed with liquid tape.
An added bonus of these BMS units is that you can monitor the health of your battery cells amongst other things as it connects to an app on your phone through bluetooth)
I highly recommend picking up one of these grounding matts with antistatic wristband to handle the BMS, https://www.ebay.co.uk/itm/294453161431 as I heard from a few places now that they are much more susceptible to damage from Electro static discharge than the PC hardware you may be used to, as PC hardware is designed for installation by home users, wheres BMS are assuming professional installation at a ESD safe area at a factory.
Though don't quote me on that as I have not yet fully researched this...
Then one of these spot welders, one of the best for the price and has worked a treat for me: https://m.youtube.com/watch?v=WxGErteGyZQ&t=1s
(Use eye protection work goggles as there will be sparks and you may be close in with your face to examine the placement as you spotweld)
Paired up with one of these Zeee Lipos https://www.ebay.co.uk/itm/143968625270
The individual spot welding probes that come with it are adequate but I picked up one of these spotwelding pens with springloaded tips that adjust for good contact when you press em down for a spotweld, and it made a world of difference for me....
https://www.ebay.co.uk/itm/403527924629
Perfect spacing every time (after adjusting the angle of the probe ends), no worrying about a tip slipping and coming into contact with the other probe (which makes quite a bang! Also damages the tip and risks blowing a hole through the cell casing... Don't ask me how I Know....)
Plus frees up a hand to hold the nickel plate secure, so no chance of a short circuit between cell groups from it jumping out of place at one end when pressing down on the other end for the first spot weld on that plate...
Springs are a little stiff stock, but the screws that hold the probes from going too far forward can be backed off till the head of the screw is above the plastic, so its the thinner threaded portion that is holding the probes from falling out of the plastic. This loosens the spring tension a little and gets it about right. I replaced the stock screws with longer ones so they can be backed out like that without being near to falling out themselves.
All things considered they made the job of spotwelding so much better that it's now easier for me to do two layers of plate on a whole battery than it was to do one side with a single layer with the old separate probes.
One thing to note, is it's best not to place a spot welding probe on the direct center of the negative end of the cell as this is where the "jelly roll" inside is connected to the outermost casing via a rail that runs the entire length of the 18650 cell.
You don't want to risk damaging that connection by blasting a spot weld right on it.
The positive end is usually fine as there's usually a raised plate separated from the cell itself there.
Other bits and bobs that I also needed....
Connectors
https://www.ebay.co.uk/itm/125154344755?var=426206089245
Wire for discharge leads
https://www.ebay.co.uk/itm/361296232202?var=630634243728
Heatshrink for insulation after soldering connections.
No link for this one as I haven't bought any recently, I'm still working with the bulk supply I bought from hobbyking for RC stuff years ago...
kapton tape is optional, but is a good thing to have around, especially if you have to run the thin BMS balance wires over the nickel in a battery pack, as with time and vibration the insulation of the wires can chafe through and short on the nickel strips.
So best to put some kapton tape between them for more chafe resistant insulation
https://www.ebay.co.uk/itm/373299713754?var=642255724573
I recommend putting an inline midi fuse somewhere on the input leads of your controller, protects the battery in the case of FET in the controller failing closed or dead short.
Something like this: https://www.ebay.co.uk/itm/313160298270
You will probably need a lower amp fuse to match your lower Amp hour battery.
Maybe 30A if you have a 20A limited controller.
Good baseline for your fuse is for your max normal load to be around 75% of the Midi fuse rating as shown here:
https://www.google.com/url?sa=t&source=web&rct=j&url=https://m.littelfuse.com/~/media/automotive/datasheets/fuses/automotive-fuses/littelfuse_automotive_bolt_down_fuse_midi_32v.pdf&ved=2ahUKEwjPrsGlren2AhWMSPEDHYzGAAAQFnoECAMQAQ&usg=AOvVaw1xYzGHesn5EzRA4lDBjvOx
Also make sure voltage rating is sufficient for the voltage of your battery at its max state of charge
Easy enough to solder in line with your wire, then reinforce with a few layers of heatshrink.
Also if you are Autistic like me, and extremely fussy about getting the details right, you can use one of what I use to check and ensure all the cells in a parallel group are similar in internal resistance.
https://m.aliexpress.com/item/4000080760970.html?spm=a2g0n.order_detail.0.0.3feef19cHssIGj
The importance of which is explained here: https://www.sciencedirect.com/science/article/abs/pii/S0378775313019447
If you don't already have a soldering setup, what I use is a weller 80w
https://www.ebay.co.uk/itm/384885709079?hash=item599cf9d917:g:FuUAAOSw3X1ifUUy
And this solder is excellent
https://www.ebay.co.uk/itm/144124119919
It's an eutectic alloy, with a sharp transition beween liquid and solid.
Good for a beginner as it is more resistant to being disturbed from movement as it cools and solidifies causing a "dry joint", as well as having one of the best Rosin flux already included running through its core to help it "wet" onto the surfaces being soldered, helping result in a physically and electrically good shiny solder joint.
You can also save some money in the long run by doing what I did and buying a 1lb roll of it for around £40
https://www.amazon.com/Kester-24-6337-0010-Rosin-Solder-SPOOL/dp/B00068IJWC/ref=sr_1_51?crid=9J3R5ZU2XAGH&keywords=63%2F37+%22kester%22+solder&qid=1652632400&sprefix=63%2F37+kester+solder%2Caps%2C209&sr=8-51
Should last you a lifetime.
Or if you are in the North wales area...
I could help put it all together for you