Puch R50 Project

Joined
Mar 6, 2022
Messages
10
Hi,

I'm starting to convert my Puch R50 to electric :bolt: :flame:
puch.jpg

I want a top speed of +80 Km/h and a range of +40km.

I brought the QS 138 70h v3 + Votol EM-150 kit.

The battery I have some doubts about it. For now, I want to buy a battery already made to keep it simple. I was thinking to buy a 72V 30Ah with 60A BMS(https://a.aliexpress.com/_mNtm1Vu) but all the posts I see use custom batteries with much higher BMS(150/200/250/300A).

For the sprocket ratio, I see this 39T 428 sprocket(https://www.amazon.de/-/en/Sprocket-Teeth-Pitch-Chain-Z%C3%BCndapp/dp/B07QN6WKK3) that fits on the position of the original 35T 415(I think) and use the 15T 428 sprocket that came with the QS motor. Some doubts about the top speed, what is the best way to calculate? The wheel is 12"

I need your help to solve my doubts :D
 
The battery must be able to supply all of the power (voltage and current) that the controller/motor will ever ask for. If you use a battery that cannot do this, it may be damaged by the demands on it. It's not just the BMS--the cells have to be able to do it too. See my post here for some detail about that:
https://endless-sphere.com/forums/viewtopic.php?f=14&t=116314&p=1716992#p1716992
which has a further link to more info as well if you need it.

Regarding the speed: you should use one of the online calculators (google can find them for you) that converts actual road speed to wheel RPM based on actual tire diameter.

ONce you know the wheel RPM for your max speed, and you know what hte maximum *loaded* RPM is for the motor at the voltage you will be using (ask QSmotors, they can help with that). Make sure you use the *fully discharged voltage of the battery* so that it still gives you top speed even when almost empty!

Then you can divide the one by the other to get the gear ratio you need between them. Then you can use that ratio to find the right sprocket sizes to give you that ratio.


For range, you'd need to know what wh/km power usage a bike like yours will have at the speed you want to go, *under the specific riding conditions you have*. If you are not sure, you can use the http://ebikes.ca/tools/simulator.html to see how this works, using the built in ebike parts to play with your conditions, and then if necessary you can then use custom entries for controller, motor, battery, etc., to see what it will take to get the results you need. That will give you a better idea what parts it will take to make the bike do what you want.


renatofmpinheiro said:
I want a top speed of +80 Km/h and a range of +40km.

I brought the QS 138 70h v3 + Votol EM-150 kit.

The battery I have some doubts about it. For now, I want to buy a battery already made to keep it simple. I was thinking to buy a 72V 30Ah with 60A BMS(https://a.aliexpress.com/_mNtm1Vu) but all the posts I see use custom batteries with much higher BMS(150/200/250/300A).

For the sprocket ratio, I see this 39T 428 sprocket(https://www.amazon.de/-/en/Sprocket-Teeth-Pitch-Chain-Z%C3%BCndapp/dp/B07QN6WKK3) that fits on the position of the original 35T 415(I think) and use the 15T 428 sprocket that came with the QS motor. Some doubts about the top speed, what is the best way to calculate? The wheel is 12"

I need your help to solve my doubts :D
 
The biggest thing is figuring out what terrain your ridding MOST OF THE TIME and AT WHAT SPEED, then match the turn count of the motor to your battery voltage, play around with www.ebikes.com motor simulator and their trip simulator is excellent too.
 
Nice Vespa! :thumb:

This motor only comes in one turn count and it has a kV motor constant at about 60 rpm/volt. It’s not in the ebike simulator (it can be simulated if you put in correct parameters of course).

72V and 60rpm/volt, that’s 4320rpm unloaded, about 3700 loaded with a percentage of 0.85 loaded/unloaded rpm (85% has been ok estimation for me on my builds)

130/70-r12 (as an example of a 12” tire) has a circumference of 1.529m, 3700rpm is then 5660 m/min and 339.4kph loaded speed without gearing. (Going to a smaller tyre dimension like 110/60 r12 could also get you to a lower gearing)

339/80 will then be your wanted gearing so 1:4.24 is needed, 15 tooth front and 64 tooth rear, or any similar combination.

The 39t sprocket will give a top speed of 339/(39/15)=130kph so it’s not the best match.

One thing to note: People have had trouble with loosely fitting sprockets from QS causing wear on the axles of this motor so if your sprocket is the same it’s adviseable to replace it anyway.

A 10t like this: https://www.ampsprockets.com/shop/amp-sprockets-qs-motor-138-3000w-70h-bldc-motor will give roughly the correct ratio. With field weakening it will go closer to 100kph so you’ll have some oomph left at 80kph which is nice! :D
 
Many thanks all for the tips :thumb:
larsb thanks for the calculations :thumb: I will try to order the 10T sprocket.

In terms of battery, I can limit the max current on the controller right? Does the max continue current influence the acceleration only or influence other aspects?
 
Max continuous current will set the boundary for your drive when going at a higher speed, the battery you linked will be too weak. I’d rather recommend to get some EV cells that can match your motor and controller and then make your own battery with a known bms. Chevy Volt, VW GTE, nissan leaf cells pop up here in the for sale section at times or go to the local car junkyard. The EV cells can’t be beat in price/performance and it’s not hard to build packs with them since they come in modules :D

Getting a battery from aliexpress (if the seller isn’t well known and reputable) is a high risk for all kinds of unwanted surprises :flame:

I’d set 200A output battery and BMS for ballpark figures of what you want and a larger capacity like 40-50Ah to get the range. Here it’s really good to use the ebikes.ca calculator to find an estimate for the ranges and speeds - it is a fantastic and powerful tool.
 
larsb said:
Max continuous current will set the boundary for your drive when going at a higher speed, the battery you linked will be too weak. I’d rather recommend to get some EV cells that can match your motor and controller and then make your own battery with a known bms. Getting a battery from aliexpress is a high risk for all kinds of unwanted surprises :flame:

I’d recommend a 200A output battery and BMS for ballpark figures of what you want and a larger capacity like 40-50Ah to get the range. Here it’s really good to use the ebikes.ca calculator to find an estimate for the ranges and speeds - it is a fantastic and powerful tool.

So I will have to spend more than expected on the battery :D
What cells and BMS recommend? Any European shop where I can buy the cells?
 
I just updated text above :wink:

For BMS the LLT BMS and ANT BMS (ANT can be bought from icgogogo store at aliexpress, LLT at their web site) is used a lot here. I’ve seen some ANT BMS failures on here, never had a problem myself but i run LLT right now, https://www.lithiumbatterypcb.com/

These are OK Quality smart BMS’s but not higher class BMS like Orion or Emu BMS.

What i would use today for a street motorcycle build is probably this one:
https://www.lithiumbatterypcb.com/product/7s-to-20s-200a-smart-bluetooth-bms/

It’s a smart/programmable BMS with integrated contactor. I haven’t seen it used but the integrated contactor removes some of the mosfet bms risks.
 
Example of cells:
https://endless-sphere.com/forums/viewtopic.php?f=9&t=90395&start=50#p1716687

Four of these in 2s2p for 20s60Ah (if you can fit them), would be a good sized pack. They are OK, not the latest cells so energy density is not on par with the latest and greatest, still good cells and a very easy solution to build a pack
 
someone else will have to answer on those. I think later generations of the leaf cells are preferred since they advanced a bit. I'd put a question in the battery technology thread and do some google studies. How do they compare for power density (W/l or A/l) and capacity density (Wh/l)?

Edit: checked the lev40 cells. 40Ah 300A continuous. I think a 22s battery with those would be great. Not sure about the range if a single cell series will do, depends on how fast your average speed is and all stop/starts.
 
larsb said:
Where would you get the lev40 cells? I might invest in some :D

larsb
The price is 700€ for 20 modules. I asked for 20 because 3.65 * 20 = 73V, what you think?
I can ask if we sends to you, where are you from? I'm from Portugal.
 
Sweden :D

What year were they produced and what is their mileage or guaranteed capacity?

I’d go with a 22s with charge to 4.1V so 90.2V full charge. This is about the max i would consider for the Votol (my votols came with 90V overvoltage setting from QS). It will give you a bit of extra energy and speed and also lower stress on the cells from charging.

(20*3.65*40 is 2.92kWh, 22*3.65*40 is 3.21kWh)
 
I just compared batteries and i think it might be good to look around before settling on the lev40 cell.. two things: 3.65V nominal shows it's probably an older lev40 cell, the latest generation seems to be 3.75V and i also looked at some other packs here: https://evshop.eu/en/13-batteries
Outlander(Lev40) is at 92wh/kg, vw id3 214wh/kg :bolt: the difference is huge.
 
larsb said:
I just compared batteries and i think it might be good to look around before settling on the lev40 cell.. two things: 3.65V nominal shows it's probably an older lev40 cell, the latest generation seems to be 3.75V and i also looked at some other packs here: https://evshop.eu/en/13-batteries
Outlander(Lev40) is at 92wh/kg, vw id3 214wh/kg :bolt: the difference is huge.

The seller say that is from a car of 2015-2016
The guaranteed capacity os about 75-80%
 
I will never understand how cells under 80% still sell for over 200€/kWh even 100€ is too much.
 
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