Fingle
1 mW
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Building custom mid drive ebike need some advice, school project
- Thread starter Fingle
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Fingle
1 mW
Building an e-bike conversion for school, doing DT A-level so decided on this as a project. budget is fairly low as I'm still in school. For the motor I bought this motor and controller kit off of aliexpress. (https://www.aliexpress.com/item/100....order_list.order_list_main.17.21ef1802fklJOF)
Says it handles 2000watt, but the controller will probably only supply like 1500 from what Ive read. Got this motor connected up with a reducer to the front chainring. Motor spins at 4300rpm, and have got that reduced down to around 120 rpm for the middle chainring. This will give me a speed of between 30-40mph in theory.
Bought some Samsung INR 18650 cells a while back, thinking about using those for my ebike battery. Initially I thought Id do 13s 6p, but am now worried this will be too high of a voltage as my motor tends to overheat.
Could potentially do 12s 6p, but don't think that would give as much power/performance. would be much easier to charge though as Im planning on splitting it into two 6s batteries and charging those individually.
Built some custom batteries in the past but never any this big, so am unsure how I charge them once they're all spot welded together. Splitting a 13s battery would be much more difficult and I'm not sure how to charge these.
The batteries i have built were all charged from this hobby rc charger that does up to 6s. This balances them for you and is much simpler. However I did buy a bms for this project just in case. its a Heltec bms off of aliexpress
( https://www.aliexpress.com/item/100...o.order_list.order_list_main.4.641418022HUrcK)
Any suggestions at all, could really do with some advice on my battery, unsure whether this fairly cheap motor kit will handle anything too high
Says it handles 2000watt, but the controller will probably only supply like 1500 from what Ive read. Got this motor connected up with a reducer to the front chainring. Motor spins at 4300rpm, and have got that reduced down to around 120 rpm for the middle chainring. This will give me a speed of between 30-40mph in theory.
Bought some Samsung INR 18650 cells a while back, thinking about using those for my ebike battery. Initially I thought Id do 13s 6p, but am now worried this will be too high of a voltage as my motor tends to overheat.
Could potentially do 12s 6p, but don't think that would give as much power/performance. would be much easier to charge though as Im planning on splitting it into two 6s batteries and charging those individually.
Built some custom batteries in the past but never any this big, so am unsure how I charge them once they're all spot welded together. Splitting a 13s battery would be much more difficult and I'm not sure how to charge these.
The batteries i have built were all charged from this hobby rc charger that does up to 6s. This balances them for you and is much simpler. However I did buy a bms for this project just in case. its a Heltec bms off of aliexpress
( https://www.aliexpress.com/item/100...o.order_list.order_list_main.4.641418022HUrcK)
Any suggestions at all, could really do with some advice on my battery, unsure whether this fairly cheap motor kit will handle anything too high
harrisonpatm
10 kW
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Voltage isn't what makes a motor overheat, it's amperage, or overloading with more current than what the motor can handle. Let's say the motor actually can put out 2000w. Max charge for a 13s would be 54.6v. Check that against your batteries. 2000w/54.6v = a max current draw of 36 amps. You want to do 6p, so 6A current draw per cell. You said you're using Samsung INR 18650, but can you be more specific? Are your individual cells capable of 6A? If not, then the motor won't be the weak link, the cells will be.
And how about the controller? The aliexpress link has a bunch of spec sheets about the various motors, but almost no info about the controller. It says 48v; what's its actual max voltage? That's what you should be looking at in terms of what can handle 13s vs 12s, not the motor.
That's not a BMS, it's a balance board. It has no overcharge/overdischarge/overcurrent protection. All it does is balance the cells.
Fingle
1 mW
So, I've got some design sketches I did briefly for school. I needed a reduction of around 1 to 10 for the right angle reducer. This means that the output rpm is lowered enough so it works for connecting to the middle chainring.
Fingle
1 mW
Fingle
1 mW
Thanks for the info, Ill send a link for the batteries. These are reclaimed but after testing the individual cells they are all in pretty good condition. (Samsung INR18650-20R 2000mAh - 22A - Reclaimed - 18650 - Li-ion - Rechargeable batteries | NKON)
They say they're capable of 20 amps so I'm hoping they wont bottle neck the build. Do you think that I should with 13s in this case then. From what I understand if I up the voltage Ill be pushing more amperage through the system.
Yeah I agree the specs on the site are fairly vague so I'm unsure of what the controller is capable of. Ill have a better look, worst case is I test the controller manually and risk ruining that. Not too bothered about the controller it wasn't too expensive, was thinking about upgrading that component in the future.
I bought the balance board just for charging, not planning on running the system through a bms. Unless you think that is necessary. All I'm looking at for the moment is how I can charge my pack safely and without spending a huge amount on the charger. I have seen some 13s chargers but theyre very expensive.
harrisonpatm
10 kW
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Not necessarily. There are a lot of intricacies regarding specific use cases, how exactly you'll be using all the components together. But in general, think of it this way: If you need 2000w to go forward, higher voltage = less amps, for the same amount of total power (if the controller can handle it, which is an unknown). That's just ohms law basics.
Yes your batteries look plenty capable.
I always think a BMS is necessary. You don't have to agree with me, there are plenty others on the forum that run systems without a BMS. Be safe.
If you want to charge your pack without purchasing more equipment, then yes, you can use your 6s hobby chargers, if you limit your pack to 12s. What's your budget?
Quick Aliexpress search, this guy can charge your pack in 4.5ish hours and only costs $17usd. That was just the top of the list, there's plenty of other options
Fingle
1 mW
Yeah thats very true, I'm hoping to use the full potential of the motor as my gearing will need the higher power output. Will definitely go with 13s then, if the controller can manage the voltage. If not as long as there is no damage to the motor ill just replace it.
Will definitely get a bms long term, just want to charge the pack for now. Would like to test the system properly.
I'm willing to spend a decent amount on a charger, I'd like to do this project safely and take care of my batteries well. The cells were the only truly expensive part of the project. So would like to treat them to a good charger. Probably a budget of up to 100-150 pounds, will likely reuse the charger for future projects.
Yeah, looked briefly at what amperage I might need for my charger. Looking at around 3-4 amps at 48v ideally. Saw somewhere you should charge with 25 percent of your batteries ah rating. So a charger that could provide around 3 amps would probably be safest for my 12 ah battery.
Note that the first post of this thread and this reply to it were another thread, instead of being part of this one that discusses the same things that was started later. So my reply below may cover things others already discussed, as I have not (and won't) be reading the rest of the thread--I just moved the OP's post and my reply into this one to keep all the info together.
What exact voltage range is your controller designed for, or what is it's LVC? (the link goes to a page with many options, and doesn't select one).
Most controllers have LVCs for either 13s or 14s. If used with 12s they will shut off the motor from battery voltage below their LVC quite a bit before the battery is near empty.
If it doesn't have an LVC then there's no worry about that.
BTW, "Vevor" as a "brand" hasn't inspired a lot of confidence in some of the threads and posts around here. (they dont' make anything, they just sell (all kinds of) stuff).
What exact voltage range is your controller designed for, or what is it's LVC? (the link goes to a page with many options, and doesn't select one).
Most controllers have LVCs for either 13s or 14s. If used with 12s they will shut off the motor from battery voltage below their LVC quite a bit before the battery is near empty.
If it doesn't have an LVC then there's no worry about that.
BTW, "Vevor" as a "brand" hasn't inspired a lot of confidence in some of the threads and posts around here. (they dont' make anything, they just sell (all kinds of) stuff).
Fingle
1 mW
Yeah, sorry about that wasn't sure how to delete a thread properly. I didn't include much information in that first post so did another one. Thanks for moving it into this one.
I've got a screenshot of the motor I chose and its specs. I'm assuming it should run on 13s. Just wanted to see whether I could run it off 12s because then I could split the pack nicely into two 6s batteries. Then wire those in series, just makes charging easier.
Alright, thank you, Ill probably go with 13s in this case. As I reckon It would cut out like you said, with the under voltage protection. says that is around 41 v.
Yeah little bit worried about their motors, from what I've read they overheat very easily, so thinking about making either a heatsink or doing some sort of water cooling jacket for the motor. Just chose the kit as it wasn't massively expensive and wanted to give this bike design a shot without committing to an expensive motor kit.
Mainly wanted to test my mid drive design, I may upgrade the electronic parts in the future.
Still unsure though of how you can charge 13s packs. Can you split them into two or more different voltage battery packs and put those in series or does that really mess with your cells. 13s is impossible to split nicely, If I cant split the pack, are there any chargers you would recommend that could do around 3 amps at 13s.
harrisonpatm
10 kW
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Didn't I link a 13s 3A charger in my earlier post?
Fingle
1 mW
No, sorry link didn't work for my location. Said it wasn't available to the Uk. Would like to spend a bit more on the charger though, not sure if id trust any of the really budget ones.
harrisonpatm
10 kW
- Joined
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It'd probably be okay, Aliexpress is a bit of a grab bag
Fingle
1 mW
Yeah Ill give that a go then, see how it works out. Ill post some updates when I've got it together.
