Hi, I think this is the right place to post this, as the Builds category looked like it was for completed builds, but I’ve been planning a semi-budget E-MTB build for some time for my first DIY build. My idea is to base off an MBS complete, and fit a chain drive as a medium between cost(belts) and durability(gears). I don’t have the capability to build my own packs, so I’m thinking about using LiPos, given I already have some form of charging infrastructure for them and they’re more familiar.
This is my planned parts list, and I would really appreciate getting a set of experienced eyes on this. Does this seem like a reasonable build? Are there any components I should switch out, compatibility issues, or anything I should add to the list that I forgot? It would also be great if I can shave off some costs in some places, such as ordering from the same manufacturer. Thanks in advance for any help!
Part
Name
Cost
Quantity
Total
Base
Complete
MBS Comp 95 “Birds”
400
1
400
0
Drivetrain
0
Motor Mount
Boardnamics Matrix II Mounts
25
2
50
Drive
Momentum Matrix Chain Drive
85
1
85
Motors
Maytech 6374 Sensored 170kv
120
2
240
0
Electronics
0
ESC
Flipsky Dual FSESC 6.6
220
1
220
Switch
Flipsky Smart Antispark Switch
50
1
50
Remote
Flipsky VX1 and Receiver
50
1
50
Battery
Turnigy 12000mAh 6S 12C
110
4
440
Series Y Connector
XT90 Series Battery Harness
5
1
5
Parallel Y Connectors
XT90 Parallel Battery Harness
7
2
14
Wire
10AWG 1M Black
3.5
2
7
0
Hardware
0
Battery Enclosure
Monoprice 6.6L Weatherproof Case
26.46
1
26.46
Standoffs
Vibration Dampening Standoff 10-32
2.63
4
10.52
ESC Enclosure
Apache 550
14.99
1
14.99
Lock Nuts
10-32 Nylock Nuts 4 Pack
0.99
2
1.98
Cable Sleeving
Silicone/Fiberglass Expandable Tube Sleeving .23" x 10’
+1 on FSESC and antispark. But Stormvore is overkill for your build IMO. especially if you are trying to shave off some dollars.
There are other good options that will fit your budget better: Neobox or the upcoming TB6.6
I looked into these and really did consider it - but after seeing how they (momentum) dealt with some issues on this board before I opted to go another route myself. I’m sure the Chain Drive is bullet proof, but something to take note of.
Edit:
Also on the speed controllers, Im going to echo everyone else here and say I’d spend the little extra and go for the NeoBox. You’ll be much happier, trust me.
Yeah I’m aware of the issues with Momentum completes, but the way I’m thinking about it, the actual drive on his boards don’t seem to be the point of failure, and it seems like a good price for a system.
You’re absolutely right - and I agree. But, they haven’t posted on the forums since the fopa and, I’d rather put my money toward a builder/outfit/community member that seems more deserving.
Just my opinion man Im Jealous of the chain drive, I really did want to go that route but I opted for a belt drive system and went with MBS’s own Rockstar II Wheel Pulleys and a pair of 15mm HDT5mm motor pulleys from TorqueBoards.
I appreciate the help! The only part I’m not sure about is building a pack, since I don’t have the necessary tools to weld the batteries together. If I were to use 21700 batteries for 12S4P plus a BMS, it might be slightly cheaper in terms of raw cost, but factoring the cost of having someone else build the packs for me, I think it ends up evening out. At that point I’m not sure how the performance of LiPo vs Li-Ion compares.
Thanks for the recommendations! I actually hadn’t heard about the NeoBox until now. What differences would I need to worry about for programming two separate ESCs versus one? I’m guessing there’s a Master/Slave configuration?
With your motors and speed controller, I don’t think there’s going to be a big difference. Most people don’t really cross 3kW power at all. That is enough to accelerate up a hill. 3kW at 12s is around 60A (real amps, not specs).
You’ll want some margin to have less sag, so with an ~100A spec’d lion battery you won’t feel much difference to a cheap LiPo.
That could be a 12s5p of 30Q, 12s3p of 40T or more. For more range you can also go with cheaper cells but more in parallel.
Just decide on how much range you want and if you have some special power need.
That’s right. It’s exactly the same (with the exception of some forked specialized VESC based duals like the unity).
Edit: The only difference: you connect the two ESC with a two-wire cable (can-bus) to each other. Duals just have that already on the PCB. Done. Rest is the same.
For your use and budget I’d recommend something like a 12s4p of QB26800 if you want range. If you want pure power and quick charge, A123 cells. For the best balance of both Worlds, Samsung 40T or 30Q cells.
I guess I don’t really have a predefined power or range target. In similar builds, it looks like the board is more traction limited than power limited, and it looks like people are getting ~25-30 mile ranges. That seems like it’s more than enough for almost all of my expected riding with this thing. I decided against getting larger motors because it doesn’t feel like I’d get anything more out of them aside from reduced range and a bit of speed. The only constraints with the batteries is cost and to a lesser degree space requirements.
As an aside, if I do go LiPo, I should get more than enough current with just half the batteries (12C so 144A continuous), and maybe 8-10 miles of range. I don’t think 12S2P Li-Ion can maintain enough current. That’s honestly enough for 70% of what I plan to do with it, so I’m wondering if it’s doable to disconnect a bank from the 12S2P LiPo to spread out charge cycles and preserve battery life by keeping one at storage charge, or would there be issues if I parallel them back up with different cycle counts between them. My worry is that if they become too imbalanced in charge counts, the voltages would start differing and that could cause issues.
Doable: yes. But it would achieve the opposite of your objective (life) and potentially be dangerous (if connected at dissimilar voltages).
If you have two in parallel, both only need supply half the amps. Losses are related to the square of current. The closer you run than at their C-rating, the faster they will degrade. Also, you’d only have half the range. Else you’d switch em out and then cycle the other one, too. Better one big pack.
I would recommend you to read up on batteries a bit. It’s worth while understanding them well, and interesting!
Based on what you need and your last post I would strongly recommend not to get LiPo batteries and instead a LiIon or LFP cell-based pack. They are more than you need for your application and far more forgiving.
I guess the better solution is to just keep the batteries together, but max out charging at 70%. I was more concerned about leaving the batteries unused at high charge over weeks if not months of nonuse, but I forgot you could simply limit the final charge voltage
Are there any places I can find prebuilt LiIon packs that aren’t flat? Preferably at a similar cost and performance.
But it will be better this way.
Im Jealous of the chain drive, I really did want to go that route but I opted for a belt drive system and went with MBS’s own Rockstar II Wheel Pulleys and a pair of 15mm HDT5mm motor pulleys from TorqueBoards.