FYI those look like black oxide coated. The reason everyone likes to use stainless is bc of the corrosion protection (and bling), but they’re much weaker than alloy steel (as Brian pointed out.)
Black oxide is pretty poor corrosion protection. In a humid enough climate, those will rust in 6 months without ever going through a puddle. You want zinc-coated alloy steel bolts.
If you need black for your color scheme, paint them.
Idler or no idler pulley? 15/40 T, ca. 75 mm center to center distance. I saw this question being asked earlier in this thread, but never answered.
I’d like to go no idler, but won’t if there’s a big risk of belt slipping.
What do you guys think?
That’s a pretty small c2c distance. Can we get a pic of the setup?
I don’t have it set up yet as I haven’t bought my motor mount yet. I’ll probably get the Boardnamics caliber II 63mm motor mount if I don’t need the idler, and go with the caliber idler version if end up needing the idler. But I do have both pulleys, so I tried to place them 75mm apart and wrap a string around. I can post a pic of that if it’s of interest?
When I wrapped the string around it seemed like the string (belt) would grip about 5-7 teeth aka ca. 120 degrees of the small 15 t pulley
ah shoot ordered already
its not a humid climate but i occasionally ride in the rain
It’s LiFePO4 (3.65V) cells, which are very different from 4.2V li-ion cells…
I personally don’t care too much for idlers, but they’re not that bad either.
It’s more stuff that can break, and more things to adjust, and it wears the belt on both sides instead of just one. But it also has some benefits, generally speaking. Not in all setups though.
I agree with what you’re saying there, that’s why I’d like to avoid using an idler. But I’m worried that my belt will slip due to the big gear ratio 
I tried to figure out a way to calculate if the belt will slip, but wasn’t able to figure it out. I’m wondering if any of you guys know if the belt will slip with this setup (if I’m not using an idler)?
would there be any problems running a 10s8p with a 2s8p in series and the 2s having a different bms or connecting the 2s to the 10s assuming i have a adjustable bms?
What setup? Volts / series count, motor Kv, motor pulley tooth count, wheel pulley tooth count, wheel diameter in millimeters
Yes, there is a lot wrong with that, unless all twelve 8P packs have cells from the same batch, same age, same number of cycles, et cetera, as all the cells in the other battery. Basically in perfect laboratory conditions it will work fine, but in reality, IDK, it’s unlikely to be good.
With 96 cells it’d be much better to make a 16S1P in parallel with a 16S5P using the same number of cells and a BMS for each pack. That would work MUCH better. If 16S is too high then an 8S2P in parallel with a 8S10P.
Volts / series count: 10s
motor kV: 149
motor pulley: 15 t
wheel pulley: 40 t
wheel diameter: 97 mm
You’ll max out at 20mph (33km/h) with that setup, but have excellent range and torque.
That will be fine without an idler, but consider a 190Kv motor, it will be faster at 26mph (42km/h).
That’s what I’m aiming for 
Sadly I have to obey local laws which means top speed at 20 km/h (12,5 mph), but I think that will probably be enough for my n00b ass anyway.
Thanks for the feedback! Sounds like I don’t have to worry about the idler then 
can i ask why those 2 other layouts would work better? isnt there still 80 “old” cells and 16 “new” cells?
Different cells MUST be connected in parallel, not series.
They also have to be the same voltage, cells, etc. Or else. Although, I never did that myself.
Doing that, you will not be getting what you think you will be getting. If connecting in series, you’re basically gonna just get a 4s8p instead since the 2s will be drained more than the other. And because the esc will still drain power from both, instead of the one with more cells, you’ll soon realize that the other pack will have either a sudden fire ball or it will be overly drained to no return, or very weak power output (guaranteed the weak power one).
Edit: it will also damage both cells badly.
This is why you must put them in parallel.
If you must use mixed old and new cells in a pack (which is already not recommended btw), you must must must have each p-group contain an equal number of old and new cells. This either means tearing apart the old pack and shuffling things around, or in your case, adding a second pack of new cells in parallel with the old ones.
If you go series instead (like your initial idea), or just add a new p-group of fresh/different cells, the capacity and discharge characteristics of the new and old cells won’t match up perfectly. (Yes, depending on the wear the mismatch can be small. Any mismatch at all is No Bueno.) That will cause the p-groups to be imbalanced, and possibly wear unevenly, which will make them more imbalanced, which will make them wear more unevenly, in a downward spiral that ends with you buying a whole new battery at the minimum.
By going in parallel, you spread the unevenness across all the groups, so the above can’t happen.
so if i were to take away 2 old cells from all 10 groups of 8p and replace it with new same model cells, so 6 old cells and 2 new cells each p group. then use those old cells i took to make 2 more groups of 8p also having 6 old and 2 new cells for each of the 2 “new” groups. that would work? since i kinda made all the groups “even” while increasing the amount of groups.