DIY Mountainboard and 12s4p samsung 30q

How-Tos & Esk8 mechanics
#1

Hi!
I want to build two boards. One for carving on the streets with urethane wheels and directdrive system and a mountainboard. I want to start with the mountainboard since I already have an electric street board but now I got a good price for a 12s4p battery that would eventually go into the diy street board. Is the 12s4p too small to use temporarly on the mountainboard? How do you think it will voltage sag? Around 15 miles range without much sag would be ok for me.

The plan is to upgrade to a way nicer battery eventually… With very high quality cells so I can put not much cells and have very nice power.

The specs of the mountainboard:
Haero Bro deck
90kv Maytech 6374 motors
Gearbox ratio 1:30, 1:33 or 1:26 (I will use low kv motor so gearbox ratio is low so more quiet)
Bkb zenith or Spintend Ubox vesc if I decide to go 14s or 16s
I will buy 8 inches and 9 inches tires
I am 200 lbs

I would like this board to go around max 40kmph but have great torque.
I have not chose right now if I will go 12s, 14s or 16s for the final battery. Maybe 12s is enough since I do not want to go faster then 40kmph…

Please share your thoughts about that small battery and about going 12s 14s or 16s for my needs.

Thank you!

1 Like
#2

I highly doubt that you would get 15 miles on pneumatic tires, and I would also expect it to sag a fair bit

Maybe 10 miles if you’re riding moderately, probably less if you ride hard

#3

Nope. I use 10s4p 30q on my mtb and get around 12.5 miles out of it (as a fat guy)

2 Likes
#4

Wow really? That’s crazy, my 12s7p of 30q cells only gets like 17 miles on 6 inch pneumatics…

That’s riding fairly hard though

1 Like
#5

Does it sag a lot? Can you describe the ride?

#6

It’s possible to get 15 miles, but if it’s a used battery I doubt you’ll hit 15 reliably

#7

They are used but almost new.

#8

I can get it to sag if i want to but usually it’s not a concern the way i ride… If you go ham on hills it sags but still gets you to the destination. Short term - definitely works. Long term i would go with a higher P count.

Your mileage may vary. Same goes for my streetboard, i can get max 16.7miles out of a 2 year old 6.4Ah battery or kill it within 5miles.

15 miles on 4p is probably doable as Zach said but not as fun. You definitely feels the sag at 30-34v

I can easily sag 6v uphills. 39-33v

1 Like
#9

Check who it sells and how they are made. Compare pricing to some of our battery builders to possibly get an even better deal.

#10

90kv motor, 1:30 gearing, and 16s is still only 7mph / 11 kmph top speed loaded.

You need to get a higher kv motor and higher voltage battery if you want to use a massive reduction like that.

Or

If you want to use a 90kv motor with 12-16s battery, you’re going to need a much lower gear ratio.

Play with the calculator at the top of this page for some more realistic estimates.

#11

Venom, are your caculations right?

image
image672Ă—855 44.9 KB

#12

You’re doing 10:30 or 1:3, not 1:30 in yours.

Also you’re going to want to drop efficiency to 70% to account for pneumatic tires.

3 Likes
#13

I think you meant 1:3.0, 1:3.3, or 1:2.6 or unsimplified 10:30, 10:33, or 10:26

1 Like
#14

Hover over “Efficiency”

1 Like
#15

You are right!! Imeant 10:30 etc in the first place!! Sorry for that!

#16

Thank you very much! I did not know about 70% efficiency for tires. Also i made a mistake, i meant 10:30 or 1:3 etc in the first place.

#17

a 12s4p 30q can totally do 15miles you just got to take it easy, also your efficiency heavily depends on tyre pressure

1 Like
#18

This would be the gearing ratio I choose if I need to put 70% efficiency because of the tires:

image
image678Ă—726 27.4 KB

I think that is enough torque for a mountainboard and I will decide if I get a battery that has more that 12 s groups to boost speed afterwards.

Please feel free to comment!

#19

imo it’s way better to run higher kv motors and have a larger gear ratio,
personally i’d run a 1:5 gear ratio 170kv motors

1 Like
#20

Are there even 36T pulleys for MTB hubs? That seems really small, and you’re probably going to need a custom pulley to reach the bolt holes. Also the Wh/km seems a little optimistic for pneumatics.