Help me choose cell type and cell configuration for my street-offroad build.

How-Tos & Esk8 mechanics
#1

Hey guys. So I think I’ve learned a chunk about choosing a battery set up from all the awesome posts found here, I am however having trouble making a final decision on which direction to go. Here is my build details.

MBS comp 95, 8" wheels hybrid street and light offroad duty build using TB3680 190kv 80amp x 2 motors, Stormcore 60d. I live in a large spread out city, shooting for 60km range geared for 50km/h top speed.

Top mounted battery, max width dimensions of battery enclosure is approx 11.5" inches by 9", height can vary a bit, but hoping to keep it less than 5", thinner the better. The following options fit within my battery box size constraints. I’ve been using the 3dservisas calculator to run these numbers.

Option 1. 12s8p using 40t cells set up for 25amps max discharge per cell as I have read this battery tolerates this level better than the full 30amps. This gives me 200amps pack output, 32AH, 57 km/range, 49km/h speed, 34 ft/lbs torque.

Option 2. 12s8p using p42a cells. Gives me 360 amps on the pack, 33.6AH, 60.5km range, 49km/h speed, and 34 ft/lbs torque.

Option 3. 10s10p using t40 cells, Gives me 250 amps on the pack, 40AH, 60km range, 50km/h speed, 33 ft/lbs torque.

Option 4. 10s10p using p42a. 450 amps, 42AH, 63km range, 50km/h speed, 33 ft/lbs torque

Option 5. 10s14p using 30q. 280 amps, 42AH, 63km range, 50km/h and 33 ft/lbs torque

Option 6. 13s11p using 30q. 165 amps, 34AH, 65km range, 50km/h, 33 ft/lbs torque

Option 7. 12s14p using 30q. 210 amps, 42AH, 75km range, 50km/h, 34 ft/lbs torque

Some of these options are more desirable to me than others. The larger p-group options don’t make much sense to me because of the high cell count, but I’ve included every option I can think of that would fit the most power density into my given battery compartment space. I’m not too keen on building the battery pack higher above the deck, hoping for the most minimal looking enclosure possible. I have someone lined up to fabricate a fibreglass or carbon fibre enclosure once the battery is fully assembled. What do you think? Is there a cell I’m not considering? or a cell configuration that might work better? I’d prefer to run the cells with some headroom and range is also an important priority. Any feedback super appreciated, I’m spiralling into certain doom around this decision haha.

#2

Molicel 50E or Tesla 3 will give you more range and at 10P or more it’s okay that the cells are only good for 10A

1 Like
#3

Hey Zack, that’s an interesting cell. It could bump me up to around 75km but depending on configuration the pack amperage is below 160amps which my motors might pull. Would it be safe to say this would be risky using a battery that slightly undercurrents what the system my need? Thanks for the suggestion

#4

And sorry, what do I search for to find the Tesla 3 cell?

#5

I think it’s the Molicell M50A

2 Likes
#6

It depends how fast you go, the battery current is scaled by the ratio of your current speed over your max speed

If I have 2 motors and they can pull 60A, and I made my board geared to 30MPH but I only go 20MPH, the most current I can pull is 80A total from the battery

#7

Lol my bad, yeah 50A

#8

Thanks for the input. I have removed the 50e from consideration as the pack will deliver quite a bit below the amperage that my motors can use.

#10

yeah this Molicel 21700 M50A is pretty interesting cell, considerably more expensive than the p42a’s at the moment at least. I really like the range boost, but again just concerned about it being able to “just” provide enough amps for my motors. I always get nervous using a component when its used right to the end of its ability, its good to have some headroom. I should have mentioned in my opening post, I also have some steep grade hills in my area, they are not super long but they push 40% grades.

#11

Your strategy will take you far. Stay on course and don’t be dissuaded. This is an A+ plan.

3 Likes
#12

Thanks man.

#13

There are a lot of folks around the DIY esk8 scene that will suggest to design everything to be used at 99% capacity, et cetera. Don’t fall for it. That kind of stuff works great for a few rides.

1 Like
#14

I think most of my stuff has double the specs I really need if not more, the exception being the single drive board

#15

Is it 12S li-ion on 60V parts?

#16

10s 35A battery, 4.12 esc with 30/-12 40/-24 settings, 6355 190kv, hella torque gearing. Exclusively for very lazy cruising

Oh and the antispark is rated for like 200A or something

1 Like
#17

I hadnt considered this at first but I can actually get better range numbers with power and speed equal using 11s10p in the calculator. More cells but it fits my battery compartment allowance. Is 11s a thing? Is there even BMS’s available for 11s?

2 Likes
#18

11S is definitely a thing. You can easily obtain 11S BMSs

https://www.litechpower.com/product-detail/HCX-D127V2LI11S15A.html

and chargers

and you can also often use a 12S BMS for an 11S battery, but not always. It’s probably better to use an 11S BMS.

2 Likes
#19

Awesome! Thanks for the info, adding this to list of options

2 Likes