One is fine IMO.
2 Likes
I’m new to DIY esk8 and I have a question. Can I make 12s3p samsung 40t battery pack for “Direct Drive Motor Electric Skateboard 12S KIT” from Onsra, because I don’t know if 105A gonna burn esc or it’s only
a bottleneck. Sorry for my english or this is wrong section for this question.
1 Like
Cheers man
Pretty sure the onsra kit uses a vescs so u can set the current to how high or low you want
Here’s an extremely easy way to calculate whether you are good with nickel. Divide the expected max continuous current by the cross sectional area of your thinnest point that is normal to the direction of current.
05A / mm^2 is overkill
10A / mm^2 is good
15A / mm^2 is okay
20A / mm^2 is bad
25A / mm^2 is awful
In the image below I am expecting 8x 20A through an area that is 65mm by 0.15mm, or 160A though a 9.75mm^2 area, or 16.4A / mm^2 which would be concidered an okay setup (this is a low power draw board since it’s only dual 6355 for light use which means it will be in the good range)
Edit: every weld is good for about 5A each, which means that top layer is good for 24x 5A or 120A total which is also fine
11 Likes
You’re thinking about this wrong. Your battery does not “push” amps to your ESC. Rather, your ESC “pulls” the amps that it needs at any given time. Your battery can handle 90A continuous, and 120A pulses, so your ESC (or ESC’s, if you have more than one) can “pull” a total of 90A safely from your battery.
The Hobbywing ESC will have a fixed amp draw which it can pull from your battery. As long as your battery can handle that (and it can) then you are ok.
3 Likes
Thank guys. That’s good, what about BMS for battery pack. Can you advise me somethink suitable. I was thinking about 12s Li Ion 100A BMS from lithiumbatterypcb but I don’t know if it’s good.
1 Like
It would be wise to run the BMS in bypass so just buy the 30A 12s smart bms from them that is what I have done.
If you run a discharge circuit it bms would shut off your board including brakes when the current is too high to protect your set up but if your travelling anything above 10mph this is going to be very dangerous.
I would rather the set up gets a bit fried and I can brake and come to a safe stop etc.
3 Likes
This for sure, being able to stop can be a matter of life and death, if the board gets incinerated but you get to live and tell the story it would be 100% worth it. Hospital visits leave lasting scars on your body, new boards only leave fillable dents in your wallet…in the US the hospital visit would also leave a large hole in your wallet, just adding insult to injury
1 Like
So what should I do, can you give me some example how to do that and what are the chances that my board will broken by doing this and why?
Instead of connecting the negative terminal of the battery to the BMS then the BMS to the ESC, just connect the negative terminal of the battery directly to the ESC
You will still need to connect the negative terminal of the battery to the BMS but only for the charge current rather than the discharge current
2 Likes
So I should buy 12s 30A BMS, connect negative terminal of battery straight to the ESC and to BMS at once?
1 Like
I would get this or similar as I said 30A 12s as long as you don’t pull more amps than you battery can handle it won’t be an issue and won’t damage your board 95% of people run theirs BMS in this way and just use it to protect the battery whilst charging. All you do is not connect the discharge terminal on the BmS form memory and this will bypass it.
1 Like
In terms of order you wanna do battery negative to BMS B- then all the balance leads…after that it doesn’t matter
2 Likes
Anyone know where to get just the connector used by the LLT smart bms for the balance leads? Can’t tell if it’s a JST style connector or not. I want to make some harnesses with longer wires.
1 Like
I believe it is JST XH 2.54mm pitch, and you should be able to find the housings/pins from the usual suspects (digikey, mouser, etc). Got the right crimper?
3 Likes
You know it, I’ve got the Engineer. Finally got fed up with soldering on extensions to these things.
1 Like
Im rapidly approaching this point myself. Just need to psyche myself up for dropping $60~$100 on crimper, housings, and crimps.
4 Likes
@Skyart @longhairedboy @A13XR3 Can I get some help? The positive electrode on my K-Weld isn’t making good welds…trouble shooting tips? The ends are clean, and it doesn’t make a difference if I have the rounded or pointy side of the electrode. 0.2mm nickel at about 45J. And it’s only on the steel of the cell, the nickel to nickel joints are fine.
@BenjaminF I’m pretty sure you’re a Malectrics boy, but a welder is a welder…have you had this issue before?
2 Likes