Curious, at what point do you think one those ESC’s needs a heatsink? When it’s pulling 150A maybe?
When its getting too hot too quickly
3 Likes
So much depends on how they’re being used, how they are cooled, and what your priorities are (highest performance, longest life, etc.).
For a good balance of performance and overall life I recommend staying under 25A continuous. This helps reduce the voltage sag you get at higher current levels. But you can run them at 45A for short periods without frying them as long as the cells in the center of the pack don’t get more than a bit warm.
If you’re consistently over 25A or so then I recommend Samsung 30T’s.
1 Like
so perhaps 23A would be a more balanced setting?
But your also saying I could have them at 45A? Have I understood that correctly? Seems crazy, does all this depend on riding style, like if I would careful to ride moderately and just push it when needed you can have the Amps much higher?
@Battery_Mooch am I correct in assuming that the ratings you are testing for are made with e-cig use in mind, where the load is set to one current amount, and its on or off with that amount?
If thats the case, then I think its important for all us Esk8 folks to keep in mind that our load is constantly variable depending on an endless number of factors.
@Geo_Engineering_FTW what that means for your question is that just because you set your battery max to 100A, that doesn’t mean you will be pulling 100A constantly. In fact, you likely will NEVER pull 100A, even peak. I have only pulled 82A peak for a couple seconds. I think most riders on this forum dont pull nearly as much current as they think they do.
5 Likes
Unfortunately…it depends on lots of things that take time to work out. Not what we want to do when we just want to frakkin’ ride! 
Any cell can be used at far above its continuous current rating (assuming not near where it would be considered a short circuit). But the tradeoff is huge voltage sag and reduced cell life and there’s not a lot of hard data to guide us because almost none of the large commercial/industrial/aerospace customers for these cells want to run them that hard.
This means we have to decide ourselves what we want to risk and how hard we want to push them (without supporting data). 25A is just a rough number as a compromise for hard you can run them for the damage you do to them. Some stay way below that, some go far above.
We can’t be ruled by numbers though. The differences between running at 23A, 25A, 27A, or even the differences between 20A and 30A, can be smaller than the differences caused by pack temp and how we store and charge the cells.
None of this is what folks want to hear, I know that.
We all just want a good/bad, safe/unsafe, long life/short life number to use. But they just don’t exist. All we have are rough guesses that we make lots of assumptions for.
You can run them at 23A (or anywhere around 25A) when cruising and if the pack doesn’t get more than a bit warm and the pack is not charged abusively then you should get long life.
You can do bursts of 45A (or whatever) if you want but that will affect overall cell life. We can’t say by how much. It depends on how often it’s done, for how long, how old the cells are, how hot they get, etc. All we can say is that running at 45A is stressing the cells harder than running at near 25A. You have to decide if that is acceptable or not.
I’m assuming you have a good BMS that monitors each cell’s voltage because running at higher current levels accentuates any differences in each cell’s performance/aging.
Heat is enemy number one though. Do a hard run and then carefully feel the pack. If it’s warm through the fish paper/tape/heat shrink then the pack is probably getting hot enough in the middle to speed up aging of the cells (at least 60°C). Decide then whether changing the way you want to ride is worth it for possibly extending the life of the pack (assuming not abused in any other ways).
No right or wrong answer here, just your priorities and preferences.
6 Likes
My ratings are always true continuous current ratings, for any possible use of the cell.
“Pulsed”, or non-continuous, ratings are impossible to set without knowing the desired pulse length, duty cycle, desired cycle life, etc.
You are absolutely right though about the current varying hugely during a ride! Using a continuous current rating offers a good safety and performance margin when calculating what cells to buy and pack configuration to use but we should remember that the current levels will often be much, much lower than the ESC settings.
It’s often a lot easier to just use the continuous current rating, and assume that’s how the cells will be used during the entire ride, when recommending cells though since that covers all sorts of different situations and leads to a safer and better performing pack. But if we are willing to dive into the details with the person who is asking then we can fine tune our recommendations, tweak the pack configuration, and dial in the ESC settings for a better match for their riding style.
6 Likes
Very clear info Mooch. Thank you 
I’ve got an Apex Customs BMS…seems like standard one around here🤞
1 Like
Completely agree. Thanks for the excellent info as always!
2 Likes
Please help. I updated my FB Unity to v5.1 using the latest version of the VESC tool (redownloaded tonight). Once I updated, I was no longer able to connect to it. I have restarted both it and the computer a great number of times for varying lengths of time and I waited at least a full minute after updating it to restart it. Any suggestions are more than greatly appreciated. I just want to get back to riding 
.
Also, I don’t believe I bricked it considering that there are no out of place lights and I am still able to connect to it using the Stormcore App and get data.
Theoretically, no. They should perform as if they were not connected together.
There’s always the possibility of some weird software thing, but in theory it should be fine.
(you will of course need two separate ESCs. You can’t run two motors from one ESC even if the shafts are locked together, unless you also match the stator and rotor phasing/timing of them as well.)
1 Like
Yeah ive decided to move away from uart. I like trigger remotes, so am going to try the Alien Power Systems transmitter.
1 Like
Is it better to have long battery >> ESC leads or long motor phase leads?
1 Like
Always better to have long motor phase wires. You want your battery leads as short as possible. There was actually a thread about this recently.
4 Likes
I’ve done experiments around this subject and found no perceivable differences in the numbers obtained with or without a drivetrain attached or a load on the motor.
It doesn’t matter.
4 Likes
It makes zero difference except during the connection. It puts a 5.6ohm resistor in series in the circuit for a few milliseconds before the plugs make contact and short out the resistor. While it’s not being actively connected, it’s the same thing.
Empirically, I have found this to be the case.
OMG no! I’ve had bad experiences with those. I advise to avoid them. I think they’re designed for metal.
Use these (in wood):
Also put a tiny bit of epoxy in the hole before you screw them in
You can thank me later
And don’t use the notches to screw them in, put a short bolt in them and use that, like an M4x8mm hex socket cap bolt
5 Likes
this, i’ve learnt my lesson, now its the time to remind everyone about it
2 Likes
It depends if your connecting the circuit when it’s live or not
I use a AS Switch and have a back up XT90s on the out side of the board but will use normal XT90 on the inside as I know I will never be useing them when the Caps are depleted.
Ok, though @Athrx said to avoid brass at all costs, who’s right?!? My deck is a hummie, so a combo of wood and carbon fiber, not 100% wood