Apologies if this isn’t exactly the right category to post in. It seemed right after I spent time browsing the forum.
I’m new to esk8 and I just finished my first build a few weeks ago. I ordered everything, assembled the board, and got it up and running with an experienced friend of mine who has been doing esk8 for years. Unfortunately, after day 2 of using the board with less than a mile traveled at no faster than 15mph, the DRV chip burned (image 1). I got a replacement under warranty as we thought it was a defect since my friend has never had that issue in his Unity boards and we couldn’t determine another reason. We just assembled the board with the new Unity a couple days ago, and it got through a mile yesterday with no issue, but after another mile today, it died on me again (image 2).
Does anyone have any idea why this has happened to me twice? We programmed the board exactly how my friend would program any of his boards. It’s running two flipsky 190kv motors on a 12s3p battery with approx. 3 feet of wire running it from the front enclosure to the unity in the rear enclosure (image 3). I can provide photos of the (somewhat disassembled) build itself should that help.
I’d assume they’d have asked for a copy of your settings when you replaced the first bad one, but just to be safe you should probably post a copy of the config settings. It doesn’t look like any of the fets got fried (first picture at least), so I would lean towards them getting a bad batch of DRV chips. RMA and try again.
Unfortunately, since both of the VESCs won’t turn on, I can’t access photos of the config. Here are some of the important settings we changed. Let me know if you have any further insights, but everything we did in the programming should be pretty standard.
Motor current: 65A, -65A braking (both sides)
Battery current: 35A , -12A regen (both sides)
ERPM limit: 80000, -80000
Limit duty cycle current limit start to 85%
It could just be a bad batch of DRV chips, but since its happened twice I think I’m going to get a different VESC (Stormcore) and adjust my build to reduce future risk. Nothing against the Unity per se.
Right. Unfortunately, I can’t quite place the cause at this point. Reducing the length on the battery leads is probably going to happen though. I can change orientation so the wires can be shortened by a foot and a half. I’m also going to get different wires as I can’t exactly vouch for the quality of what’s in there right now…
How would I go about adding capacitance? At this point, I’m going to do what I can within reason to reduce any risk of future damage.
Haha I’m able to get a refund on it right now. I think I’m gonna go with the Stormcore as I can afford to do so and I don’t need to risk another Unity blowout.
I’m new to esk8 so I’m not super familiar with everything despite being an engineer and having decent intuition. So setting the max ERPM is limiting what exactly? I understand what you’re saying for setting the duty cycle, but why shouldn’t I change the max ERPM numbers? Again, my friend is pretty much guiding me through this process and he was directing me to set it to 80000 based on his experience.
That’s great. Keep both wires next to each other. Twisting them together along their length is even better.
Not to sound flippant but you do that by buying capacitors.
The ESC has some already there so you could just buy another set of equally rated ones but installing them requires electronics knowledge, soldering experience, and a good awareness of the safety precautions you need to take. Unless you have done things like this many times before I recommend not trying it.
If you’re getting a Stormcore just do the wire shortening thing.
Another consideration…too much capacitance can burn out anti-spark switches that aren’t rated to handle it.
Duh. Nobody would ever guess that I took an electrical engineering course at my university just a few months ago.
Given everyone’s advice, I think shortening the wire will be sufficient. I also saw there are a couple more capacitors in the Stormcore (which is what you’re implying I think).
Setting the electrical rotational speed above (or below) which the ESC does not send/receive current to/from the motor.
Because each ESC has defaults set by the manufacturer, and for esk8 it’s best to leave them alone. If you were driving a propeller or something, you may opt to lower them in certain circumstances. For esk8, all it does is “cut brakes (& throttle) above X speed”. It’s not limiting the motor speed.
He probably hasn’t hit his limit yet and doesn’t understand what it does. It’s not limiting the motor speed. It’s limiting throttle and brake output. Use duty cycle to limit the motor speed.
And yet another consideration is that if the extra capacitance is on the battery side of the antispark switch, it won’t [accelerate the process to] burn out the switch but it will “leak” battery current while it’s turned off and can very slowly drain the battery, possibly destroying the battery if left to its own devices for too long.
Why is it that its always seem to be the 8301 that blows and not the 8303 on the unities?
Both DRVs runs identical settings but the 5V is taken from the 8301… coincidence?
Is the buck converter the weakest link?
Overloading/ shorting the 5v rail?
He actually sells boards. Off the top of my head, I think he has three unities of varying ages. However, he has sold 70+ unities in boards including recent sales in the last six months. Both of the unities I popped were brand new.
