FOC Box Unity burned out twice

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 and we can’t determine another reason as every other component on the board seems fine. I can provide specs for the board if that helps.

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If you purchased a unity nowadays, they will unfortunately fail. Not sure whether it was cheaped out because mosfet failed, antispark failure and it overcurrent, or set up caused it. Probably the first two.

What was the set-up from vesc tool?

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That seems odd given that my friend has multiple boards with new unities and has sold a lot of boards with unities without running into issues. Neither he nor I are sure what’s going on even after doing a little bit of reading around for similar/identical problems.

We used version 3.0 of vesc tool to program the unity both times.

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Was the battery connected right on the unity? Or does it have those XT90 with an XT90 antispark? If its the antispark one, thats the newer ones. Sometimes you get lucky and it doesnt happen. But Unfortunately, the antispark on the unity fails and can cause this issue. I’ve read so many of that and its the diode on it that blows out.

If you want to save the money you’re losing, get a stormcore 60D. It’s basically a more powerful unity.

Edit: Do not buy the xenith. I was told its a bad product.

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Thank you for the recommendations. I’ll definitely take a look at those.

Is there a reason why the unity would just start going out on me? As I said, my friend has sold (70+) boards as a business using the unity with the XT90 antispark and there haven’t been any issues. It seems odd to both of us that it would blow up on me twice given his personal history with the part.

Also, do you know if there is any other possible cause? Neither of us want to assume it’s the VESC, buy a different one, and break that as well. We’re pretty stumped and getting a little paranoid now given that I’ve literally spent no more than 3 miles on that board with two different VESCs.

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You could check your battery before purchasing and see if its fine. If your battery wires aren’t on a very long wire extension; since that has caused issues before, you should be fine. The shorter the better. It is unfortunate that this happened.

Do you remember how you’ve set your vesc tool for the unity? That could also be a factor if the previously mentioned isn’t used. Sometimes its user error. Also, your motor choice and amps pushing and regen can cause it.

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My board is essentially a custom boosted. We used wire extensions to get from the front enclosure to the back enclosure. These are two three-foot lengths of 10-gauge wire. Everything we know about 10-gauge wire would suggest that this shouldn’t cause any issue at the voltage/amperage for such a board.

Unfortunately, I don’t personally know vesc tool well yet (first board). Talking through with my friend, we programmed it how he would based on his years of experience doing so. I’m using two of these flipsky motors with 190kv and we programmed it accordingly. 65A (and -65) for the motor current, battery current 35A per side, -12 for regen.

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The length of battery cable is concerning. Are you using a 12S battery?

Will you post screenshots of your current settings?

What are the chances the motor has loose phase wire connections?

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This sounds like a myth.

The antisparks have always been weak, but aside from that I think they’re the same thing for the most part.

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Yes. I have a custom 12s3p battery with P42A cells. Would this really be an issue for such a short length of cable? I hope I’m not being annoying with “my friend” but I am getting most of my information from him to begin with. That being said, my friend also has a custom boosted with approx. 3 feet of battery cable but running on a 10s battery.

Unfortunately, I can’t get screenshots of the settings from vesc tool since the unity is… dead. We do know what settings we put in there so if there’s something specific you’re hunting for I can likely tell you.

It’s unlikely that the motor phase wires are loose. We played around with them a bit.

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The 12S tension will make long battery cables much worse than a 10S tension. Although I’m not sure that’s the problem, it could be. You could always add a 1mF+, 75V+ capacitor to the battery input wires to check.

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Do you know the probability of this being the issue? I’m trying to come up with another orientation of my battery that might be able to reduce that to a length of approx. 1 foot.

Fair point.

This is the info needed. What settings did you put for motor amp, battery max, battery regen, etc.

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%

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Its likely the long cable if im honest then. The longer the wire, the more dangerous the inductance. Best to lessen the length. Im not gonna say its 100% the cause. Just one of a factor.

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Gotcha. Thank you so much for your help. I think at this point, I’m gonna switch to a Stormcore (nothing against Unity), get new wires just in case the quality was poor (can’t exactly vouch for the hobby store I went to), and reconfigure to shorten the length.

Thank you too @b264

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Change one thing at a time to try to isolate the cause.

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Enjoy the stormcore if you get it.

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Good point. Unfortunately, I don’t have the money to burn through Unities and determine root causes even though I totally wish I could. I think I’ll make the reasonable adjustments to eliminate what I think is the cause based on your help and everything else I’ve been reading up on.

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