DRV8302 Magic Smoke

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vitormhenrique
Posts: 16
Joined: 30 Dec 2015, 19:02

DRV8302 Magic Smoke

Postby vitormhenrique » 18 Mar 2016, 04:34

I bought two vescs from enertion back on the end of January, but only got the chance to play with them today.

After doing some tests using a 5s battery I connected two 5s lipo in series, to get a 10s battery. Well, the new tests did not end so well..

Magic smoke came out after few minutes. It blew the DRV8302 chip.

Any ideais why this happened?

IMG_0488.JPG
IMG_0488.JPG (300.82 KiB) Viewed 3992 times

theBob
Posts: 7
Joined: 22 Feb 2016, 03:13
Location: Australia

Re: DRV8302 Magic Smoke

Postby theBob » 19 Apr 2016, 15:27

Hey,
I also got a VESC from enertion, seems in the same batch. The DRV on mine has blown in exactly the same way. I managed to get ~20kms of skating out of mine and after a thorough post mortem I can't find a cause for the failure.

Did you ever figure out what happened?

I am running 10s, the damage is nearly identical:
IMG_20160420_003921.jpg
Blown DRV.
IMG_20160420_003921.jpg (533.45 KiB) Viewed 3805 times

Nordle
Posts: 34
Joined: 23 Mar 2016, 17:04
Location: Italy

Re: DRV8302 Magic Smoke

Postby Nordle » 19 Apr 2016, 19:24

Would like to know the best source to buy quality VESC too^^

benjamin
Site Admin
Posts: 280
Joined: 15 Dec 2015, 08:38
Location: Sweden
Contact:

Re: DRV8302 Magic Smoke

Postby benjamin » 20 Apr 2016, 07:41

This has happened to me a few times as well, and as far as I can tell it was because the electrolytic capacitors failed. I had a batch of almost 10 year old capacitors that I bought from an auction, and some of them where not working at all and some lost all their capacitance after using them a bit. In one case I had a good capacitor on a small PCB which got disconnected due to vibration (one leg was bent off), and that moment I got the same failure.

You can try to check and measure your electrolytic capacitors and see if they seem OK. I also got an old enertion VESC from an even earlier batch, and there the capacitor was poorly soldered to the battery cables and I could pull one of the legs off quite easily, so the issue can also be poor soldering.

The cause of this problem is described here:
http://cds.linear.com/docs/en/applicati ... /an88f.pdf
The ceramic capacitors together with the cable inductance can cause very high voltage spikes, which can make something fail easily. If you don't have the electrolytic capacitor, simply connecting a 12s battery will make the drv blow up.

So the capacitors are one cause that I can think of, but it could also be something else...

vitormhenrique
Posts: 16
Joined: 30 Dec 2015, 19:02

Re: DRV8302 Magic Smoke

Postby vitormhenrique » 20 Apr 2016, 14:33

Benjamin,

I'll check my capacitors tonight and post it here!

Thank you for the response!

rew
Posts: 939
Joined: 25 Mar 2016, 12:29
Location: Delft, Netherlands.

Re: DRV8302 Magic Smoke

Postby rew » 20 Apr 2016, 18:36

FYI, I am building a DCDC converter based on VESC hardware. With 5V output, I had about 7V of ripple on the output.... That was with a low-ESC 100uF electrolytic.... Adding a ceramic 10uF cleaned things up. No noticable ripple..... Really, the capacitors are important.

theBob
Posts: 7
Joined: 22 Feb 2016, 03:13
Location: Australia

Re: DRV8302 Magic Smoke

Postby theBob » 21 Apr 2016, 03:18

Interesting Benjamin!

I've just pulled one of the caps (the worst looking one) and tested it and the results are really odd:

- If I test capacitance it reads 0.6nF for a few seconds then my DMM jumps into uF range and says 'OL.'.
- If I test resistance it ramps up to 40MOhm and stays there.

From what I can read online it seems the cap is bad? I should be getting OL. for the resistance and a correct reading (680uF) for the capacitance correct?

I've also searched the brand (SAMXON) and most conversations I can find seem to say they are crap caps.

Given this, would you suggest I should replace the caps at the same time I replace the blown DRV?

Pretty disappointed they would use cheap caps when I paid so much for the VESC. :(

rew
Posts: 939
Joined: 25 Mar 2016, 12:29
Location: Delft, Netherlands.

Re: DRV8302 Magic Smoke

Postby rew » 21 Apr 2016, 07:16

40MOhm is so much that it would read "OL" on my multimeter. That''s so much that you can't tell the difference from "proper" behaviour. Moreover, you're testing leakage. If your capacitor had a 100k leakage (you measured 400 times more, remember!), about 0.5mA would flow at 50V. With a motor drawing multiple amps, that's not a problem. It might even be "within spec". So... that one is not a "clear" indication that your capacitor is broken.

The other measurement is "fishy". I understand you have an autoranging multimeter. Can't you pin the range to the 2000uF range? Does it have that range? My multimeter goes up to 200uF. So 680uF would measure as "OL" (overload / out of range).

That said: Finding a capacitor that qualifies for VESC duty is difficult.

Nordle
Posts: 34
Joined: 23 Mar 2016, 17:04
Location: Italy

Re: DRV8302 Magic Smoke

Postby Nordle » 21 Apr 2016, 16:01

Do you think I'm fine with 50v caps on 10s, cheapos from aliexpress, but sanyo... Will test them for sure before use now!

pf26
Posts: 296
Joined: 28 Mar 2016, 14:37
Location: FR Valence

Re: DRV8302 Magic Smoke

Postby pf26 » 21 Apr 2016, 18:28

Maybe you want to try with reduced max battery regen current (below 10 Amps). Just to see if DRV failures still occur.
Obviously this will affect braking capacity.


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