Veteran Sherman on Overheat Hill

[Alj]

(not my video)

https://www.youtube.com/watch?v=DFavoAFEcDw

To save time fast forward to 42:00 then to 59:30

 

Edited July 14, 2020 by mrelwood
Typo in title.

[Alj]

From what it looks, a cap exploded.  Some "KKJ" unknown brand. So whoever has those wheels, replace that "KKJ" junk to something more trustworthy (like Nichicon - https://www.mouser.com/ProductDetail/Nichicon/UCY2C561MHD?qs=%2Fha2pyFadujuHIr5Yj8HTZAEG6x9RB%2FLXUas5hyoen4%3D ). Also capacitors should never be placed on top of MOSFETs like this, the max temperature for good caps is only 105C and they start to age quickly when operating in hot places. Kingsong did a great job installing those caps facing away from the board on KS18L (and they are also 4x the capacitance value there).

 

Edited July 14, 2020 by Alj

[Chriull]

2 hours ago, Alj said:

Kingsong did a great job installing those caps facing away from the board on KS18L (and they are also 4x the capacitance value there).

It's understandable now that KS mounts them on the fans: https://forum.electricunicycle.org/topic/15349-can-someone-show-me-a-photo-of-the-ks18xl-motherboard/

2 hours ago, Alj said:

and they are also 4x the capacitance value there).

Should be a "voltage problem"? The 100.8V wheels have to take 160V capacitors, KS with the 84V wheels can use 100V caps.

From the pictures the 1000uF 100V look very roughly about the same size as the 560uF 160V... And Kingsong managed to get three of these inside...

And from some looking through datasheets it seems that the bigger the capacitance values, the more ripple current they can take?!

3 hours ago, Alj said:

From what it looks, a cap exploded.  Some "KKJ" unknown brand. So whoever has those wheels, replace that "KKJ" junk to something more trustworthy

Somwhow looking at the thin legs of the capacitors i can't fight the feeling they are not really designed for the burdens they have to take in EUCs anyhow

 

FYI: Marty linked this video in "his" topic here: https://forum.electricunicycle.org/topic/18975-my-sherman-trials-tribulations-and-triumphs/?do=findComment&comment=319996

So there are actual news, infos and discussions regarding this incident...

[Alj]

9 hours ago, Chriull said:

 

And from some looking through datasheets it seems that the bigger the capacitance values, the more ripple current they can take?!

Yes that naturally should be proportional... Capacitance depends on foil surface which defines max current.  But series resistance, overall quality and ambient temperature are all factor into it as well. I never save on a good cap brand (elna, nichicon) because budget brands not so much cheaper but quality is usually "just enough so they buy", they just don't last very long, esp if you put it on top of piping hot MOSFET.  Good example is budged LED light bulbs, which suppose to last longer than incandescent ones but they don't because they soon lose electrolytic cap which goes bad due to poor quality and hot temp.

Also actual ripple current will depend on a capacitor value. I e the bigger the value the bigger current there will be and also the bigger current cap can take, so its not like "put bigger cap and problem solved". it is rather "put better cap with lower ESR into cool location" thing.

Edited July 14, 2020 by Alj

[Lubo Paliev]

Small update after checking the burned control board