I recently bought a 36V BLDC motor controller (the $10 ones from ebay) without taking into consideration that when fully charged my battery voltage is actually 42V.

I found a similar question where they suggest adding a voltage regulator/converter which seems like a viable solution, however at my power rating (500W) there will be a considerable amount of losses.

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By inspecting the board it's visible that there is no lower voltage input and there is actually a 5V output for a potentiometer which means that there is probably a buck converter on there. In standalone buck converters the output voltage does not change if input voltage changes as long as it's in some range.

So the question is will I fry the board if I connect 42V to it and if yes is there anything I can do besides buying a higher voltage board?

  • \$\begingroup\$ How can anyone tell unless they recognize the item in the picture? \$\endgroup\$
    – Andy aka
    Oct 16 '19 at 11:24
  • 2
    \$\begingroup\$ "If it doesn't have a datasheet, it doesn't do what you want." General rule to live by with electronics. Yes, items like this from Ebay are cheap, but that comes at a cost. Pay more and get something with a datasheet, or pay less and risk it. \$\endgroup\$
    – Puffafish
    Oct 16 '19 at 11:34
  • \$\begingroup\$ @Andyaka that's primarily what I'm hoping for \$\endgroup\$
    – php_nub_qq
    Oct 16 '19 at 11:41
  • 1
    \$\begingroup\$ My comment on one of your previous questions was this: Don't buy important stuff from ebay is my policy. Don't buy components that don't have a data sheet is my other policy. \$\endgroup\$
    – Andy aka
    Oct 16 '19 at 11:45
  • 5
    \$\begingroup\$ I'm voting to close this question as off-topic because it is a question about how to compensate for shopping mistakes. It is not a question about electrical engineering theory or design. You failed to spend the time to select carefully and now you are asking others to spend time figuring out if there is a way to compensate for that. You could spend some time looking for the same item sold with more information, but the information you have indicates it is not really intended for your battery. \$\endgroup\$ Oct 16 '19 at 13:02

Chip markings can be useful. So we have an ST LM317 A14A15 in the top, that one goes up to 40Vpp Vin-Vout.

Then we have 3* JY21L, which, after a bit of searching reveals the high-side supply goes up to +150V.

There also a TI LM339, which is rated up to 36V.

And lastly a JY01 (can't even read it but after searching for JY21L you'll know it's there), but it doesn't matter that much.

With already two components specced at max 36/40V, I wouldn't try 42V, altough it just could hold for a fair bit...

  • \$\begingroup\$ More like a guesstimate than an answer, refine it. \$\endgroup\$
    – Sorenp
    Oct 16 '19 at 13:16
  • \$\begingroup\$ The big unknown will be the 6 FETs on the other side of the board. Given the tradeoff of voltage rating for low Rds, these likely won't have a lot of margin, and contain the highest amount of magic smoke. \$\endgroup\$
    – Phil G
    Oct 16 '19 at 15:41

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