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bigchief   100 mW

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Re: Upload Your Circuit Schematics & Requests Here...

Post by bigchief » Jul 26 2019 5:13pm

fechter wrote:
Jul 26 2019 10:46am
bigchief wrote:
Jul 26 2019 3:22am
I have a 48v ebike controller that I'm trying to adjust the LVC down for a 36v battery. I'm really sleep deprived at the moment and my brain isn't working well enough to sort out the exact resistor I'm to replace:
Check out this thread:
viewtopic.php?f=2&t=101242&p=1480347&hi ... r#p1480347

Looks like the same controller.
Thanks, it is definitely the same manufacturer but it seems to be a slightly different layout, possibly because mine is 48v nominal when his was 36v nominal, or maybe because it is just a different PCB revision. I posted an inline pic of the resistor I tried changing, in the thread you linked me to. Changing the resistor to less resistance makes it cut out more easily, but making it a higher resistance doesn't improve it. Maybe on my PBC it is a high voltage cut off and not a low voltage cutoff? Hopefully someone smarter than I can eyeball it and let me know what I should be trying.

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fechter   100 GW

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Re: Upload Your Circuit Schematics & Requests Here...

Post by fechter » Jul 26 2019 7:09pm

Try completely removing the resistor like he did and see what happens. For sure there is a way to lower the cutoff point, but to really trace it out from a picture is challenging. If you had a good picture of the bottom of the board, I could take a look.

Also good if you attach the picture here instead of a hosting service. Just go to the bottom of the page where it says Attachments and attach the picture files.
"One test is worth a thousand opinions"

bigchief   100 mW

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Re: Upload Your Circuit Schematics & Requests Here...

Post by bigchief » Jul 27 2019 1:58pm

Removing the resistor makes it cut off just about instantly. I think I'm messing with the wrong resistor. Maybe it's actually the really tiny one next to it marked "222" and not the "2001".

I was using file hosting services because the forum caps at 512kb which isn't that high of a resolution. Here's a pic of the bottom as an inline image and the source file. Thanks for taking a look!
IMG_20190727_1446162.jpg
IMG_20190727_1446162.jpg (501.36 KiB) Viewed 241 times
https://imgur.com/TdddY9R

bigchief   100 mW

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Re: Upload Your Circuit Schematics & Requests Here...

Post by bigchief » Jul 31 2019 5:12pm

This thing is really kicking my butt since I'm reduced to trial and error.

I took out the SMD for the 2000 and 2200 ohm resistors and replaced them both with higher and lower resistance. I also took out the 25k resistor and replaced that with higher and lower resistance.

None of these value changes improved the low voltage cutoff, only messing with the 2000 ohm resistor caused it to cut off much more quickly. For now I have it so the 2000 and 2200 are both replaced with 2200 (my pack of resistors didn't have 2k flat) and I left the 25k replaced with an 18k for now (33k didn't help either). So the current status is as in the picture attached.

I've probably opened this thing up 30 times now. Spending this much time I'm thinking I should just call it a day and get a Kelly programmable controller instead.
Attachments
IMG_20190731_140341.jpg
IMG_20190731_140341.jpg (229.99 KiB) Viewed 189 times

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amberwolf   100 GW

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Re: Upload Your Circuit Schematics & Requests Here...

Post by amberwolf » Jul 31 2019 8:00pm

I realize this is is probably so obvious it's already been attempted and failed, but:

Since there are four existing jumpers for battery choices, with increasing resistance as voltage goes down, why not leave all the rest of the circuit alone, and just change out one of the resistors on one of those jumpers, jumper it in?

You'd calculate the resistance you need based on the existing four values and voltages; dunno how to make a formula for it but can't be that hard with all the internet calculators out there, must be one of them that does this sort of thing. ;)

I'd guess you calculate the value based on teh average voltage of the pack, not the LVC, based on the numbers printed on there.

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fechter   100 GW

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Re: Upload Your Circuit Schematics & Requests Here...

Post by fechter » Jul 31 2019 11:23pm

It's just a voltage divider circuit that feeds to the microprocessor. The thing to do is trace out the circuit so you know which resistors make the divider, then do some math on the resistor values.

I couldn't trace it out from the picture. An ohmmeter would be better.
"One test is worth a thousand opinions"

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