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Battery protection low voltage disconnect issue

thread240-494314

Battery protection low voltage disconnect issue

Battery protection low voltage disconnect issue

(OP)
Hello all,

just got my first EasyEDA project back from JCLPCB and it’s almost as I envisioned it.
My issue is the under voltage protection. It correctly disconnects the battery but I can still measure 0.7V between Vcc and GND.

My question: how to track down this issue?

I have attached the full circuit, the bottom part is the charger which was a public circuit I just integrated. It seems to be a standard implementation of the parts.

Thanks in advance,
Markus

https://files.engineering.com/getfile.aspx?folder=...

RE: Battery protection low voltage disconnect issue

Try blocking the light hitting the LED's, I suspect the LED's are generating a small voltage that you are seeing.

RE: Battery protection low voltage disconnect issue

I'm with Clash3. Check again in darkness.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Battery protection low voltage disconnect issue

(OP)
I ran the darkness experiment and it has no impact. I do not even understand why it would matter as the battery monitor disconnects GND from Battery Minus (via the FS8205A component).

RE: Battery protection low voltage disconnect issue

Lift the pins that tie FS8205A to ground and see if the voltage changes. Alternative, cut the trace(s) to those pins.

RE: Battery protection low voltage disconnect issue

0.7V is suspiciously a Si diode voltage.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Battery protection low voltage disconnect issue

(OP)
So i removed the FS8205A and I still measure 0.7V
what I can measure now is a is -0.2V (when the battery is completely removed) coming from the 25x WS2812 LEDs when they are exposed to light.

RE: Battery protection low voltage disconnect issue

So that leaves U4, which sits between the battery and ground.

RE: Battery protection low voltage disconnect issue

(OP)
This means I remove R8 as a test?

RE: Battery protection low voltage disconnect issue

Seems reasonable. That's the problem with unexpected conduction - keep removing items until the conduction goes away on the paths that seem most likely first. Same thing with mystery short circuits in car wiring.

RE: Battery protection low voltage disconnect issue

The circuit may be entirely correct but the components selected might have a problem - do you have a link to the data sheet of the U4 component?

RE: Battery protection low voltage disconnect issue

(OP)
To solve the puzzle: attached is the fixed circuit.
In- and output to the mosfet module was swapped

RE: Battery protection low voltage disconnect issue

Well - that would do it. Thanks for the update.

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