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Battery protection low voltage disconnect issue

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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