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xorbit / LiFePO4wered-Pi

Access library, command line tool and daemon for the LiFePO4wered/Pi module
GNU General Public License v2.0
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What is the target battery voltage/loading curve? #67

Closed Commifreak closed 5 months ago

Commifreak commented 5 months ago

Hey,

LiFePo4 batteries does not play well with temps below 5° / cold temps in general. I observed a small voltage drop when the night is cold. However, this night, the voltage got below the shutdown threshold so the Pi had some ordered reboot cacles due to LiFePO4wered-Pi detected that the voltage is low.

I checked my normal battery voltage history and the voltage is a bit low. I dont know when my copy of the battery was produced: Is it worth swapping the battery to a new one to get better voltage?

At what voltage is charging being stopped?

grafik

The Pi is setup outside, so the next winter will bring the voltage down again. Any other advise for my setup? Another kind of battery?

Thanks!

xorbit commented 5 months ago

I'm not sure, do you think your setup is power positive enough during winter to significantly raise charge level? That's usually the first issue to check, during winter solar panels tend to produce way below their advertised power levels. The nominal battery voltage is 3.2V. I think K2 produces some batteries that are specified to be used in low temperatures: https://k2battery.com/product/k2-energy-3-3v-1-35ah-lithium-ion-phosphate-power-cells-lfp18650p-1350/

Commifreak commented 5 months ago

I'm not sure, do you think your setup is power positive enough during winter to significantly raise charge level?

Power comes from a 230V AC to 5V DC power supply

I will see if I can optimize some things.

at which voltage does the Hat stop charging the battery?

xorbit commented 5 months ago

Oh sorry I misunderstood, I thought it was solar powered. It stops charging at 3.6V.

Commifreak commented 5 months ago

Thats interesting because it never got this far later in that graph?

xorbit commented 5 months ago

Agreed, very odd. Now if the battery had gone bad, I would expect it to lose capacity and it should reach 3.6V quicker when external power is present. Which makes me think somehow it's getting insufficient input power. Which board revision do you have? Are you monitoring Vin by chance?

Commifreak commented 5 months ago

Yea, just after my last post I checked my VIn history. And somehow it dropped to 4,8V. Will check that.

xorbit commented 5 months ago

That's on the low side, the system may be limiting charge current to prevent the input voltage from going lower. Revision 7 and 8 hardware use a charge chip that deals with this better than older revisions.

Commifreak commented 5 months ago

I believe the cable is bad. The power supply delivers 5.3V now and VIN only shows 5.03V now. Anyway, case closed.