Lipo behavior and pAlarm

[jevermeister]

Hi,
I am now using pAlarm, thanks Hamburger!

I did some calibration flights to finetune my parameters but have some strange thing going on here.

My palarm is set to go off at 1700mAh. I calibrated it pretty close so expected to recharge around 1700mAh into the LiPo after the flight.

First Time I had to refill 1900mAh. Strange.
I attached a Multiplex Wattmeter to my copter while flying and it measured exactly 1700mAH while my copter measured 1702mAh - close enough for me.
But the charger recharged 1890 mAh.

How is this possible, is there a thing about Lipos I missed!?

Thanks for your help

Nils

[Hamburger]

assume the battery was not fully charged when you started the flight,
then both your pAlarm and the multiplex wattmeter measured how much was drawn during the flight - a perfect fit in your case I might add,
then you recharge the battery.
In goes what you drew in last flight plus what the battery was lacking to a full charge prior to the flight.

If you want consistent values, always charge your battery in close timely proximity to flying; use the same charger for pre- and post- flight charging with same charging program (balancing mode, normal speed etc.)

[jevermeister]

Hi,
that was what I thought, but I charged the LIPO 5min before flight :-/

[Hamburger]

try again and see if a pattern emerges?
Repeat with another battery?

[wilco1967]

Did you balance charge ?

during balancing, the charger will waste some of the mAh from the highest cells, and extra charge the lowest cells.... this will give higher mAh readings from the charger.

[jevermeister]

Hi,
I always do balance charge

what does "some" mean
?

Nils

[doughboy]

charging is not 100% efficient. if battery needs 1700mah, and you charge 1900mah, that is about 90% efficiency.
if your charger can do charge/discharge cycle, you can run it to see how much mah is needed to charge the discharged capacity, and it will not be 100% match.

[jevermeister]

Hi,
thanks for that useful info.

So what should I do, decrease the alarm threshold to 1600 or live with the current drain?

Nils

[Hamburger]

1. Try charging in normal mode not balancing.
2. Do not run copter for long time in configuration menu. It has own loop and psensor is not read during config.

[jevermeister]

hamburger, the code works.my wattmeter is showing the same values.
I always charge in balance mode.the rc pros told me to.

[Hamburger]

so doughboy's explanation of balancing == burning is the best so far.
Do you have a newer battery which would hopefully need less balancing to try again?