New to this and learning step by step - on to batteries. Had a situation yesterday where the quad dropped out of the sky and pretty sure it was down to a flat battery. Really appreciate the help so far…
Questions
I have calibrated the voltage now by comparing missionplanner values to measurements taken with a multimeter - using a 3s 5200mah battery - what should be my failsafe trigger?
How do I calibrate the amperage (it seems very low). Voltage is easy because I can just measure across 2 terminals on the PD board, but for amperage I would have to connect up my multimeter as part of the circuit - is this the std way to do it? Also the amp draw appears to be calibrated as an amps per volt - this seems very hard to measure? Any tips?
Is it possible to add a buzzer alarm before the failsafe engages? E.g. buzzer at 35% power, failsafe at 15% power?
How is the % remaining calculated? Right now when the battery is flat, missionplanner is still claiming 80% remaining - assuming this is to do with the amperage calc being out?
with my 3S batteries (16000 & 12000mAh) I have sucessfully used 10.5V as the failsafe threshold the last few weeks - although I have found that what triggers before the battery even reaches the 10.5V level nearly always is the mAh failsafe (which I set to 20% of the the battery capacity).
I think your approach with the multimeter is OK - what you need is a confirmed amperage measured, then you adjust your amp per volt parameter until you get the same amperage in MP.
I personally use a Mauch power sensor which comes with a calbration slip that shows the exact amp per volt value to enter for the specific sensor in hand, so I can skip measuring myself.
I assume that once you have the amp’s per volt parameter right mission planner will also give you the right % remaining…
What I did until I had the calibrated Mauch sensor was to iteratively increase the flight time minute by minute until (after the flight) I got the desired “recharge” amp amount, i.e. I determined with several tests how many minutes I could fly until later during charging the charger pumped in 80% of the battery capacity until fully charged again. ( a crude workaround of course, but it worked well)
Does the battery I am using have an impact on the current calibration? E.g. if I switch between 2 different brand 3S 5200mah batteries or a 3S 5200 and a 3S 10,000, do I need to re-calibrate the current?
No, I don’t think there is a connection between which battery you use and the calibration.
The way I think of it this:
With the calibration you simply ensure your power sensor measures correctly (within it’s inherent technical accuracy). That is totally independent of the chatacteristics of your battery used later.
Your actual physical battery characteristics will then influence how quickly you reach the voltage or mAh left failsafe levels.
Smaller batteries with high C rating (eg.40C or 60C) or large batteries even if they have a lower C rating like mine can tolerate higher absolute currents without experiencing a large voltage drop so on those you might hit the “mAh left” failsafe first.
On lower C rated smaller batteries you might hit the low voltage failsafe first if you push your drone hard (lot’s of current consumed).
But either way you do not need to recalibrate when switching battery types.