When we enter in the Mah for each battery we are using in our fix wing UAV, we noticed the BatRemaining data field is often incorrect, and we end up looking at the BatVolatge data field instead. For example we use a 8000Mah 4cell, battery in our FixWing UAV. We were told by the manufacture not to let the battery drop below 14.8volts. Yet when the battery gets down to 14.8 volts, the BatRemaining data field often shows the battery % remaining is over 50%!!! WHY?? And what is the best practice for ensuring we get the best life span out of our costly batteries.
On my Cessna and my quad I use the mah used option on MinimOSD, but I believe you can also see it on the mission planner hud (battery_usedmah).
But either my way or yours requires the power module to be accurately configured and it’s taken a while to get my quad accurate. The Cessna is still off but I’m getting closer.
The setting is BATT_AMP_PERVOLT.
I’ve found that if you make a note of how many mah are shown as used from the battery (on the hud or osd), then charge the battery to see how many mah goes in you have enough info to get close by using the formula - old value * actual mah used / osd reported mah used = new value.
Took 1 go to get the quad perfect and 2-3 to get the Cessna close.
As for the 80% rule, I think theres some misunderstanding on that. I have 5000mah 4s batteries and I run them to 4900mah used without issue so long as the per cell voltage stays above 3.2v.
But, I pull less than 80% of the maximum current rating from them.
IE, 1000mah battery that has a 25c constant discharge has a constant supply of 25amp.
So you can only pull 80% of 25amp (20amp) from that battery.
Given my quad only pulls 60amps for a second or two when I initially punch full throttle I take that as my target constant amp. I spec the battery to have to supply 75amp constant which for a 5000mah is 15c constant. More over specced than under.
I run Turnigy 4s lipo’s of 20-30c (constant-burst c) and usually have an end voltage of around 3.5v per cell. Last flight iIused 4465mah (thats what the charger put back) and that had a resting voltage of 15.06v or 3.765 per cell. Flight before that was a 30mph auto flight that used 4196mah and had a loaded voltage of 3.6875v per cell, not sure what the resting voltage went up to.