I measure my airplanes similarly to Michaels. My Giles 300 consumed about 300ma during a 10 minute flight. They were normal flights from run up, hard aerobatics, to landing and taxi to the pits. Its be best way to measure the actual draw of an airplane since its real world, vs theory or bench measurements.

I base my fly/no fly decision on the knowledge that two 2000mah packs give me 4000ma total, and that I can safely get 8 flights on a charge, and still leave me with enough for a couple more flights as a safety margin.

With that knowledge, and a ESV reading loaded at 1amp prior to each flight just to be sure everything is on track, I am very confident of where my batteries are.

If you measure your airplanes in the same manner, and log each ESV reading after each flight, you will have the best method of tracking your battery capacity, and making a go/no-go decision. But it does take some up front work, and it all depends on how you value your airplane and your time on whether or not its worth it. On some of my planes, I just use a loaded ESV and fly no lower than 1.2v per cell. On my more expensive airplanes, I use the duration/capacity method.

Here is how to use the duration/capacity method.


Cycle your battery a couple times till the full mah capacity stabilizes. Lets say its 2000mah. Fully charge your batteries. Log the ESV reading before a flight, and immediately after. Fly for two or three flights, but do not go below 1.2v per cell. Log the ESV for each flight before and after.

Then discharge the batteries with a cycler/discharger and not the remaining capacity that was taken out. Lets say the remaining capacity was 1000mah. This means you used 1000mah during 5 flights, or 200mah per flight. You are at 50% capacity at 5 flights if everything is normal.

This means your battery should give you 10 flights on a full charge till dead. However, you want a buffer there for a couple flights just in case, and also to keep you away from the steep curve at the end. So subtract 400mah (2 flights), which leaves you with 1600mah usable, or 8 flights total. I like to leave about 30% reserve, which is my no-fly point. However, I usually stop flying around 50%.

On a full charge, you now know you can safely fly 7 flights, and still have a reserve of 3 flights just in case. In a perfect world, you wouldn't need to even check your batteries with an ESV. However, its not a perfect world. So, keep a log of the ESV readings before and after each flight. Use that as a secondary check just to make sure your packs are operating normally, and your 7 flight regime is on track. If the reading vary for any reason by any significant amount, you would quit flying and check the batteries.

Its a little bit of upfront work, but well worth it for peace of mind on the more expensive airplanes. Once you have the initial log done, which only takes a couple flight sessions with cycling at the end of the day, the rest is business as usual.