will it damage the batteries if they run all out of power while in the sky ?
Yes! When the battery percentage shows zero you need to land right away. If they discharge much below that they will not take a charge anymore.
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@Pdwhite @zjwhitehead perhaps consider a safety power off feature that shuts down the power if the batteries get below a certain point (2%?)
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Electronic Speed Controls (ESC) for model aircraft used to start cutting total available power or shut down the motor when the voltage dropped below a certain point. Typically around 3volts/cell under load. This protected the batteries but if you were hitting the low voltage cutoff every time the batteries wouldn’t last as many cycles.
In this application one might like to have an ‘emergency reserve’ available that allows you to sacrifice the batteries to save your @$$ from a really bad landing. Normally you should be landing with some reserve battery time available just like you would if you were burning petroleum byproducts from a tank.
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hi Guys may I ask what your using to check battery percentage in flight? during my ground testing for my project im having a hard time trusting the DVM readings as they fluctuate like mad under load but seem to recover when speed reduced … I understand im drawing a lot of current but is there a way I can saftly gauge remaining battery power so as not to hit the LVC point on my ESC 
I trust the readout on the throttle controller when the motors aren’t running. I don’t agree that it fluctuates under load unless you are fluctuating the load. The higher the load the lower the voltage reads. Here’s what I do if I want to milk out that last little bit: When my batteries are low and the display reads close to zero percent I will often just use less and less throttle to keep that value above zero. Eventually I can’t apply any throttle without it dropping to zero and that’s when I land. After landing my battery percentage is almost always above zero. I only milk out that last little bit above the landing zone. Actually, my number one rule when I fly is that at any moment during my flights I can glide to a safe landing area if something were to go wrong.
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Hiya Many thanks for the feedback my unit is not Openppg at moment as I started my Eppg build before this great project started but you guys have been seeing great progress and im loving the way things are going here… My project is 18S @20 amp/hr lipos and can see 130 amps at full throttle during ground testing . the fluctuation I badly describes I suppose is battery sag under load ? most of my testing sorrta stops once I hit 30% remaining mark mainly because of the DVM reading ( connected across battery leads to ESC , My project is not at Flyable stage yet until im past confidant ground duration testing really appreciate the Input and it seems the Open PPG throttle has a decent display of the battery state so will see what I can maybe adapt to suit mine until I jump ship as they say can post Youtube link of my attempts but no laughing guys …
From my electric R/C experience (15 years)…
If you are getting anything more than gliding distance away from your intended LZ or alternate LZ then you’ll want to be very familiar with the overall health of your batteries as well as the current voltage. The way to do that is to record your flight times, note conditions and power profile for the flight, and track how many watt/hours it took to recharge. Any ‘gauge’ will only give you an approximation of remaining time at a given power setting. This will change over time as the cycles build up, ambient temperature, average loads over time (full power climbs vs cruising), storage, and charging system all have some small effects on the batteries.
Question: How sophisticated is the openPPG battery gauge? Does it sense voltage only or does it sense current and track wattage used over time as well?
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