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Battery strength discrepancy
461 3 2015-12-26
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sifu128
lvl.4

United States
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Hey guys, I have a question and I a curious about something. The battery information on the main screen states that my battery is at 100% but the actual strength indicator states 37% which I believe because there are only 2 green lights on the battery when its it. Is this normal or a bug? Shouldn't both of these match, or is the 100% the overall health of the battery / cycles?

Battery Strength Indicator

Battery Strength Indicator

Battery info

Battery info
2015-12-26
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ronday
lvl.3
Flight distance : 423301 ft
Netherlands
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On the second screenshot where it states 100% is the battery life. This is the overal state of the battery health and not the remaining charge. So it wil always show different numbers.
The battery life will drop after so many cycles, so that way you can check how healthy the battery is and not how many energy is left in the battery.

The number in te first screenshot is the most important number and shows the remaining energy. And a pro tip. Always fly with fully charged battery's !!
2015-12-26
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sifu128
lvl.4

United States
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Thanks Ronday! I was hoping that this was the case I am testing the overall flight length and just basics. It really does help having multiple batteries
2015-12-26
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Cessna172
Second Officer
United States
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A fully charged battery does not necessarily equate to a healthy battery.
It can easily be shown that a battery with very low current capacity can read more that the voltage rating for that battery by overcharging the remaining healthy cells.So while voltage may read 13v for a 12v battery for example, the cells do not have adequate storage capacity for the designated CAPACITY (mAh) or Ah

As such, it may be that the batteries in DJI Phantoms can display ample voltage, yet once the operator lifts the Phanom into the air, the aircraft soon falls due to a disparity between the measured voltage
and the actual capacity.   Remember, you can fly with a battery at even slightly less than 11v BECAUSE it still can supply the necessary current.   Note however that flying your Phantom on a lowered voltage increases the demand for current which can cause motors to get very hot.   A bad thing.    This is why I do not personally recommend going for the longest possible flight by lowering the battery warning thresholds.

Many flights that began with sufficient indicated charge ended in a crash due to exhaustion of batteries CURRENT capacity.
I am not sure to what degree the internal logistics of DJI's batteries are able to determine capacity, but if it is limited to voltage that is not sufficient.
I would take a guess that some mechanism is built into the battery logistics to determine capacity but draining battery energy across a known resistance load for a predetermined amount of time is required.  It is difficult to incorporate the necessary mechanish to properly test capacity in such a small and sensitive environment as exists inside a DJI Phantom.
Still, due to the number of crashes reported on batteries at 60-70%, I would say there is likely a deficiency somewhere in that internal logistics / test path.

To shorten all this junk down to something useful....what might be really beneficial is to charge your battery fully, then wearing safety goggles and holding your Phantom from flying away or better yet,  strapping your Phantom down to a table, run the motors at 75 - 100% of full throttle until the warnings come on and put your Phantom in RTH mode.     That will give you a real world idea of your batteries health.  
2015-12-26
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