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Battery Question

Old 08-13-2019, 01:59 PM
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tomgreen
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I have A Flite 3S 11.1V 1300mAn (14.4Wh) that I am using in my glider. When I start have a battery reading of 12.6 All, #1 4.18, #2 4.20 and #3 4.20).When I land , this is the reading All 11.3,( #1 3.76, #2 3.78 and #3 3.7). My question is how much more can I let the battery get down safely.
Old 08-15-2019, 10:46 AM
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ticedoff8
 
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My suggestion for this kind of question is to first check how many mA your charger is putting back into the 1300mAh pack when you recharge it.
Then when you recharge, do a quick calculation on how many mA was put back in vs. the capacity (1300mA)
You never want to go below 80% of the capacity of a LiPo (1300mA x 0.80 = 1,040Ma used).
Measuring voltage is easy, but knowing the energy used is more accurate
As a simple example,
lets say you fly for 5 min with the motor running intermittently. Then, later, you recharge and add 800mA back in when the pack is at 100%.
That means you were averaging 160mA per min of flight (5 min x 160 = 800mA) based on your flying style.
Adding 800mA back into a 1300mA battery also means it was around 60% discharged.
Assuming you fly consistently throughout the flight, you could fly for another minute or so (at 160mA per min) and hit the 80% discharge point on the battery.
If a hypothetical 5 min flight consumed 800mA, then a 6 min flight would consume 960mA.
But, the "do not exceed" cut off should be 1040mA .
So, if you flew for 7 min, you would have consumed 1120mA
This was an example - your system will be different.

And, since this is a glider, you really want to set a timer on the transmitter that starts and stops with the motor running. Then you can fly for as long as you like and not over-discharge the LiPo (its a glider and gliders are meant to "glide" without a motor).

Also, keep in mind that the battery's resting voltage is going to be higher than it was when you finish your flight.
If you want to base your flight time on voltage, check it as soon after the flight as possible and not 2 or 3 hours later at home.

And, I recommend spending a few bucks and buying a LiPo checker rather than using a simple volt meter.
Tower Hobbies has the Hitec LiPo Checker and Balancer for $19.
You plug it in to the balancer port of the pack and it tells you the % of capacity that is remaining and the individual cell's voltage.
This will tell you as soon as you land what the capacity of the pack after a load.

Last edited by ticedoff8; 08-15-2019 at 11:04 AM.

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