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Battery mod thread

Justinswidebody

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Whoever is doing battery mods please post your creation. Also please tell us your setup and how much flying time you achieved.

I'll go first. 2 sanyo 18650ga 3450mah with jst connector soldered onto the pads in the picture below.

Battery can not be flown without stock battery in place. If you try, you will get a power error on the screen.

My time test flight will be tomorrow. I removed one of the vent holes and ran my wires through it.
 

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Interesting, it seems dji only charges their batteries to 4v per cell equalling 8volts and only discharges it to 3.5volts per cell equalling 7volts.

These batteries can be charged to 4.2volts per cell and discharged to 2.5volts per cell. I wonder why they're being so conservative....
 
Actually Winter time in Germany. Flight tome may increase by pre heating the battery before flight to app. 40°C.
We have tested that with a 5kg T-Rex (6S-5000mAh) around freezing point. The flight time and performance was close to double with the "hot" battery.
 
Interesting, it seems dji only charges their batteries to 4v per cell equalling 8volts and only discharges it to 3.5volts per cell equalling 7volts.

These batteries can be charged to 4.2volts per cell and discharged to 2.5volts per cell. I wonder why they're being so conservative....
Even with these batteries, bad idea to go lower than 3.0v. For LiPos, definitely don't.
I'm pretty sure voltage is 4.2v. I'll have to check next time I fly. Touch battery icon and it shows voltage.
But yes, DJI is conservative so to protect the battery from damage. I'm surprised the MM doesn't force land at 10%. Others do though you can override by up throttle.
 
These batteries can be charged to 4.2volts per cell and discharged to 2.5volts per cell. I wonder why they're being so conservative....

Keeping any of the lithium-chemistry batteries between 30% and 80% of full charge can greatly extend the number of charge cycles in the battery's lifetime. But 80% charge happens shortly after they reach 4.2 volts during charging, so if your measurement of the top end is accurate, yes - very conservative.
 
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Keeping any of the lithium-chemistry batteries between 30% and 80% of full charge can greatly extend the number of charge cycles in the battery's lifetime. But 80% charge happens shortly after they reach 4.2 volts during charging, so if your measurement of the top end is accurate, yes - very conservative.
For LiION optimum cycle life seems to be achieved with terminating the charge at 3.92v. The trade off is usable capacity. Every reduction of 70mv is around 10% reduction in W/h. I can’t see DJI being happy with over 25% reduction in flight time setting charge voltage to 4V, that 30min is a big ticket item in the soec sheet. It’s always a compromise.
 
Force land happens at 5% @ 3.3v.
Whats the "Cliff" voltage for LiIon batteries? DJI LiPo's would force-land on 10% and cliff voltage was about 3.2v.
My concern with this new quad is DJI's inexperience with this type of battery- dont know if they're cutting it close or being too conservative.

Full charge voltage is 4.14v or so. I tend to store them with 50% charge, then charge up and fly that day so they dont sit >4v for too long (preferably <12hrs). Once flown, cool to room them and charge back to storage level ready for next time.

My interest is given DJI was trying to get this <250g - if there was perhaps a higher capacity battery (official/aftermarket) for those who are already registered and dont care about the 250g limit.
 
Liion batteries can be taken to 2.5volts per cell safely... And can be charged to 4.2volts per cell safely... 18650 batteries are great for mAh/weight. Unfortunately I have not been able to surpass my 33:45 flight. Guess I'm going to have to try some graphene batteries. DJI isn't cutting it close at all. I fly airplanes with liions for 5 hour flight time and land them at 2.8volts per cell to be safe.

Force land happens at 5% @ 3.3v.
Whats the "Cliff" voltage for LiIon batteries? DJI LiPo's would force-land on 10% and cliff voltage was about 3.2v.
My concern with this new quad is DJI's inexperience with this type of battery- dont know if they're cutting it close or being too conservative.

Full charge voltage is 4.14v or so. I tend to store them with 50% charge, then charge up and fly that day so they dont sit >4v for too long (preferably <12hrs). Once flown, cool to room them and charge back to storage level ready for next time.

My interest is given DJI was trying to get this <250g - if there was perhaps a higher capacity battery (official/aftermarket) for those who are already registered and dont care about the 250g limit.
 
This is my 33:45 second flight

With 100g more load is MM switching to S mode right away, can you post log from that flight?

I noticed by adding just 42g battery drain was almost double, and MM switched to S mode just to hover in 0 wind conditions.
 
Liion batteries can be taken to 2.5volts per cell safely... And can be charged to 4.2volts per cell safely... 18650 batteries are great for mAh/weight. Unfortunately I have not been able to surpass my 33:45 flight. Guess I'm going to have to try some graphene batteries. DJI isn't cutting it close at all. I fly airplanes with liions for 5 hour flight time and land them at 2.8volts per cell to be safe.
I guess the question would then be - can the aircraft itself sustain flight @ 2.5v/cell or 5v for 4 motors? Fixed wing is one thing as they generally only require 1 motor but multirotors??

Apparently Mavic Pro's cutoff was 9v minimum to sustain flight.
 
If M2 can be any example, you can sustain flight as long as 2 minutes beyond 0%. Not sure what the voltage is, and it is LiPo, not the cylindrical LiIon. Of course you have to counter the desire for AC to land.
 
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If M2 can be any example, you can sustain flight as long as 2 minutes beyond 0%. Not sure what the voltage is, and it is LiPo, not the cylindrical LiIon. Of course you have to counter the desire for AC to land.
Dropping below 3.0V on any cell in the M2 forces controlled descent thr cannot be countered. That 3.0V value can be changed in parameters to as low as 2.5V, so some value below 2.5V is likely fatal.
 
I guess the question would then be - can the aircraft itself sustain flight @ 2.5v/cell or 5v for 4 motors? Fixed wing is one thing as they generally only require 1 motor but multirotors??

Apparently Mavic Pro's cutoff was 9v minimum to sustain flight.
Your concern re number of motors is largely irrelevant. Each motor has a seperate speed controller so for the purpose of establishing Vmin it is the same whether 1 motor or any number.

2.5V (loaded) for most 18650 LiION packs is pushing it. Best scenario cycle count and service life will be significantly impacted. 2.8V is a much better compromise.
 
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