This may not interest you so just go to the bottom for some summaries. For others, feel free to correct any information, I did not go back and review before posting, and keep in mind your results will probably vary a lot.
OEM CHARGER:
Rating:
the OEM charger is 60W (17.6V at 3.41A) and can only charge ONE battery at a time. Even when using the 4 battery hub, it is still goes through one battery at a time. The two USB ports are rated at 2A total for both (1A each). Clearly, we can do better.
Time to charge:
the OEM charger takes about 1.5 hr per battery. For 7 batts, that is 10.5 hrs! (and you have to change out batteries!)
AFTER MKT 3 in 1 CHARGER:
Rating:
the 3 in 1 charger on Amazon is rated at 236W (17.6V at 13.4A total), and 4.7A per the 3 batteries!. The two USB ports are still just 2A total (but I use an external 4.8A (2.4/port) USB charger anyway).
Time to charge everything
At 4.7A it takes about 1 hr to charge the battery, and it does 3 at the same time. I have two of these chargers, so I charge 6 batteries in 1 hr! Then I charge the 7th using the OEM charger, so total is a little over and hour. I also charge the remote and iPhone and these take longer. The remote has a 3,950 mAh battery but can only charge at 2A (not sure, but that is less than 1C = 3.95A) so that is 3.95/2 = 1.98 hrs , and the iPhone 6S has a 3.915 mAh battery but can only charge up to 1.6A (again less than 1C to increase battery life), so that is about 2.5 hrs. So the remote and iPhone is the limitation.
BATTERY SPECS:
Mavic 2 Pro Intelligent Flight Batteries specs and charge rating
Battery Type: Four-cell (4S) LiPo battery
Rated Capacity: 3850 mAh, 59.29 Wh (Typical Value)
Rated Voltage: 15.4 V (3.85A each)
Limited Charge Voltage: 17.6 V (note this is max of the my chargers)
CHARGE RATES:
At 1C charge = 3.85A. The OEM charger is 3.41 so it is under that, which will extend battery life. So use OEM charger when not in a hurry, if you have a lot of time! The After Mkt charger is 4.7A which is 4.7/3.85 = 1.2C. This will reduce battery life slightly, but you already get about 200 cycles and maintain 80% capacity (think iPhone).. this is if you take care of them and store at 40% which is about 3.8V.. my discharger is calibrated to 3.8V (3.8*4 = 15.2V). Charge rate, storage temp, shelf life all affect this, it's complicated. The main idea is to charge at close to 1C or below, store at room temp and 3.8V per cell (15.2V for 4S battery)
FLY TIME and limitations imposed by remote controller and iPhone:
You can safely discharge to a 3V cutoff voltage, and the M2P is rated at 31min max flight time. Capacity in mAh is specified as time to cutoff (not full depletion). So how much average current draw of 3.85Ah for 31min? That would be 3.85 Ah / 0.52h = 7.4A. With 7 batteries, and I run to about 20min / battery to stay safe, that is 140 min flight time. After battery change outs and setup/teardown, it's about 3 hours in the field. Does the remote limit this fly time? The remote battery is 3,950 mAh (which is pretty good), and draws 1,800mA (DJI specs), so it lasts about 3.95/1.8 = 2.2 hrs. Well, it must last a little longer, because after 140 min (using 7 batteries) the remote is still at about 15%, so I have some juice available to also charge my iPhone - which goes low after about 6 battery (the DJI app and wi-fi on consumes a lot of power, and my iPhone batterY is getting older). So I turn of charging from the remote which brings down the remote time somewhat.
So you can safely use 7 batteries and fly for about 3 hours without charging the remote or iPhone in the field. This is all super general but you get the idea. Your results will vary a lot I am sure. The air temp (colder=less time), cycles on the battery, etc. etc. But for about 70 deg air temp, I have flown for 3 hours may times so for me it works.
Note: the intelligent flight batteries have a self-discharge after X days (used to be able to set it, now it is 10 I think, which is pretty long). So if I charged up and cannot go out, I use the ISDT FD-100 80W Discharger which properly depletes each battery to 3.8V*4S = 15.2V storage voltage. I use the M2P charging cables from eBay, cut off the banana jacks and replace them with a XT60 connector.
OEM CHARGER:
Rating:
the OEM charger is 60W (17.6V at 3.41A) and can only charge ONE battery at a time. Even when using the 4 battery hub, it is still goes through one battery at a time. The two USB ports are rated at 2A total for both (1A each). Clearly, we can do better.
Time to charge:
the OEM charger takes about 1.5 hr per battery. For 7 batts, that is 10.5 hrs! (and you have to change out batteries!)
AFTER MKT 3 in 1 CHARGER:
Rating:
the 3 in 1 charger on Amazon is rated at 236W (17.6V at 13.4A total), and 4.7A per the 3 batteries!. The two USB ports are still just 2A total (but I use an external 4.8A (2.4/port) USB charger anyway).
Time to charge everything
At 4.7A it takes about 1 hr to charge the battery, and it does 3 at the same time. I have two of these chargers, so I charge 6 batteries in 1 hr! Then I charge the 7th using the OEM charger, so total is a little over and hour. I also charge the remote and iPhone and these take longer. The remote has a 3,950 mAh battery but can only charge at 2A (not sure, but that is less than 1C = 3.95A) so that is 3.95/2 = 1.98 hrs , and the iPhone 6S has a 3.915 mAh battery but can only charge up to 1.6A (again less than 1C to increase battery life), so that is about 2.5 hrs. So the remote and iPhone is the limitation.
BATTERY SPECS:
Mavic 2 Pro Intelligent Flight Batteries specs and charge rating
Battery Type: Four-cell (4S) LiPo battery
Rated Capacity: 3850 mAh, 59.29 Wh (Typical Value)
Rated Voltage: 15.4 V (3.85A each)
Limited Charge Voltage: 17.6 V (note this is max of the my chargers)
CHARGE RATES:
At 1C charge = 3.85A. The OEM charger is 3.41 so it is under that, which will extend battery life. So use OEM charger when not in a hurry, if you have a lot of time! The After Mkt charger is 4.7A which is 4.7/3.85 = 1.2C. This will reduce battery life slightly, but you already get about 200 cycles and maintain 80% capacity (think iPhone).. this is if you take care of them and store at 40% which is about 3.8V.. my discharger is calibrated to 3.8V (3.8*4 = 15.2V). Charge rate, storage temp, shelf life all affect this, it's complicated. The main idea is to charge at close to 1C or below, store at room temp and 3.8V per cell (15.2V for 4S battery)
FLY TIME and limitations imposed by remote controller and iPhone:
You can safely discharge to a 3V cutoff voltage, and the M2P is rated at 31min max flight time. Capacity in mAh is specified as time to cutoff (not full depletion). So how much average current draw of 3.85Ah for 31min? That would be 3.85 Ah / 0.52h = 7.4A. With 7 batteries, and I run to about 20min / battery to stay safe, that is 140 min flight time. After battery change outs and setup/teardown, it's about 3 hours in the field. Does the remote limit this fly time? The remote battery is 3,950 mAh (which is pretty good), and draws 1,800mA (DJI specs), so it lasts about 3.95/1.8 = 2.2 hrs. Well, it must last a little longer, because after 140 min (using 7 batteries) the remote is still at about 15%, so I have some juice available to also charge my iPhone - which goes low after about 6 battery (the DJI app and wi-fi on consumes a lot of power, and my iPhone batterY is getting older). So I turn of charging from the remote which brings down the remote time somewhat.
So you can safely use 7 batteries and fly for about 3 hours without charging the remote or iPhone in the field. This is all super general but you get the idea. Your results will vary a lot I am sure. The air temp (colder=less time), cycles on the battery, etc. etc. But for about 70 deg air temp, I have flown for 3 hours may times so for me it works.
Note: the intelligent flight batteries have a self-discharge after X days (used to be able to set it, now it is 10 I think, which is pretty long). So if I charged up and cannot go out, I use the ISDT FD-100 80W Discharger which properly depletes each battery to 3.8V*4S = 15.2V storage voltage. I use the M2P charging cables from eBay, cut off the banana jacks and replace them with a XT60 connector.
