3. but I think I need 1 more. The only thing is when you travel by plane in the US if your carrying it on board you can only take two.
Wrong, I often tsa with 5 never an issue. Don't fix what's not broken [emoji3]
Rbruz, you are correct. TSA doesn't bother you with your 5 batteries.
Shield2160 you are 1/2 correct & 1/2 incorrect. You are limited to 2 for carry-on...but that is only if the batteries are over 100Wh.
Here is straight from TSA site:
Lithium ion batteries (a.k.a.: rechargeable lithium, lithium polymer, LIPO, secondary lithium).
Passengers may carry all consumer-sized lithium ion batteries (up to 100 watt hours per battery). This size covers AA, AAA, cell phone, PDA, camera, camcorder, handheld game, tablet, portable drill, and standard laptop computer batteries. The watt hours (Wh) rating is marked on newer lithium ion batteries and is explained in #3 below. External chargers are also considered to be a battery.
With airline approval, devices can contain larger lithium ion batteries
(101-160 watt hours per battery), but spares of this size are limited to two batteries in carry-on baggage only. This size covers the largest aftermarket extended-life laptop batteries and most lithium ion batteries for professional-grade audio/visual equipment.
#3 gives the equation to get Wh. "To determine watt hours (Wh), multiply the volts (V) by the ampere hours (Ah). Example: A 12-volt battery rated to 8 Amp hours is rated at 96 watt hours (12 x 8 = 96). For milliamp hours (mAh), divide by 1000 (to get to Ah) and then multiply by the volts."
So 11.4V x 3.83A (which is from 3830mAh / 1000) = 43.66 Wh. It is clearly marked on the Mavic Pro battery but I was bored and felt like doing the math.
Oh btw, I have 4 but want 1 more. So 1 in the bird and 4 on the charging hub being charged up for the next session either the same day or the next. Always stored at 45-60%.