TB47 vs. TB48 Battery

ElGuano · Nov 30, 2014

Economically it's one thing, but don't forget to take into account the additional flight time deficit of 100g for the heavier battery. Unfortunately you never get 1:1 increase in battery capacity to flight time; in reality you are lucky to get 1:0.75 because of the added weight and overhead.

In the end, I agree it's still likely well worth it if you need the extra time (4 minutes doesn't sound like a lot but given the same situation it is actual, useful time not spent in transit).

ultraturtle · Nov 30, 2014

ElGuano said:
Economically it's one thing, but don't forget to take into account the additional flight time deficit of 100g for the heavier battery. Unfortunately you never get 1:1 increase in battery capacity to flight time; in reality you are lucky to get 1:0.75 because of the added weight and overhead.

In the end, I agree it's still likely well worth it if you need the extra time (4 minutes doesn't sound like a lot but given the same situation it is actual, useful time not spent in transit).

Agree to a point. Probably should have added the efficiency loss as a disclaimer, although I cannot understand why you would attribute a 3% mass increase to a 25% efficiency reduction. No doubt your credentials trump mine, but my lowly undergraduate degree in aerodynamic engineering suggests something closer to a 2% efficiency reduction (75% of the weight increase). That would reduce the 3 x 5.7Ah battery option from something significantly over 46 minutes to something just over 45 minutes of loiter time vs a solid 46 minutes for the 4 x 4.5 Ah battery option. Apologize for not drilling down to the details.

What I find most remarkable is that DJI offers its higher capacity battery at a lower cost per Wh than it does the lower capacity one. Most gadget manufacturers charge a ridiculous premium, not a discount.

Hat's off to DJI on this.

Or maybe - we should all buy a bunch of 5.7 Ah batteries quick, before DJI realizes their mistake!!!!

ctp · Dec 1, 2014

ElGuano said:
Economically it's one thing, but don't forget to take into account the additional flight time deficit of 100g for the heavier battery. Unfortunately you never get 1:1 increase in battery capacity to flight time; in reality you are lucky to get 1:0.75 because of the added weight and overhead.

In the end, I agree it's still likely well worth it if you need the extra time (4 minutes doesn't sound like a lot but given the same situation it is actual, useful time not spent in transit).

I did the original math in another thread that suggested the 4 minutes extra. The straight math suggests almost 5 minutes extra, which I rounded down to 4 minutes to account for the additional 100g of weight and the shift in COG. DJI later confirmed the 22 minute figure for the larger battery.

My biggest use case is 3D capture modeling. The extra 4 minutes can easily be the difference between 1 flight and two, or 30 minutes on site versus 50 minutes.

LeesburgAirlines · Mar 15, 2015

ultraturtle said:
You need to do some math. 30% more battery capacity for 25% more cost is an incredible bargain:

Ref :http://www.dji.com/product/inspire-1/spec

The 5.7 Ah battery has a potential of 22.8 volts, and therefore 129.96 Wh.

The 4.5 Ah battery has a potential of only 22.2 volts, and therefore 99.9 Wh.

Staying on scene for 30% more time to get more shots, regardless of usage pattern, is worth far, far more than 25% more cost. Not just wasted time on the ground swapping out batteries, but the compounded waste of driving to and from the scene.

Compare the following two scenarios, both using 75% of DJI's stated capacities:

Total flight time for 4.5 Ah battery = 13.5 minutes
minus 4 minutes to fly to and from the scene = 9.5 minutes
Total on scene time with 4 batteries = 38 minutes

Total flight time for 5.7 Ah battery = 17.5 minutes
minus 4 minutes to fly to and from the scene = 13.5 minutes
Total on scene time with 3 batteries = 40.5 minutes

Total cost for batteries to give you 38 minutes on scene with 4.5 Ah batteries is $636.
Total cost for batteries to give you 40.5 minutes on scene with 5.7 Ah batteries is $597.

There is simply no value comparison to be made.

Note that the comparison does not even take into account the waste of your time making an additional battery swap.

I agree on the min/air trade off for $$. This is some great information. Thanks! AND, the thing I'm still not seeing much of on any of the forums is confirmation if I can travel on the airlines with my Inspire TB48 batteries. ElGuano, have you or anyone you know actually taken the TB48 onto a plane in carry-on? I plan to do some deep-sea video in the Caymans this year and don't want any problems when I pass through TSA. Thanks all!

damoncooper · Mar 15, 2015

The TB48's absolutely rock. I had gotten used to 13 minute flight times with my P2 laden down with transmitter, ground station, gimbal, GP, iOS mini, etc.

I literally am having trouble adjusting to planning flights that make use of the 16-20min of flight time and can't believe I still have 35%+ battery left on landing.

Simply awesome.