Battery charge strategy for continuous, back-to-back flying

[lomposlapos]

I am out in the middle of nowhere and only have 2 car cigarette lighter female and car battery power inverter available.

What are the best options (minimum number of batteries, minimum number and type of chargers, and usage strategy) to continuously keep flying the M2P back-to-back (landing for battery and memory card change only, then take off = 5 min between flights)?
In other words, I am looking for the minimum equipment that will provide charged batteries faster than they are being used for flying.

(As a part of this question: in real-life situations, how long it takes for the hub ( DJI Battery Charging Hub for Mavic 2 Pro) to charge one (1) battery in full?)

 

[lomposlapos]

For example,
[Upgrade Grounded] Powerextra Mavic 2 Pro & Zoom Battery Charger, 5 in 1 Rapid Smart Battery Charger Hub (Charge 3 Batteries & 2 USB Ports Simultaneously) Compatible with DJI Mavic 2 Pro/Zoom
If the charger above, in fact, is able to charge 3 batteries simultaneously to full in 60 min, then, 3 (theoretically) or 4 (in real life) batteries would provide continuous supply of charged batteries. ... and assuming that 3rd party chargers are "intelligent" enough for DJI.

 

[Mossiback]

Don't forget a USB power supply for the RC.

 

[Not A Speck Of Cereal]

The batteries take far longer to charge than they do discharge during flying. You should land well before 10% too, so there's that. The DJI M2P manual states an hour and a half to charge one using the supplied AC charger.

As Mossiback states, there's also the RC to consider.

Then there's the device (tablet, phone, crystal sky, etc.).

If you had a 4-battery charger (3-rd party parallel, not the DJI hub), you would then have about 100 minutes of flying (4x25 minutes), during which time, you could be charging another 4 batteries to about 2/3 capacity. Given that you want that to go to 100%, you're looking at at least 3 banks of 4 batteries.

HOWEVER, the 4-battery charger just doesn't work well on a single 12V battery. Even if you chain more batteries to the inverter, you're only extending the period of time it can charge, not the amount of juice it can deliver (it won't make the 4-battery chargers work -- someone correct me if I'm wrong). So to do that, you would have to find another source battery solution that would deliver enough (amps? watts?) to an inverter with a 120v output.

I'm not smart enough to tell you how to do that though, I just know from experience that a single 12v car battery won't do it, especially one with TWO cigarette-lighter adapters tapped into it.

Chris

 

[DanMan32]

To figure out power needed and get through voltage conversions, use watts.
Each M2 battery takes 60-70 watts. 4 of them charging simultaneously would be up to 280W. At 12, that's 24A, regardless if you're using a car charger or AC charger with inverter. Add 10% for conversion loss.

Don't forget to allow for the battery just flown to cool off before putting it on charge.

If you get 20 minutes of flight from a battery, and it takes 90 minutes to charge, you probably need 5-6 batteries if charged sequentially.

But then there's the RC like others have pointed out.

 

[old man mavic]

apart from the stress you would be putting on the airframe and electronics from continuous flying what would be the point of wanting to do it in the first place,you would need at least 2 controllers so you could be charging one while flying with the other, and two devices for the same reason and to give the batteries time to cool and recover between flights if you had 10 batts at 20 mins per flight then without having to worry about charging them that would give you over 3 hours flight time

 

[lomposlapos]

Don't forget a USB power supply for the RC.

Yes. SC can be charged from the car cigarette lighter, while being used, I assume. Correct?

 

[agchenry]

Yes. SC can be charged from the car cigarette lighter, while being used, I assume. Correct?

yes, you can use sc and charge at the same time

 

[offtheback]

I am out in the middle of nowhere and only have 2 car cigarette lighter female and car battery power inverter available.

What are the best options (minimum number of batteries, minimum number and type of chargers, and usage strategy) to continuously keep flying the M2P back-to-back (landing for battery and memory card change only, then take off = 5 min between flights)?
In other words, I am looking for the minimum equipment that will provide charged batteries faster than they are being used for flying.

(As a part of this question: in real-life situations, how long it takes for the hub ( DJI Battery Charging Hub for Mavic 2 Pro) to charge one (1) battery in full?)

I have a small USB A outlet battery that I velcro to the bracket that holds my crystal sky+remote.The remote,when plugged into the battery,stays close to 100% charge when in use.The external battery can be swapped out as needed.

 

[Mossiback]

Yes. SC can be charged from the car cigarette lighter, while being used, I assume. Correct?

If the car cigarette lighter is convenient. If you need to be away from the car you can use a portable USB power supply carried in your pocket or otherwise attached to the RC.

 

[Bramavic2]

yes, you can use sc and charge at the same time

From my limited experience, it seems the RC draws much more power than and usb connection(non quickcharge) could provide. So your RC will discharge, although slower it you are able to charge it.

Not mentioning that if you´re using an android device, the RC will keep charging the android device.

You didn't mention if you will also have a car available, otherwise you will need quite a big car battery to use it for such a long time. With a car, you would need to keep it on. Also for simultaneous charge of so many batteries you will need to use thicker cables directly from the battery, normal cigarette lighters won't do.

 

[Aerialman]

The batteries take far longer to charge than they do discharge during flying. You should land well before 10% too, so there's that. The DJI M2P manual states an hour and a half to charge one using the supplied AC charger.

As Mossiback states, there's also the RC to consider.

Then there's the device (tablet, phone, crystal sky, etc.).

If you had a 4-battery charger (3-rd party parallel, not the DJI hub), you would then have about 100 minutes of flying (4x25 minutes), during which time, you could be charging another 4 batteries to about 2/3 capacity. Given that you want that to go to 100%, you're looking at at least 3 banks of 4 batteries.

HOWEVER, the 4-battery charger just doesn't work well on a single 12V battery. Even if you chain more batteries to the inverter, you're only extending the period of time it can charge, not the amount of juice it can deliver (it won't make the 4-battery chargers work -- someone correct me if I'm wrong). So to do that, you would have to find another source battery solution that would deliver enough (amps? watts?) to an inverter with a 120v output.

I'm not smart enough to tell you how to do that though, I just know from experience that a single 12v car battery won't do it, especially one with TWO cigarette-lighter adapters tapped into it.

Chris

I've just read this post with great interest because 1. I'm traveling and don't have the info I need now and internet is very poor here. Lucky to be able to get on here. 2. I'm new to DJI drones and 3. I'm ex military and older than dirt. So my question is I fly the Mavic Pro 2 and charge batteries & smart controller using the Powerextra for Mavic 2 after each flight and fly every day. 3. Have my minimum Battery % set at 30%. Question is I'm not getting any where near 28 - 30 minutes of flight time. Closer to 15 - 18 min. Is my 30% to high? I do charge sometimes before I hear the warning. Any help will be appreciated.

 

[Not A Speck Of Cereal]

28-30 minutes is marketing material for the most absolute best / ideal conditions and flying to the max. voltage before landing (probably far less than 30%). The real flight-time numbers are always going to be smaller than that.

This is why I have 6 batteries.

I think 30% for the first warning is fine. Remember that you have a critical warning after that, so you can use the first warning as an indicator that you can "keep flying, but be sure to be closer to home now in case you fly so long that the critical warning fires off". It's very nice to have if you are a long distance away from home point, a clue for you to start heading home, but you're not so far down that you can't do some more shooting on the way back. And if you're already close to HP, it means even less.

Chris

 

[Aerialman]

28-30 minutes is marketing material for the most absolute best / ideal conditions and flying to the max. voltage before landing (probably far less than 30%). The real flight-time numbers are always going to be smaller than that.

This is why I have 6 batteries.

I think 30% for the first warning is fine. Remember that you have a critical warning after that, so you can use the first warning as an indicator that you can "keep flying, but be sure to be closer to home now in case you fly so long that the critical warning fires off". It's very nice to have if you are a long distance away from home point, a clue for you to start heading home, but you're not so far down that you can't do some more shooting on the way back. And if you're already close to HP, it means even less.

Chris

Thanks Chris, I appreciate your input. I have 3 batteries. Will get more. All/ most of my current flying is very close to home in that I'm still learning things like point of interest etc. Longest distance has been 5,000' with a clear view no obstructions but it was a quick flight since I got my low battery warning. I'm going to use my smart controller flight record to look at actual times once I figure out where to find it. Thanks again.

 

[Not A Speck Of Cereal]

Glad to help. The "H" icon on the battery power left meter is always helpful (head for Home when you hit it), but be mindful of head-winds on the way back (something that meter cannot accurately predict for).

Chris