This topic was discussed many times here and on other forums, and still remains confusing to many. Since my aerial photography and filming is almost exlusively done in remote landscapes, this issue is of paramount importance. Here are my thoughts, based on real life experience.

Field battery charging is - unfortunately - more complicated than most of us is expecting. The reason? Power supply. You need a plenty of stored or fabricated energy available out there. Relatively small, single Phantom or Mavic battery can be charged off a car cigarette lighter or auxiliary output, assuming good shape of vehicle power plant, socket, internal wiring and fusing.  DJI's offering suitable chargers for such. However, try to charge more than once or twice without re-conditioning car battery and you may end up looking for a good people with booster cable next morning.

Still, for recreational use this approach may be good enough. For Inspire/Matrice class drones, however, intensive filming in remote locations requires reliable power source. The obvious and simple solution is a generator, 2000W Honda as being the most loved by pros. Add an multichannel charger to feed 4 batteries simultaneously, sufficient number of spare batteries and you're happy. flying without interruptions other than lunch break.

Than we have solutions for brave ones: huge 12V battery and 1000 or 2000W inverter in the trunk as an equivalent of a noisy and smelly generator. 200Ah led battery weights 60-70kG, but - when fully charged - will provide enough juice to charge several TB48's or TB47's. This approach, however, carry a serious safety issues. Heavy wiring aside, such monstrous load must be securely mounted and isolated, avoiding the risk of catastrophic shorts. Not cheap though, and definitely not for weekend warriors ...

There's similar, but cheaper solution. Equally challenging, however, for a few of us only familiar with soldering gun. Huge storage battery is still required, but the charging voltage and current is provided by widely e-Bay available DC-DC Step-Up Converters. Here's a DIY double channel charger, set up for Phantom 3 batteries with moderate charging rate. Note approx. 4.5A charging current for each battery, but the total drain is about 15A! The wiring from battery terminals must be at least of 10AWG to avoid noticeable voltage drop. Converters itself are of CV/CC type (Constant Voltage/Constant Current). allowing for wide output parameters adjustment to charge Inspire batteries as well. In this case, however, the drain is even bigger, reaching 20-25 A current. Naturally 24 VDC battery will provide much better source, but this option may be available for some truckers and boaters only.

Bottom line: drone batteries are hogs and will demand a lot of power. A portable generator is still the best, simple and safe ...

Good post Dobmatt, thanks very much.

I looked into DC-DC solutions a while ago -> http://forum.dji.com/thread-15075-1-1.html
What I found at the time was that the ebay sourced dc-dc modules I could find were very electrically noisy.
At the time I didn't want to subject the batteries to that sort of treatment.
I'd be interested to hear how the units you have been using go?

I tried some additional filtering (chokes and large capacitors on the output) but it didn't reduce it much, so I reverted to the large AGM battery / pure sine wave inverter combo you mention in your post.
I don't think that there's a 1 size fits all solution here - really depends on your individual requirements and what facilities you can carry with you.

I will strongly agree with you however that there is a BIG 12VDC power requirement, especially if you are charging multiple TB48s!

Safe flying

Farnk666 Posted at 2017-3-21 18:51
Good post Dobmatt, thanks very much.

I looked into DC-DC solutions a while ago -> http://forum.dji.com/thread-15075-1-1.html

Although I've never had a chance to visually check the smoothness of output, both Phantom and Inspire batteries seems to be happy with such roughly prepared meal until fully charged. The unit  you've employed is an older incarnation of 600W model, which indeed doesn't perform good enough in terms of stable current management. 1200W model seems to perform much better, providing stable current with negligible small and short peak demanded by DJI batteries at approx. 30 minutes of charging and almost linear drop until full saturation at 60-65 minute. Again, how really smooth is this output remains unknown to me, but bigger caps does help for sure.

BTW, I just finished charging four TB48's at once using 4 of these 1200W units wired to 24V battery and set to 6A charging current. With average 15% power left it took 60 minutes, but 12 AWG main wire get noticeable warm supplying 25A current. Imagine this with 12V battery!  

Cheers, Brother.

I have something similar to this:

https://www.backupbatterypower.c ... A6tICFYmLswodIcQBLw

LiFePO4 backup batteries are coming out in droves with built-in inverters and many of them come with solar charging capability - I have a couple of 80W roll out solar panels that I hook up to the battery to keep it topped...

-john

ocelot27 Posted at 2017-3-22 08:15
I have something similar to this:

https://www.backupbatterypower.com/products/lithium-ion-portable-battery-backup-ups-v2-0?variant=34092761486&gclid=CPb1z-HA6tICFYmLswodIcQBLw

Yes, these may suit recreational activity on camping, but for bigger commercial job will not deliver unless you've got a 1kW solar array plugged in. Been there,did that ...

Dobmatt Posted at 2017-3-22 14:15
Yes, these may suit recreational activity on camping, but for bigger commercial job will not deliver unless you've got a 1kW solar array plugged in. Been there,did that ...

I have a Yamaha 1000W generator that is near silent and very portable - I have used this and it has plenty of power to charge several chargers simultaneously...