After this weekends get together and discussion of possibly loosing use of the area in the future, I gave thought to flying some “off the beaten path” spots.  Then the thought of battery charging popped up..  What would I need? Some locations have power, others don’t.. should I toss a extra 12v lead acid battery in the truck? Or a “battery box”, maybe with 12/24v power supply inside…
  I’m thinking something not to big, But small enough to just “grab” along with my quad bag / lipos and just head out on a moments notice and charge a couple lipos as I get things set up… then charge others as I am flying. 
  Drainmanfpv recently showed his “battery box”, gave a quick description .. and thought that with a power supply (a/c) would be the ticket..add some smal chargers / parallel board..grab and go..
  Anyone have a set up they could post pics / specks? Suggestions? Things to stay away from..?

I do like to parallel charge at home and have them permanently connected to both of my Hotas but I only do that when the batteries are really close together in charge. One thing about specs, these Hotas have high "balance current" which makes them charge most batteries in no more than 40-45 mins at 1c. Other chargers I've used are more like 1hr. The HGLRC parallel board is nice because it gives you xt60 and xt30 on the same board.

But for on the fly charging in the field not sure that parallel can help as much since you can't just throw one on in the middle of another charging. So multi channel chargers make sense to have on hand, but keep the balance current spec in mind on chargers that have more than 2 channels.

I guess it all depends on how long you plan on dwelling at a site, you could also fly 4 packs back to back but land early and use a smart discharger to bring them down to the same storage level. I've got the smaller idst discharger that I use on batteries that I didn't use or fully use on a given day.

For quads, I just take more batteries..................  

MANY years experience (more than 50!  , where does the time go?) of taking starter gear for fixed wing, both for glow plug and motor starter.  Began with a small sealed lead acid of the type beloved by alarm engineers to install in houses as power fail backup.  As engines got larger they ceased to have enough grunt or capacity.

Then I went to chat to a car battery replacement shop, and I was offered to freely take anything from the replaced pile.  The guy happily went quickly down the stack load testing them with his prong tester.  A car needing 100-120A will usually fail leaving plenty of grunt for model engines, even those of 30cc.

Have now followed that path for thirty years plus, usually buying the guy a beer for his trouble.  Always have to suppress a chuckle at the poor souls buying and lugging around expensive "leisure" batteries.

Picking the battery type for very small cars (1 litre "Micra", etc) and with handles can get to a "pick up with one hand" size. 

But that's still not on for tramping woods any distance, great for close to car or if able to trolley it with an old folding shopping cart frame.

More recently a 5000mAh 6S will power a plane motor starter for ages, even for 30cc petrol, and I have used them to power a LiPO charger for 1300 6S or 1800 4S enough times to supplement the number of packs.

You need to closely calculate the requirement to avoid having to carry excess weight, and frankly a starter "box" IS unwanted weight!

The problem of using batteries is usually solved with the help of mathematics. You need to calculate the capacity of one battery in watt-hours. Suppose approximately, 6S Li-Po 1300mAh is 6 cans * 4.2V * 1.3Ah = 32.76 Wh. The battery is not fully discharged, so let's just assume ~25Wh. Car battery (for example) 12V * 50Ah = 600Wh. So you can (600Wh/25Wh=) twenty-four (24) times (actually less) charge your battery. You also need to have several chargers, several batteries for the drone, remember that with a heavy load, the car battery drains less than 10.5V faster, and so on..

.. did some research.. and of course.. things get out of hand.. I had to remind myself “your not building “the ultimate” field box”.. but it’s hard to keep things “small” when the “big power” is only a few dollars more .. I am speaking of dc power supplies..
The “MATH” on all this is supposed to be “simple”.. but not for me.. unless I’m missing something.. I will dig some more..

So my van has 100w solar on the roof, 130Ah 12V AGM battery and a VSR to allow it to charge from the alternator. That setup along with my B6 allows me to charge many 2-3S Lipos, in fact by day (on most days) i could charge probably 10's of lipos at once, all day without issue. But i tend to run 450-660mAh 2S lipos.

If on the other hand you actually mean a portable power supply you throw into a rucksack and lug out into the middle of nowhere, well that's a different problem. I would probably approach it as maybe carry 2x smaller batteries in series, say like 2x 22Ah batteries (11kg AUW), to get to 24V (which is a similar voltage to 6S), 2x 50w or 2x 100w (wired in series for higher voltage in cloudy conditions) cheap semi flexible solar panels (they are light) and PWM charge controller. Even on ambient cloudy days it should charge the main battery pack. Beyond that whatever charger you want to use, a basic auto fuse board or distribution unit, a cigarette lighter socket and QC 3.0 USB socket. Total weight should ideally be less than 20kg. Especially if you are hiking out somewhere in rough terrain.

In either use case, having some solar will be useful. Also remember not to discharge a lead acid beyond 50% capacity. So that 22Ah is actually around 11Ah.

So using StSV's example. We know your 6S Lipo needs 33Wh of power. The batteries have 24 x 11 = 264Wh. 264 / 33 = 8 times you can recharge your lipos. This assumes you have no solar panel topping the batteries up. With solar it's nigh on impossible to give a perfect answer, but if you can top up say an additional 3-5 times, is it worth it? For me I would say yes. On a sunny day, you will probably get at least double the charges if you are at the site for 5-6 hours.

@Rob, I would spend as little as possible on it. It all depends on your usage. If it is a truck/car/van/camper type setup, i would get bigger batteries and mount/glue the solar to the roof. For portable as in carry to site, I would use smaller and accept the limitation.

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So this summer I am going to a drone meet. I will be taking 100-200w of (ground mounted) solar, a 20A PWM controller, a second 130Ah 12V battery and a couple of B6 chargers and parallel boards. My intention is to fly all day for the length of the meet, so maybe 50-100 packs a day for 2-3 days.

Don't forget that a car is first of all a generator of electrical energy, and only then a vehicle) Just fill a full tank of gas, start the engine, and charge the drone batteries for a long time) F**k fuel economy)

Hey Pathfinder, have you looked into MTTP solar controllers? I did some testing PWM against MTTP And you'll get about 30% more in your battery with the MTTP. Check it out it's worth it.

MPPT, ie, Maximum Power Point Tracking?

Yes I have one in my van, a 30A Epever XTRA, part of another project. When i get time I will swap the 100w panel out for a Perlight 295W panel and change the 130Ah AGM for maybe 280Ah of LiFePO4. Set it up to run a Microwave and Compressor Fridge. Right now it runs USB ports, lights and a diesel heater. Kind of overkill for what i use it for. It cost quite a lot as well. It's one of these (and yes it did cost quite a lot, but has a lot of cycles).

https://www.tayna.co.uk/industrial-batte...a-12130dt/

The PWM controller is more due to having several 10A controllers lying around from old projects. I would love a 20A MPPT for field charging, but it's like dropping £55 on another controller. For the two to three days I will be out in the field and need it, PWM will be fine. The second 130Ah battery will be used to charge 1S, 2S and 3S batteries via my B6 Evo, BetaFPV Charger and I suppose if anyone else at this meet needs to charge any Lipos, they can do that with it. What i might do is buy a second B6 to run from it and a parallel or series charging board. I could see me flying at least 50

Oops my bad it is mppt

I saw a YouTube video a while back that was doing a a comparison and decided I'd try comparing it myself and was pleasantly surprised. I picked mine up for only about $50Aud. I've now fitted all our 3 current dailys with dual batteries and fridges and a fold up solar blanket thats portable for whichever vehicle we take. 

In the pic is a Companion PWM solar controller, in the middle is an amp meter and volt meter ( measures what is going into the battery) on the right is a 20amp mppt controller.
   

Originally I was building my camper van from a Transit and i was going to run 400W of solar into the 30A MPPT. Then the Transit fell apart. I now have a much smaller van, so 100-200w is probably it for mine, apart from those Perlight panels that measure 1.5m x 0.66m. But right now I only have space to maybe add a small compressor fridge. Still it has a bed, cooker and toilet. As long as you have the basics.

But on the transit i had secondary and tertiary charging capabilities, kind of a failover of a failover. I ended up with 6 solar panels on the roof. The 10w controllers are left over from that little experiment. One kept the vehicle battery topped up and the other charged a backup battery in case the other two failed.

For the two to three days I need the system for, PWM will be fine. If I was going off grid for a couple of weeks, maybe MPPT would be better, but at the same time, I did originally think about adding an external connector to allow a second panel to be used outside on the van to increase charging.

I love having the extra batteries in the cars, good to be able to have the fridge when we go to the city. We can then get different foods and meat we can't get at home, have cold water or soft drinks with us etc. Good to be able to jump start anything, charge the phones, have aux lighting etc even charge the fpv batteries ;-)

For charging 1S from USB it's brilliant. Even 2S from USB is possible. But I now have an XT60 lead off the leisure battery fuse board that can be plugged into my B6 and then i can charge anything.

My sister and brother-in-law live in Aus. They haven't worked out the second battery thing yet, which amuses me considering they've lived in the outback for about 11 years now. They don't even have solar panels on their house roof. Go figure. You live in a sunny country, but don't exploit free energy (per se).

Sun, we have an abundance of. Yep put 5kv on the roof just after we bought the house about 11 years ago, now leave the Aircon on while at work and come hm to a cool house. The portable solar is great for topping off the tractor battery or keeping up the charge on the battery when we take the fridge down to the lake.

This is what you need