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Dry Box To Charging Box

I wanted a good way to charge my LiPo batteries in the field without being dependant on my vehicle’s battery. After searching through RC forums for guidance I found that many people focused on getting the largest amount of charging capacity available per dollar. Coming out on top with that criteria were deep cycle marine batteries. The EverStart Maxx Deep Cycle 125 Ah battery costing ~$100.00 is a common recommendation for getting the most capacity/dollar.

I currently fly small foam airplanes and a mini quad so my ideal charging solution is not a large 60+ lbs (~27 kg) lead acid battery even if it is the most bang for my buck. I’m not going to haul around such a heavy battery given what I fly. After thinking about my average flying time and the typical batteries I needed to charge, I came up with the following requirements for my field charger:

  • Relatively small
  • Not extremely heavy or unwieldy to carry
  • Decent battery capacity so it can charge ~6 1400Mah LiPos before needing to be recharged
  • I can use it not only run my LiPo charger but also charge USB devices
  • I can easily see the source battery capacity and know when I’m getting close to 50% discharged and I need to recharge

With a little bit more research I found that for those wanting a lighter solution, car jump starters were recommended. Here are a few examples:

PowerAll PBJS1600R
ABN PowerAny 12000 mAh

These are definitely light and portable but I was not sure how well a lithium ion battery would hold up over time or if they were deep cycle batteries. Since I wasn’t very confident in these I decided to build my own charge box with a sealed lead acid battery that would have less capacity but would be lighter than the large marine batteries.

Finding the battery I wanted to use was pretty easy. For ~$37.00 at Amazon I found a 18Ah deep cycle sealed lead acid battery that weighs 12 lbs (5.4 kg).


Finding a box to put this battery in was a bit more difficult. After running around to a few stores, trying unsuccessfully to modify a Plano tackle box, and looking online, I finally found the Flambeau Outdoors Dry Box with the proper dimensions.


With the base requirements out of the way I picked up the other items I wanted:

Banana Plug Jacks
Banana Jack.jpg

Battery Capacity LCD Indicator

Momentary Push Button Switch
Push Buttons.jpg

Dual USB / Lighter Socket
USB Charger Panel.jpg

With a bit of measuring cutting and gluing this is how it turned out:

Top.jpg Capacity.jpg Top_Tray.jpg Inside_Tray.jpg Side.jpg Charge_Ports.jpg Charging.jpg

Charging Box ~$40.00
18Ah Battery ~37.00

Parts List:

Great project SlowPass! A neighbor gave me a old jumper box with a dead 12v 18ah battery and I was able to replace the sealed lead battery with (3) 12v 5ah lead batteries that I had on hand. It worked great for those charges away from the vehicle. I also used it to power a led stick similar to one shown on one the episodes I think from CraftyDan. Unfortunately my 2yr old son acquired 3 old power wheels and so the batteries have found new homes until I pick up one (or two) of these 12v 18ah batteries.
David's Portable Charging Station

Great job SlowPass. Seems like you and I were on the same wave link. Yours looks great. I built a wood box to hold my battery and cig lighter adapter. I do think it came out pretty well. You did give me the idea to use a meter for the charging battery. I am experimenting using one of those low voltage beepers to do the job.

See you at FliteFest...
David (Beanie Hat) Holcomb

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I can see the pics. Really nice work!

I have that same battery and it has been going strong for 4 years. I use a small solar panel maintainer (float charger) when it isn't in use to keep its life up.

The links don't seem to be working for me either today. I have sent a message to the administrator. Don't know why they didn't show up in the post itself. Let me try again.










Skill Collector
You made me do it! :)

So this thread got in my head, and I kept coming back to this idea of simple and cheap case that not only carried power and a charger, but also had plenty of extra room for cables, connectors, and some battery packs too.

So I picked up a 12 amp hour battery and the same case from the link above, and started cutting away. I had a spare volt meter in my junk drawer, and basically tossed it all together in an evening.

I put the volt meter and button in the vertical part of the lid so the insides would be better protected from crushing into any parts I put into the upper tray.


Plenty of hot glue to insulate connectors, provide strain relief, and keep the wire heading back to the battery in place.


I had to cut one half of the tray handle out so my charger would fit inside, but the handle still feels secure


Rather than get fancy with the main wire connection, I just used wire nuts for the moment. Thinking about something more secure eventually so they don't fall off in some weird scenario and short out, but for quick and dirty it all works great.


That's a cheap Battery Tender clone wired into the circuit there so I can plug it into a generator if I'm at a site that has one, and I can leave it plugged in for a couple days (or months) at a time to keep the battery in good shape. I'm also keeping the alligator clip connectors in the box so I can connect to a vehicle battery too.

Plenty of room inside to add a second 12 amp hour battery if I need 'Moar Power' in the future.

Thanks for 'making me do it' :)
If you’re looking for the device to charge your batteries, then I could advise you ROCKPALS RP300W solar generator. Once, I was preparing to go camping and was looking for a power backpack, so I could have the ability to charge my devices during some emergencies or power outage. A friend of mine has already had this Rockpals generator, with which he was really pleased and so, I decided to buy one and check this thing out. I would say that it’s relatively small, it can charge not only your LiPo battery, but also charge USB devices. You can charge your camera, cell phone, laptops, drone, whatever device you want. And you’ll always see the power condition and the battery level of your device due to its handy display. The generator itself charges for about 6 or 7 hours on an AC wall outlet and also can be charged using a car charger. It provides you with power for about 24 hours on a full charge. It is extremely versatile and I felt protected by this little genny during my trip.