I had previously been using a smaller charging device, that of an FMA CellPro 4S one that only output a wopping 4 amps, which is very limited for modern larger batteries. So I knew I needed something with more horsepower and it would require constructing a whole new setup to charge anything from Nicads to 4S and beyond batteries and two at once was my minimal goal. There was some merit to going with two separate chargers, but I liked the all in one design of the Reaktor and was willing to risk it dying completely vs having two separate chargers. I looked at various possible charge box options and chose this type of “suitcase” aluminum charging box. I could have gone with a more vertical “toolbox” style, but this one offered a bit of flexibility. In this article I’ll show the equipment I used to make it and how it was put together as well as the fire-safe box I ended up creating for both charging and transport.
Specs and Parts
First up are the various parts used in this build. Hopefully I have covered everything that went into the build here…
Charger: Turnigy Reaktor 2 x 300W 20 amps per port Dual Charger $115
PSU: 24 volt 60+amp PSU (purchased off of the RC classifieds from “DSW”) for around $125
Dimensions: Length 11″, Width: 3.5″ Height: 3.5″ Weight 5.25 lbs; Watts: 1800, Max amps 75, jacks were rated at 60 amps though
PSU Straps: Plastic Pipe Hanger Straps $3-$5 at lowes
Hinges for the “Lid” (elmers foamboard)
Parallel Charging Adapter: EP Buddy SAFE 40A PARABOARD V3 – XH WITH T PLUG $17.95 x 2
Case: Harbor Freight Aluminum Case 18 x 6 x 3 $29.99
Power Switch: Digi-key CCM1916-ND $9.99
Heat Shrink Tubing: Vktech Assortment $7.99
Fans: APEVIA CF6025S 60mm Case Fan 12volt $3.99
Fan Cover: Chrome Steel 60mm $3.00 x 2
Right Angle Brackets: 90 degree shelf supports, Qty 10 $2.30
Carbon Decal: 20×30 cm decal paper $1.68
AC Y Splitter Cable: Startech PXT101Y 6 foot NEMA 5-15p 2xC13 $7.79
JST Connectors: Neewer 10 pair 150mm/15cm male and female
Smoke detector: Any simple $5 one at Lowes works well.
Barrel Connector Deans to male 2.1mm $3.49 (for charging)
Battery Extension/Cable: Female deans to female XT60 (at least 2-4 for charging)
Battery Extension leads: 4S balance extensions x 8 (at least)
Battery Extension leads: 3S balance extension x 8 (at least)
Battery Extension leads: 2S balance extension x 8 (at least)
Battery Extension leads: 6S balance extension x 2 $8.99 (for the Parallel boards to be extended)
See Also: FPV Ground Station Build Log
Installation and Wiring
Be sure to check out the video above which outlines many of the details below and the final state I ended up with.
The first thing I had to do was cut the holes you see on the left and right of the Harbor Freight box (See below). These will be for the fans to pull air in and out as a safety measure. I used a hole saw with my power drill and cut them. After that I took the pipe hanger straps and screwed them into the box, using small wood screws I had on hand.
The trickiest part was wiring the on/off toggle switch (Digi-key). I had found a diagram online showing the way to wire it. The way I did it below worked out perfectly, there was no explosion or impending fire of doom as a result.
The other end of the wiring for the switch goes to the dual output AC plug and I just shortened it before doing the wiring (above). I also secured the 60mm fans and fan grills on the case at this point.
Note, you can sort of see above, the wiring I did to make the 12 volt fans work on this 24 volt PSU. I basically tapped into the 12volt wiring coming from the existing fans and used those leads to power each fan.
My initial thinking was to use these clay pots found at the local hardware store to both transport and do the charging. These turned out to be very heavy and harder to deal with than other options. But initially I did charge next to the box in this plate. I added extensions to all my leads off the paraboard to make it easier to reach the charging “location”.
A few months later I decided to move the charger off the top of the elmers cover and put it down in the case. I did this because i couldn’t close the lid properly if i wanted to transport the charger to the field. I simply cut a hole as seen below and this became the final state of the charging box.
Below you see the final state of both the charging box and the fire-safe lipo container.
Lipo Fire-Safe Box
Here are few details on the box, which was relatively easy to make. I had considered other options in the past as well, such as the ammo boxes many use. I didnt want to put more than one battery in at a time, if one goes they all go. My goal was a box that had individual protection and from reading up online, this option was the next best bet while also giving extra protection from flames and heat of the box itself causing nearby objects to catch fire in the event a disaster occurs. You can see it in the video at the beginning of the article as well.
Metal tool box: 20″ variety either from lowes or one like this model on amazon (Excel TB140-Black) $29.99
Drywall: 1/2″ type, found at lowes in large sections for around $5
Glue: Gorilla (white polyurethane glue) and some water based glue such as TiteBond II (mix about 3 parts gorilla + 1 part water glue) This mixture helps fill in the gaps.
Electrical tape: To insulate metal parts so contact can’t cause a short
Construction of the Fire-Safe Box
I measured out the base plate for the box, leaving about 0.5″ on each side for the side walls. I determined how high to make those side walls and cut them to size (using my band saw, though you could just use a knife and make a cut and snap the boards). Once ready to secure, i took my 3 parts Gorilla and 1 part water and mixed it in a container and using a popsicle stick I spread it on the sides. You only have about 90 seconds to work with. I then moved on to do the back and front walls of the box.
As far as the rest goes, I just calculated how many “compartments” i would need for each battery. I’ve seen other builds online that had the batteries horizontal and given I have a good many batteries, I figured the vertical arrangement was best.
I used black electrical tape to line the outer edge of the box to prevent shorts.
The end result was the box shown in image above.
I had made a “mistake” at one point, spraying PlastiDip on the lid (inside) and a slight amount on the walls edges. Technically PlastiDip can catch fire if hot enough, but largely from what I read, the amount I used on the walls was so minimal, the worst that could happen is some charring. Still, if i did this again, i would not coat the walls with Plastidip and probably not the inside of the lid. The original reason I did this was because the drywall was flaking off easily and I wanted to seal that in.
I should mention, with the batteries all inside and ready to transport, this box is pretty heavy, but still do-able. I may end up making a smaller 6 battery case for quicker transport when I dont need them all at once for my Twinstar II or V303.
Calm Skies and Happy Flights all.