LIPO Charging & Storage Bunker Alternative

LiPo safety is well documented and YouTube videos are prolific on the subject.  I love the article by Red20RC on LIPO Safety as well as the links and comments that accompany his article.  Flite Test and ipetepete also published good solutions.  I definately needed to improve in the area of safey and so building from the knowledge and creativity of so many others, I created a battery bunker/charging solution that works for my shop, my vehicle, and my flying needs.  My requirements included:

    ♦  Portability - I wanted to be able to charge and store LiPo's safely in my car, at the field, and in my shop
    ♦  Size - I needed the solution to be sized to handle a typical day of flying needs for me and my son
    ♦  Multiple Use - I wanted a solution for both storing and charging LiPo batteries
    ♦  Fireproof - if it does not contain and supress the effects of LiPo fire...it is a fail
    ♦  Non-Conductive - Unfortunatley I have shorted multiple batteries on metal surfaces
    ♦  Charging Multiples - I wanted to seperately and safely charge multiple batteries simultaneously
    ♦  Affordable - I was looking for cheap and effective hoping to use stuff I already had laying around 
    ♦  Alarmable -  Not shown in this article is a small smoke detector (see FT article) I plan to add this

With these requirements in mind, I created a battery bunker and storage box that can charge up to eight batteries (from 2s to 6s) at a time in non-conductive compartments in a small box.  The charging compartments are isolated from the charger(s) by extention wires protecting my charger(s) in the event of fire. When not charging, the box doubles as a storge box that can hold several batteries per compartment. 

Here is the list of the materials I used:

1 - Hardibacker Cement Board (used commonly as a tile underlay)
1 - Aluminum angle iron (1"X1"X60" - 1/16" thickness) - used for edging around the lid - my box required 60"
8 - Charge Cables w/ Male XT60 4mm Banana plugs
8 - XT60 Panel Mounting Kit
8 - JST-XH Wire Extensions 6S (20cm)
4 - Small right angle corner brackets (optional used to strengthen the base of the box)
1 - Velcro Strap to secure the lid 
Gorilla Glue, Liquid Nails, CA glue, epoxy

The tools I used included hacksaw blades, table saw with an abrasive blade (see pictute at left) to cut the Hardibacker (can be done with a hand saw or good utility knife per manufacturers instructions), dust mask, drill, screw drivers

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In the picture at right you can see the general construction of the box. All surfaces exposed to the batteries are non-conductive and fireproof. The box has eight compartments each with the ability to balance charge 2s to 6s batteries with XT60 connections .  The overall size, compartment size, number of compartments, or wiring could easily be adjusted for your individual needs.

STEP-1 Design the size and configuration for your optimal box.

Below are general dimensions and specs of my box:

STEP-2 Cut and prep the cement board

Standard Hardibacker cement board is ¼" thick; take this into consideration when designing your box sides, compartments and spacing. Make your bottom dimensions 1" larger than your sides; this allows you to have a good base to work from and facilitates the addition of the corner brackets and liquid nail glue fillets. Make your lid dimensions ¼" larger than your sides. You want your lid to be slightly loose so that it is not completely air tight.  This will allow an increase of air pressure to be released but will still effectively prevent flames from escaping the box. I would suggest cutting the intersection of the compartment pieces half way through on each piece (see photo). If you are using a table saw to cut, protect yourself from harmful dust.  When all cuts are complete, wash all the pieces thoroughly in the sink...don't worry this stuff cannot be hurt by water.  Once the pieces are dry you are ready for the next step.

STEP-3  Glue

You would not expect a seperate step for gluing but the reality is that cement board is a bit chalky and some glues don't love it. What worked for me was to run a bead of thin CA along the edges of the cement board before assembling the box.  The cement board soaks up the CA quickly and this seemed to seal and harden the edges.  I then used Gorilla Glue (or Elmers Ultimate) to assemble the box.  At this time I also glued the corner brackets in place.  After this dried, I overkilled it a little with fillets of liquid nails on every seam.

STEP-4 Wiring