LIPO Charging & Storage Bunker Alternative

by Desert Wings | October 3, 2014 | (25) Posted in How To

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 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

abrasive blade for skill saw or table sawThe 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

Cement Board Battery Bunker.



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

From my materials list, specs, and the photo at right, you can see how I wired my box.  I started by drilling a hole for each battery compartment that I wanted to use for charging.  I made my holes big enough to 

Wiring Picture

install  Hobby King XT60 panel mounts  then holding two hacksaw blades together I cut a thin slit to the side of each  hole for my JST-XH wire extensions. When deciding where to place the holes keep in mind that you do not want to pinch the wires or interupt the seating of the lid when it is placed on. It is also advisable not to make the wires difficult to reach with your fingers.  I went as high as possible  without interrupting the lid in the center of each compartment.  After creating all the holes and slits, I then secured and sealed the JST-XH wire extentions with epoxy.  When the epoxy was dry, I installed the XT60 panel mounts.  Note that the JST-XH wire extensions I used are for 6 cell batteries, I modified the plastic shroud around the plug so that it will accept 2 to 6 cell batteries (you can see this if you zoom on the picture). In doing this you need to be careful when subsequently plugging the balance lead from your battery into the modified ports.  I have never had an issue with this modification and it allows me to charge all of the batteries I currently use without having a seperate balance plug board for every compartment.  Alternatively you could get different extention wires and make each compartment specific to a battery type. 

STEP-5 the Lid 

The lid is simply a piece of cement board with an aluminum angle bracket edging.  I used a hacksaw to cut 90° triangles from one side of the aluminum and then bent the other side to go around each corner.  This process was repeated at each corner and then the resulting aluminum frame was Gorilla glued to the cement board lid.  I clamped the lid, let it dry and then cleaned off the excess glue.  Once dry, the lid can be secured to the charging box with a velcro strap.  Note that though the lid slides down over the base, it is designed to be loose fitting and not airtight to allow gases to escape in the event of a lipo fire.  See remaining pictures below.  I plan to test the effectiveness of the bunker and post a video update when complete.   I have also linked other safety and battery bunker articles to this article.  My bunker might not be a good solution for you but, please use some form of protection when storing and charging your LiPo batteries whether it is LiPo bags, cinder blocks, modified ammo boxes, safes, fireplaces, dive tanks (pretty awesome), ceramic boxes.......





 STEP-6 Please take time to rate this article and leave comments so improvements can be made.


Gopherdave on October 7, 2014
Very nice build and article! I was wondering how much it weighs?

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Desert Wings on October 7, 2014
As shown with all the wiring and lid, the box weighs 10.4 lbs or 4.7 kilograms. Thank you for the feedback.
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danallen82 on October 7, 2014
Your idea is nothing of short of genius! The thin ceramic walls are prefect for this application. My only change would be to use a standard 4mm ports on the inside, since not every battery uses XT60. I use XT60, but a lot of my friends use the funky PowerPoles which I'm not a fan of. Great work!
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Desert Wings on October 7, 2014
Great improvement idea. Extending 4mm banana plug charge ports to the panel sides would allow you to plug any type of charge cord you want to into these ports and tuck them inside the box with the battery when you charge. I think I may modify two of my compartments to do this so I can charge my oddball batteries. Thanks for the feedback.
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danallen82 on October 7, 2014
Glad to add feedback. Yeah using premade 4mm extension cables will be the easiest way. Thanks again for sharing the idea.
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Sky Walker on October 7, 2014
This box is totes awesome!
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vwflat4 on October 8, 2014
Nice build, only toughs/changes might be to add a carrying handle, and or removable hinge for the lid. Good job, I can see one of these in my future.
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Desert Wings on October 9, 2014
You have identified one of my box drawbacks. The lid does not lend itself well to a traditional hinge because it slides down over the base. I think a small "U" shaped piece of aluminum strap could be laid across the lid and used with a hinge on one side and a clasp on the other to secure the lid and eliminate the velcro strap. A handle could then be attached to this aluminum "U" strap.
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zbaron19 on October 9, 2014
just a quick question. Is there enough ventilation? I wonder if you could put even small laptop cooling fans on the top or sides to improve. Other than that awesome idea!!!!
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Desert Wings on October 9, 2014
I charge at 1.5 amps on 3 cell batteries max. At this charge level I have not noticed any significant warming of the batteries, I usually charge 5 batteries at a time (one four port charger and one 1 port charger) and have not noticed any heat build up in the bunker when removing the lid. When designing the box I focused on fire containment rather than environmental control. I will test the temperature change in the box and post an update if it appears that heat build-up when charging is an issue. The small laptop fan is an affordable and good idea if heat becomes an issue. Because the box is not airtight around the lid, the fan would pull/push air from the edges and ventilate the whole box.
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Old Cobra Pilot on October 17, 2014
I originally took an ammo can and glued fire bricks inside. This works great BUT it weighs a ton. Your idea is fantastic and I'm headed to Home Depot to get some backer board now. What did you use to cut your backer board?
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Desert Wings on October 17, 2014
I used an abrasive blade that fits into my skill saw or table saw. I added a pic of the blade in the article so you can see what it looks like. The dust is dangerous so if you cut with a power saw do it outside and protect yourself from the cement dust. The table saw works really well and makes it easy to cut the compartment panels very consistently.
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Desert Wings on October 17, 2014
The more I use this box the more I love it. It has been so much more handy than any previous method I have used to try to protect against fire. I love that I can move it around my shop and take it with me when I go fly for both storage and charging. I think my box size is great and I don't think I would go any bigger. I would consider smaller a good option and can see how two small boxes would be great for portability.
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PapaLima on November 4, 2014
I was rolling a similar idea around in my head when I found your terrific article! I really appreciate all the details you put in.
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Desert Wings on November 4, 2014
Thanks for the kind words. I hope you can use some of the ideas to customize a box to suit your needs.
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Mogeley on November 8, 2014
Nice, I like this design.

The lid could be modified to include a layer of sand that would extinguish a battery fire. Though it could make it much more heavy.

A second idea to the lid would be some sort of visual heat indicator. Something like some thermochromic paint could be used on the top of the lid to indicate if there is a lot of heat build up. This would be to prevent opening the lid to a flare up...

Have you been able to test a battery fire in this yet?
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Desert Wings on November 14, 2014
I plan on testing the box for a lipo fire and posting an update. Thanks for your comment.
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Splatwillicrash on June 30, 2015
Did you ever do the Test? I would be interested to find out how well it did. This seems a great build, and though I charge in LIPOSACKs I think this would be a great way to go. All I would need is a set of adapters for EC3 and Deans, and I would be good to go. Nice article.
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Desert Wings on July 20, 2015
Yes the test was successful. I am going to post an update article and smoke filled video soon. I successfully over charged a battery (15V/5A 'till it blew after about 20 minutes) then tried some ground flower firework simulations as well. The box did good releasing pressure/smoke but containing fire and heat. I still would not want this to happen inside my house or car purely from the amount of smoke a LIPO can create.
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LIPO Charging & Storage Bunker Alternative