Solar Battery Box

Travel trailer > Mods > Solar battery box

In the summer of 2016 I was contacted by Torklift International with an offer to choose one of their products to evaluate. After some thought I settled on the PowerArmor Solar - a locking battery box with room inside for two group 31 or T-105 6V batteries and equipped with a 10W solar panel.


The box arrived in good order.

Unopened box

The contents were well packaged and undamaged.

First reveal

Inside were the box and lid (with solar panel attached)...

Three quarter view - 4



Absorbent mat...

Acid mat

Parts bag...

Parts bag

And keys (yes, these are the ubiquitous CH751 keys that open all stock trailer storage compartments. I'll be changing this lock).

Key... doesn't lock!

I soon discovered that the lid does not hinge in a conventional manner. Instead, tabs on the box align with slots in the lid and it slides into locking position. While a little more time consuming, this does not appear to be problematic on a box that is not opened frequently, and I imagine that this design enhances security.

Looks like it hinges open (it kinda does)*

I only found two problems with the box. First, the locking tab was installed in this direction...

Lock tang installed in wrong direction

... but the box wouldn't lock that way (I couldn't turn the key far enough). Reversing the tab solved the problem. However, the tab seems to be bent (whether by design or by accident is unclear) and tightening the bolt fully with the tab in the reversed position causes the lock to bind. I think there is a design or construction issue here, and I think that the tab would probably work in the original position if the end were trimmed a bit. More investigation is required; watch for updates in the Experiences section at the bottom of this page.

The second problem? A peeling safety sticker. A strip of packing tape made a quick fix.

Safety label peeling

Platform Design

Because the battery box is longer and wider than my stock battery tray I decided at the outset that I would mount it atop a wooden platform that would be secured to the tray. Why wood? I'm equipped and skilled to work with it, neither of which can be said for welding. And I don't like drilling holes in a trailer unless necessary.

I started with measurements. I did measure the length of the tray (23-3/16") though it's not shown here.

Bottom of angle bracket to top of frame - 3" D
Lower section - 23-13/16" L x 8" W
Upper section platform dimensions*

The three inch difference between the bottom flange of the battery tray and the top of the A-frame was perfect for dimension "two-by" lumber, which is one and a half inches thick. I would use a pair of two-by-fours topped by a length of two-by-ten trimmed to eight inches in width.

Battery box platform - Lower section rails
Battery box platform - lower section platform

Here are the parts of the bottom platform, cut and ready to screw together.

Lower section platform on rails*

The battery tray weld beads interfered with the bottom of the platform...

Weld bead

The waste sections were marked...

Waste section - closer

And out came the chisels for some relief mortising.

1/2" chisel to mark the back and remove the waste
One section cleared

Once the platform was bolted together and I had tested the fit in the stock battery tray one last time, out came the painting equipment. I like semi-gloss black exterior acrylic for my outdoor wood projects - it's durable, spreads easily, dries quickly and cleans up with water. I applied the paint with two well-used foam brushes.

Favourite outdoor wood project paint*

First coat.

Painter's pyramids

All done!

First coat of paint


Installing the box was not just a matter of bolting it in place, putting the battery in and hooking it up. Here are the obstacles I faced.

Tongue jack power lead

Early in the process it became clear that the positive lead on the power tongue jack was not going to be long enough. I made an extension from matching 10-gauge black wire, using dielectric grease in both ends of the bullet connector and covering it with two layers of heat shrink.

Dielectric grease for the tongue jack power lead extension
Extension end crimped and heat-shrunk
Tongue jack lead extension installed and heat shrunk

Battery ground lead

Also too short was the battery ground lead. I stopped by my local RV store and bought some 8-gauge white wire and a pair of matching terminals.

May as well finish the longer negative lead.

Here's the new, longer lead connected to the frame.

New negative lead installed

Box placement

The original plan was to mount the battery box directly atop the lower platform with the hinge to the rear. When I put it in place, however, there was a ruh-roh moment. Even with the hinge facing front the box mount would have to be moved further forward.


There would have to be a top platform mounted to the bottom one to move the box far enough forward. A section of 3/4" plywood cut to a depth of 12" would do nicely to start.

Upper platform in place*

With the positioning of the upper platform complete I held it down and marked the edges to cut. There are three workbenches in our basement but they were all in use. Any port in a storm...

Cut lines

Checking the placement of the battery box on the upper platform. Looking good. I marked the attachment holes down through the box at the same time.

Test fit and hole marking

Now it got a little tricky. The upper platform had to be screwed to the lower section without interfering with the 5/16" lag screws that hold the lower pieces together. And the battery box had to be screwed to the upper section. I did all my marking on the board. The upper platform attaches to the lower with four 1/4" x 2" lag screws; eight of the twelve battery box holes use #14 x 1" wood screws, and the other four 1/4" x 2" lag screws.


I routed a roundover on the top edges of the upper platform.

Top edge of upper platform routed

This cleat is attached to the underside of the upper platform at a point where the upper overhangs the lower. The cleat is glued and screwed in place and gives the forward two lag screws something to hold on to.

Cleat glued and clamped in place

Test fit with everything bolted on.

Box bolted in

Upper platform painted and bolted in place.

Upper platform bolted on


Once the obstacles were overcome, installation was a breeze. I started by cutting the slots in the battery mat, and that started with a brad point bit to drill some holes.

1/4" in brad point bit

My favourite way of cutting through soft materials is to run the drill in reverse with a backing board underneath. The resulting holes are nice and clean.

Holes drilled in battery mat*

A ruler and a hobby knife turn the two holes into slots.

Utility knife and ruler
Slot cut
All slots cut

I threaded the straps through the box, screwed the box in place and threaded the straps through the mat.

Battery box bolted in, strap routed, mat laid

Once the box is bolted on, the straps are trapped in place. Next time I have to remove the box I'll put a washer or two beneath where each screw comes through, to give the straps a chance to slide back and forth.

The battery is now in the box and strapped in place.

Battery strapped in

The connections are made - positive (red) and power tongue jack (black) to the positive terminal, and ground (white) to the negative.

Battery connected

The lid is on and locked and the installation is complete!

Box install complete*

Solar Charge Regulator

You probably noticed that in the previous photo the solar panel is not plugged in. Because we have a single battery, we need a regulator to prevent overcharging. I'm in luck... Torklift sent me one!

Box, manual and parts.

Charge controller - in the box
Charge controller - Manual
Charge controller - Parts

I brought the battery box lid down to the workshop for the installation.

Battery box lid

The solar panel must be removed from the lid - It's secured by these four screws.

Four screws to come out

Screws out.

Screws out

The regulator sticks to the bottom of the solar panel with double sided tape. It was supposed to be included in the parts bag but was not; good thing I had some on hand.

Tape on the charge controller

Here's the charge controller adhered to the bottom of the panel.

Charge controller stuck in place

The regulator has two female sockets to connect both the original solar panel and an optional second panel. I just have the one, so I'll just use one connector.

Female connectors*

When I received the battery box I noticed that Torklift had packed the solar panel connection socket with dielectric grease. Since this connection will also have some exposure to the elements, I figured I'd do the same here.

Dielectric grease
Dielectric grease in female connector* socket

Because I didn't want a stray wire to get in the path of a screw, I used a couple of adhesive zip tie anchors to keep everything in place.

Zip tie anchor*

Everything in place!

Wires connected and anchored

Because the charge regulator installs on the bottom of the solar panel, the panel must be reattached to the battery box lid with spacers.


The original #8 x 5/8" screws that attach the solar panel to the battery box lid (left) are too short to work with the spacers. Slightly longer (#8 x 7/8") screws are provided (centre) but I wanted something a little longer yet - #8 x 1" (right). The fact that they're Robertson head screws (versus Phillips) makes them that much better.

Three screws*

The regulator and wiring are constrained by the outer rails on the back of the solar panel, so even if they were to come unstuck they wouldn't move far.

Panel installed - gap between charge controller and battery box lid
Panel installed - gap between anchored wiring and battery box lid

Time to connect the box's charging socket to the the battery. Here's the positive fused lead connected...

Fused positive lead connected

... which is then plugged into the battery box socket positive lead.

Positive connection complete

Now for the negative lead.

Negative lead connected

While reinstalling the completed battery box lid, I noticed a little rust in the head of the solar panel socket connection screws.

A little rust on the battery box screws

There's a fix for that...


That's better. All connected!

Screws cleaned - panel plugged in


As an everyday reader and frequent writer of technical documents I'm terribly picky when it comes to product literature (it's a thing; see below for proof).

Battery Box

This manual is pretty good. A few changes that I would suggest:

Page(s) Suggestion
4 Step 2, para 2: Change ...the battery straps will not be able to slide... to ...the battery straps may not be able to slide...
5 Add a fifth option for a wood platform (details in new section Step 3: Option 5)
13 Step 5, para 1: Change ...additional battery cables may be required... to ...additional battery cables or accessories may be required...
15,16 The sections on wiring multiple batteries would benefit from information on the gauge and length of battery cabling to be used

Charge Regulator

This manual is also quite well written. A few changes that I would suggest:

Page(s) Suggestion
1 Parts list - double sided tape (specified in step 2) was not included.
2 Step 2: References to left side may be misconstrued depending on how the PowerArmor battery box was mounted. Change ...closest to the left side of the Power Armor to ...closest to the side of the PowerArmor with the solar charge connection socket
3 Step 3: References to left side may be misconstrued (see notes above)

General Recommendations

Overall, both manuals would benefit from the services of a professional editor (which I am not) to clean up issues with punctuation and capitalization. Suggestions:

Exclamation marks should be used singly:

Right: Warning!
Wrong: Warning!!

Regular nouns in a body of text should not have initial capitals:

Right: Secure the angle extension brackets to the box...
Wrong: Secure the Angle Extension Brackets to the box...

Terminal punctuation follows parentheses:

Right: ...on each side of the battery box (see figure 0.1).
Wrong: ...on each side of the battery box. (see figure 0.1)

Quotation marks should not be used for emphasis:

Right: They are a wear item...
Wrong: They are a "wear" item...



Overall I would say that the installation went well and that this is a solid product. I have my doubts that the solar panel will be of much benefit once it's connected, for the following reasons:

  1. The box is nestled in a valley of sorts between the propane bottle cover and the front of the trailer. I doubt the solar panel will be visible to the sun for more than half an hour a day, and then only if there is no other shade in the way (like clouds or trees).
  2. We rarely camp without hookups - we wouldn't get far on our puny group 24 battery (though the capacity of the box invites upgrades).
  3. During camping season the trailer is usually at home and plugged in, so the converter is charging the battery.
  4. Outside of camping season the trailer is at the storage lot but the battery is at home, inside, on a 3-stage charger.

I do have an experiment planned.

After our last trip of the season (mid October) we will winterize the trailer and put in storage. Instead of bringing the battery home immediately I'll leave it in place and connected for a week or two to see it if the panel maintains a charge.

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