DIY Custom Cold Weather Battery

Winter temperatures can spell disaster for batteries of all types. They lose capacity and charging them at sub zero temperatures causes permanent damage.  

For more info read our blog on Cold Weather Charging

We work all year to innovate and develop solutions to provide our customers with the energy they require, anywhere they may go, but, once temperatures begin to plummet, field testing becomes challenging. Here in Newfoundland, Canada, the winter is long and cold! We need a way to keep our test equipment batteries healthy for year-round field testing.

In the following paragraphs, you’ll  learn about the box we custom designed to store and dispense energy in the downright frightful weather conditions, just meters from the cold North Atlantic ocean. We know this is a problem for many people, so we decided to share our design. We hope you find this fun and easy project useful to learn about or to build yourself.

Water/Wind Lily Cold Weather Field Test Box Specifications

Illuminated Main Power Switch 

Lighting On/Off Switch  

Photo Switch (dusk to dawn lighting)

Lights (to serve as a dump load + performance/health indicator)

Input from WaterLily via SAE Connector

USB Type A Female Plug with Dust Cover

Battery: 12V 7Ah Gel Cell

Rain Proof


We needed a battery design that was simple and rugged enough to deal with rain, sleet, blizzards, and charging in sub zero conditions. This box uses the golden standard of value and reliability: a 12V Gel Cell.

The idea is that the lights drain the battery each night so the device under test is always getting a workout. The lights let us keep tabs on this test location from a distance, too. No light means something has gone awry. After all, because it is set up on top of a giant hill, where it will see the most abusive winds, it's a bit of a hike to get there! We don’t want to get too much exercise hiking up and down to to see if things are working properly. The light lets us know that everything is still working over the course of long term testing, and one of our team members can even spot it from home!

The small dot is the light

Here is a list of parts:

Plastic Ammo Container - $5 (Princess Auto)

Lighted Switch - $4 (Princess Auto)

Regular Switch - $3 (Princess Auto)

12V Auto LED 3 Pack Panel Mount LED truck Lights (5.5W Total) - $15 (Princess Auto)

12V Dusk to Dawn Switch - $12( Amazon)

12V 7AH Gel Cell Battery - $26 (Amazon)

Power Meter - $25 (Amazon)

SAE Connector with pigtail - $9

Wire - $2

Grommets (optional) - <$1

Wire Terminals (optional) - <$1

Solder or wire nuts or crimp splices or twisty twist with black tape - <$1

Heat Shrink - <$1

1 ½” foam - FREE

House Siding cold weather underlay or similar - FREE

We purchased most of the supplies from Princess Auto

Here is the Wiring Diagram:

We created a video to help you visualize the project from start to finish and see what's involved.

If it looks like a bit too much electrical work, you can simplify your build considerably by housing a regular power bank in an insulated box.  Here's a video showing how you can use left over building materials to insulate an ammo case for your electronics.

Thanks for reading.  Questions or comments?  Let us know at support@waterlilyturbine.com

Copyright Seaformatics Systems Inc. 2021