Build your own Batt...
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Build your own Battery Box

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Florian Rossmark
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Joined: 2 years ago
Posts: 63
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Needed a Battery Box for my sonar, as this should always be a different battery than the one you use for your trolling motor. Why? Simply because the motor will cause a huge amount of interference, and this makes a huge difference especially on modern side scan sonars.

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Got to say, this box can be used on a boat, in the tent for charging various equipment and many other things. You could even build it out to have a solar panel attached to recharge it, that would be next level. But lets dive a little bit deeper into what I did and my though processes.

After going through a bunch of options in battery size, I settled for one with plenty of buffer, 50Ah should give me all the power I need for power the sonar for many day, charge phones and cameras and so on. It could ever be used as backup for the trolling motor, though that one is even bigger.

There are many batteries out there. If you want my recommendation, only settle for a LiFePo4 battery. This battery type is less likely to cause a fire as compared to e.g. Lithium batteries, it is super light and small for the amount of power you get and sealed tight, what can be a requirement on many waters (old school acid batteries like in a car aren't very environmentally friendly if your boat should sink etc.., besides that these are not made for that, but batteries are a topic on their own). Last reason is, these batteries have a BMS (battery management system) and can be recharged around 3000 times without loosing their power. If you do your math, you can recharge the battery almost once a day for 10 years - that's quite impressive and justifies the higher price point easily.

While there are some European sonar stores that have such battery cases, they are all but cheap and not likely to ship to the US in my case. But I also wanted more power and be more versatile, like being able to use it in the tent to recharge systems there, as I got enough power. I wanted a cigarette charger port as well as USB, I main switch and a voltage display as well as seeing how much charge was left (estimated) in percent. 

After some searching, I decided for a water tight hard case that is normally used for e.g. camera equipment, it even has a pressure valve that you can open to make it easier to open it. 

Got me a panel with all the outlets and features I wanted as well, I decided for that one as it was fitting the size of the box and was modular, so I could even exchange parts if I wanted too. 

Most important was that the module also had a little fuse, so a short or water in any of the outlets would not cause any major damages.

  • First I put the panel on the spot I wanted it and marked the four holes I needed to cut out. 
  • Drilled them and used a cutter knife to carefully remove the little leftover plastic between the drilled holes.
  • Next I used my Dreml with a circular sanding tool to make the edges of the holes round and fit the insert tightly in.
  • Put it all together and tightened it all up, it might not be 100% water sealed but if very likely will hold up quite a while and shouldn't have issues with rain, fog or splashing water at all.
  • Fitted the foam in the box so the battery would sit nice and snug.
  • Attached the battery to the panel cables and powered it on.

TIPP: Before you disassemble the cables from the power modules, take a few pictures so you can easily assemble it again. There should be markings there as well.

Think the result is rather pretty. I even decided to remove the sonar monitor from the boat pole mount for the transducer, as it tended to annoy me there and made it harder to pull it up and down.. instead of drilling more holes, I left the mounting plate for the pole screwed on and used a small ratchet strap to hold it on the box. This makes it more versatile and allows me to change my mind or disassemble it easily, without extra holes or another mount on the box. 

Below some pictures of the results, hope this helps you. It was a pretty simple and easy project and the results are pretty nice.

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This topic was modified 10 months ago by Florian Rossmark

Florian Rossmark
Germany / USA - Carp Angler