12V 50Ah portable battery bank

batt bank and light bar

Here’s a portable battery bank I put together for camping and power outage use. Rated capacity is 12V 50Ah (via 3 x 12V 12Ah batteries and 2 x 12V 7Ah batteries wired in parallel). These are used freebies which are sitting at between 60 – 90% so capacity will be a bit less than rated, but for the price I can’t complain. Weight is 18kg.

The case is a Supercheap Auto safe case (found here). Cost $35, which I think is an absolute bargain, as these cases are well designed, if sometimes a little iffy on the quality control of assembly. I also bought myself one of the smaller $18 ones, which is also great value.

Batteries are a bit snug, but this also servers to hold them in place well. They are held down using lengths of 25mm nylon webbing. Small slots were cut in the sides of the case to allow the webbing to wrap around fully. Much simpler than affixing internal brackets to hold. Waterproofing is compromised, however I don’t mind this, as I would prefer the case to have some capacity for ventilation in case of hydrogen build up.

Batteries are wired using 6mm and 4mm automotive wire (what I had lying around) and insulated crimp connectors. There’s a mini blade fuse inline with the output, and a 2 pin JST SM 2.5 connector as the main output. This connector isn’t high capacity (3A max), but I will primarily be using this to run LED lighting, charge USB devices and to power ELV devices (eg plugpack replacement).

The light strips I have pictured above are simply a set of these LED light strips screwed to short sections of PVC pipe with hanging loops. Some twin core figure 8 speaker wire is used for power leads. each tube, which consists of six modules, draws around 250mA at 12V.

Another shot of the side, showing the battery straps:


batt bank


Things to improve/add:

  • 4.65mm^2 wiring and higher quality brass female spade connectors for batteries, with PVC covers
  • multiple JST SM 2.5 outputs (collectively fused at 5A) for running ELV devices and also for charging input
  • small solar panel and charge regulator, probably in a separate case
  • main isolator switch
  • terminal block / busbar to neaten up wiring
  • 50Amp anderson plug (fused separately) for heavy loads (eg inverter)
  • power switches on each light module

Once some bits and pieces arrive from ebay for the above improvements I’ll update.