I designed this to make an inline voltage monitor when using batteries.

As well as the printed parts, you will need:

• 1x 0.28" LED volt meter module - easily found on eBay / AliExpress etc (see photos for dimensions).
• 4 x Anderson Power Pole connectors, plus a crimping tool or soldering equipment.
• 2 x short (~5cm) lengths of wire - 12AWG will just fit. Be mindful of current limit.
• Glue (probably).