These two holder designs allow either 2x 18500 LiPo cells, or 2x 18650 LiPo cells, to be charged in parallel by connecting it to your existing LiPo charger with an XT-60 cable. You need to use an actual charger with this holder, not just a power supply!

The cells will be connected in parallel, so your cells must already be at a similar voltage before you put them into this holder. Otherwise the more-charged battery could push a large current through the flat battery. This is only likely to be a problem when combining a nearly-charged battery with a nearly-flat one, batteries that are used as a pair won't develop large voltage differences like this.

There is no reverse-polarity protection, and fault-current protection is provided by using thin 26 AWG wire - there is no dedicated fuse. The wire should fuse in around 10 seconds with a 20A fault current.

Required components:

• XT-60 connectors x 3 pieces total
• Keystone 5202 negative AA terminal x 2 pieces
• Keystone 5224 positive AA terminal x 2 pieces
• Solid core 26 AWG wire (I'm using Kynar). Wire must be solid-core due to the installation method required, gauge must be 24-28 AWG
• Thicker stranded wire for making an adapter cable to connect to your charger, e.g. 14 AWG silicone
• Heatshrink tube
• Liquid electrical tape is useful too
• M3 hex nut x 2 pieces
• M3 machine screw x 6-9mm length x 2 pieces

Required tools:

• Soldering iron etc
• Soldering flux (e.g. a flux pen)
• CA glue (superglue)
• Multimeter
• Hammer