Battery replacement/upgrade for the Yamaha DX7ii. Replace batteries easily. Solder the red wire to the hole where the positive pin of the original battery was and the black to the negative. Instead of unsoldering/resoldering a new battery cell each time the batteries need to be replaced, you can simply pop out the old commonly available CR2032 coin cell and pop in a new one. Each holder comes with a small piece of high-quality velcro on the bottom.
Due to shipping regulations, the CR2032 battery is not included. However, these are readily available for a dollar or two.