The last essential 9x upgrade. After this it will get really fun.

Trustfire batteries, Why?

• Cheap (about $14 for a pair)
• Safer, no risk of fire like lipos.
• More efficient, the 5v regulator inside does not need 11.2V and is happy with just 6.5V.
• Less heat, more battery life and more regulator life.
• The new pack fits better than the original.

Although it is more work, my implementation differs from others such that.

• You can use the new battery pack on standard chargers and for other things.
• With open9x you can calibrate to get a true voltage reading and custom low voltage alarm. (no need to hack the main board)
• Reverse voltage protection for the 9x from the battery and external power.
• You can leave the batteries in the radio and charge with 9v in the side of the unit.

Interested?. Read on.