With the x6100,I use the 20ah battery from my go box with a 9vdc output dc/ dc inverter. Pulls 10 watts with no problem with 9vdc. Just remember to turn off charger in radio.
73,
Steve
Also, I seen a recommendation to reduce power voltage to 10-11v. It should be still enough even for 10W output, but with less heat. I bought DC->DC converter, but still not check it.
