Some radios have a built in diode that restricts charge rate thru the radio to very low currents. Futaba 3PM has a diode that will not allow any higher charge rate than the output of their purpose built wall charger which is less than 100ma, I think 70ma. You could try a veryu low rate and see if that works - its not very timely though.

You're going to have to pull batts out of tx to charge at higher rates. I use a lot of AAs for my digicam and rates above 1amp are not recommended for AAs. The 1C rule does not apply to AAs - charging 2500s at 2.5a will def lead to shortened life! I use a professional level AA and AAA recharger made by Powerex and it uses 1amp as a fast charge, 0.5 as a slow charge and 50ma as a trickle. Their advice is to slow charge as much as you can and only fast charge when you have to.

I started using lipo in my tx and so far really like it.