Just wanted to know if anyone had a good idea of what to use. Transmitter battery lipo for the 3Pk. Thanks

I've got two 3PJS in which that I use the CommonSense RC transmitter battery. The same bettery fits the 3PK. I recharge them after about 12 hours of use and they take 1400 or so mAHr. They are rated at 2800 mAHr. I've heard the 3PK uses more juice than the 3PJS so you might not get as much runtime. They are supposed to have a circuit that protects from excessive discharge so if you make a mistake and leave the radio on you won't ruin the battery.

I second that vote, common sense RC has a battery made for the 3PK, comes wired with the right plug. All you need to do is add some foam to the battery area to hold it in place. I have used mine for 22 hours and not had any trouble, the best part is how quick you can charge it. 2.8 amps doesn't take long.

No foam needed. Just use the rubber boot that came with your 3pk radio for a lipo pack. Simple and the radio comes with it. Then just use the charger that came with the radio. Nothing extra to buy

Rob @ Windtunnel

The charger that comes with the radio is cc/cv? Or is it safe to use because of the really low output?

I use my LRP Pulsar3 to charge mine and it lasts several months racing every week.

Not sure using the charger that came with the radio is a good idea if you want it fully charged. If you only want to add some voltage on race day then it's prob safe but don't go leaving it on over night.