I absolutely hate to charge batteries in the plane. What a PITA to get at them with the planes in the trailer. And then, if you forget to charge them, you have to wait to charge them before flying versus just putting in some fresh ones. Also you are committed to the batteries in the plane. If you detect a weak battery = no flying, at least for an hour. And, ... then there is stopping in the middle of the day to charge them back up again, ... another hour. This also forces you to carry a generator or a 12 Volt battery, if you don't mind waiting for a longer charge off a battery. And then you have to remember to charge that battery before you go.

Also, if you do not have permanent batteries, you can use just a couple packs for multiple planes. This way you don't have to have dedicated packs for each plane. Saves $s and you don't have to worry about putting batteries in storage mode when the plane is not being used for a while, etc.

If there is any way to avoid installing batteries permanently in a plane I do it. You don't know what your missing until you set up the plane to allow easy battery removal for charging and just swapping in fresh ones.

I do have one plane that I am forced to have installed batteries. I have A123s because they are not supposed to catch fire. Also, Electro-Dynamics has a nice setup for balance charging these in the plane.

We have had one jet in our club burn down with LiPo charging in the Plane. That fire also got a second plane. Can not attest to how that battery was being charged. But I have never had a LiPo go up in smoke when charging. And I have charged LiPos that were bashed, puffed and had marginal cells. I even still have one I use that puffed and I bled off the gas in each cell and resealed it, ... two years ago. It still works and charges fine! Although, I would never charge that one in a plane.

I do like LiPos. I use all HV Digital Servos and some sort of powerbox or power expanders. In a plane that does not need the fast servo response or higher torque, I cut the voltage back. A HV servo will never burn out on 6 volts. I trust LiPos. But I do not charge them in a plane as I enjoy the advantages of them not being permanently installed.