RE: field charging lipos
I have a box with 3 chargers - 2 for power packs and one for Rx/Tx. We have power at the field, but truthfully, I rarely get more than 5 flights in a day. It would be easier to just have 5 fully charged packs and bring them to the field. I usually end up having to dis-charge something.
Of course it all depends on your routine. If I'm alone, 4 solo flights and I'm bored. If my friends are at the field, I end up chatting and get in about 4 flights between breaths.
Of course there are many ways to skin a cat, so do what you think will work best for you. My thoughts are that it is best to store lipos at a storage charge, and charge just before use. My opinion is that a 12v is just another battery to charge.
I have considered getting a 12v many, many times. Considered up to the point of walking into Walmart or Auto parts store, looking at the battery, picking it up, then putting it down and walking out. To me it's just not worth it. 5 packs charged is more than enough for now, and maybe one day I'll have a nice Japanese generator.