I am in the same situation sometimes and also use the Hobbico MKII. I can charge up on the way to the field and be ready when I get there (30min).
I have had problems with the gel cells though, I have found that I cannot fully charge my rec and transmitter batteries fully. The gel is fine for topping off, but I use 20 2000mah nicads for my field power source.
4000mah of power and I have never come home with it anywhere near drained. I picked up the cells used for about $25.

Dbow