Well... Do you have a nexcell pack yet? We could use your help... As previously discussed there's an RV product that's basically a 12v powered electric blanket bag you can put your Lithium battery in and we could design something similar for Prius packs, perhaps a range of designs based on easy to hard to install... I'm leaning toward some kind of inexpensive 12v heating pad that installs underneath the hybrid pack. We also need to decide if we want something that heats with lots of power so it warms up fast, or something that is low power and is left on all night. Then next step is adding some temperature sensors in the pack. Research question being: what's the easiest/most efficient way ensure the pack is no longer too cold to take a charge when you're down below sub-zero. Let us know how you can help?