Quoting Dialcaliper:
Hrm - before you go out and buy a jumpstart battery...
I just did a sanity check, and a 250W block/oil pan heater requires a constant 21 amps. That will drain most jumpstart batteries in just over an hour! You'd need a much bigger deep cycle battery (at least 160 Ah) which would be a pain in the ass to lug around (about 100 pound marine battery- the big optima blue tops are only 75 Ah). It doesn't look like that's very feasible, and your alternator would take almost 3 hours at full load to charge it)
The other option you might consider is a very low power battery heater (max about 10-20 watts). A small deep cycle battery should be able to handle that - don't forget that it will also get cold
) Put the battery in a closed box, and the heater will keep it warm (which will prevent it from going weak in the cold). Combined with thin oil and 60/40 or 75/25 coolant/water, plus blocking off the radiator flow a bit you should be fine.
Or just get a bigger starter battery with an insulated box so you have plenty of margin for cranking in the cold.
I'd been considering this kind of option but came to the same conclusion that you did. It's just not feasible to have a mobile power supply for even a 125W heater. I just switched to M1 0W30. I was hoping for Castrol Syntec 0W30 but no luck. I priced out some 120V oil pan heaters and if I can get a neighbor from across the street to let me plug in sometimes I'll get one. That seems like the best plan because most places you go you can get 120V if you need it. I'm running Peak Long Life antifreeze now at about 70% Glycol in both the radiator and my Air/Water IC. I haven't put the cardboard over the radiator cause even with wind-chill you can't ever actually cool anything to below ambient temperature. Still, it's probably not a bad idea as it'll help keep the engine bay temps up which will help it warm up initially. A new battery isn't in my budget at this point but I really don't think that's the issue. Trying to start it this morning my TT was saying 11.0V which isn't really that low. I had trouble getting it going but I think that was the thickness of the oil mainly. If I continue to have issues I'll look into a bigger battery.
Thanks for the offer of help Ryan. About the only thing that I don't have available is a floor jack so if you have one I may borrow it at some point. If I have any other issues that I could use a hand with I'll let you know.