Block heater.

[puddleglum]

Something else you may want to investigate as an alternative to a block heater is an oil pan pad heater. They are available for 12 volts and draw less power. You would need a fairly flat area on the oil pan. They heat a little slower but the lower power might allow you to use the battery you were thinking of. They do work pretty well since heat rises. They have their advantages and disadvantages compared to a coolant heater.

[cRiPpLe_rOoStEr]

I guess you have never even considered a fuel-burning supplemental heater. But anyway, maybe insulating the engine compartment and getting a warmer air intake (eventually trying an adjustable one similar to what is used in small aircraft to prevent carburettor icing) would be the most cost-effective options for you.

OTOH if you decide to try a heating pad at the oil sump, the extra load on the alternator would be likely to help you reach the operating temperature quicker.

[JockoT]

I don't think a sump heater would work as the Jazz has an in sump transmission with the casing all webs, etc.
Using supplemental heating in the garage is illegal and dangerous, owing to the houses immediately attached to the garage and lack of flue. I cannot run a generator to supply power for that very reason (not that that would be an efficient way of saving a few mpg).
Because it never gets really cold here and because my cold start trip is only 4 miles and 10 minutes duration, I don't feel I would gain much from getting the engine hotter, quicker, on the trip. Only real benefit would be if I could have it warm to start with.
Perhaps I will just have to live with it. At over 50 mpg UK at the moment, any gains I make may not be economically viable (never mind the humping of batteries and all that rigmarole).

[cRiPpLe_rOoStEr]

Originally Posted by JockoT

the Jazz has an in sump transmission with the casing all webs, etc

I thought the original Mini and some old Citroën/Peugeot and Renault econoboxes with the "suitcase" engine were the only cars to feature this layout.

[JockoT]

The transmission isn't actually in the sump (like the BMC engines) but attached to the end of the sump. This is the sump:


And in Plan.

[roosterk0031]

Some of the jump packs have air compressor, light and invertors built in, mines not as heavy as a lead battery and useful for other things.

If it has an invertor built in you can use a cheap clock timer to turn it on and off. Don't need a battery charger either. You need to verify the watt draw of block heater to be sure the invertor has the capacity you need. You could always rig up an external invertor and use the 12v cable to power it instead of the 12v power outlet.

[JockoT]

I take it I would just take the jump pack into the house, and plug that in to recharge it.

[roosterk0031]

Yep, wouldn't need a battery charger, handy to have around, I use mine for lots of different things, I picked up a 12v fuel pump for $7 and use it to transfer fuel from boat tank to cars. Run a air compressor to pump lawn mower or wheel barrel tires. Power goes out can charge phones and the little LED light would probably run for a week.

Closest gas station is 10 miles, kids cars used to pretty much just go to school and back 4 miles each way, and fuel is cheaper where I work. Burn a gallon to go fill them up or fill the boat tank when filling my car and transfer it to my other cars.

DEWALT 2800 Peak Amp Jump Starter 1000-Watt Power Inverter with Digital Compressor-DXAEPS2 - The Home Depot

Thank one would do it, but pretty expensive.

Another thought if all you really want is 110v, a computer ups. Make sure you get one that you can turn the beeping off.