Alright, think I found a combination that should be low cost and increase the longevity of the battery pack.
Construction of a 24 V 'PowerCan' to charge a tesla for 9 extra miles travel range. Some 2.2kWh of energy in a suitcase from 196 Sony VTC6 18650 cells
This idea for a portable "gas can" to get a Tesla car, out of the woods, is essentially what we need, at half the size. So 12V(16V) instead of 24V(29V).
A plastic tool box, half the size depicted, fitted into the "trunk" of a typical fossil fueled car, would be the best place to keep the cells cool during the operation and keep from heat damage. Which if you know about these batteries, they can heat up from the internal resistance of each cell, placing them next to a large engine block, under the hood. Is sort of asking for a fire. Keeping the lithium battery pack in a plastic tool box and fitting it to the trunk. Better all around.
So some 100, 18650 cells is more than enough. To delete the alternator.
For larger car needs. Probably above a 3 cylinder and tested all the way to a V6.
To make deleting the alternator worthwhile.
You might complement this with the need for a 6 in series ultra capacitor pack, that fits in the place of your old lead acid battery.
6 series 2.7V 400 Farad, boost pack, hand crank for 10 mins start a V6 car
With these 6 caps complementing the ~100 chemical batteries, the capacitors are rated for near hundreds of thousands of start cycles, though while having limited energy storage. The Capacitors are a better fit for the high high amp demand for electric torque, in engine starting. With the auxillary power unit, the chemical batteries, for dedicated energy storage, to run the car electronics and recharge the Cap-bank, without the demand(slow damage), that starting directly from the chemical batteries will cause.
The Capacitors should extend the longevity of the chemical battery pack and would add some 70 dollars to your build in materials. If this is truly worthwhile and the alternative use of that money toward adding an additional 70 dollars of extra chemical batteries works out better?
Only years of testing would tell.
Though with tesla(elon musk) buying Maxwell capacitors recently, the combination may win after a few years and as a guide, for our less demanding usage case, it has been done before with capacitors and a lithium battery pack, undersized though it is and re-charging off the alternator. The premise is the same. Just make the battery pack larger. To some 100 Ah from the lowly 10 Ah used.
hybrid super capacitor + 10Ah Lithium car battery, trunk installation and engine starting
However, if you're like me. Right now, the easiest and most affordable fit for a 3 cylinder geo metro equivalent. Is a pure chemical battery build. Following the 1st video moreso than the other 2.
However to end. The hand crank solution does seem appealing if attached to a foldable bicycle, you'd never be without a lithium battery recharge, even if the entire electric grid goes down.