Battery/Battery Hybriding

Though having the greatest power and energy density (very desireable in an electric vehicle) and excellent throughput efficiency (all-round desireable), Li-xxx batteries are rather expensive in terms of cost/energy(over the lifetime).

Posited is that some common driving patterns lend themselves quite well towards using more than one chemistry - in terms of cost-efficiency over the lifetime of the vehicle - even considering the extra energy expended because of in/out inefficiency and added weight.

If the first few kWh a (sub)urban vehicle which spends most of its time running to the store, or kids' hockey practice, or on the work commute, were from a cheaper (in terms of lifecycle) battery, then the Li-xxx packs could be smaller, and would last much longer.

The two chemistries which immediately pop into mind are nickel-iron (expensive but lasts forever) and lead-acid (very cheap to replace). Use a battery pack of either for short runs, saving the expensive pack for longer sojourns.