I don't really think of bulk capacitance as bypass capacitance, but here the role is similar (on longer time scales).
Cars are unlikely to have huge supercapacitors useful for changing the charge much, too. (And there's not much point in moving power stored in a capacitor to be stored in a battery).
The main use of this is to provide short duration power, as you describe. That is, lithium batteries have great energy density but not as great power density or cycle life as capacitors. So a small amount of bulk capacitance can improve battery performance and reduce stresses on the battery.
This is more useful for short range vehicles like plug-in hybrids, because they have smaller packs. Larger vehicle packs tend to have plenty of power available, as a side effect of being designed to store tons of energy.
Makes me wonder if there might be a viable hybrid with no battery, just a supercapacitor. It wouldn't allow you to reclaim energy off hills or the like, but give the advantage hybrids have in city driving without the downside of that battery pack that will wear out in time.
Cars are unlikely to have huge supercapacitors useful for changing the charge much, too. (And there's not much point in moving power stored in a capacitor to be stored in a battery).
The main use of this is to provide short duration power, as you describe. That is, lithium batteries have great energy density but not as great power density or cycle life as capacitors. So a small amount of bulk capacitance can improve battery performance and reduce stresses on the battery.
This is more useful for short range vehicles like plug-in hybrids, because they have smaller packs. Larger vehicle packs tend to have plenty of power available, as a side effect of being designed to store tons of energy.