They use combinations of the cells and batteries.  The capacitance cells do
not have the capabilities of batteries in storage of mass power.  However a
capacitor can provide max power (depending on its capacity) immediately to a
full discharge.  These systems have been used for years to start large
electric motors.  Using this system you could get power immediately to the
motors without a major surge load to the batteries.  I have seen quite a few
systems using this technique with their large motors.  Large bleeder
resistors needed to safely handle these.
jimt

>> there are other storage technologies and one of the things
>> you don't hear about is that hybrids also use something called a
>> capacitance cell
>>
>> I include a Google link cause lots of these docs are PDFs.
>>
>> Essentially they are capacitors which permit larger capacities, quicker
>> responses and are more appropriate for uses in a hybrids.
>>
>> I've wondered for years why we still use lead acid batteries to start
>> our cars.  Capacitance cells would be trouble when discharged but should
>> charge and jump the same as a lead acid.  ...I'm guessing since they
>> don't have internals that will eventually stop holding charge they would
>> wreck the battery market.  They might fail eventually but they should
>> last much longer than a lead acid battery.
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