first off i just bought my 08 escape hybrid last week, first timer to the game. ok i used to really be big into car audio. with the thunderous bass and such. we would install capacitors to help lower battery draw and help with the big watt bass hits. the capacitor would run in parallel with the battery. now from what iv read about our escapes, has anyone tried to install a capacitor in our hybrids to work with the hv battery? i would think that first initial stop light run would pull max amps from the cap before the hv battey....

 

Considering the voltage and amperage of the battery pack, I am not sure how much you can accomplish with caps. I have wondered myself, why car manufacturers don't put supercap cells in parallel with the battery packs, but I am not even sure they don't.
They should help to reduce the parasitic series resistance and thus make it possible to absorb and release higher peak currents, which should also help to extend the battery lifetime significantly. I can only imagine that it makes battery management more complicated.
My advise: Don't do it. I think the software reads the cell voltage and when you add caps yourself you may screw that up. In which case the computer may think something weird is happening and could disable your EV mode or maybe overextend the batteries.

 

I think they do something like that in the prius, If not i know for certain home builders do this. I think it would be a good thing to try

 

In a lot of situations, the computers in modern cars can't handle a spike in voltage. Since most capacitors provide a sudden "hit" of voltage, the engineers who design these cars have either eliminated the possible use of capacitors or have tried it and didn't get good results.

I do like your "out of the box" thinking, though. This is the kind of "what if" thinking that has given us the hybrids and electric cars of today that were pretty much science fiction just a few years ago.

 

Capacitors can produce a spike of CURRENT, not VOLTAGE. It is very difficult to suddenly change the voltage on a capacitor as it requires extremely high currents.

The difficulty here is that UltraCaps usually are limited to under 3 volts or they self destruct. Either you have to put a large number of UltraCaps in series (reducing the effective capacitance and requiring balancing circuits) or provide a DC-DC converter to step up the voltage or a combination of both approaches. This can be done effectively, but is a significant engineering design effort.

JeffD - Electrical Engineering Professor

 

well to say capacitors dont boost voltage is wrong. and in the correct application it definately will. i work for the local electric provider and we use large banks of capacitors on the electrical grid and substations to equalize, and raise voltage also to help keep ampacity up. i dont design the system i just run it, but the size of caps we use are as large as a suit case (some not all). i forgot were i was going with this. like angunther said just trying to think outside the box. ohh and these are the size of caps i used to use in my stereos, not little microfarad caps in electronics class.. http://carstereo.pricegrabber.com/se...oduct/sv=title

 

Actually he is correct. I think your company is most likely using capacitors to stabilize voltage (thus keep the voltage from dipping or keep the "voltage up").
Regardless, a capacitor will keep voltage constant. The rate of change in voltage is proportional to current according to:
dV/dt=I/C
Thus, a voltage spike (large dV/dt requires extreme currents).

As Jeff mentioned, adding caps is often done via a bidirectional DCDC converter. Putting them in series is no guarantee that the voltage will equally split between caps.

Wikipedia has an interesting article about combining batteries with ultracaps for Hybrid cars:
http://en.wikipedia.org/wiki/Ultrabattery

In either case, I discourage you from fuzzing around with your battery. You could screw up your computer that is finely tuned to your battery characteristic curve.

 

ohh i didnt plan on hacking anything on my truck, just throwing an idea i had out there. but if someone needed a hand doing it to thiers id give em a hand...