I have 22x2600f super caps in series in my ev. They are simply
paralleled with the battery pack and perform two functions: the first is
that they take all the heavy grunt in terms of initail power start up
much means that the batteries don't see the big spikes and are treated a
lot better therefore prolonging their life. The second point is that the
caps can take far higher charge currents compared to the battery so when
regen is active, higher regen currents can be extracted. The charge goes
into the caps first which then feed it out to the batteries.
Anything else and the capacitors will need a dc-dc converter(s) that is
bidirectional to allow the rising and falling voltage to be allowed for.
These are not cheap. This is why I opted for the simple parallel them
up. Take care with them - they can source and sink thousands of A albeit
for a second but it is enough to weld wire/contacts. When connecting
them to batteries, the caps need to be charged up with a constant
current supply until the voltages match. Otherwise it is arc welding time!
On 26/02/2019 22:56, EVDL Administrator via EV wrote:
On 26 Feb 2019 at 21:48, Lawrence Rhodes via EV wrote:
I think the 300 dollars of caps would protect the pack and increase
performance.
Probably not all by themselves. The problem with capacitors is that, unlike
batteries, their voltage falls rapidly as they discharge.
What you're trying to do is exactly what Solectria did experimentally in
2000, but what they had that you haven't mentioned is the wide-range input
DC:DC boost converter that kept the caps' voltage up where it needed to be
as the caps discharged.
http://www.evdl.org/docs/supercap_leveler.pdf
The EEs here can correct me if I'm wrong, but I'm afraid that a DC:DC with
that wide an input voltage range is going to cost you a bundle. And you
will probably find, as Solectria did, that its efficiency isn't all that
great.
But you might scout around where the small Chinese industrial and hobbyist
electronics manufacturers hang out (Ebay, Aliexpress, maybe Banggood) and
see if you can find something usable, reliable and/or affordable (pick two).
I've seen a few constant voltage regulator boost and buck/boost modules
offered. Maybe you can find one that would work for you, at least until its
magic white smoke escapes. :-)
David Roden - Akron, Ohio, USA
EVDL Administrator
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