Are their app notes or designer guidelines to help us size the ultra capacitor for the cell size and capacity?
For example, single cell NiMH, LiON chemistries, and lead-acid batteries are going to have practical charge and discharge limits, typically a multiplier of the cell C rating. Given the C limit, what sort of capacitance provides what sort of C range extensions?
I know this reads like a Gadge Freak proposal but having a guide lets the designer make a practical choices.
The capacitor(s) are smaller and lighter than most would think. I agree with what Jermey is trying to say in his article. My company www.koldban.com has been marketing our KAPower supercapacitors for engine starting for several years. The key here is that no one current technology offers both power and energy. Power being how much and energy being how long. By using a supercapacitor (a.k.a. ultracapacitor) in combination with a battery, it will minimize a battery's exposure to any high power transients. Thus, allowing the battery to do what it is good at and that is providing energy. In addition, in applications with multiple batteries one or more of the batteries can be removed since they are no longer needed to supply power. ie: engine starting.
Jim, I tend to agree with your statements, but there is so much more that is not disclosed by the author. This is more of a puff piece than what I would expect in something published by engineers for engineers. What is the basic technology? What are the tradeoffs? I remember the earliest ultracaps (just a few years ago) were very low voltage (a few volts WVDC at best) and had an absurdly high internal resistance. What allows these units to be described as essentially lossless? Without some hard information and checkable references, this could easily be pie in the sky!
The article doesn't address the size of cap needed for this. Let's say we have 1000F. The delta V ov the cap is say 100V on top of the normal 380V rail. This contains enough energy to power a 50Kw motor for 100 sec. assuming everything 100% efficient. While this would fill gaps for accelleration/decelleration, How big and heavy is a 1000F cap rated at say 600V?
It will be interesting to see how they manage surge currents. Unlike a battery where the voltage drops considerably when a near dead short occurs as a starter engages, ultra capacitors will instantly pump near infinite current. They'll need to have a very robust wiring and electrical contact switching system to handle this.
Anytime you have to start up a motor repeatedly a big cap is the way to go. Most of the time the expense of the capacitor precludes you from including it in the design, but an electric car is the perfect application. The Bill of Material cost just isn't as important as performance is. At least, for now.
I have gotten to use super capacitors in an application where battery life was very important.
Good article which presents many good points. In addition to the previous question on why we haven't seen these earlier (cost/economic reasons?) it would also be interesting to know the weight per capacity tradeoff (i.e. larger capacitors can carry a larger charge, but are also heavier and can slow vehicle performance). How is the size of the capacitor optimized for each vehicle?
I can follow the wonderful things ultracapacitors can do according to the article. The items listed sound logical and seem to be exiating technology. So why haven't we seen or heard about automakers doing these things? Are they married to battery makers? As far as gasoline prices going down when consumption does I don't think that will ever happen. If it does it will be in far, far distant future.
What should be the perception of a product’s real-world performance with regard to the published spec sheet? While it is easy to assume that the product will operate according to spec, what variables should be considered, and is that a designer obligation or a customer responsibility? Or both?
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