What's one of the best way to kill batteries? If you answered "charge or discharge to fast" than you're right! In today's plug in electric vehicles (PHEV's for short) one of the main causes for battery life to shorten is the fact that acceleration draws a large amount of power from the batteries.

On the flip side the re-generative braking can't capture all the power that's produced because batteries have a limit to how much power can be dumped into them (know as C). Many batteries will have a rating of 1C up to 5C (5C batteries are usually lithium variants).

Before we move any further we need to understand the C value. Batteries have an amp hour (Ah) rating. Let's say that your batteries hold 200Ah. To figure out how much peak current your battery can 'give up' we multiply the amp hour rating by the C rating. So if the C rating was 2C you multiply 200 X 2 and come up with 400 amps. That battery could provide 400 amps continuously.

There are actually two C ratings on batteries: one for charging and one for discharging. The charging C rating is usually lower than the discharge rating.

So what's the problem? Well, we want a car that can charge very fast, and one that can dump a lot of amps when discharging as well. The trade off is that by doing this you shorten the life of the battery pack.

That's where the idea of using capacitors (really big ones) comes in. If you don't know what a capacitor is it's basically little battery. The difference is it can be charged and discharged very rapidly many many times. The trade off with capacitors? Well, they don't hold nearly as much energy as any standard chemical battery.

By combining the two together we can get the best of both worlds. While charging the battery you can fully charge the capacitor (you should be able to charge it that fast, but it depends on how much power you have available) in a couple seconds and slowly charge the batteries. By charging the batteries slower they will last quite a bit longer.

The beauty of the ultra capacitors is when you're accelerating and braking. Accelerating an electric motor draws a huge amount of power which the capacitor can provide without putting such a huge load on the batteries. After you've reached speed the capacitor could draw an even amount of power to recharge itself. Since we're not putting so much strain on the batteries they won't wear out as fast.

Now we come to the best part... re-generative braking. Since a capacitor can capture a lot of energy in a short period of time much more energy can be captured when you brake.

In the end it all adds up to electric cars and hybrids that are more efficient, but don't cost more. I can't wait to see some of the test results from some cars with these ultra capacitors in them.

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