Good news: Ultracaps are coming right along

I just became aware that commercially available ultracaps have obtained an energy density of 10.1 wh/kg. In comparison, a standard lead-acid battery such as the one we typically use to start our cars sports an energy density of around 40 wh/kg.

This means that within about four times the weight (and comparably additional volume) of said battery, we could use ultracaps (and the appropriate control electronics), to completely – and permanently, as ultracaps have multi-million charge/discharge cycle capability – replace our vehicle’s starter / power battery.

This capability is considerably further along the development and commercial availability road for ultracaps than the last time I really paid close attention. Then, ultracap energy density was down in the 2.5 wh/kg range, and so it would have taken sixteen times the weight (and volume!) of them to do the same job. That’s a lot tougher to justify.

A system designed for a vehicle would probably consist of the ultracaps, some high-power controller circuitry to keep the output voltage of the ultracap array stable, and a small solar panel to keep the charge up when the vehicle is parked. The solar panel is a good idea because most ultracap technologies suffer from a low-rate self-discharge, so you have to keep ultracaps gently topped up if you want them to always be ready to go. Not a problem, just something that has to be taken care of properly.

For instance, I drive a pickup truck. It would be no problem at all to dedicate a small section of the pickup bed to a system like this, and then forget about ever buying buying batteries again for the lifetime of the truck. For that matter, when the truck dies or is sold off, I could just move the whole assembly to my next truck. And sell the battery the new truck came with!

Another use case that is ready for ultracaps right now is low-demand devices.

For instance, a shaver or an electric toothbrush. Both of these are typically used for a few minutes, a few times every day, and then put down. That’s an ideal application for ultracaps. When manufacturers design a battery system for devices such as these, they make sure they can take a charge sufficient to run them over quite a few uses. This is so they are sure not to run out of power when you’re using them, because if they do, you’re done — at that point, you have to put them down, stop what you’re doing, and wait for them to recharge. So the battery systems are much larger than they really need to be in terms of powering one use.

With an ultracap-based power supply, that’s not necessary at all. Instead, a small ultracap is designed in that can store enough energy for one typical shave or tooth-brushing episode. If you need to go longer, you just touch the device to its base / charger, and within a fraction of a second it is fully charged again, ready to go — and you simply carry on. You’d never have to worry about the battery aging and making the device useless, or be unable to use it because you forgot to charge it.

Another great use case is within devices that just don’t use much energy anyway, such as a typical infrared or bluetooth remote control. With these, we put batteries in them and don’t replace or charge them for months at a time. Game controllers are a great target for this as well.

In all these use cases, because such an ultracap can be charged essentially instantly from the human point of view, and because it’s much easier with an ultracap to tell when it actually needs charging, the day when we never, ever have to replace a battery in devices like these could be upon us as soon as the engineers responsible for them can get the designs approved and produced. Who cares if such devices only hold a charge for a month if you can recharge them instantly, at any time or all the time, and never, ever have to replace a battery?

Ultracaps are also superb for keeping a system alive while you change its battery, if it actually still needs one. For instance, if you have a small computer that has battery operated systems that need to keep running, but inevitably you’ll have to replace the battery, adding an ultracap to the power supply design can allow the system to remain powered for quite some time while no battery is present. This use case applies to all manner of things like AC outlet timers, calculators and so on. Any small device that needs to hold on to its settings while it’s batteries are changed.

They’re also already in use in applications where surges of energy of greater magnitude than a battery can supply are anticipated. This is another perfect fit for them, as they offer considerably higher surge energy delivery than batteries do.

As a short aside, the reason I keep mentioning control electronics is because unlike a battery, ultracapacitors ramp down in voltage continuously as current is drained from them. Consequently they require circuitry to convert that constantly changing voltage to the steady output voltage most electrical and electronic systems need. So you rarely can replace a battery with an ultracapacitor alone. The good news is that such controller circuitry isn’t a big deal at all for the majority of things you’d use around your house. For a vehicle we are definitely talking about a much higher power use case. So there’s a significant cost involved for both safety and reliability reasons. But just remember: Once this hurdle is leapt, you should never have to worry about replacing your vehicle’s power source again.

I’m feeling very optimistic. Ultracaps have finally moved into the zone of practical systems I could make use of in the three areas most important to me: price, energy density, and reliability. Considering that I can design such practical systems at home for myself, just one engineer working alone, believe me, big companies can do it and do it very well. Consequently I fully expect to see ultracaps to begin replacing batteries more and more as each day passes.

The first company to integrate ultracapacitors with the required support electronics in standard battery packages (D, C, A, AA, etc.) will have me as a customer they very day I learn about it, even at 1/4th the energy density of the equivalent size battery.

It is technological shifts like this that make me think to myself, “I’m living in the future!”

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