Plastic Batteries Coming Soon?

Roland Piquepaille writes "Engineers at Brown University have built a prototype of a hybrid plastic battery that uses a conductive polymer. The system, which marries the power of a capacitor with the storage capacity of a battery, can store and deliver power efficiently. For example, during performance testing, 'it delivered more than 100 times the power of a standard alkaline battery.' Still, it's unlikely that such a device can appear on the market before several years."

Comments

summary is pretty bad, this is not a revolution

[arete]

The summary is pretty bad. If I'm reading the article right:

This is neat, but not a revolution, it's exactly the hybrid of a battery and a capacitor - it has some advantages of both.

This device has similar or less storage capacity than a battery, but can deliver its power much faster.
It has similar or less power delivery abilities than a capacitor, but twice the storage capacity.

In MANY devices, the real problem is that the batteries drain. This doesn't help that in the least bit. This will not make your electric car go farther. This only helps the situation with ultra-high-drain requirements, where a normal battery just wouldn't work.

Re:summary is pretty bad, this is not a revolution

[arete]

Yes, according to the article: A BATTERY has high storage, low power. A CAPACITOR has high power, low storage.

This has more storage than a low-storage capacitor and more power than a low-power battery.

It does not in any place, at all, say that it has more - or even as much - storage as a battery or power as a capacitor. If it had 100 times the storage of a battery it would change a lot of things.

Re:Five to ten years...

[jellomizer]

Batteries tend to improve linearly while electronics tend to improve exponentially. So this really makes batteries seem like they are stagnant. If batteris went at the same speed as electronics. A nuclear power-plant will be in a AAA Battery.

Re:Five to ten years...

[luder]

Well, unless I'm missing something here, if it delivers 100 times more power than an ordinary battery then it also increases it's life:

P = V*I
100P = V*I
I = 100 (P/V)

For example, most powerfull easy to find rechargeable AA batteries can deliver 2.5A, or 3W, at 1.2V.

P1 = 1.2 * 2.5
P1 = 3W

This battery can power a 3W, or 2.5A, device for an hour.

With an increase of 100 times more power we have:

P2 = 100 * P1
P2 = 100 * 3
P2 = 300W

The new battery could power the 3W device for 100 hours, instead of the 1 hour that the current battery can do, or a 300W device for a single hour.

Re:Five to ten years...

[flooey]

Well, unless I'm missing something here, if it delivers 100 times more power than an ordinary battery then it also increases it's life:

You're confusing power with energy (which is easy to do, considering your "power bill" is actually a bill for energy used, not power). What it's saying is that its peak power delivery is 100 times that of a normal battery, so at a given voltage, it can deliver 100 times the current of a standard battery. It could well be able to store the same amount of energy, though, which means that if you're running it at its improved full power it dies in 1/100 the time of a normal battery.

Re:Five to ten years...

[hernick]

Yes, you are missing something very important.

You've introduced three units in your calculations:
  * Power (P, in Watts W)
  * Voltage (V, in Volts V)
  * Current (I, in Amperes A)

However, these units only measure energy at a single point in time. But we're dealing with finite energy sources. We need to introduce another unit:
  * Time (T, in Hours h, or in Seconds s)

Let's take a new look at your formula, adding a variable for time:
  P * h = V * I * h

Now, let us consider a the same NiMH AA battery that you looked at earlier. To know how powerful that battery is, we need two know two things:
  * Its cell voltage: 1.2V
  * Its capacity rating: 2.5Ah (normally quoted in mAh / you'd see 2500mAh in the specs)
  * It's maximum power drain: 2.5A

These two numbers tell us that roughly, this AA battery can deliver its quoted voltage of 1.2V for one hour if the current drain is 2.5A.

P1 = 1.2V * 2.5A * 1h
P1 = 3W * 1h = 1.2V * 2.5Ah
P1 = 3Wh = 1.2V * 2.5Ah

This battery can power a device with a power draw of 3W (equivalent to a current draw of 2.5A at a voltage of 1.2V) for one hour. It has a capacity of 3Wh (equivalent to a capacity rating of 2.5Ah at a cell voltage of 1.2V).

Let's assume that these are the specs for our new battery:
  * Its cell voltage: 1.2V
  * Its capacity rating: 2.5Ah
  * It's maximum power drain: 250A

Now, this is where you get it wrong. What we're doing is increasing the power drain by 100, not increasing the capacity by 100.

P1 = 3W * 1h = 1.2V * 2.5A * 1h

P2 = 3W / 100 * 100 * 1h = 1.2V * 2.5A * 100 * 1h / 100
P2 = 3W * 1h = 1.2V * 250A * 0.01h
P2 = 3Wh = 1.2V * 250A * 36s
P2 = 3Wh = 1.2V * 2.5Ah

So, the new battery could power the 3W device for 1 hour, or a 300W device for 36 seconds.

Now, in reality, this new battery/capacitor hybrid is likely to have a far lower capacity rating (quoted in mAh on the box) than your typical NiMH AA cell. Also, the typical AA cell has a higher maximum power drain, which can be increased further by cooling the battery as you discharge it.

Also, in the real world, things don't work out quite as nicely as in these equations - there are power losses that vary based on a lot of factors. How fast is the battery discharged? How hot is it - and the more quickly you discharge it, the hotter it becomes, the less efficient it becomes. Is it a continuous discharge load or are we looking at spikes that give it time to cool down?

Anyway. This battery isn't quite the revolution your flawed calculations would indicate.

Good replacement for NiCd applications?

[billstewart]

Currently there are three kinds of rechargeable batteries used for electonics and toys:

• NiCd - low energy, high power, nasty heavy metals - good for driving small motors that need high current for a short time.
• NiMH - about 4-5 times the energy of NiCd, lower power, medium life - they'll discharge in under a month even if you're not using them, so they're not good for some applications.
• Rechargeable alkaline - medium energy, lower power, long life, full 1.5 volts.

For toys like remote-control model cars or model airplanes, Nickel Cadmium is the main choice, because it can dump a lot of power for a given battery weight. If this new technology lives up to its promise, it sounds like a good replacement, and we can avoid the heavy metal toxicity problems of cadmium. The article doesn't talk about what voltage it generates (some things really like 1.5v better than 1.2v), or how long the charge lasts if you're not using it.