Where's the energy stored?

I checked through my emergency stuff this morning in anticipation of the hurricane (I’m right in the path and storm tracker says tomorrow afternoon) and I checked my emergency radio and one emergency flashlight, both have battery and dynamo power. I removed the batteries when I put them in storage and didn’t put them back in, just spun the dynamo on both. The radio worked for over an hour on just a dozen or so turns, the flashlight worked for 15 minutes with about the same number of turns. Where is the energy stored? The batteries are removed! Rocketman

Either a capacitor or a separate small rechargable battery. The removeable batteries are just regular ones (alkaline or carbon), right? They’re not (easily) rechargeable. There must be a separate system.

My emergency radio has a dynamo and a super capacitor or ‘cap’. A cap is a device kinda like a rechargeable battery with the ability to charge fast but usually can only store that energy relatively briefly because of the way they are constructed.
Super caps can hold that charge longer, along with having a larger capacity for storing energy.

Stay safe. It is supposed to get bad tonight here in CT.

Definitely a super cap. I have a few of them laying around on the order of a farad or two. They can store enough energy to keep my digital clock working through a power glitch or when moving it from one room to the next without needing to be re set.

There’s a steady, heavy rain and the wind is picking up here west of Baltimore. I might change out of my pjs later. Nah, I’m way too comfortable. It would be nice if the power stayed on for a change, though. I’m thinking about a natural gas generator system. Any suggestions?

jtsanders – down here in Silver Spring many in my neighborhood researched and selected Boyland Electric and have been happy. I don’t know if they go up your way. (I think the generator brand was Generac.)

Thank you for comments! I may be “electrically impaired” but I still don’t comprehend how so much energy can be stored (seemingly) nowhere and be so easily recharged. I continued to use both devices and only charged them by a dozen or so turns and they continued to run for a pretty long time. I didn’t take either apart so I cannot speak to the hidden rechargeable battery in either, nor can I speak to the “cap” or capacitor, and cannot understand the spring explanation asecular mentions. I see this as easily rechargeable and fairly long-lasting electric power which is underexploited in our energy consuming world. Rocketman

What makes you think it “takes so much energy”? That radio needs a miniscule amount of energy to do its job. Caps like those used can absorb energy very rapidly.

TT: That’s what I mean by electrically impaired. I don’t comprehend the concept of so little force (a dozen turns) powering a flashlight for over an hour. Where else are capacitors used? Rocketman

Just for fun go buy a ‘crystal radio’ kit (Radio Shack used to have them). You’ll have a radio that works (through a small ear piece) with NO external power source. As for capacitors, they’re common in high-powered stereos to handle peak power demands.

I would bet the flashlight you have uses an LED bulb, right? Those have much lower power needs than an incandescent bulb.

Texases: You’re correct about the LED, but I had it on “high beam” for over an hour! Amazing! I’m gonna take you up on the crystal radio set . . . I can’t imagine how something works without energy. Gotta be a butterfly effect somewhere. I believe you, but I’m curious. Does anyone know if there is a use of these high energy capacitors in hybrid vehicles? Seems like a good fit. Rocketman

The crystal radio gets its energy from the radio waves it picks up, that’s why it can’t power a speaker. As for using capacitors in hybrid/electric cars, it is being considered, I don’t know of one using it yet. Since they don’t need rare earths, I’d think that would be a major advantage over batteries.

rocketman - The earliest “batteries” developed in the 18th century were, in fact, capacitors. Check out the Wiki on how capacitors work and their history here: en.wikipedia.org/wiki/Capacitor

Where else are capacitors used?

Remember the old cartoon character (using phonetic spelling), they’re like Sabwah Fair, he’s everywhere! and so are they. Chances are very good that every single electrical circuit you own has a number of capacitors on/in it. They are used to filter signals and store energy.

The main battery in your vehicle is essentially a giant capacitor for the power bus. It’s smoothing out the ripple on the supply and providing a huge reservior of energy although the physical makeup is quite different from the type of capacitors that started this conversation.

An analogy for the crank radio example would be a 5 gallon pail- that is the capacitor. It has the ability to store energy, in this case water. Now use a brad nail and punch a tiny hole in the bottom. You can fill the pail very fast by pouring water in the top. It drains out very slow through the nail hole. The crank is filling the bucket, running the radio is draining it…

One reason batteries are used in cars instead of capacitors is that batteries can store LOTS more electricity per pound, accoding to wiki:

“The amount of energy stored per unit weight is generally lower than that of an electrochemical battery (3–5 W·h/kg for a standard ultracapacitor, although 85 W·h/kg has been achieved in the lab as of 2010 compared to 30–40 W·h/kg for a lead acid battery, 100-250 W·h/kg for a lithium-ion battery and about 0.1% of the volumetric energy density of gasoline.”