battery density

I realize today that battery capacity is a limiting factor in designing something. Theoretically would it be possible (one day in the future) for a battery the size of a AA to have a capacity of say 12 volts at 20 amps an hour? I realize we are far from this, but about how long do you think it will take?

our only hope for anything remotely like that hangs in the balance with graphene.

Maybe a fuel cell will be able to do that.

You are talking about half a small car battery capacity there, there are urban legends that smaller better cheaper batteries have been invented over the years, but the big battery manufacturers buy the patent and throw it in a cupboard.

I think though that the boom in hybrid cars will lead the way in battery design ..

Moors law doesn’t seem to apply when it comes to batteries. Maybe the energy density doubles every 30 years. So 120 years.

Look at how much less power electronics use now compared to 40-50 years ago. That trend should on the way down meet batteries on the way up.

Use of earbuds instead of speakers, leds and LCD's and other efficiencies may have room to go yet.

And there's lots of room for self-power. The hand-heat powered flashlight is one beginning. Piezos in shoe soles is another. Put solar cells in your project, been around for decades. With super-capacitor improvements to store generated power, batteries will just be another choice.

My dilemma is that I need 150 watts of power to drive a cricket scoreboard ( for example ) if it is facing the sun.

So if somebody wants a battery powered scoreboard they have to basically park a car behind it.

The new generation LEDs show up fine in direct sunlight, but I use 4 LED strings per segment ( of the 7 segment displays )

If I could drive just 2 rows on overcast days they would show up fine, but to power the other 2 rows from a solar panel would cost half the price again of the scoreboard.

I use LCD displays on some of the remote controls, but they are useless in sunlight ( at least the cheap backlit ones I have used. )

I havn't had chance to read up on LCD displays, but presumably there is a limit to the amount of light the display can block when the crystals are aligned ?

It would be nice to be able to have a simple backlight for low ambient light, and to have a mirror / lens arrangement for the sun to illuminate from behind on sunny days, but I don't know if LCD screens could handle this.

Would it be any good to use flip-dots? Or some kind of stepper-driven card rolodex?

I have made quite a few boards to replace flip dot types, they just cant take the heat in the sun.

( I made a hotel roomrate board for a swanky hotel , and they insisted on a stainless steel case for it. If I have to do a service call on it in summer, I take gloves to take the lid off as it is so hot you could fry an egg on it. Strangely enough, even though LEDs are not supposed to like heat, I have only had about 6 fail in 2 years in this board, out of the 1500 in that sign. The fan doesn't last a year though and has to be replaced )

I have thought of some sort of rotating tubes driven by a cheap motor, for the 7 seg displays but haven't had the time to experiment yet.

Another problem is if they require team names, and I end up with 35 LED strings per character, with usually 8 letters per team so its another 560 LED strings to be powered - if I multiplex it, it brings down the current but the LEDs are hard to see in sunlight.

I think I must keep an eye on the prices of solar panels as they come down, but how do you find a reliable one?

That has all the sounds of a need to be met. How much solution can they afford?

Therefore all progress depends on dispairing clients :D

There not a lot of money around at the moment, so everything has to be cut to the bone, to keep the quotes down.

Have you tried shading the board?

Up until about a year ago I used to fit the LED in routed grooves in a plastic front panel, to shade each row of LEDs. It was fiddly and expensive to do, and if the board was pointed towards the North East the sun still got to the LEDs in late afternoon ( we are in the Southern hemisphere )

( I love it when they ask for a southern facing board so it is always shaded )

Now the LEDs are so bright that shading is not needed, but it still needs a double row :-

These are leant back looking straight into the sun so not shaded by the grooves, and are perfectly clear.

The latest ones are even better, and for evening sport the auto dimming I have had to fit turns them right down to less than 10% duty cycle.

One of the problems is that schools and clubs want the scoreboard across the field from the clubhouse, often where there is no power. Sinking cable around the field is very expensive, and could kill the sale, so if I can get affordable solar panels ( and deep cycle battery ) it might swing some sales.

I'm waiting for the nuclear batteries.

I don't know if I can wait that long, but perhaps my Great Grandson , now 2 year old , will use them :-)

Maybe just expand on this

Urine-powered mobile phone a reality with new microbial fuel cells

http://www.belfasttelegraph.co.uk/news/local-national/uk/urinepowered-mobile-phone-a-reality-with-new-microbial-fuel-cells-29432070.html

Our our home grown version

http://makerfaireafrica.com/2012/11/06/a-urine-powered-generator/

but I think they are taking the pee :-)

1 Liter of urine gives you 6 hours of electricity.

I wonder at what voltage/current level?

Boffin1: Up until about a year ago I used to fit the LED in routed grooves in a plastic front panel, to shade each row of LEDs. It was fiddly and expensive to do, and if the board was pointed towards the North East the sun still got to the LEDs in late afternoon ( we are in the Southern hemisphere )

( I love it when they ask for a southern facing board so it is always shaded )

Now the LEDs are so bright that shading is not needed, but it still needs a double row :-

And you have problems with powering and heat.

These are leant back looking straight into the sun so not shaded by the grooves, and are perfectly clear.

The latest ones are even better, and for evening sport the auto dimming I have had to fit turns them right down to less than 10% duty cycle.

One of the problems is that schools and clubs want the scoreboard across the field from the clubhouse, often where there is no power. Sinking cable around the field is very expensive, and could kill the sale, so if I can get affordable solar panels ( and deep cycle battery ) it might swing some sales.

The shop I worked at made the "Odds Windows" for the Delaware Race Track (horse races, long field, big stands, etc) IIRC in 1980 or 81. Every set of lights to make 1 digit/character set at the bottom of an open front box perhaps 20 cm deep. The box grid was made of 1/2 mm aluminum strips with slits that horizontal and vertical interlocked. Using aluminum strips to go in a steel frame was probably not a great idea (dissimilar metals, eventual corrosion) but it worked well.

You could try just for your own look-at, find a cardboard box big enough and set digits inside with the front open and see what that does to your power requirements. Less would help, wouldn't it?

I don't know about Africa but here the sun is not so bright when it's low in the sky.