battery density

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.