I have a sun battery which produces around 55V / 5A at most. I need to regulate this to 24V. I wanted to use the L7824 family, but they have a maximum DC input voltage of 40V so it would burn down. I was looking for some eaiser solution for this but couldn't find anything. Could you recommend a simple regulator circuit that would fit to this sun battery?
If you use a linear regulator, you're going to waste more than half of the available power. I would recommend some sort of switching converter. That's a pretty high input voltage, though. I don't know of any good switchers offhand that will run with a 60V+ input voltage.
I would suggest taking a look at the power converter availble from Linear and TI. It looks like linear has a few that will work:
The LTC3810 looks like a good candidate - it will work on input voltages up to 100 volts and it can provide output voltages from 6 volts to 55 volts.
It does take a handful of external components to work, but the datasheet walks through the calculation of the various passive components.