Thanks to
Theo van der Heijden
I've been able to put a circuit-diagram of an electronic voltage regulator on this page. Finally we can ride our bikes into the night, without worrying when our lights will stop working. We can ride during the day as well, without our batteries boiling dry within half an hour or less...
As you can see, there's a jpg on this page, but the
original diagram (in pdf-format) is here.