Philo's solution to NXT batteries
Take a visit over to Philo's website to see a set of instructions for building a power-supply insert for the NXT brick that uses an AC power adapter to provide power to your bots. Not for the everyone (especially those of us with not-so-great electronics skills), but a great start for the hacks and homebrew fans.
Reading your story on battery life I have the following comment. For some time now also Lithium-Ion rechargeble AA (LR6) batteries exist on the market which do run on 1.5 Volts per cel. I use these for some years know and they are perfect. For example the brand Rayovac but there are also others. The advantage over the NmMh standaard is the 1.5 V instead of 1.2 Volts. It requires a different charger that can be purchased but these batteries are a good solution to the 1.5 Volt Non-rechargeble batteries without loss of power for the many of us. Check out the site of www.Conrad.com where I buy these 1.5 V Lithium Ion rechargeable AA's.
Regards from also a big Lego Mindstorms Fan, Franklin
Many regards from a big dutch Lego and Mindstorms Fan...Franklin
I have heard of Rayovac rechargeable alkaline cells for some time, but never tried them. Some people seem happy with them (http://news.lugnet.com/robotics/?n=17492) but current limitation (about 400mA from what I've seen) seems to be a real bummer for the NXT. I confirm that a single heavy loaded motor can consume up to 800 mA connected to NXT (up to 2A when directly powered from an external supply!), 600mA sustained.
Moreover I went to the website of Rayovac and of Conrad and found no mention of rechargeable alkaline batteries. Looks like they gave up on this product.
My opinion is that NiMH provide a good solution for all mobile NXT applications, except for the most demanding ones. At 7.2V the NXT+NXT motor deliver more work than a RCX with 2 parallel motor under 9V...
you may look for these numbers:
If it here on the market now, I am most definitely buying my son a set of lego's just so that can be my excuse! :)