Any ideas on how to transform a 12 volt battery into 7.2 volt use safely for the XL1? Thanks

Think I may have answered my own question. Dolgin Engineering offers a step down transformer for $139. Looks hefty and safe.

Why couldn't you use a 7.2 vdc zener diode for the step down voltage?

Better yet, get a 7.2V battery pack. You will probably lose a lot during the 12V-7.2V conversion and the expense of the converter will more than pay for a more powerful 7.2V NiMH battery pack that will be lighter.

Do the batteries that fit on the camera really last as long as they are rated?
Do they maintain whatever the rated hours charge capacity as listed perpetually, or do they lose their poop as they get older?

No battery lasts forever. In fact, everything degrades over time. If you make your own 7.2V battery pack instead of rigging a motorcycle battery to output 7.2v, you will probably save money and get the product you really need. The cost of the batteries themselves is no longer very high. A 7.2V NiMH 5AH pack at batteryspace.com is only $36.

If you are trying to avoid buying the batteries designed for your camera, your best bet would be to simply buy those batteries or get an Anton Bauer adapter kit. What are you trying to accomplish? What camera do you use?

most of the big names in camera are selling accessories like 12v car converter.
12 battery is great when you need to use an external LCD or lights, but li-ion battery a infinitely better at powering a camera.
the biggest battery for sony VX2000 can power the camera for almost 8 hours.

Thanks Marcus and Giroud. I guess I'm looking at dirt simple. There's a certain appeal to having oodles of DC cam power on hand. I've found the older batteries for my Xl1 don't hold a charge as well as they are rated after awhile. For the two larger sizes, how long should the Li ions last at the rated capacity? In other words for how many months should they work at capacity and how long in hours would that capacity be for the Xl1 for the different basic ones? I guess I'll need about two or three and they should be noted as to date of manufacture.
What about the CB 910? If I ran out of the grey market ones on location would the CB 910 hooked to a lead acid bat be a good backup and a good in the field charger. Also, the Canon manual warns that certain replacement batteries might give misleading data on the menus. Any ideas whidh ones do that?