Aghh, turns out the battery charger is not good. I've been playing around with the back all weekend, ready for a shoot tomorrow and drained both the batteries.
Plugged them into the supplied charger - 0% and not charging. And only one side of the dual battery charger is lighting up 
store is closed until tuesday - bah and no shops around here seem to stock BP-195 type batteries.
I wish Phase had included a power supply function for the back. I know I can power it with firewire cable, but that needs a firewire device to plug into - my workstation has one, but I am not dragging that around on set.
A regular power socket on the back would make so much sense. Even more so if it could also charge the battery at the same time (or even have the firewire charge the battery)
A couple of more ideas.
First it may be the actual batteries, they can reach a point where they will not charge and if these are batteries from the original back, you may want to try a new battery in your old charger. The first round of Phase batteries I believe were either 2400 or 2500 milliamp and they did not last that long, then Phase came out with 2900, and currently are at 3400, (the new batteries should also work in your back). They have always been Li-On, but even these will age over time and reach a point where they will no longer charge.
Also remember, the cells are basically Canon Video camera batteries, that are re-branded to Phase One. Team Phase One does not make them, even the new 3400 cells are made in China.
With the IQ back's Phase created a body where the battery is inside the back, where as with the P+ backs, the battery is on the outside. Canon made an AC adapter made around the same size as the 2500 millamp batter. Google this and you will find a lot of hits on it. The part of the AC adapter that fits into the camera is the same size as the LiOn battery. So if you are working in a studio, you can run off AC. Again, 2 years ago, there was a lot written about this and many photographers were using this solution. There was quite a lot of it posted on this site, and it may still be out there in the Archives. The Canon AC adapter was available on ebay. It was a very common solution until the IQ backs started to ship and then the solution would not work as you could not close the battery door due to the cable.
I sure would check your charger with another new battery before buying a new one. But no doubt, if your batteries are the oldest from Phase One, it's probably time to replace them anyway.
The two key things to remember, the voltage for a Phase One back, is 7.2 volts. The milliamp size just lets you know how long the battery can last, i.e. 3400 milliamp will have more charge time than 2400 or 2900.
Paul C
