MH-C9000 it only does 4 at a time but seemed to give greater control options for charging and conditioning.
I got them through Thomas and using Amazon found a good deal I think.
So far I have not been out shooting and had dead packs. I have shot with 4 strobes at a time sometimes which gives me 4 loaded strobes and 2 sets of spares.
I put the strobes in the air on stands in pairs and remote trigger them and it would be a pain if they die during an event.
The strobes slave from a controller on the camera so I don't know how much power they are always using but they will go for 400 or 500 shots a night fired from 2 different cameras without dying.
On a related note I have been using a Fenix E21 for a few months now and I really like it. Bright as hell even on low setting and well made too.
I just picked up a StreamLight P90 too which is like a mini Army style right angle LED job which I can clip onto things. I have it clipped into the Synapse all the time and it is great though it does use 123's I buy them through Alarm Distributors very cheaply.
I loves me some flashlights!