I already said this, but look like I need to say it again:
Watch out which third party battery you buy, because I bought five 428 battery with two charger (came with cigarette lighter cord too), on e-bay for $60 shipping included from Toronto to Windsor ON Canada.
NON OF THEM WORK FOR MORE THEN 10 SECONDS.
Doesn't matter I used the JVC charger or the third party charger. I sent them back, and they gave my money back.
So, look like the Power2000 OK, but theese wasn't!
I don't know which brand was these. Was only "Replacement for JVC 428" on the batteries.
This happend with me with the Sony 960 batteries too. (from different supplier, different brands) Some brand worked with the FX1 some others not.

Laszlo

I still think this is because these batteries couldn't sustain the current drain the camera required of them, not an electronic rejection of the batteries as non genuine.

We talked before Lazlo, I was about to purchase some cheap 3500 mAh batteries before you tell me that yours didn't work, so I decided to purchase these ones... not so cheap but trustworthy. I also purchased a Sony replacement battery for my camera light and it doesn't work, it's another brand. I will send it back.

I think the problem isn't the camera that rejects non JVC batteries, the problem is that these cheap batteries are crap. But here's my message, if your looking for good and cheaper batteries try these Power2000.

I already bought the IDX adaptor, so I can use my Switronix V-mount batteries.
Work great

Laszlo