^ You're welcome Ricola. I'm amazed that you know Poogie Bell. He's from here in Pittsburgh.
OK, you're on the right track with the links you provided. The only problem is that there's no indication whether or not the connector at the opposite end of the hirose connector on that cable would fit properly into the RAV Power battery. The size of that connector isn't provided in the specs of the battery, though the size of the cable connector appears to be 2.1mm. It would be awful to order both products only to discover that the cable doesn't fit the battery properly.
I have a TON of Tekkeon 3300 and I love them. These batteries include a cable that connects with a special connector into the battery. The other end is a generic adaptaplug connector. The package includes maybe ten or so standard size power connectors that all plug into the adaptaplug. I happily found out that one of these standard connectors fits perfectly into the 12V socket on the back of the F8. Since these adaptplugs are all right angle, they fit just perfectly in the bottom of my gear bag. On mine, the connector is very solidly seated in the socket, so I have no concern with the connector coming out of the socket, especially since when I put the F8 in my bag, it's resting on top of the right angle of the connector which serves to keep it in place. So, I'm perfectly happy powering my F8 with this method. I don't think I'm even going to bother with having a cable made to connect my Tekkeons with a hirose connector, since when I'm in the field I already have redundant powering between the back connector and the AA battery tray.
If you look in US ebay, there are some Tekkeon 3300's listed FOR CHEAP! The reason they're cheap is even though they're unused batteries in new packaging, they are fairly old from a shelf life perspective. So, these batteries are at least a few years old and probably even older. Some people on taperssection bought these batteries and they arrived dead. However, for what I paid I've had good luck with them. I've got 23 of them!! Of the 23 that I bought well over a year ago, all 23 worked fine when I got them and one has died since I got it. Four out of the 23 don't give me full capacity so I think they're on their way out...I'll refurbish them when that happens.
One of the full capacity Tekkeon 3300 batteries powers my Zoom F8 for about 9 or 10 hours if I'm recording to two channels, with 24V phantom turned on (my mics use 12V phantom, not 48V), with none of the output channels turned on, and with the unit powering a pair of ATH-M50 headphones the whole time.
So, I think if I was you, I'd consider buying some of these Tekkeons and using the 12v connector on the back instead of the hirose. MUCH cheaper option even after paying overseas shipping of the battery. Since they're so cheap, perhaps you should buy...say four of them. That way if any of them arrive dead, it's no big deal...at least in comparison to paying 90Euro's for the RAV power battery. (For what it's worth, I refurbish batteries, so if any of mine go dead, I'll simply crack it open and replace the cells inside.)
If you'd like, buy your batteries and have them sent to me and I'll test them for you. I'll remove them from the packaging and send the good batteries (and all of the accessories) to you in Germany. If there are any bad batteries, you can decide what to do with those. Without the packaging the box would be much smaller and less expensive to ship. Just a thought...consider it an option.