I'm not sure I'd recommend a split cable to you. You should be aware that the mini-me is a reverse polarity device...tip is negative. I'm not 100% sure about the HD-P2, but other Tascam products I've owned are normal polarity (tip is positive) so I'm gonna say that I'm pretty sure the polarity on the mme is opposite from the P2. Here's the thing...the mini-me
IS NOT reverse polarity protected. So if you build a Y cable, you'll want to MAKE SURE you never accidentally connect the cable wrong, or you'll fry your mini-me. Apogee will fix it for you for $179 excluding shipping (can you tell that I have personal experience with thes?
).
However, if the connectors for the P2 and mme are different, then the above concern would be a moot point. If that's the case, then you wouldn't be able to accidentally swap the connectors since the P2 connector wouldn't be able to fit into the MME and vice versa. What I'd do is WITH POWER DISCONNECTED, see if the wall wart connectors for the MME and P2 can be mistake for each other. If they can be swapped, NO WAY should you attempt powering both of these from the same battery. I mean, you could have a Y cable made with one branch reverse polarity and try to make sure the reversed polarity branch of the cable always goes to the MME, but that's an accident waiting to happen right there.
Nevertheless, I'll assume the above isn't an issue and I'll answer your basic question.
What you're asking for is going to require a custom build. You're gonna need to start out by figuring out what battery you want to buy and work forward from there.
First let's figure out the capacity of battery that you need. I checked the specs on the HD-P2 and it says it pulls 6W. The mini-me specs don't say what it pulls, but I owned one and I don't recall it being overly hungry, so let's assume it also pulls 6W. 12W at 12V means you need 1amp or 1000ma for every hour of operation. Therefore, to get 8 hours you'll need a battery that gives you 8000mah at 12V. Let's give ourselves some headroom here in case my mini-me assumption isn't right and say that you probably need a 9 or 10 amp-hours battery. Remember, battery specs can be deceiving if you don't understand the specs...they like to quote really high mah ratings, but those are usually at real low voltages, so don't be fooled by ebay ads that say a battery has 20,000mah...that might be 20,000mah at 3.7v which doesn't cut it for your needs. 8000mah at 12V is a fairly large capacity battery.
The problem here is that there aren't many metered batteries out there with this capacity and they're REALLY expensive...like over $200. Here's the battery that has become really popular on ts.com. I own two of them and love them. So, you could buy two of these which would give you what you need. Each one of these should give you between 5 hours or so and alot of people own these batteries here on ts.com.
http://www.ebay.com/sch/i.html?_trksid=p2050601.m570.l1313.TR0.TRC0.Xnaztech+pb15000&_nkw=naztech+pb15000&_sacat=0&_from=R40Since you were asking about an eco-charge, I'll assume you aren't concerned with using lead. I still like using lead batteries...they're cheap and reliable. In fact, I have a battery that exactly matches this spec...it's not light but in the grand scheme of things 6 pounds is no big deal. Here's a link and I can pick these up at my local Batteries Plus store for less than $40.
http://www.batteriesplus.com/product/40570-WKA12--9F2-Werker-12V-9Ah-Battery-with-F2-Terminal/100085-1/102629-SLA-Sealed-Lead-Acid-Batteries/102645-Werker/12V.aspxIf you go this route, you'll of course need to buy a charger for the battery. Basic SLA chargers are $25 or so.
So, this battery doesn't have a meter, but you really don't need a meter. All you have to do is hook up all of your stuff to the battery and set it up to say record the TV or a stereo. Let the battery run down and you'll have a run time estimate of how long the battery will last with the gear you'll be using.
What you need to do then is buy some kind of connector for the battery terminals. They should have these at Batteries Plus, but you could so what I do. I go to Radio Shack and buy a Tamiya connector and solder it onto the terminals. Red wire goes to red terminal (positive terminal) black wire goes to black terminal (negative). Just remember to flux the wires and terminal before soldering to get a good solder connection.
Here's a link to the connector I use...
http://www.radioshack.com/product/index.jsp?productId=2062132Finally, the reason I said you start with the battery first is because you need to know the specific connector type the battery needs. Since now you know the connector on the battery, the mini-me, and the HD-P2, contact one of the two cable builders on ts.com (tgakidis or darktrain) and they'll custom build you a 'y' cable with all of the appropriate connectors at each end of the 'y' so you'll be able to hook everything up.
Actually you don't need need to know the connector type of the mini-me or the HD-P2. Ted Gakidis already has figured out all of the connector types on the major gear that's used on ts.com. It's shown in a chart here on ts.com somewhere.
I hope this helps.