Hey Jax,

Each AA battery is 1.5 volts so 8 in series will give you 12 volts. Most units actually have a working range of from 10 - 16 volts or so, so you can also use a 10 pack which will give you more battery run time. Also, since you have the straight X4, you will have less power consumption than with the pro so good move there. I got the Garmin Echo 100 last spring and its about as close to the X4  as any unit out there. I don;t use it as heavily as you intend to, basically just checking for occasional depths, reefs and drop offs then turning it off. On my spring trip, using regular Alkalines, it lasted the whole 5 days easy. The last 2 days I kept it on all the time I was fishing to test when the batteries would wear out. They didn't ( 4-5 hours a day). I then used those same batteries on a few more trips that summer, although not keeping it on all the time. Even if you take 2 sets of back up batteries, the AA's are so light its way better than standard portable set ups. I have some pics of mine so I'll post some (they are also posted on BWCA.com). As to your hull, I have heard aluminum may not work but I heard teh same thing about cedar strip hulls and it works fine shooting through my cedar strip hull. I used a foam cut out siliconed to the hull, add a few drops of water and then place the ducer in there. That way my transducer can be removed for car topping and winter storage etc. I put the battery pack in a starfritt water tiight plastic container from Walmart.

Moonman.

Magicpaddler makes a good point. You should check voltage requirements for your specific unit before any wiring is done. Most manuals are online, although not always easy to find.

Moonman.

Fuse is necessary for safety of the unit but there should be one inline on the power cords that come with the unit. It will work without the fuse but you are taking a risk re a power surge.

Moonamn.

no it didn't come with fuse parts but i did get the in-line fuse holder and fuses from radioshack. i also used a 'project' box that they sold for 3.00 to house the batteries n such but really don't like it. very small metal screws thread into plastic. the box moonman used sounds like a far better casing.

Magicpaddler wrote on Mar 23^rd, 2012 at 4:42pm:

Re: Lithium vs Alkaline batteries.
Magic Paddler is correct about the voltage differences between the two types of batteries. Additionally each type "decays" with slightly different characteristics. With alkaline batteries there is initially a fairly quick drop in voltage to about 11.5 volts and then the drop becomes very gradual. You may not notice it but performance is also decreasing gradually as the voltage drops. First thing you may notice is that your locater will not find the bottom in very deep water. That starts happening at about 10.5 volts and is generally not a big problem as far as fishing goes since you're not going to be fishing bottom in over 100' anyway. You also might notcie the display becomes a bit lighter and more difficult to read in bright light. All of that said, with alkaline batteries your locater will probably function reasonably well all the way down to about 9 volts as long as you fish in less than 60' of water. The good thing is that you can constantly track the decay of alkaline batteries and predict when and what the problems are going to be.
Lithium batteries behave differently. As MP pointed out they start at a higher voltage and maintain that higher overall voltage much longer than Alkaline batteries providing much better performance for a much longer period of time. The problem is that once the voltage drops below 11 the decay can become quite rapid and unpredictable with a variety of problems in the performance of the locater. Weird stuff can happen like the locater will not  turn on the next morning or it turns off unexpectedly or the display gets unreadable etc. Regardless of these minor annoyances lithium batteries will outperform alkalines throughout their lifespan which is somewhere between 5 and 7 times alkaline batteries. Yes, they are worth their much higher cost.