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

You have received suggestions of using lithium batteries and you have also received suggestions of using 10 batteries.  I have found that 10 alkaline batteries work better in my unit than 8 alkaline.  Lithium batteries are a higher voltage battery than a alkaline battery.  In other posts it has been stated that some detectors work better on 8 lithium than 8 alkaline and I think this is because of the higher voltage.  I would be concerned that a 10 pack of lithium batteries may over voltage many detectors.  Two good pieces of advice added together might equal bad advice.

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.