It would not give longer life to have 12 of those in series although it would do no damage (12 batteries 1.4 Volts each = 16.8 Volts).  You could label the batteries 1 through 12.  For the first day of fishing use batteries 1 through 10.  That night take 1 & 2 out and replace them with 11 & 12 for the next day.  That night remove battery 3 & 4 and replace them with 1 & 2. Continue with this sequence and after 6 days of detector use your batteries would have 5 days use on them.
For this to work you would need to use the detector less than 3.8 hours per day.

One set of 8 lithium batteries will supply 3000mAh of current.  You are looking at taking 4 sets that would be 12000mAh of current. I see 2 other options.
Option 1:  4 X 8 = 32 Lithium batteries 12000mAh. $60.00 for one trip 14.6Oz
Option 2: 5 X 10 = 50 Duracell Quantum Batteries 12000mAh. $20.00 for one trip 2Lb 9Oz NOT COPPERTOPS
Option 3:  3 three cell Lipo 5000mAh battery packs 15000mAh $80.00++ for many trips 3Lb 3Oz
The Lipo battery pack I was looking at is at the following address.
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Notice that the cost of Option 3 is $80.00++.  The ++ stands for the extras you need to not destroy the battery.  Lipo batteries require special chargers so as to not over charge any cell. I believe the following charger is one that would work $25.00
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Lipo batteries require protection to prevent any individual cell from being over discharged.  There are 2 readily available options for protection boards. 
Protection option 1:  Is easy to hook up.
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All it does is sound an alarm and turn on a LED when any cell goes below 3.3 volts. You can still leave your fish detector on and destroy the battery. But it is easy to hook up. If you leave your detector on overnight or while you are away from your canoe and the battery goes down it will destroy the battery. But it is easy to hook up.
Protection option2: A circuit that opens up a switch and shuts the power off to the fish detector when any cell goes below 2.4 volts. $10.00
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This does not come with connectors and must have leads soldered to the board.  The connectors can be gotten by buying some adapters form Hobby king and cutting the connector off that you need.  I have charged through one of these boards and it will protect against overcharging preventing the destruction of the battery but it does not balance the charge reducing the battery capacity.
Let us know what you decide to go with.

Another thought concerning depth finders which have a lot of power (or use a lot of power). I have often wondered if fish can sense a depth finder and who knows, maybe the more powerful versions are actually counterproductive? Who knows?

Magicpaddler wrote on Sep 13^th, 2014 at 9:04pm:


I'm with you MP.......but then again maybe not. Last trip I had quite a bit of "stuff" including one reel which weighed in at a solid pound. So I decided to triple portage. It wasn't bad at all.....so I roll in an hour later, no bigey.

Of course I was solo so I could pretty much call the shots.

Anyone ever watch the bigfoot search/reality type cable shows? They make me laugh just thinking about them.

What about using C or D cell batteries? Is there an easy volts/hours/weight vs cost and ease of use formula? The original Lo-K-Tors had two six volt lantern batteries in the case. My new unit came with a D size battery pack. I take ~12# of photo gear alone plus some fishing luxuries. I'm willing to carry and paddle it because having access to those tools makes me happy. I'd have to drop the photo and fishing gear to double portage. It could happen some day but the extra weight still adds to the memories+ column.

Can fish hear? Do they attack squeaky spinner baits to shut them up so they can hear their natural pray move about? Tick tick tick tick braaap. Tic tick tick tick… is what my finder says on a quiet evening. I bought a fish caller from the back of Boy's Life once. It went down six feet and ticked. I could hear that too.