azalea wrote on May 20^th, 2011 at 3:44pm:

Heck with the air conditioner, what about the cooler itself.  Now, we're talkin'!  Leave the thermoelectric cooler in your vehicle (connected to a solar charger) filled with an after-trip supply of brews.  Maybe I could make it light enough to carry.  I'd be tempted to haul along a 6-pack if I could have a cold one after a long, hot day of paddling.

NOW we're talkin'!

Alas, all of the thermoelectric coolers seem to pull about 4 amps or more!  That's a tad more than my wimpy solar panel will supply.

dd

Thanks!  I will have to crack mine open and take a look...

S_D
The case came open with the removal of 4 screws.  I was concern that the path through the small bulbs was required so I found a bulb lead that I could solder back together if things did not work out and clipped it.  There were 4 or 5 bulbs in series so when I cut one that took them all out.  I am sure that ended the warranty but now I can use it.
MagicPaddler

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Great idea!  

I'd like to hear more about how you did this...

DD
My Eagle unit had that power up spike also.  I found that during the power up it ran the back light at full output.  I cut the wires to the back light and that solved that problem.  That also solved the problem of accidently turning the back light on during the day.  Took my battery drain down by a factor of 50!   

Well, MY face is RED.  

Just for grins, I hooked up the aforementioned solar panel to my Cuda 168.  At the moment (in full sun) it is running (in simulator mode) like a top.  I guess I need to go back and check my math! Either that or the Cuda draws much less power than I suspected.  I can tell that 300 mA is near the lowest level that will do ... in partial shade, the Cuda turns itself off (for lack of power).

I guess its time for a field test to see if there is ample juice to run the transducer.  I CAN hear it pinging, but that's no indication that the signal strength is sufficient to produce a clear bottom image.

dd

Postscript:  I guess it pays to read the manual.  The documentation for the Cuda 168 indicates that the current draw is 110 mA with backlight off and 250 mA with backlight on. 

So, the original question:  Can you power a depth finder from a solar panel?  The answer is:  It depends on your depth finder power draw (and solar panel output).  But for the specific configuration I tried, the answer would be YES. 

BTW: 

I did try the depth finder with another solar panel that only produces 60 mA and that was insufficient to power up the Cuda (which, based on the manual, would be the anticipated outcome).  This also explains why my 300 mA solar panel kept the Cuda running when 1/2 of the individual cells were in shade.

So, refigurring how long an 8-pack of 2500 mA AA's would last:

2500 X 8 / 110 = 181 hours.  (I guess THAT's why my battery pack is sufficient to last for a 2-week trip!) 

On a side-bar note:  I think you will find that the current draw at power-up is somewhat more than 110 mA.  So apparently there is a power-up spike.  This would explain why I could not do a power up with some of the individual solar cells in shade, but would run with the same number of cells covered.

mastertangler wrote on May 19^th, 2011 at 9:53pm:

Really? If intensity = distance/2 that's a small difference IMO. Angle maybe but I fried my forehead on a really nice day like a month ago. Next day was puss, next was blood and scabs....

tonyt74 wrote on May 20^th, 2011 at 3:37pm:

Well, its not so much a matter of volts as amps.  The solar panel mentoned above is rated at 15 volts, but only 300 milliamps.  So the weak link to power a fishfinder directly is the amp output ... and 300 milliamps (.3 amps) is insufficient to power most electrical devices directly.  To illustrate, the manual for the Cuda 300 fishfinder indicates that you should place a 3 amp fuse in the DC power line.  This translates to an operating power draw of less than that.  So, I'm guessing that a typical draw would be on the order of 2 amps.  Consequently, the solar panel produces on the order of 15% of the power needed (.3/2).

Consequently, it will be necessary to use this solar panel to recharge batteries.  (In this context, the solar panel operates as a trickle charger, producing a maximum of .3 amps per hour.)  I run my Cuda on an 8 AA pack.  The individual batteries are on the order of 1.5 volts and something above 2000 milliamps.  So the 8-pack produces 12 volts and 16 amps.  This configuration should produce about 8 hours of continuous use.  (But since I'm currently using lithium batteries ... 3000 amps, this is more like 24 amps or 12 hours of continuous use).

Of course, these numbers are only approximate and depend on a lot of additional factors (e.g., temperature, battery efficiency, etc.)

As indicated in the original post, I paid $57.77 for the panel I purchased.  It is possible that you could find it cheaper.

dd

To heck with the tent on stuffy nights!  Sleep under the tarp.

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Heck with a fan, create an air conditioner for your tent. 
There is probably a way to take the cooling system out of one those coolers you plug into the cigarette lighters of your car.   Does the solar panel work on moon-light?