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Old 07-04-2010, 15:51   #1
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'King Volt and Sir Electron'

"king volt and sir electron" is what my dad would always mumble as he showed me the basics of 12volt systems. I just bought a new depth finder and am trying to calculate how long my battery can run it.

It has a power output of 300watts(rms) 2400watts(peak)

I have one 12 volt 120 amp battery.

300watts/12volts gets me 25amps at 4.8 hours.

Is this right or am I missing something?
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Old 07-04-2010, 16:08   #2
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What size fuse does your manual say? I am betting it is not 25amp!! what model?
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Old 07-04-2010, 16:13   #3
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I believe it is 1amp. The model is a Humminbird 365i Combo. Do you know what I am missing in my calculation?
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Old 07-04-2010, 16:18   #4
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300 Watts RMS is the effect of one transmitted pulse, but it doesn't transmit continiously. How often it transmits depends on the range it's set to. The power consumption for different ranges should be i the specs.

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Old 07-04-2010, 16:23   #5
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that makes sense, thank you very much.
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Old 07-04-2010, 20:30   #6
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Remember, if you want your battery to last a long time, do not allow it to discharge below 50% of its capacity. A voltage of 12 volts is telling you you have reached this point. The depthsounder won't use a lot of power, unless you are driving a monster that reaches deep down, not too useful, normally, for a small sailboat. You will also be using power for the stereo, reading and nav lights, and possibly other things which will pull the voltage down. Your original question made it sound as though the depthsounder is the only use. If so, a digital depth unit uses much less power than one that displays the bottom (a fishfinder) which needs an electron-hungry display unit. Simple black and white matrix screens, though, use less power than color, high def screens.

I'm sorry, Dudeman, I wasn't carefully reading your original question. I checked the specs for your particular unit, the 365i. It uses virtually no power at all (350 milliamps) for a grey-scale display, depth sounder transducer and GPS. That's a great combination at a good price. You can run that puppy day and night for longer than you will probably be using the boat at any one time.
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Old 07-04-2010, 21:00   #7
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Page 108 of your manual:
http://store.humminbird.com/media/do..._5317281_A.pdf


Current draw 350 mA


So drawing your battery down 60 amps (50%) gives you 170 hours or 20 days.


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Old 07-04-2010, 21:10   #8
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I did a quick check on how long you could run the 365i before depleting a single, type 31 flooded battery to its half-way point. The battery holds about a hundred amp-hours of juice. At about a third of an amp, times half the capacity, it approaches almost 150 hours of operation, very roughly. Electronics are getting really miserly of demand.
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Old 08-04-2010, 09:44   #9
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Thanks for the help guys. I'm still fairly new to boat electronics and this website has been most helpful.
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