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Discussion Starter · #1 ·
I've done some searching through the forums so I have to ask about fish finder batteries.

I noticed the power draw on units varies ALOT. The units Im looking are Humminbirds (586c,596c,778c) and Lowrance Elite-5x and all run around 300-500 watts RMS and theyre color units.

***** How long would the typical 12volt 7ah battery last with one of these 300-500 watt units ?

I know the greater the watts then the faster the power drain on a battery.

******* Would a larger battery like a 12volt 10ah work at giving me more juice for a larger unit...or more running time in general over the 7ah battery ?

Im just trying to make sure that I get a big enough battery to last me a full day...say 12hrs of straight fishing. I'd buy two batteries so I always can have a good battery while the other charges if needed.

Thank you for all responses :D
 

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Red X Angler
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I'd say 12-15 hrs is a safe bet unless you are swapping functions alot, as that increases draw. the simpler units go easily 8-10 hrs on 8 aa batteries.
 
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I might have my math wrong, but my figures show that you can run a 300 watt device for .28 hours off a 7 amp hour battery.

300 watts / 12 volts = 25 amps
7AmpHrs / 25 amps = .28 hours

I may be wrong, but I think this is the right formula

**this is power output, not power usage...
 
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Not sure about the math, but i'm running a mid-size color unit maybe 6-7 hours, then another outing before i recharge. 12v 7ah
check your 'backlight' level to conserve...
 

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The specs on my B/W Humminbird 535 say 250 Watts RMS power output. Not sure what the "output" refers too - total consumption or power of transducer signal. I'll get 24+/- hours of runtime on a new and freshly charged 12v/7ah battery before the battery voltage drops below 9v. Winds up being several trips between charges.
 

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ok... I found that on the Lowrance Elite-5, it has an operating current of .7 amps with backlight on and .4 amps with the backlight off. This would give you 10 hours with backlight on and 17.5 hours with backlight off.
 

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Discussion Starter · #7 ·
Thank you for all the responses :D

I dont claim to know anything about batteries/amps/and such so I had to call on the knowledge thats on the site.

Thanks Rodnocker, I will have to check out the owners manuals of all the units and do the math based on what you
came up with.
 

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Discussion Starter · #8 ·
I might have my math wrong, but my figures show that you can run a 300 watt device for .28 hours off a 7 amp hour battery.

300 watts / 12 volts = 25 amps
7AmpHrs / 25 amps = .28 hours

I may be wrong, but I think this is the right formula

**this is power output, not power usage...

So does .28 hours mean it will run for almost 17min ? or do u mean 28hrs ?

I found this... http://www.powerforceusa.com/Design%20Considerations%20for%20Engineers.pdf

According to the info in the link:

7 amp hour battery = 7000 milliamps

7000 milliamps / 650 milliamps ( the current draw of a Humminbird 778ci)
= 10.77hrs

So with that I can say that 500 watt RMS ( the 778ci ) current draw is about 650mh

To find out anyother system is simple then...

( 500watts / 300 watts ) X ( 650mh / X ) = x= 390mh
So a 300 watt RMS system would draw 390mh

Still with me ?

So if that is all correct a 12volt 7ah battery will last:

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I hope that sounds about right.
 

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Red X Angler
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in other words, Yeah it'll work lol!
 
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