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Discussion Starter · #1 ·
Is there really any difference in the dual purpose starting/deep cycle batteries and single purpose starting batteries with large reserve capacity. Ive got 800 MCA with 180 reserve starting battery and still its down to 11.6 volts in no time at all with a depth finder/gps, radio and livewell running. THat really is not that much of an amperage draw. I mentioned 11.6 volts because that is just where I've set the battery alarm warning. I cant mount two batteries due to lack of space. Whatcha think?
 

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When you get to 11.6 volts, measure the voltage right at the battery terminals. It may surprise you and be higher. This is because there might (or might not be) be a significant voltage drop from the battery to your instrument. Your instrument might also be reading a bit off.

The reason I am pointing this out is that it sounds as though you are reading the voltage at the instrument and taking that as the absolute voltage when it may not be. So, check your voltages with an independent source (voltmeter) and go from there.
 

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You didn't stated what voltage you're starting at or qualify "no time at all", how many hours is that? GPS and DF shouldn't draw much power unless you're using the backlighting. The livewell could be bringing down the battery. Motors can be power hogs. The radio shouldn't draw much power but if it's not a good marine radio it will start corrodeding rather fast and create electrical leakage paths below the fuse setting. What voltage is your alternator putting out? Are all of the connections clean? Measure voltage with a meter directly from the battery and see if reads different than the dash gage.
 

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Discussion Starter · #4 ·
I appreciate the advice guys but I'm familiar with electronics and charging systems. The question I posed was concerning the Dual Purpose batteries. Starting with a deep cycle will destroy the battery in a short time as will contiuous draw on a starting battery. Different design. Are the dual purpose worth a damn or simply larger cranking batteries with higher reserve capacities.
 

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The dual-purpose battery, similar to deep cycle, is designed for a prolonged current draw with better recovery. Cranking batteries are designed for short term high current draw and fade rather fast under a continued load. I run two dual-purpose batteries, one for the engine and one for the electronics, isolated via Perko switch. The battery powering the DF, GPS, VHF, and stereo seems to run forever. Never had a problem, even when on a week long camping trip. I charge the electronics battery with a charger at home and rotate the batteries yearly to distribute the degradation.
 
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