Dual Purpose vs. Deep Cycle

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David

Time to change the Batteries on my C30. I'm trying to decide between 1 deep cycle & 1 dual purpose or 2 deep cycles. Budget is an issue, unfortunately. I mostly day sail with the occasional overnighter. My electronics draw is about average. (VHF, normal electronics, autohelm, no refridgeration). I would love to hear the thoughts & ideas from those who have done it along with the pros & cons of each. Thanks
 
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Steve Treppa

Two Dual Purpose Batteries Worked For Me!

I replaced my batteries last year with 2 duals purpose units. I have a similar usage pattern with daysailing and the occasional overnighter. I spent 3 days on a mooring with only about a 45min. engine run each morning with no problems. I suspect that in the long run the duals won't last as long as deeps, but given the price difference it may be a wash in terms of $$$? Steve
 
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Bill

I've got the same

We bought our Cat 30 last March on the Hrrd with about 12 inches of snow in the cockpit. It had 2 Sears Diehard Dual purpose batteries on it,pretty dead. I borrowed a friends Car battery charger and threw a charge in each one before she went in the water.(have since bought a deep cycle battery charger) I kept one as a starter from May to about Sept. The other for overnights (about 6) and instruments while daysailing on the weekends and club racing on Thursdays. I only ran the engine approx 15-30 minutes each sail. (In and out of the mooring and circling while waiting for crew members.) In Sept the Starting battery was getting pretty week so I switched to both batteries for starting and that lasted through Oct when I took her out of the water. They are right now happily recharging on my workbench. I try to top them off with a weekly trickle charge throughout the winter as I 've read this prolongs the batteries life. I've thought about investing in a small solar trickle charger for the mooring while not in use during the week, but the hole just keeps getting deeper if you get my meaning. Good Luck, Bill
 
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Joe Luciano

Deep Cycle

You can buy deep cycle batteries at Costco or SAMS for a fraction of what they cost at Marine stores. Deep cycle batteries have thicker plates and will last longer. They're meant to be discharged about 50 %. You can get a 100 amp hour size 24 battery at these places for about $45. The best way to make them last though is to invest in a multi-cycle battery charger or you'll be buying them again sooner than later. With one of these and being plugged into shore power, you'll always be topped off and ready to go.
 
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Ron

Batteries ?

Before replacing mine. I did some footwork on batteries. Batteries are designed differently for different applications. Deep cycle has bigger plates and Starting batteries have "lotsa" plates. Why not do this... Buy a Good Starting battery and call it battery (1) Get a Deep Cycle and call it battery (2) Get a switch to keep them separate. Use battery (1) to start the engine. And when sailing or docked use #2 for the house bank. You could add an isolator, combiner, solar charger, Heart interface... My father once told me "Son you get what you pay for." I won't scrimp on batteries, they run my VHF radio!
 
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Dave

Deep cycle

Hi David: If you look at a comparable size deep cycle vs dual purpose, you will find that the deep cycle has just as many Marine Cranking AMPs (MCA's) or more than the dual purpose. The Deep cycle well stand up to your starting loads and provide more deep discharges. I would go with two deep cycles. Dave S/V Westwind
 
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David

Thanks! Any more Ideas?

I appreciate the advice! Any one else got an opinion? Is it bad to go with 1 dual purpose & 1 deep? Should the batteries be the same? Also, I have a 2 batteries switch. Can I wire the deep cycle type together on "1" put a starting battery on "2"?
 
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Rob Rich

1 Starter, 1 Dual Purpose

I use one starter for my inboard engine, and one dual purpose for my electronics. Having an inboard requires a little more umph on the start, so I use the starting battery there. Electronics run on the dual-purpose, which seems to run great. I can start off it too, very easily. The reason for this setup is that I never want to be without my engine when I need it. The other day my starting battery was dead because I accidently left the circuit open when I left the boat. The radio was on, and so was a light. A simple throw of the battery switch to the dual purpose lit the engine right up. When out at anchor, you can run the dual purpose completely down, and still be assured of a powerful crank from the starter battery, and the running engine will start to recharge the depleted battery. Mind you - I generally don't stay out for more than a weekend. Any longer than that, and a deep cell might pay off. By the way - I have heard that starting off deep cell batteries is not good for them, and that they can't put up the amps a dual purpose can when partially discharged. I have not been able to verify that myself however. Check out other folks setups in your marina, cross-reference with their crusing styles and a good dose of battery knowledge. If you look up deep-cell on a search engine, you will find lots of info. Good Luck! Rob
 
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