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Forced to buy a 'dual purpose' battery. Now what?
Hi all - this is my first post so I hope you'll all be gentle with me :-). I've been studying this forum for some time now and learning a LOT. I know, however, that some of my question has been answered many times on this forum. But I'm not completely confident in my proposed plan (below) so would love to hear your thoughts.
My two 4D wet cells are 5 years old and one of them died on the first day of a multi-day cruise. In a bit of a panic I purchased one (1) 'dual purpose' wet cell 4D from West Marine. It has 135 Ah, 290 Res. Min. and 1050 CCA. Price was $368 plus tax. I knew 100% at the time that I was probably not getting the optimal battery for my needs - but it was a pressure situation and I had the admiral and kids staring me down... It was the only battery that came close to my needs anywhere local.
Here are my 2 questions:
- Are these 'dual purpose' batteries any good? I wanted a deep cycle but there weren't any in the area and the West Marine guy promised me that this was a good choice. They seem to have small capacity compared to size (135 Ah for a 4D?)
- What should I do about the 2nd battery? It still seems to be going strong but I know people say it isn't good to have old and new batteries comingled. Can I wait? And what should I replace it with? Deep cycle or dual purpose? I know enough to get wet cell versus other.
Here is my electrical situation:
- The old battery is a deep cycle with unknown capacity (stock with a Catalina sailboat). Standard 1/2/off switch setup. No starter battery.
- 100% on moorings or anchor (no shore power) with a 50 amp alternator and internal regulator (stock Westerbeke). We generally don't want to run the engine to charge the banks more than 60-90 minutes a day. This makes me think that we may not want huge Ah capacity since we may have trouble keeping the batteries topped off.
- Refrigerator on low, auto pilot, chart plotter (no radar), and very modest lighting needs. We use the bow thruster and windlass only with the engine running.
My hypothesis, based on reading this forum, is that I should:
- Buy a new companion battery soon. Thinking 2 6V wet cell deep cycle Trojans
- Use the Trojans as primary house battery
- Use the dual purpose for starting and as backup for the Trojans. So when the Trojans drop to below 50%, cut over to the dual purpose and plan to recharge soon.
Thanks in advance for your help!
Catalina 350 sail
Last edited by Downeaster; 08-09-2012 at 02:05 PM.