I'm going to replace the batteries in my 84 C 27, primarily for peace of mind, as they are several years old. Here's what I have: the usual two bank 12v system, identical group 27 batteries, OFF-1-BOTH-2 switch. As far as starting loads, I have the Universal M-18 (2 cyl) diesel. Other electrical loads are usually light: 2-3 hours of daysailing with depth finder, knot meter, gps, and vhf running, occasional bilge pump cycling. At this point, night time usage is minimal, and time at anchor is minimal. Occasionally, we take an overnight trip. I have shore power, but no on board charger. Should I opt for two group 27 deep cycle batteries? Or two "dual purpose" starting/deep cycle batteries? (I always keep one battery in reserve for starting.) My concerns in order of priority are 1) always have enough power to start the diesel. 2) have enough battery capacity to run all the electronics, nav lights, and the bilge pump for a significant length of time (maybe overnight) in the event of complete engine failure. 3) battery life, and 4) cost. I'd appreciate hearing your thoughts... Randy
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Bryan C.
Here's my system
People use different systems, with your limited usage you can go either way. If I were in your shoes, I'd get the biggest deep cycle you can fit, preferable two, for the house. For the starter just pick up a regular automotive battery. The deep cycle batteries will probably have enough amps to start your engine; I have two 90 amp hours for a house and they start the 3 cyclinder engine just fine. Then the starting battery becomes an emergency battery. Check it and top it off every now and then, if you need it it will start your motor. But otherwise use the house for everything. Simplifies matters, and with a bigger house bank you'll have more energy to use without worry about not being able to crank her up.
People use different systems, with your limited usage you can go either way. If I were in your shoes, I'd get the biggest deep cycle you can fit, preferable two, for the house. For the starter just pick up a regular automotive battery. The deep cycle batteries will probably have enough amps to start your engine; I have two 90 amp hours for a house and they start the 3 cyclinder engine just fine. Then the starting battery becomes an emergency battery. Check it and top it off every now and then, if you need it it will start your motor. But otherwise use the house for everything. Simplifies matters, and with a bigger house bank you'll have more energy to use without worry about not being able to crank her up.
Get a charger first.
Randy: Get yourself a good smart battery charger before you do anything. If you are not recharging your batteries properly you are not doing anything to maximize their life. I would recommend a Statpower True Charge 20 plus. Then I would recommend that you take a look at your battery options. You can stay with flooded batteries if you like. Your other options are to move up to AGM or Gels. I see no reason not to go with two (2) deep cycle battery banks. You may also want to consider a battery isolator. If you have a smart charger it can handle any of these types. If you decide to stay with the flooded batteries it even has the smarts to run them through a cycle which helps to keep them from sulfating. This is their equalization mode. If you decide that you want to add an additional battery to your house bank, it can handle that. I have recently switched from Gels to AGMs. I purchased these for about $120 ea. I am hoping to get similar battery life from the AGM's as I got from the Gels (10 + years). If you always charge on both and only run from one battery you should not have a problem starting your engine. As far as cost goes, your TYPICAL flooded battery is going to cost about $60 and is going to last about 3-4 years. This is assuming that you are charging them properly and keeping them topped off with water. If you go the "more expensive route" you should double or even triple the life and only double cost. You will also eliminate maintenance (no terminals to clean, no water to fill, and no fumes to worry about). Check out your options.
Randy: Get yourself a good smart battery charger before you do anything. If you are not recharging your batteries properly you are not doing anything to maximize their life. I would recommend a Statpower True Charge 20 plus. Then I would recommend that you take a look at your battery options. You can stay with flooded batteries if you like. Your other options are to move up to AGM or Gels. I see no reason not to go with two (2) deep cycle battery banks. You may also want to consider a battery isolator. If you have a smart charger it can handle any of these types. If you decide to stay with the flooded batteries it even has the smarts to run them through a cycle which helps to keep them from sulfating. This is their equalization mode. If you decide that you want to add an additional battery to your house bank, it can handle that. I have recently switched from Gels to AGMs. I purchased these for about $120 ea. I am hoping to get similar battery life from the AGM's as I got from the Gels (10 + years). If you always charge on both and only run from one battery you should not have a problem starting your engine. As far as cost goes, your TYPICAL flooded battery is going to cost about $60 and is going to last about 3-4 years. This is assuming that you are charging them properly and keeping them topped off with water. If you go the "more expensive route" you should double or even triple the life and only double cost. You will also eliminate maintenance (no terminals to clean, no water to fill, and no fumes to worry about). Check out your options.
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Tim McCarty
I switched to dual purpose...
last year as a kind of experiment. I bought three champions for 50.00 each at Sam's Club. I use two for the power and one for reserve. This is year two and they charge easily, keep a charge, and do fine all around. I think a lot of it depends on how much you use the boat, although, I've got to say, I use my boat quite often, primarily for day sails. I know all about gelcells and their reliability,but, like I say, this is an experiment.
last year as a kind of experiment. I bought three champions for 50.00 each at Sam's Club. I use two for the power and one for reserve. This is year two and they charge easily, keep a charge, and do fine all around. I think a lot of it depends on how much you use the boat, although, I've got to say, I use my boat quite often, primarily for day sails. I know all about gelcells and their reliability,but, like I say, this is an experiment.
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Rob Rich
My set up
My setup is identical to yours, but I have a dual purpose to run the house electrical. My aft battery is a standard marine starting battery. I generally charge the dual purpose with a battery charger that has auto-shutoff, so I hit it with 15 amps when I leave, and come back to a fully charged battery. It seems to last for days/nights at a time, and, should the emergency battery fail, can be relied upon to fire up the old Atomic 4. Kind of like a double back up, which is why I like having a dual-purpose for the house bank. I always start the engine with the starter battery, and run the engine on this cell. That is basically how I charge it, so it stays in good condition. Have yet to have a problem. Steve Dion has a good point about the newer batteries though, especially if they last for 10 years. Best Regards, Rob
My setup is identical to yours, but I have a dual purpose to run the house electrical. My aft battery is a standard marine starting battery. I generally charge the dual purpose with a battery charger that has auto-shutoff, so I hit it with 15 amps when I leave, and come back to a fully charged battery. It seems to last for days/nights at a time, and, should the emergency battery fail, can be relied upon to fire up the old Atomic 4. Kind of like a double back up, which is why I like having a dual-purpose for the house bank. I always start the engine with the starter battery, and run the engine on this cell. That is basically how I charge it, so it stays in good condition. Have yet to have a problem. Steve Dion has a good point about the newer batteries though, especially if they last for 10 years. Best Regards, Rob
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Les Andersen
New Batteries
Randy, Since you are going to replace both batteries you might want to look at type 31s. They are physically only slightly larger than 27s but carry quite a bit more charge. The battery box will need to be replaced as 31s need about 1/2 inch more length. I use 3 deep cycle wet cell 31s in a 1-2 setup and haven't had any problems with power. Think I paid about $80 per battery. Good Luck, Les s/v Mutual Fun
Randy, Since you are going to replace both batteries you might want to look at type 31s. They are physically only slightly larger than 27s but carry quite a bit more charge. The battery box will need to be replaced as 31s need about 1/2 inch more length. I use 3 deep cycle wet cell 31s in a 1-2 setup and haven't had any problems with power. Think I paid about $80 per battery. Good Luck, Les s/v Mutual Fun
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