#1
IP: 75.30.115.157
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Batteries 12V vs 6V
Here's a question I'm pondering...
I bought a (another) 12V battery last week after finding my less than 18 month warranty battery died an untimely death. I was able to get a full refund instead of getting a pro-rated dollar amount, so I'm a happy camper. My new battery is just a standard Group 24 AGM Deep Cycle still heavy as sin 12V battery. My slip neighbor mentioned a chapter in the "12 Volt Bible for Boats" where it discusses using 2-6V batteries in series and or 4-6V batteries in series and parallel. You not only get more storage capacity but longer battery life. Another option was having 2 12V's in parallel but all the batteries had to be the same types and amperage's. Again I think having them in series prolongs the battery life. For the moment I have 3-12V batteries, 2 of which are the same but one is dying slooooooowly. I'm considering getting 2 new 6V batteries and placing them in series for my battery #2 on the battery switch and leaving the new 12V battery on #1. Does this make any sense?
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1979 C&C36 'Dionysus' |
#2
IP: 38.102.24.136
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I don't know about the pros and cons from an electrical standpoint, but I would certainly look at an apples-to-apples comparison of weight and space consumed.
The only other thought which comes to mind is that one bad battery can take out a good one. That would suggest a greater probability of failure with two than one, all other factors being equal. Bill |
#3
IP: 161.213.49.1
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Crash
Are you using a battery charger? If so check the output. You may be over charging the batteries and burning them up. It happened to me. The charger was supposed to trickle charge after the battery was fully charged - it was't doing that. It was putting continous full charge on the battery and not going down to the trickle charge mode. I was burning batteries up right and left. TRUE GRIT |
#4
IP: 75.30.115.157
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Well here's a brief history of what happened to the 12V battery that died. Since it's an AGM type battery I'm to believe that you shouldn't allow it to run all the way down until its dead. One week several months back I forgot to recharge it and had (something) on that ran it down. I for the most part resurrected it by charging it on a car battery charger. Guess it didn't help that much.
Bill: currently each battery is connected separately and thusly charged separately. I do agree with you that one bad battery can/will take out a good one and why if wired in a series (as noted) won't? John: I with you on this one too, connected my charger and watched how it performed powering up. The idiot lights told me it went from fast to trickle charge and stayed at trickle charging after it went through its typical start up cycle. I checked it again 2 hours later and it's still showing me trickle charging. The 2 older batteries are 5 years old and as I was told by the PO the charger is the same.
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1979 C&C36 'Dionysus' |
#5
IP: 24.152.131.220
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Crash,
AGM's require a different charging profile and voltage than wet lead-acid batts and because of that I think your old charger did very little to keep them in good condition in the first place. It's for this reason that we are advised not to join up batts of different types for use or charging. Apples and oranges. Factor in AGM's are double the cost before you spring for a new charger and for me they'd have to whistle Dixie before I'd drop the dough. My old technology lead-acid batteries, charged by either an old technology NewMar battery charger or an internally regulated fixed point alternator are now over 6 years old and still perform well.
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Neil 1977 Catalina 30 San Pedro, California prior boats 1987 Westsail 32, 1970 Catalina 22 Had my hands in a few others Last edited by ndutton; 10-15-2011 at 07:59 AM. Reason: learn to proofread you moron |
#6
IP: 173.166.26.241
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I like to buy cheap deep cycle group 31 batteries and keep them charged as high as possible. Never let them go below 50%.
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#7
IP: 108.23.219.10
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Less is best!
Crash, unless you are going to upgrade the charging system stick with the lead acid batteries. And the problems that start in a battery are usually a cell going bad. If you are using 2 12V batteries you have 12 cells that could cause trouble and each one can kill that battery. If you have 2 6V ones you only have 6 cells to worry about. I use the 235 6V on my house side and a grp 24 deep cycle 12V for the start side. This was the configuration that gave e the most amps on the house side. If you have room for the 6V golf cart style they are quite durable and if you have room to go to a taller battery with the same footprint there are some 335 amp ones available that are a couple of inches taller, I wish they would fit in my battery box.
Dave Neptune |
#8
IP: 75.30.115.157
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A-hah!
Met my mechanic at the boat this morning to take care of a leaking shaft seal (dripless), no go...have to pull the boat for a big repair. Gonna do a bottom job while she's out of the water, mo monay. Made arrangements to motor over to the yard but my "new" battery wouldn't kick the engine! It must be the charger!?
Dave, I plan on using the new 12V grp 24 for starting and getting 2-6V (in series) for house. I do have the needed real estate so it should be okay??? Here's another battery related question: won't the gases from a lead acid battery be hazardous inside the cabin when recharging? Aside from spilling acid while heeled over wouldn't this be a concern? This is one reason I stuck with AGM batteries.
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1979 C&C36 'Dionysus' |
#9
IP: 174.94.27.242
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Quote:
I'd like to see a schematic of your current battery/charger system...my guess is you have been charging your AGM batteries with a charger that is set up for lead acid batteries. Like Neil says - it won't work because the charging profiles are different for AGM and lead acid batteries. Marine lead acid batteries are usually well sealed and unlikely to leak acid into the vessel - same with gasses from the charging/maintenence cycle. As long as your battery compartment is well ventilated I don't think you will have much of a problem. I have a 27 house battery and 24 starting battery fitted to an isolater which prevents the bad battery from drawing down the good battery. My charger is coupled to both batteries on seperate circuits...each one gets what it needs from the charger...I can add a third battery to the system if needed. The charger allows me to select which charging profile I want to use - either lead acid or AGM but not a combination. There are a couple of good books sold through Amazon on marine electrical systems - they are highly reccommended for sailors IMO. Cheers! |
#10
IP: 24.152.131.220
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What 67 said
Regarding vapors, a lead acid battery can emit hydrogen gas during charging but it is lighter than air and if the battery compartment is well ventilated as 67 said the gas simply migrates up and out of the cabin. Our boats are well sealed on the bottom but no so on the top.
As for spillage, it is prudent to place the batteries in a containment just in case. The common plastic battery boxes are specifically designed for that. Any sulfuric acid solution that finds its way out of mine is truly microscopic but I still want control over where it goes. The actual spillage issue I have is during distilled water replenishment due to my own sloppiness.
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Neil 1977 Catalina 30 San Pedro, California prior boats 1987 Westsail 32, 1970 Catalina 22 Had my hands in a few others |
#11
IP: 173.166.26.241
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I do not regard any type of battery as "safe" in the cabin area of a boat unless it has positive continuous uphill overboard ventilation via a dedicated hose.
Last edited by hanleyclifford; 10-15-2011 at 10:26 AM. |
#12
IP: 108.23.219.10
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Venting
I am a real stickler when it comes to fumes on a sailboat especially gasoline thus my "How do you use your blower" thread. Yes lead acid batteries do produce a bit of hrdrogen when charging and it is a lighter than air gas. I have not seen many boats sail or power that will float water tight upside-down so the gasses will escape on their own. I have seen many huge battery stacks on power boats that have a craving for electric power and the stacks sit in the engine room which is usually well vented. The only times I have ever heard of battery hydrogen being a problem is when enclosed or the enclosure vent gets plugged . It would take a lot of charging power and a bunch of batteries to produce a dangerous amout of gas, something our A-4equiped boats just don't have the POWER for.
I have been using lead acid batteries for over 40 years and have been knocked down a few times. I have not had an acid spill however I have found a few drops on the top of them and the acid is contained in my fiber galss battery boxes. I think most of this comes from the charging anyway. Now if I was going blue water sailing they would just be secured a bit better for a possible over 90 roll sometime. I still would not contain them in a box relying on a vent line which would only be reliable when regularly inspected. Dave Neptune |
#13
IP: 75.18.171.12
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67: I've attached the wiring diagram of my Chargetek TPRO 320 as requested. Pretty simple set up. I've also sent an email to the company down in Carmarillo, CA asking how to determine when a unit has failed when I have a brand spanking new battery and no shorts in the system. We shall see....
Ventilation in the battery "box"...okay that I'll have to check as the only way for ventilation (I can think of) is through a hole where the battery cables comes through from the engine compartment, then is exhausted via blower out the stern. It may or may not be adequate but its how its set up now. Oh the battery "box" is the nav station/starboard settee seat so there's access from above by lifting the cushion and access panel. So a dedicated ventilation hose is none existent (for now).
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1979 C&C36 'Dionysus' |
#14
IP: 24.152.131.220
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Not to discount Hanley's recommendation, it is an admirably high standard for battery ventilation but I can't recall ever seeing a boat manufacturer go to that length.
I mention manufacturers because besides being my background, the vast majority of us have manufactured rather than custom boats.
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Neil 1977 Catalina 30 San Pedro, California prior boats 1987 Westsail 32, 1970 Catalina 22 Had my hands in a few others |
#15
IP: 75.18.171.12
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Update and as suspected..
Soon after dinner yesterday (Saturday evening) I get an email response from the manufacturer of the battery charger indicating that I remove the charger from all batteries as it may be discharging the batteries. It goes on to say to call them to speak live with the technician so I did. How's that for customer service!? He wanted me to be at the boat and run some tests to see so off I ran to the car and off I went. Got to the boat and called him back and we ran the tests with the volt meter, turns out he was right they were discharging ever so slightly. So I was instructed to send the unit back to them for further testing. This unit is 7 years old but it was one of their first technology chargers so its due for a new one.
Back to the original question I asked re 12V vs 2-6V I think I'll stick with 2-12V (parallel connected) on bank one and 2-12V (parallel connected) on bank two. and the reason is trying to achieve sufficient amp hours for the size of boat., in my case its 300 ah.
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1979 C&C36 'Dionysus' |
#16
IP: 161.213.49.1
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I use a battery maintainer not a battery charger. It has worked well for me and the way I use my boat.
I have 6 + years on my engine start battery using the maintainer and it is still going strong. I like it. The only time I use a charger is when a battery is seriously discharged. TRUE GRIT |
#17
IP: 75.18.171.12
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John, what's the difference as most boat "chargers" maintain batteries once they are fully charged? The unit I have have has 3 levels of...charging modes Fast, Absorption and lastly being "Float" which I assume is only to maintain a fully charged battery.
__________________
1979 C&C36 'Dionysus' |
#18
IP: 161.213.49.1
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Battery Charger, Maintainer, or Hybrid?
I use my maintainer a couple of ways to monitor the health of my batteries. The same could be done with a charger that has maintainer features.
Once a battery is charged the maintainer will cycle between charging and not charging. If the maintainer is continously charging, the battery is shot. This needs to be used with a little finesse. If the battery is severly run down it will take a while to charge. This is when I get out my 10 amp charger. Eventually though, when I hook the maintainer on, it will cycle if the battery is good. Once a battery is fully charged I let it sit for a week then try to start the engine with it. Any fully charged battery that won't turn over a little low compression engine like an A4 after sitting for a week is off the boat. No messy hydrometer needed. Crash: Here's the blurb on the maintainer. You can see if your charger has a maintainer feature. TRUE GRIT |
#19
IP: 75.30.187.198
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Here's what I've learned..
The TPRO 320 battery charger is still being tested / checked out. It has the "smarts" to detect and maintain all battery types (in my case it's AGM's). It can sense the battery charge and change charging modes to maintain the batteries once they're fully charged.
I brought out my old 6/2 amp car battery charger in the garage and recharged all 3 batteries one at a time on the 2 amp setting. The older batteries were still good and holding a charge after a week after being fully charged. So it was the boat battery charger after all!! Not having much faith in the old charger I'm looking at buying a new one now. I kinda thinks the other batteries I returned or replaced were in fact still good and needlessly spent money for new batteries when I didn't have to. Thanks everyone!
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1979 C&C36 'Dionysus' |
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