I have two Group 24 maintenance-free batteries on my boat. Both are in their second season and have a relatively easy lives: I only use the batteries to start the diesel, listen to the VHF, run the depth sound, and plug my GPS into. When cruising and anchoring, I hardly ever use much juice, preferring candles/lanterns/portable radios and disk players, etc. Im a minimalist.... I have been maintaining these batteries with a 5-watt solar cell. I check both batteries before each sail with a DVM. Most times, readings are 12.6-12.8v. I realize this just tells me their state of charge and not their cranking amps. I also check the alternator output now and then and it seems to be charging well at around 14v. The other day, both batteries were "legally dead." That is, voltage was around 12v. I hooked them up to the boat's two stage charger and charged them at 15 amps for a while. They seemed to be taking the charge ok, but later with the charger off, I could see the charge falling on the DVM. I do not leave anything connected on the boat when I leave it and the main switch on the batteries, and on the panel, is always left in the "off" position. I could find no random voltage anywhere on the boat and no appliances/systems seemed to be drawing power. Do batteries less than two seasons old just go dead? What would cause this?
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Questions
Are they deep-cycle batteries? What technology are they - wet, gel, AGM? What brand? El Cheapo, or a well known marine brand? Could they be discharging through the solar cell - is there a diode in the circuit? Can you do and equalization charge on the cells? (Only for a wet-cell battery). If they are wet cells, is there any way to measure the specific gravity of the acid? You have to be careful in interpreting no-load battery voltage with a DVM. A "charged" battery will show about 13.3 volts immediately, but that voltage will slowly decay to about 12.6 volts. I just had two 4D deep-cycle batteries fail completely after 1.5 seasons! I replaced them with 4 Trojan T105's.
Are they deep-cycle batteries? What technology are they - wet, gel, AGM? What brand? El Cheapo, or a well known marine brand? Could they be discharging through the solar cell - is there a diode in the circuit? Can you do and equalization charge on the cells? (Only for a wet-cell battery). If they are wet cells, is there any way to measure the specific gravity of the acid? You have to be careful in interpreting no-load battery voltage with a DVM. A "charged" battery will show about 13.3 volts immediately, but that voltage will slowly decay to about 12.6 volts. I just had two 4D deep-cycle batteries fail completely after 1.5 seasons! I replaced them with 4 Trojan T105's.
For Derek
My batteries are sealed wet cell deep cycle types,so I know no way of testing specific gravity. The ICP solar panel claims to have a built-in diode to prevent discharging at night, but I'm testing that now with a healthy battery at home. It puts out around 19.5 vdc in direct sunlight, but only milliamps. Tonight I'll move it into the garage and see if I detect any discharging. How else would one test the diode? I don't recall the battery brand, they were provided to me new by the broker I bought the boat from 2 yrs ago. Not sure how long he may have had them on the shelf however. The price tags are still on them and indicate they are middle-to-low price range batteries ($69 ea).
My batteries are sealed wet cell deep cycle types,so I know no way of testing specific gravity. The ICP solar panel claims to have a built-in diode to prevent discharging at night, but I'm testing that now with a healthy battery at home. It puts out around 19.5 vdc in direct sunlight, but only milliamps. Tonight I'll move it into the garage and see if I detect any discharging. How else would one test the diode? I don't recall the battery brand, they were provided to me new by the broker I bought the boat from 2 yrs ago. Not sure how long he may have had them on the shelf however. The price tags are still on them and indicate they are middle-to-low price range batteries ($69 ea).
wild guess is water
My wild guess is the maintenance free aspect. It has been my experience that maintenance free means it needs water less often. If it has been two seasons or two years then you have very little acid/water left to cover the cells. I don't have any confidence in maintenance free batteries. Gel or AGM batteries are exceptions to this.
My wild guess is the maintenance free aspect. It has been my experience that maintenance free means it needs water less often. If it has been two seasons or two years then you have very little acid/water left to cover the cells. I don't have any confidence in maintenance free batteries. Gel or AGM batteries are exceptions to this.
Battery Life
Batteries have a strange life cycle. I was a mechanic in the military and learned more about batteries than I cared to know. In short: as baterries charge they sluff part of the cell plates and the material falls to the bottom of the case. When enough material falls to the bottom it comes in contact with the plates and shorts out that cell. (dead cell). Longer life batteries have a deeper case bottom which allows more sluffed material to collect before the cell shorts. One of a batteries worset enemies is heat, from charging and outside temp. Heat causes the water to evaporate and the cell to have less area for charging. A little food for thought.
Batteries have a strange life cycle. I was a mechanic in the military and learned more about batteries than I cared to know. In short: as baterries charge they sluff part of the cell plates and the material falls to the bottom of the case. When enough material falls to the bottom it comes in contact with the plates and shorts out that cell. (dead cell). Longer life batteries have a deeper case bottom which allows more sluffed material to collect before the cell shorts. One of a batteries worset enemies is heat, from charging and outside temp. Heat causes the water to evaporate and the cell to have less area for charging. A little food for thought.
Research
Pete You've been chronically undercharging your batteries. Download and Read the Ample Power Primer at www.amplepower.com. Complete and proper charging of batteries is a subject too long to discuss here. Stu
Pete You've been chronically undercharging your batteries. Download and Read the Ample Power Primer at www.amplepower.com. Complete and proper charging of batteries is a subject too long to discuss here. Stu
If everyone did what
Gee, Fred, I'm not suggesting questions stop, just recommending some reading to avoid a lot of retyping of material. I figure the old adage of teach a man to fish still works. Keep the cards and letters comin' in!!!! Stu
Gee, Fred, I'm not suggesting questions stop, just recommending some reading to avoid a lot of retyping of material. I figure the old adage of teach a man to fish still works. Keep the cards and letters comin' in!!!! Stu
Dead Horses and Batteries
Stu, et al: I don't want to kick a dead horse (or battery) and, while I think you are probably right about undercharing my batteries, and I found the "Ample Power" site interesting, and I agree that battery maintenance is a complex topic....the problem I have (other than run-on sentences) is not understanding how batteries producing about 12.8vdc on the DVM one day drop to 12v or below just a few days later. If these batteries had been undercharged for a long period of time, why would they be reading like fully charged ones? And wouldn't the decline in voltage we less precipitous? FWIW, I have once again gone over my boat's electrical systems and can find no shorts or anything drawing power with the main switch in the "off" position. The only thing connected to the batteries is the bilge pump (which is always dry and I have not reason to think it just runs when I'm not looking) and the 15 amp 2-bank charger. Is it possible for the charger to be sucking voltage from the batteries instead of providing it when I (infrequently) turn it on?
Stu, et al: I don't want to kick a dead horse (or battery) and, while I think you are probably right about undercharing my batteries, and I found the "Ample Power" site interesting, and I agree that battery maintenance is a complex topic....the problem I have (other than run-on sentences) is not understanding how batteries producing about 12.8vdc on the DVM one day drop to 12v or below just a few days later. If these batteries had been undercharged for a long period of time, why would they be reading like fully charged ones? And wouldn't the decline in voltage we less precipitous? FWIW, I have once again gone over my boat's electrical systems and can find no shorts or anything drawing power with the main switch in the "off" position. The only thing connected to the batteries is the bilge pump (which is always dry and I have not reason to think it just runs when I'm not looking) and the 15 amp 2-bank charger. Is it possible for the charger to be sucking voltage from the batteries instead of providing it when I (infrequently) turn it on?
batteries
Maintenance free batteries that cost 69.00 each are definately el-cheapo's. Stu is right, there is more stuff about batteries, charging systems, etc. in the archives then you could read in a week. Most DVM's have a amp meter setting. If yours does, disconnect the ground terminal from the battery when everything is turned off and that will tell you if anything, like your charger, is drawing current. Be careful, most DVM's wont read over 10 amps and will blow an internal fuse if you accidently try to read over 10 amps. A few thoughts, though. A "maintenance free" battery that is not an AGM or gel is definately for starting apps, not deep cycle use. Buy quality batteries, you get what you pay for. If you REALLY want to know whats going on with your electrical system, install a meter that totalizes the charging/discharging amp hours, such as a Link 10 or similar
Maintenance free batteries that cost 69.00 each are definately el-cheapo's. Stu is right, there is more stuff about batteries, charging systems, etc. in the archives then you could read in a week. Most DVM's have a amp meter setting. If yours does, disconnect the ground terminal from the battery when everything is turned off and that will tell you if anything, like your charger, is drawing current. Be careful, most DVM's wont read over 10 amps and will blow an internal fuse if you accidently try to read over 10 amps. A few thoughts, though. A "maintenance free" battery that is not an AGM or gel is definately for starting apps, not deep cycle use. Buy quality batteries, you get what you pay for. If you REALLY want to know whats going on with your electrical system, install a meter that totalizes the charging/discharging amp hours, such as a Link 10 or similar
Are the batteries really dead?
They could be just discharged. Put the battery charger on them for two or three days and then check them after they sit for 24 hours. My guess is perhaps one is weak and drawing the other down or that your solar cell is slowly discharging them. You may have left something in advertently connected to them.
They could be just discharged. Put the battery charger on them for two or three days and then check them after they sit for 24 hours. My guess is perhaps one is weak and drawing the other down or that your solar cell is slowly discharging them. You may have left something in advertently connected to them.
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