I have two 12v batteries hooked up in the usual serial way to meet minimal requirements. Can I hook up a smart charger to one of them, turn the battery switch to both, and charge them both? Or do I have to charge them separately?
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drynoc
Battery Charging
They are identical batteries bought from West Marine three years ago. And right, I meant to say that they are in parallel. But I tried to charge them both at the same time with the switch set to both, and it didn't work. The charger said "full" after a while, but I was able to hook it up to the other battery and it charged that one separately.
They are identical batteries bought from West Marine three years ago. And right, I meant to say that they are in parallel. But I tried to charge them both at the same time with the switch set to both, and it didn't work. The charger said "full" after a while, but I was able to hook it up to the other battery and it charged that one separately.
Wildcard said:
http://www.sailnet.com/forums/gear-maintenance/22686-paralleling-batteries.html
Wildcard, I believe that to be another of boatings "Old Boater's Tales". Read the following thread carefully if you wish. I think it refutes the belief that parallel batteries need to be "identical in every way" quite well. Don't you?
http://www.sailnet.com/forums/gear-maintenance/22686-paralleling-batteries.html
drynoc, perhaps you could explain your wiring setup and problem in a little more detail. If your batteries are wired to the "Bat. 1" and "Bat.2" terminals on your selector switch, and the switch is in good working order, then setting the switch to both should effectively parallel the batteries.
The easiest way to make sure you are hooked up correctly is to measure the voltage on both batteries as you are charging and switched to "both". You should measure 13.3 to 14.5 volts, depending on the battery charger and battery type. If you measure less then 13 volts you have something hooked up wrong. If you are using a "smart" charger that calculates amp-hours out vs. amp-hours in you will get an incorrect "full" indication.drynoc said:
Lead acid batteries take 12 to 18 hours to charge to their full capacity after they reach their float voltage level. As long as your charger is maintaining the voltage at the correct level you will charge your batteries. If the voltage drops after the charger indicates full, you have a problem. There are so many different types of chargers out their it is difficult to know what it does without a full specification or operating characteristic.
Dave, I have a similar question, have read your various posts, but my understanding is more limited, so I'm not sure I'm following your advice properly.
I have two group 27 gel cell house batteries in parallel, and one group 24 wet cell maintenance free starting battery, all hooked up to a red charging switch that reads 1,2 or both. I also have shore power and a Link 10 inverter/charger.
My question is: am I causing damage to any of the batteries by charging them with the red switch on "both"--should I be charging the house batteries and the starting battery separately?
Thanks,
Frank.
I have two group 27 gel cell house batteries in parallel, and one group 24 wet cell maintenance free starting battery, all hooked up to a red charging switch that reads 1,2 or both. I also have shore power and a Link 10 inverter/charger.
My question is: am I causing damage to any of the batteries by charging them with the red switch on "both"--should I be charging the house batteries and the starting battery separately?
Thanks,
Frank.
Dave,
I was typing a reply to this then saw yours.
I wonder if he is using a portable charger? That is my guess. Maybe it is seeing the batts full after bulk and shuting down to read a false full? Can't he "fully charge" them, dissconnect them from the system, and check his open circut volatge for a SOC? Depending on the batteries, he should show 12.8 or greater, if I am not mistaken, at 100% SOC. He could also sepearte the batts and check the SOC independently. Assuming they are both not full, it is likely he has a charger problem and it is not accurately reading the batteries.
Thoughts Dave?
I think this underlines the importance of a good, multi-stage, deep cycle battery charger. As expensive as batteries are, it will make you money.
I was typing a reply to this then saw yours.
I wonder if he is using a portable charger? That is my guess. Maybe it is seeing the batts full after bulk and shuting down to read a false full? Can't he "fully charge" them, dissconnect them from the system, and check his open circut volatge for a SOC? Depending on the batteries, he should show 12.8 or greater, if I am not mistaken, at 100% SOC. He could also sepearte the batts and check the SOC independently. Assuming they are both not full, it is likely he has a charger problem and it is not accurately reading the batteries.
Thoughts Dave?
I think this underlines the importance of a good, multi-stage, deep cycle battery charger. As expensive as batteries are, it will make you money.
Frank,
Dave is much more of an expert than I am (FOR SURE), but gells charge different than wets. They cannot be in the same charge system. You can quickly cook a gell if it is over charged. You will need to change the wet to a similar gell or vice-versa, or get a seperate charger that you can set the wet or gell on. Make sure the charger on the gells is set to gell per the mfg reccomendations.
Dave is much more of an expert than I am (FOR SURE), but gells charge different than wets. They cannot be in the same charge system. You can quickly cook a gell if it is over charged. You will need to change the wet to a similar gell or vice-versa, or get a seperate charger that you can set the wet or gell on. Make sure the charger on the gells is set to gell per the mfg reccomendations.
Frank,
First of all, if you have a wet cell then it is not maintenance free. If it is maintenance free, it is a AGM or Gel cell.
If you are charging the battery types in parallel, be sure they take the same charge voltage, it may be on the battery itself or you may have to look it up online. If they take the same voltage, and the same temperature compensation slope, you can charge them in parallel, if not, then you are probably doing damage. You may be overcharging one type and causing it to vent and dry out, or undercharging one type causing excess sulfation, or both.
Re Cruisingdads comments, if you are using a portable charger, i.e. Wallyworld special for automotive use, STOP. They are OK for starting batteries only. You need to get a good quality constant voltage type charger.
SOC and voltage measurements are very dependent on temperature, and not that accurate anyway. A fully charged battery may have a open cell voltage of 2.5 volts if cold enough. The best way to determine state of charger (SOC) is to monitor the charge current into a battery. When it has leveled off to a few 100s milliamps, depending on the capacity of the battery bank, and unchanging, then you can say it is fully charged. Monitoring amp-hours out vs. amp-hours in (multiplied by the efficiency, about 95%) is another good way, I’ve seen some marine chargers that do it this way.
First of all, if you have a wet cell then it is not maintenance free. If it is maintenance free, it is a AGM or Gel cell.
If you are charging the battery types in parallel, be sure they take the same charge voltage, it may be on the battery itself or you may have to look it up online. If they take the same voltage, and the same temperature compensation slope, you can charge them in parallel, if not, then you are probably doing damage. You may be overcharging one type and causing it to vent and dry out, or undercharging one type causing excess sulfation, or both.
Re Cruisingdads comments, if you are using a portable charger, i.e. Wallyworld special for automotive use, STOP. They are OK for starting batteries only. You need to get a good quality constant voltage type charger.
SOC and voltage measurements are very dependent on temperature, and not that accurate anyway. A fully charged battery may have a open cell voltage of 2.5 volts if cold enough. The best way to determine state of charger (SOC) is to monitor the charge current into a battery. When it has leveled off to a few 100s milliamps, depending on the capacity of the battery bank, and unchanging, then you can say it is fully charged. Monitoring amp-hours out vs. amp-hours in (multiplied by the efficiency, about 95%) is another good way, I’ve seen some marine chargers that do it this way.
Frank... I think Dave will verify that ..yes you are causing damage. You say you have a link 10 charger but that is only a readout instrument and I assume you mean that you have a Xantrex charger/inverter with a link readout. The Xantrex chargers have a different setting for Gel and for Wet cells. If you are on the Gel setting...you are undercharging your wet cells and will shorten their life. If you haveit on the wet cell setting you are overcharging your gels. Battery capacity does not matter in charging but battery type does. Since the gels are more expensive and you have 2 of them, I would suggest gtting a gel starter battery and setting the system for gels, assuming the gels are still performing decently.
Dave...I've seen a lot of "maintenance free" batteries that are described as wet cells with vents advertised for automotive use. Are you saying that these are really gels?
Dave...I've seen a lot of "maintenance free" batteries that are described as wet cells with vents advertised for automotive use. Are you saying that these are really gels?
Cruisingdad, thanks for your reply. I have set the charger/inverter specifications for the gel cell specifications, as I understand they are a bit more sensitive than the wet cell, including no equalization charge.
As I am often away from the boat for weeks at a time, and I want to ensure that both house batteries and the charger remain as fully charged as possible, I put the charge switch on "both". Short of buying an additional charger, I'm not sure how to keep them all charged, without damage.
Thanks again.
Frank.
As I am often away from the boat for weeks at a time, and I want to ensure that both house batteries and the charger remain as fully charged as possible, I put the charge switch on "both". Short of buying an additional charger, I'm not sure how to keep them all charged, without damage.
Thanks again.
Frank.
Frank,
Not to worry, at least not too much. Wet cells are much more forgiving then their maintenance free brethren. Charging at the Gel settings will do less damage to the wet cells then the other way around.
If you equalize your wet cells every two months or so it will help reverse the sulfation that will occur with the undercharge. You will need a separate charger for that, maybe even one of those (dare I say it) portable cheepies from Wallyworld. As long as it will bring the wet cells up to their equalize voltage that should be good enough. Be sure to disconnect the wet cells from the Gel when doing this.
Not to worry, at least not too much. Wet cells are much more forgiving then their maintenance free brethren. Charging at the Gel settings will do less damage to the wet cells then the other way around.
If you equalize your wet cells every two months or so it will help reverse the sulfation that will occur with the undercharge. You will need a separate charger for that, maybe even one of those (dare I say it) portable cheepies from Wallyworld. As long as it will bring the wet cells up to their equalize voltage that should be good enough. Be sure to disconnect the wet cells from the Gel when doing this.
Frank,
The only time I ever lost my batteries was when the charger got stuck on bulk and took the batts with them.
I put in a seperate charger for my starter. I did wire it into the system so that I can pull the starter batterty into and out of the house sytem for starting or whatever... though I never use it for house (or the house for start) at least I have it as such. Thus, with such a small wet batt, you could easily buy a cheap Xantrex charger and wire it independently for the starter and have a great redundant system. They install very easily. Now the Prosine 2.0 charger/inverter... that is another story. Thus,
DAVE.VERRY, if you are reading this, can I plese ask you a question that has been plaguing me for two weeks and several busted knuckles:
WHY DO I HAVE TO RUN A MINIMUM (MINIMUM) 4/0 OR LARGER CABLE WITH A PROSINE 2.0????????!!!!!!!! The charger was cheap compared to the cost of that freaking cable and lugs, trips to the hospital, a month in confession... etc.
The only time I ever lost my batteries was when the charger got stuck on bulk and took the batts with them.
I put in a seperate charger for my starter. I did wire it into the system so that I can pull the starter batterty into and out of the house sytem for starting or whatever... though I never use it for house (or the house for start) at least I have it as such. Thus, with such a small wet batt, you could easily buy a cheap Xantrex charger and wire it independently for the starter and have a great redundant system. They install very easily. Now the Prosine 2.0 charger/inverter... that is another story. Thus,
DAVE.VERRY, if you are reading this, can I plese ask you a question that has been plaguing me for two weeks and several busted knuckles:
WHY DO I HAVE TO RUN A MINIMUM (MINIMUM) 4/0 OR LARGER CABLE WITH A PROSINE 2.0????????!!!!!!!! The charger was cheap compared to the cost of that freaking cable and lugs, trips to the hospital, a month in confession... etc.
The only reason I can think of would be voltage drop during startup inrush current. Remember, all wire and connections are resistors, with very small values. If the inverter takes a large amount of current to start, the voltage drop in a smaller wire may drag the voltage on the inverter input connections below a critical value, possibly causing it to oscillate on and off during startup. I am not familiar with this particular inverter so can't say for sure. A quick call or email to the manufacturer may be able to answer the question.Cruisingdad said:
I feel for you, many a time I've scraped my knuckles on large cable crimps. 4/0 does seem a little excessive.
Dave,
Yep, I called them, more than once, for an explanation on just that thing.
The first "gentleman" I spoke to gasped over the phone with frustration when I explained to him that there was a missprint in his manual (ie, 4/0 wire). He told me that 4/0 was the absolute minimum and I should consider larger. I explained to him that I did not know there was such a thing as larger wire and how was I suppose to run larger wire on a sailboat?? He seemed to infer some comment about putting my big girl pantys on and dealing with it. I told him I did wear big girl pantys but my wallet was on training pants and hung up on him. I then called back and spoke to the next techinical engineer that something about the, "...phase of the joobah, hooking into the jewah, causes a voltage drop in the wah-wah, and 4/0 this and that... now give me your credit card number..."
His comments were very helpful too so I hung up on him.
SO I am faced with a cable that is as big around as my leg, bends like a telephone pole, and costs more than my boat did. All of this so I can have a cup of coffee without turning on the generator. Ain't wives great!!
Yep, I called them, more than once, for an explanation on just that thing.
The first "gentleman" I spoke to gasped over the phone with frustration when I explained to him that there was a missprint in his manual (ie, 4/0 wire). He told me that 4/0 was the absolute minimum and I should consider larger. I explained to him that I did not know there was such a thing as larger wire and how was I suppose to run larger wire on a sailboat?? He seemed to infer some comment about putting my big girl pantys on and dealing with it. I told him I did wear big girl pantys but my wallet was on training pants and hung up on him. I then called back and spoke to the next techinical engineer that something about the, "...phase of the joobah, hooking into the jewah, causes a voltage drop in the wah-wah, and 4/0 this and that... now give me your credit card number..."
His comments were very helpful too so I hung up on him.
SO I am faced with a cable that is as big around as my leg, bends like a telephone pole, and costs more than my boat did. All of this so I can have a cup of coffee without turning on the generator. Ain't wives great!!
4/0 cable
Dad,
I took a look at the specs for the Prosine 2.0. With a surge capability of 4500 watts, at a low battery voltage of 10.5 volts the surge current into the inverter, assuming 90% efficiency (probably less), will be 475 amps, more then justifying the 4/0 cable. My chart says 4/0 is good for 335A continuous. Since the inverter is rated at 4500 watts they are obligated by the safety agencies (read UL) to specify a cable at least that size, probably more like 350 MCM.
With a 2000 watt rating, the minimum wire size should be at least 2/0 (211 amps). This is for safety to keep the wire temperature to a safe level to prevent fire and contact burns. I would not wire with anything less, and think their recommendation for 4/0 is prudent. I know it's a pain, but better safe then sorry.
They should have taken the time to explain this to you. It's incorrigible that they would leave you with the impression they did. The large wire size is to keep the wire temperature to a safe level (so your boat doesn't go up in flames) if there is a problem with the inverter or with a load the inverter is powering. Current = heat in wiring, the trick is to keep the heat to the minimum possible.
Dad,
I took a look at the specs for the Prosine 2.0. With a surge capability of 4500 watts, at a low battery voltage of 10.5 volts the surge current into the inverter, assuming 90% efficiency (probably less), will be 475 amps, more then justifying the 4/0 cable. My chart says 4/0 is good for 335A continuous. Since the inverter is rated at 4500 watts they are obligated by the safety agencies (read UL) to specify a cable at least that size, probably more like 350 MCM.
With a 2000 watt rating, the minimum wire size should be at least 2/0 (211 amps). This is for safety to keep the wire temperature to a safe level to prevent fire and contact burns. I would not wire with anything less, and think their recommendation for 4/0 is prudent. I know it's a pain, but better safe then sorry.
They should have taken the time to explain this to you. It's incorrigible that they would leave you with the impression they did. The large wire size is to keep the wire temperature to a safe level (so your boat doesn't go up in flames) if there is a problem with the inverter or with a load the inverter is powering. Current = heat in wiring, the trick is to keep the heat to the minimum possible.
I may be old fashioned, but I don't parallel my two batteries. Perhaps in really urgent circumstances, but that hasn't happened yet.
I do switch batteries after running the engine or charger to bring the duty battery up to charge.
Odd days I use #1, even days #2.
Fully charge the duty battery before switching it to reserve. Its charge will be your "Plan B" when needed.
I do switch batteries after running the engine or charger to bring the duty battery up to charge.
Odd days I use #1, even days #2.
Fully charge the duty battery before switching it to reserve. Its charge will be your "Plan B" when needed.
Drynoc,
There's been a lot of discussion here about configurations and battery types, but I don't know if anything has really been determined. Do you have two identical wet-cell batteries? I believe that has been the assumption herein. Are they both 12v in parallel, or is possible that you have a couple of 6v golf cart batteries hooked in series?
There's been a lot of discussion here about configurations and battery types, but I don't know if anything has really been determined. Do you have two identical wet-cell batteries? I believe that has been the assumption herein. Are they both 12v in parallel, or is possible that you have a couple of 6v golf cart batteries hooked in series?
Charging
I have two 12v wet cells set up in parallel. Now that I read all this, I am wondering about my charger. I can't remember the brand name, but it is a three stage, portable, smart charger purchased at West Marine. It has separate settings for various battery types and charging levels. I believe it is adequate to the task, but someone more knowledgeable might think otherwise. It makes sense to me that the charger ought to be able to charge both batteries if hooked up to one of them and with the battery control switch set to "both". It also appears that there is a difference of opinion on this. Thanks to everyone for the replies, though.
I have two 12v wet cells set up in parallel. Now that I read all this, I am wondering about my charger. I can't remember the brand name, but it is a three stage, portable, smart charger purchased at West Marine. It has separate settings for various battery types and charging levels. I believe it is adequate to the task, but someone more knowledgeable might think otherwise. It makes sense to me that the charger ought to be able to charge both batteries if hooked up to one of them and with the battery control switch set to "both". It also appears that there is a difference of opinion on this. Thanks to everyone for the replies, though.
Drynoc,
I don't profess to be an expert on batteries, battery types, and recharging. However, I believe your setup is straight forward. You may want to wait for the more knowledgeable to verify or elucidate before acting on what I am about to relate.
You have two wet-cell 12v batteries physically wired together, not through a switch or combiner circuit. With this configuration, you essentially have one 12v battery with twice the amperage capability of a single battery. As such, you should set the charger for one battery. Since you are experiencing difficulties, I would clean all of the terminals and check the electrolyte levels in the individual cells (if you have not already done so). With the batteries separated, you can charge them individually if you choose. My preferred charging arrangement would be with them interconnected, and with the positive charger cable connected to one battery and the negative charger cable connected to the other other battery. If this configuration does not work, disconnect the batteries from on another and try charging individually; you could find that one of the batteries has a problem.
Having reread your posts, it appears that your problem was in setting the charger to "Both". I'm guessing (always a bad idea) that your charger has two sets of cables. If so, you should be able to disconnect the batteries from one another, and charge them individually and simultaneously using the "Both" setting. This discussion may be pedantic, but it could help you to understand your charger.
Good luck.
I don't profess to be an expert on batteries, battery types, and recharging. However, I believe your setup is straight forward. You may want to wait for the more knowledgeable to verify or elucidate before acting on what I am about to relate.
You have two wet-cell 12v batteries physically wired together, not through a switch or combiner circuit. With this configuration, you essentially have one 12v battery with twice the amperage capability of a single battery. As such, you should set the charger for one battery. Since you are experiencing difficulties, I would clean all of the terminals and check the electrolyte levels in the individual cells (if you have not already done so). With the batteries separated, you can charge them individually if you choose. My preferred charging arrangement would be with them interconnected, and with the positive charger cable connected to one battery and the negative charger cable connected to the other other battery. If this configuration does not work, disconnect the batteries from on another and try charging individually; you could find that one of the batteries has a problem.
Having reread your posts, it appears that your problem was in setting the charger to "Both". I'm guessing (always a bad idea) that your charger has two sets of cables. If so, you should be able to disconnect the batteries from one another, and charge them individually and simultaneously using the "Both" setting. This discussion may be pedantic, but it could help you to understand your charger.
Good luck.
Someone WAS paying attention!
Exactly right! A single battery charger will charge a parallel string just as if it were one battery. Since the capacity is doubled it will take twice as long to get to the 80% charge level (when the battery reaches the float voltage for the battery) but charging the remaining 20% will take an additional 12 to 18 hours, the same for each individual battery alone on the charger.
You should set the charger as you would for a single battery.
Exactly right! A single battery charger will charge a parallel string just as if it were one battery. Since the capacity is doubled it will take twice as long to get to the 80% charge level (when the battery reaches the float voltage for the battery) but charging the remaining 20% will take an additional 12 to 18 hours, the same for each individual battery alone on the charger.
You should set the charger as you would for a single battery.
New Question
Dave (and others),
Thanks for your knowledgeable replies, but now I have a new question. You say that it should take 12 to 18 hours to top off a single battery, but I get a reading of "full" after two to three hours of charging. I charge the batteries every week during the winter, either by taking the boat out, or by hooking up the charger. Does this mean that the batteries haven't drained that much and there really isn't that much charging to do, or is that "full" reading misleading?
Dave (and others),
Thanks for your knowledgeable replies, but now I have a new question. You say that it should take 12 to 18 hours to top off a single battery, but I get a reading of "full" after two to three hours of charging. I charge the batteries every week during the winter, either by taking the boat out, or by hooking up the charger. Does this mean that the batteries haven't drained that much and there really isn't that much charging to do, or is that "full" reading misleading?
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