Hey fellas. I help my buddy maintain his Hunter and we were wondering about giving ourselves more battery time before motor restarts for recharging. Typically we'll listen to the FM radio on bat #2 until it runs down, then we'll switch to #1 to restart the motor and do a full recharge. We never touch the juice in bat #1, always saving it to restart the motor. We have an extra battery and were wondering if there is a way to piggy back this one onto bat #2 to give us more radio time between motor restarts...or if this is even recommended? And is there anyplace here on the net I might find these kind of jumper cables? Thanks so much friends.
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make two batteries function as one
You can wire a third battery in parallel on number two. Wiring in parallel will make two batteries function as one battery with double the reserve power. Make sure that the two batteries are similar (e.g. same type (wet, AGM, etc), same design (deep, starting, etc.), and of course both 12volt). With this setup you don't need to change your battery switch, isolator, or charging setup.
You can wire a third battery in parallel on number two. Wiring in parallel will make two batteries function as one battery with double the reserve power. Make sure that the two batteries are similar (e.g. same type (wet, AGM, etc), same design (deep, starting, etc.), and of course both 12volt). With this setup you don't need to change your battery switch, isolator, or charging setup.
Parallel ? - No way
It is not a good idea to parallel two batteries specially when they are able to supply increadible current. It would be similar to connecting two lakes of different water levels. One battery will try to charge the other battery with unregulated and incredible amount of current. This will lead to extreme heat generated, fire and explosion is not out of the question. I would recommend adding a battery switch similar to battery control switch #1 and #2. This will switch the back up battery with the weak battery. Also never connect all three batteries at the same time to charging system since the alternator may not be able to supply the current needed to charge all three of them and will self destruct. Happy sailing !
It is not a good idea to parallel two batteries specially when they are able to supply increadible current. It would be similar to connecting two lakes of different water levels. One battery will try to charge the other battery with unregulated and incredible amount of current. This will lead to extreme heat generated, fire and explosion is not out of the question. I would recommend adding a battery switch similar to battery control switch #1 and #2. This will switch the back up battery with the weak battery. Also never connect all three batteries at the same time to charging system since the alternator may not be able to supply the current needed to charge all three of them and will self destruct. Happy sailing !
Joe?
Hello, No offense Joe, but I don't think you really understand batteries or electrical systems. Battery banks built from parallel 12V batteries are used all the time. And most people will tie ALL the batteries together for charging. Finally, alternators are rated for a certain amount of power output. If the alternator is connected to one dead battery or a 100 dead batteries it will just put out full power. Barry
Hello, No offense Joe, but I don't think you really understand batteries or electrical systems. Battery banks built from parallel 12V batteries are used all the time. And most people will tie ALL the batteries together for charging. Finally, alternators are rated for a certain amount of power output. If the alternator is connected to one dead battery or a 100 dead batteries it will just put out full power. Barry
Barry, I agree with you...
Joe, again no offense but, you seem to have a lot of BAD info on batteries and electrical systems. To increase the capacity of a battery you have to add another battery (presumably similar in age, size and voltage) in Parallel.
Joe, again no offense but, you seem to have a lot of BAD info on batteries and electrical systems. To increase the capacity of a battery you have to add another battery (presumably similar in age, size and voltage) in Parallel.
Joe, some of your advise is based in good logic
Some of it is giving an impression that it can't be done. I have been paralleling batteries for years, it just needs to be done properly and if done properly paralleling 2 batteries is perfectly fine. As was mentioned to earlier, it is important to have not only have the same type, but many feel you should have identical batteries that are purchased new at the same time, from the same place. Best would be to have both batteries from the same manufacturing lot (date code is stamped on the battery). Then it would be best to just leave them paralleled for the life of its use. As was alluded to by Joe, if you let one get more used than the other there is a possibility that over time it would have more internal resistance and drain the other stronger battery. Here are some links to creating House Banks and paralleling batteries and the advantages of one big house bank and a separate dedicated Starter battery http://www.amplepower.com/primer/prefer/index.html http://www.solar4power.com/solar-power-battery.html http://www.vonwentzel.net/Battery/03.Banks/index.html Also the comment that you should "never connect all three batteries at the same time to charging system since the alternator may not be able to supply the current needed to charge all three of them and will self destruct." Is a bit misleading. I have been charging multiple batteries from both a stock alternator and "knock off" higher amp battery (really a regular alternator that just modified) and its been working fine for years (I have a 400 Ah house bank and a 50 A/H starter battery) Any decent stock alternator will produce their rated current for hours on end, many of the stock alternators are actually "tuned down" and can handle the heat dissipation at the lower currents they are speced for. Its those Stock Alternators that are brought to a local "Alternator shop" and rewired to 100 amps that you need to worry about, as they are not designed to dissipate that heat for hours at a time, be especially wary in the tropics. If you had a stock alternator at lets say 35 amps, it would work fine charging your 3 batteries it just might take longer to full charge if you ran the batteries way down. The real issue is if you live on the the hook alot and on those batteries and you only use the engine once in a while, then you would never fill back up what you are taking out. If we were being realistic & you are expecting to have a house bank of lets say 2 - 110 Amp/Hour batteries for a total of 220 A/H's. The 35 or 55 amp Stock alternators might be a little small and it would take longer to recharge that bank if fully depleted, but its doable. In fact the typical wet cell Flooded battery bulk-charged only accepts at an ampere rate of about 25% of amp-hour capacity. That would mean you'd only be able to put in about 55 amps max for that limited "Bulk Charge" phase and if you put in less it would be ok. Plus you've gotta remember that the current loss of your 3rd (Starter) battery that only needs to produce energy for 5-10 secs is minimal. Maybe 3-5 A/H's (probably less)
Some of it is giving an impression that it can't be done. I have been paralleling batteries for years, it just needs to be done properly and if done properly paralleling 2 batteries is perfectly fine. As was mentioned to earlier, it is important to have not only have the same type, but many feel you should have identical batteries that are purchased new at the same time, from the same place. Best would be to have both batteries from the same manufacturing lot (date code is stamped on the battery). Then it would be best to just leave them paralleled for the life of its use. As was alluded to by Joe, if you let one get more used than the other there is a possibility that over time it would have more internal resistance and drain the other stronger battery. Here are some links to creating House Banks and paralleling batteries and the advantages of one big house bank and a separate dedicated Starter battery http://www.amplepower.com/primer/prefer/index.html http://www.solar4power.com/solar-power-battery.html http://www.vonwentzel.net/Battery/03.Banks/index.html Also the comment that you should "never connect all three batteries at the same time to charging system since the alternator may not be able to supply the current needed to charge all three of them and will self destruct." Is a bit misleading. I have been charging multiple batteries from both a stock alternator and "knock off" higher amp battery (really a regular alternator that just modified) and its been working fine for years (I have a 400 Ah house bank and a 50 A/H starter battery) Any decent stock alternator will produce their rated current for hours on end, many of the stock alternators are actually "tuned down" and can handle the heat dissipation at the lower currents they are speced for. Its those Stock Alternators that are brought to a local "Alternator shop" and rewired to 100 amps that you need to worry about, as they are not designed to dissipate that heat for hours at a time, be especially wary in the tropics. If you had a stock alternator at lets say 35 amps, it would work fine charging your 3 batteries it just might take longer to full charge if you ran the batteries way down. The real issue is if you live on the the hook alot and on those batteries and you only use the engine once in a while, then you would never fill back up what you are taking out. If we were being realistic & you are expecting to have a house bank of lets say 2 - 110 Amp/Hour batteries for a total of 220 A/H's. The 35 or 55 amp Stock alternators might be a little small and it would take longer to recharge that bank if fully depleted, but its doable. In fact the typical wet cell Flooded battery bulk-charged only accepts at an ampere rate of about 25% of amp-hour capacity. That would mean you'd only be able to put in about 55 amps max for that limited "Bulk Charge" phase and if you put in less it would be ok. Plus you've gotta remember that the current loss of your 3rd (Starter) battery that only needs to produce energy for 5-10 secs is minimal. Maybe 3-5 A/H's (probably less)
Joe...
Joe...that is just so wrong. Paralleling is done to increase CAPACITY not voltage. Here is an example f how to wire two or more batteries in parallel for the original poster. http://www.freesunpower.com/images/parallel1.gif
Joe...that is just so wrong. Paralleling is done to increase CAPACITY not voltage. Here is an example f how to wire two or more batteries in parallel for the original poster. http://www.freesunpower.com/images/parallel1.gif
Are you charging these??
Are you charging these batteries with an outboard motor or an inboard motor? If it's an outboard you may want to invest in a solar panel. Small outboards can only put out 2-3 amps of charge no matter what the battery state is. A 12V car stereo can very easily burn up to 2-5 amps depending on volume, configuration etc.. So if you listen to your stereo for three hours you've potentially used 15Ah's. Now you would have to run your outboard motor for close to 5 hours to fully replenish the batteries (not even including for charge inefficiency). If you have an inboard motor you most likely have an alternator putting out between 35 and 55A and it would take much less time to bring the batteries back to 90%. Note that I did NOT say 100%!
The batteries decide how many amps they will accept, at a certain rate of charge, SOC & votlage, it still takes a long time to fully reach 100%. My batteries will accept my alternators full output when discharged to 50% but at 90% full they only accept 3 to 5A. On a 400 amp hour house bank 90% means you still have 40 amp hours to put back into the batteries plus charge inefficiency. At 3 to 5A and declining as SOC increases this still takes a very, very LONG time despite our large 100 amp alternator.
This is why I supplement motor charging with a solar panel. When I leave the boat on the mooring the batteries get topped off throughout the week regardless of where I left them when I turned off the motor. A solar panel is a good idea no matter how large your alternator. Yes you can parallel a house bank with IDENTICAL batteries with the SAME DATE CODES and PURCHASED AT THE SAME TIME. Avoid adding a new battery to another used battery or you will certainly shorten the life of the new battery.
Are you charging these batteries with an outboard motor or an inboard motor? If it's an outboard you may want to invest in a solar panel. Small outboards can only put out 2-3 amps of charge no matter what the battery state is. A 12V car stereo can very easily burn up to 2-5 amps depending on volume, configuration etc.. So if you listen to your stereo for three hours you've potentially used 15Ah's. Now you would have to run your outboard motor for close to 5 hours to fully replenish the batteries (not even including for charge inefficiency). If you have an inboard motor you most likely have an alternator putting out between 35 and 55A and it would take much less time to bring the batteries back to 90%. Note that I did NOT say 100%!
The batteries decide how many amps they will accept, at a certain rate of charge, SOC & votlage, it still takes a long time to fully reach 100%. My batteries will accept my alternators full output when discharged to 50% but at 90% full they only accept 3 to 5A. On a 400 amp hour house bank 90% means you still have 40 amp hours to put back into the batteries plus charge inefficiency. At 3 to 5A and declining as SOC increases this still takes a very, very LONG time despite our large 100 amp alternator.
This is why I supplement motor charging with a solar panel. When I leave the boat on the mooring the batteries get topped off throughout the week regardless of where I left them when I turned off the motor. A solar panel is a good idea no matter how large your alternator. Yes you can parallel a house bank with IDENTICAL batteries with the SAME DATE CODES and PURCHASED AT THE SAME TIME. Avoid adding a new battery to another used battery or you will certainly shorten the life of the new battery.
paralleling batteries ...
Skippers thanks for your response. The fact that batteries should not be simply paralled even if they are of the same type and size is proven with the fact that batteries used in boats are physically very large and contain the ability to deliver much more current. The voltage remains at nominal 12 volts. That is if paralleling was a good idea, then why is it that you DO NOT find 6 batteries paralled in these boats, but you find two of them with a switch. You may be lucky that they work for now. Each battery has its own internal resistance or impedance. This is the inherant ability to loose its charge even if nothing is connected to its terminals. As batteries age its ability to hold charge will decreas. This will increase the load on the battery that it is parralled with and draw more and more current. If it works for you then best of luck - but I would not try that on my boat.
Skippers thanks for your response. The fact that batteries should not be simply paralled even if they are of the same type and size is proven with the fact that batteries used in boats are physically very large and contain the ability to deliver much more current. The voltage remains at nominal 12 volts. That is if paralleling was a good idea, then why is it that you DO NOT find 6 batteries paralled in these boats, but you find two of them with a switch. You may be lucky that they work for now. Each battery has its own internal resistance or impedance. This is the inherant ability to loose its charge even if nothing is connected to its terminals. As batteries age its ability to hold charge will decreas. This will increase the load on the battery that it is parralled with and draw more and more current. If it works for you then best of luck - but I would not try that on my boat.
Peukert
Battery (bank) Amp/Hour capacity varies with the discharge rate. The higher the discharge rate, the lower the capacity. Lower discharge rates result in higher capacity. Because paralleling batteries doubles the combined (bank) A/H Capacity, a given load will discharge the bank at Half the Rate. This increases the battery bank’s effective capacity. The formula for calculating how long a battery (or battery bank) will really last can be calculated - Search < Peukert’s Formula > for more information. camaraderie ‘s link shows improper parallel connections. The load should be connected to the positive of one battery, and the negative of the other.
Battery (bank) Amp/Hour capacity varies with the discharge rate. The higher the discharge rate, the lower the capacity. Lower discharge rates result in higher capacity. Because paralleling batteries doubles the combined (bank) A/H Capacity, a given load will discharge the bank at Half the Rate. This increases the battery bank’s effective capacity. The formula for calculating how long a battery (or battery bank) will really last can be calculated - Search < Peukert’s Formula > for more information. camaraderie ‘s link shows improper parallel connections. The load should be connected to the positive of one battery, and the negative of the other.
Joe
In your prior response contained below, there are a number of inaccuracies, stated as fact, with which you should be aware - "paralleling batteries ... Skippers thanks for your response. The fact that batteries should not be simply [paralled] [sp] - paralleled- even if they are of the same type and size is proven with the fact that batteries used in boats are physically very large and contain the ability to deliver much more current." The misconception under which you are thinking is that large batteries somehow preclude the need to parallel - as only one example, I'd suggest you consider how the US NAVY operated submarines so successfully for so many years. Until someone invents and figures out how to move a 1000 amp battery, paralleling will always be acceptable, practical and appropriate. "The voltage remains at nominal 12 volts. That is if paralleling was a good idea, then why is it that you DO NOT find 6 batteries paralled in these boats, but you find two of them with a switch[?]." You might want to visit some bigger boats. "You may be lucky that they work for now. Each battery has its own internal resistance or impedance. This is the inherant[sp] -inherent- ability to loose its charge even if nothing is connected to its terminals. As batteries age [its] -their- ability to hold charge will decreas[e]. This will increase the load on the battery that it is [parralled] -paralleled- with and draw more and more current. If it works for you then best of luck - but I would not try that on my boat." My only point in repeating here is to ensure no one unfamiliar with electrical systems takes your comments above as fact
In your prior response contained below, there are a number of inaccuracies, stated as fact, with which you should be aware - "paralleling batteries ... Skippers thanks for your response. The fact that batteries should not be simply [paralled] [sp] - paralleled- even if they are of the same type and size is proven with the fact that batteries used in boats are physically very large and contain the ability to deliver much more current." The misconception under which you are thinking is that large batteries somehow preclude the need to parallel - as only one example, I'd suggest you consider how the US NAVY operated submarines so successfully for so many years. Until someone invents and figures out how to move a 1000 amp battery, paralleling will always be acceptable, practical and appropriate. "The voltage remains at nominal 12 volts. That is if paralleling was a good idea, then why is it that you DO NOT find 6 batteries paralled in these boats, but you find two of them with a switch[?]." You might want to visit some bigger boats. "You may be lucky that they work for now. Each battery has its own internal resistance or impedance. This is the inherant[sp] -inherent- ability to loose its charge even if nothing is connected to its terminals. As batteries age [its] -their- ability to hold charge will decreas[e]. This will increase the load on the battery that it is [parralled] -paralleled- with and draw more and more current. If it works for you then best of luck - but I would not try that on my boat." My only point in repeating here is to ensure no one unfamiliar with electrical systems takes your comments above as fact
Just goes to show you
You can't believe everything you read on the internet. Joe, I'm am not a certified marine electrician however I rented one for one hour to discuss how to best upgrade the electrical system on my new boat. I brought the boat to a marina that he was working in, brought him on board and together we inspected the system and discussed what works and what doesn't. It was probably the best $70 that I ever spent on the boat. I suggest that you do the same. Also pick up a book or two on marine electrical systems. This is not a radical new idea but a tried and true technique. The information is out there. 4
You can't believe everything you read on the internet. Joe, I'm am not a certified marine electrician however I rented one for one hour to discuss how to best upgrade the electrical system on my new boat. I brought the boat to a marina that he was working in, brought him on board and together we inspected the system and discussed what works and what doesn't. It was probably the best $70 that I ever spent on the boat. I suggest that you do the same. Also pick up a book or two on marine electrical systems. This is not a radical new idea but a tried and true technique. The information is out there. 4
Be careful when making the connection.....
between batteries. If one is fully charged, and the other is significantly discharged, then you'll find the one case in which Joe's advice holds true..... the fully charged battery will deliver a LOT of current to the discharged one, with potentially disastrous results. (when you work on batteries that take truckloads of electrolyte as I did, you learn to be careful about stuff like that) Joe, if you'd like to debate your ideas, I'm sure there are a lot of us who would happily join a thread on electrical issues. But if you insist on on giving advice that flies in the face of what many of us accept as good practices to those who are looking for it, I'm afraid you're going to find a LOT of dissent, especially when your advice departs significantly from the conventional wisdom. My completely unsolicited advice: Buy a copy of 'Boatowners Mechanical and Electrical Manual' by Don Casey. Read it, learn the basics and develop a sound foundation for your opinions. And don't worry, there's room here for more than 1 opinion, and the 'conventional wisdom' isn't a hard and fast rule.... but if you differ from it, you really should have a good basis for your positions. Cheers, Bob s/y X SAIL R 8
between batteries. If one is fully charged, and the other is significantly discharged, then you'll find the one case in which Joe's advice holds true..... the fully charged battery will deliver a LOT of current to the discharged one, with potentially disastrous results. (when you work on batteries that take truckloads of electrolyte as I did, you learn to be careful about stuff like that) Joe, if you'd like to debate your ideas, I'm sure there are a lot of us who would happily join a thread on electrical issues. But if you insist on on giving advice that flies in the face of what many of us accept as good practices to those who are looking for it, I'm afraid you're going to find a LOT of dissent, especially when your advice departs significantly from the conventional wisdom. My completely unsolicited advice: Buy a copy of 'Boatowners Mechanical and Electrical Manual' by Don Casey. Read it, learn the basics and develop a sound foundation for your opinions. And don't worry, there's room here for more than 1 opinion, and the 'conventional wisdom' isn't a hard and fast rule.... but if you differ from it, you really should have a good basis for your positions. Cheers, Bob s/y X SAIL R 8
Info resources, agree with Bob, Bob and Don
Joe's just plain wrong. Please download and read the Ample Power Primer. see the link All boats with more than two batteries HAVE to parallel at least two, unless they have three banks which is unusual. We have four batteries, three in the house bank and a separate starting battery.
Joe's just plain wrong. Please download and read the Ample Power Primer. see the link All boats with more than two batteries HAVE to parallel at least two, unless they have three banks which is unusual. We have four batteries, three in the house bank and a separate starting battery.
I think I know what Gord May meant
Yes, that link that camaraderie sent did have the batteries wired up correctly But once again Gord was right, the wiring could be a "tad" better not that its wired incorrectly.The "best" way to wire mutliple batteries in parallel is to have the positive lead going out to your "house +" to be on one battery and the negative lead for your going "house ground" to be on the furthest battery away from the positive lead so as to ensure as even an electrical flow as possible through all batteries. The positive and negative should be on "kitty corner" to each otherIn the picture in the link that camaraderie sent the top batteries would be sourcing a tad more current than the middle battery and even more than the bottom battery due to resistance from the cables and the batteries themselves. Its not a lot but it is something (ps. I know my electrical "stuff" pretty well, but he does know his stuff even more and he's one of the few I would defer to on this subject)Let me see if I can find a Diagram
Yes, that link that camaraderie sent did have the batteries wired up correctly But once again Gord was right, the wiring could be a "tad" better not that its wired incorrectly.The "best" way to wire mutliple batteries in parallel is to have the positive lead going out to your "house +" to be on one battery and the negative lead for your going "house ground" to be on the furthest battery away from the positive lead so as to ensure as even an electrical flow as possible through all batteries. The positive and negative should be on "kitty corner" to each otherIn the picture in the link that camaraderie sent the top batteries would be sourcing a tad more current than the middle battery and even more than the bottom battery due to resistance from the cables and the batteries themselves. Its not a lot but it is something (ps. I know my electrical "stuff" pretty well, but he does know his stuff even more and he's one of the few I would defer to on this subject)Let me see if I can find a Diagram
Tom no need...
I fully under stand but a novice may have totally misunderstood having looked at Cam's link and then reading Gord's comment. I always do opposite end take offs as it is a best practice and industry suggested.. I understand what Gord meant, but the diagram is still not wrong it could just be slightly better.
I fully under stand but a novice may have totally misunderstood having looked at Cam's link and then reading Gord's comment. I always do opposite end take offs as it is a best practice and industry suggested.. I understand what Gord meant, but the diagram is still not wrong it could just be slightly better.
Joe may have missed something here.
Joe may have missed something here. He is correct that you should not be mixing batteries of different sizes and different ages. That part of his argument is correct. As Stu points out most any boat with any battery capacity will have batteries in parallel. One of the fellows in our harbor has a brand new Nordic Tug with about 6 - 6vdc batteries in series/parallel to supply his 12vdc system. I have used this type of a system for several years on my boat without any battery problem. The larger the battery bank the less your percentage of discharge (longer life).
Joe may have missed something here. He is correct that you should not be mixing batteries of different sizes and different ages. That part of his argument is correct. As Stu points out most any boat with any battery capacity will have batteries in parallel. One of the fellows in our harbor has a brand new Nordic Tug with about 6 - 6vdc batteries in series/parallel to supply his 12vdc system. I have used this type of a system for several years on my boat without any battery problem. The larger the battery bank the less your percentage of discharge (longer life).
Thanx Tom et al
Thanks to Main Sail, Bob V, & especially Tom S (whose diagram perfectly illustrates my point).
Thanks to Main Sail, Bob V, & especially Tom S (whose diagram perfectly illustrates my point).
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