I have a two battery system on my H26 with the two largest wet cell deep cycle batteries that WalMart sells. Am going to buy a 1-2-both switch and primarily will be charging with a 2.5 watt solar panel. I'm putting the advertised-for-solar West Marine diode in the solar line and plan to hook the positive posts of both batteries together so that both batteries will charge. My questions: 1. How do I know which of the leads to put the diode in and which way the diode is to face? 2. I thought I would put a diode on the line connecting the two positive posts together to prevent the battery which powers the engine starting circuit from draining the battery powering my electronics. I would also put a diode between the battery for the electronics and the battery switch box to prevent draining through the battery switch box. So what size diodes (please be specific as I'm a 12v electronic novice. Many thanks. P.S. I've gone through the archives but haven't found these answers among the huge morass of postings.
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Online Help
Rich, I am an amateur at electronics and love to tinker in logic control. There is much online help for this type of knowledge. I used google and looked for 30 AMP diodes. I think that the size of the diode is not directly rated to size of your batteries(basically Storage area or size expressed in amp hours). The diode needs to be sized to meet or exceed the maximum load that you would introduce on the 12 volt system (amps). For instance, If you energized every 12 volt device on your boat you might draw 25 amps on your battery. In this case a 25 amp diode would be your minimum. Wiring is always sized for the load it must carry. All other devices such as swithes, relays, connectors, etc. need to be sized to meet this requirement. By merely looking at the size of the wire from your batteries, you can determine the design amp rating of your system. Another way is to look for a fuse between the battery and the battery switch. You should NEVER install a device on the system that does not meet or exceed the fuse rating. Your battery charger and alternator output should not exceed the carrying capacity of the wire to the battery. So, in my humble opinion, look for a diode rated at a minimum of 12 volts and the amperage capacity of your main wire or fuse. A diode is like an electrical check valve or backflow preventer. So the diode flow faces into to the battery on the hot side of the battery that you wish to protect from discharge. Exactly where to put it on your boat can be tricky. You would put it on the line that feeds the house circuit from your starter battery. You must make certain though, that it is not on the line to your starter circuit or electric will not flow to the starter. If there is only one wire, you will need to separate the feeds. You need to have more information about how your charger, batteriers, distribution panel, alternator, etc ar hooked up to determine how to wire it. Typically, you can get wiring diagrams from West Marine, Chapmans etc. From what you have posted, I am not sure why you intend to connect the positive terminals. Maybe you can explain what you are attempting to achieve and why. I feel certain that someone will read my reply and give you their expert opinion. Good luck Mike D
Rich, I am an amateur at electronics and love to tinker in logic control. There is much online help for this type of knowledge. I used google and looked for 30 AMP diodes. I think that the size of the diode is not directly rated to size of your batteries(basically Storage area or size expressed in amp hours). The diode needs to be sized to meet or exceed the maximum load that you would introduce on the 12 volt system (amps). For instance, If you energized every 12 volt device on your boat you might draw 25 amps on your battery. In this case a 25 amp diode would be your minimum. Wiring is always sized for the load it must carry. All other devices such as swithes, relays, connectors, etc. need to be sized to meet this requirement. By merely looking at the size of the wire from your batteries, you can determine the design amp rating of your system. Another way is to look for a fuse between the battery and the battery switch. You should NEVER install a device on the system that does not meet or exceed the fuse rating. Your battery charger and alternator output should not exceed the carrying capacity of the wire to the battery. So, in my humble opinion, look for a diode rated at a minimum of 12 volts and the amperage capacity of your main wire or fuse. A diode is like an electrical check valve or backflow preventer. So the diode flow faces into to the battery on the hot side of the battery that you wish to protect from discharge. Exactly where to put it on your boat can be tricky. You would put it on the line that feeds the house circuit from your starter battery. You must make certain though, that it is not on the line to your starter circuit or electric will not flow to the starter. If there is only one wire, you will need to separate the feeds. You need to have more information about how your charger, batteriers, distribution panel, alternator, etc ar hooked up to determine how to wire it. Typically, you can get wiring diagrams from West Marine, Chapmans etc. From what you have posted, I am not sure why you intend to connect the positive terminals. Maybe you can explain what you are attempting to achieve and why. I feel certain that someone will read my reply and give you their expert opinion. Good luck Mike D
Why I'm connecting the positive terminals
I'm connecting the positive terminals of both batteries in order to be able to charge both batteries at the same time by just connecting the solar panel through the instrument panel's lighter socket. The diode between the positive terminals is to prevent the battery on the engine's starter motor from sucking dry the battery on the electronics and light. Does that make sense? Because my solar panel is pretty wimpy when it comes to amperage, I'm concerned that the diode will decrease the solar panel output to near-zero by the time it gets to the battery...
I'm connecting the positive terminals of both batteries in order to be able to charge both batteries at the same time by just connecting the solar panel through the instrument panel's lighter socket. The diode between the positive terminals is to prevent the battery on the engine's starter motor from sucking dry the battery on the electronics and light. Does that make sense? Because my solar panel is pretty wimpy when it comes to amperage, I'm concerned that the diode will decrease the solar panel output to near-zero by the time it gets to the battery...
get aregulator
The easiest and safest thing to do is buy the solar charger regulator from West Marine. It is about $30.00 and takes all the guess work out of what size diode, etc. Simply plug the solar panel into the regulator and the regulator into a twelve volt outlet. Make sure the DC switch is on and forget about it until you return to the boat. I believe it is wise not to have it plugged in while the engine is running. Good luck.
The easiest and safest thing to do is buy the solar charger regulator from West Marine. It is about $30.00 and takes all the guess work out of what size diode, etc. Simply plug the solar panel into the regulator and the regulator into a twelve volt outlet. Make sure the DC switch is on and forget about it until you return to the boat. I believe it is wise not to have it plugged in while the engine is running. Good luck.
the diode for the solar charger
Rich, I think I understand now what you are trying to do. If you use the lighter socket then that will back feed into the house battery. You will have a diode from West Marine to protect reverse flow and draining of the battery. If you plan to connect the batteries then you will need a full size diode to meet or exceed the rating of the fuse. If the batteries are not fused, they should be. If there is no fuse on the battery then you should look at the size wire on your batteries, both to your engine and your house battery. Take the larger of the 2 and look up the carrying capacity. You also need to know the approximate length of your major battery cable from the starter or house, whichever is longer. I have put a link so you look up the amperage that correlates to wire size, length of run and amps. This will give you the minimum amp rating of the diode that you need. The reason you need to carry the full load amps is due to the fact that when you parallel the batteries it is possible that one battery could potentially carry the load for the other in unique situations. For instance, if your starter battery connection became loose, the house battery would now supplement your engine start by means of the cross over wire that you are installing. Keep in mind that my opinion is not professional advice and you should check this out with a known professional who regularly deals with this type of a situation. Good luck again, Mike D
Rich, I think I understand now what you are trying to do. If you use the lighter socket then that will back feed into the house battery. You will have a diode from West Marine to protect reverse flow and draining of the battery. If you plan to connect the batteries then you will need a full size diode to meet or exceed the rating of the fuse. If the batteries are not fused, they should be. If there is no fuse on the battery then you should look at the size wire on your batteries, both to your engine and your house battery. Take the larger of the 2 and look up the carrying capacity. You also need to know the approximate length of your major battery cable from the starter or house, whichever is longer. I have put a link so you look up the amperage that correlates to wire size, length of run and amps. This will give you the minimum amp rating of the diode that you need. The reason you need to carry the full load amps is due to the fact that when you parallel the batteries it is possible that one battery could potentially carry the load for the other in unique situations. For instance, if your starter battery connection became loose, the house battery would now supplement your engine start by means of the cross over wire that you are installing. Keep in mind that my opinion is not professional advice and you should check this out with a known professional who regularly deals with this type of a situation. Good luck again, Mike D
Many thanks!
I appreciate your input. Am now armed with diodes, wire, fuses, and a little (hopefully sufficient) knowledge for this weekend.
I appreciate your input. Am now armed with diodes, wire, fuses, and a little (hopefully sufficient) knowledge for this weekend.
Diodes
Rich, If I were doing your job I would use TWO diodes. They are very cheap. In darkness many solar panels allow a small reverse current to flow which can drain the battery. Connect the red lead + from the solar panel to one diode and then take the diode to a fuse and then on to the first (house) battery. Also connect the red solar panel + lead to a second fuse and then to the second diode, and take this to the second (engine) battery. The solar panel will then charge both batteries simultaneously, yet they cannot exchange current between them. The connections for these diodes look like the following diagram:- Panel----|>|---5 amp fuse----House battery Panel----|>|---5 amp fuse----Engine battery Sorry about the symbols but you will see something like these on the diodes. Now connect both battery negative - terminals together and to the negative (black) lead on the solar panel. Your panel seems very low power so you only require 1 Amp diodes. Don't ignore the fuses as a short could cause a fire. Also as the panel is low power there is no need to fit a regulator because the likelihood of overcharging is small. Indeed you may find the panel is not really large enough. Connect each fuse directly to the batteries rather than via your off/1/both/2 switch so the solar panel will charge whilst the main switch is off. Any problems e-mail me via the facility on this site and I will do a wiring diagram.
Rich, If I were doing your job I would use TWO diodes. They are very cheap. In darkness many solar panels allow a small reverse current to flow which can drain the battery. Connect the red lead + from the solar panel to one diode and then take the diode to a fuse and then on to the first (house) battery. Also connect the red solar panel + lead to a second fuse and then to the second diode, and take this to the second (engine) battery. The solar panel will then charge both batteries simultaneously, yet they cannot exchange current between them. The connections for these diodes look like the following diagram:- Panel----|>|---5 amp fuse----House battery Panel----|>|---5 amp fuse----Engine battery Sorry about the symbols but you will see something like these on the diodes. Now connect both battery negative - terminals together and to the negative (black) lead on the solar panel. Your panel seems very low power so you only require 1 Amp diodes. Don't ignore the fuses as a short could cause a fire. Also as the panel is low power there is no need to fit a regulator because the likelihood of overcharging is small. Indeed you may find the panel is not really large enough. Connect each fuse directly to the batteries rather than via your off/1/both/2 switch so the solar panel will charge whilst the main switch is off. Any problems e-mail me via the facility on this site and I will do a wiring diagram.
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