Electrical Set Up In Boats

[Luvit]

Started another thread as this subject always has many peoples opinions.

I have copied this from another site and it does a good job in explaining different options I think. 

I hadn't thought of 'When the boat is docked, off is selected. On odd numbered days, I'd start with battery 1. On even numbered days I'd start with battery 2' good idea and will use it from now on.

 

 The reason, I suspect, that these threads keep coming up is that there is never a satisfying answer. Most of the answers are correct given the boat they are describing. The problem is that not all boats are wired alike. These answers might describe a boat that is not similar enough to the posters boat to be helpful. To make matters worse, answers often seem to directly contradict each other. Never run on 1&2 vs always run on 1&2? How can both answers be right? While I suspect my answer is too long to be satisfying, I'll try to explain anyways. Now would be a good time to grab a beer.

First, what's the point of having two batteries on your typical single outboard boat? I think the point is to make sure you can start your engine even if one of your batteries goes bad or is run flat by overuse of electronics or pumps. You might have other reasons. If so, ignore everything you are about to read.

For a dual battery system to work it needs to be operated properly. If an owners manual was handy it could shed some light. Blind faith in what the previous owner told you might do the trick. What you did with your previous boat might work as well. Keep in mind that just because it seems to work for you doesnt mean you'll always have the option of switching to a second battery to get you going again. You might be doing it wrong but just never got caught.

You can run a battery pretty far down and still have a good shot at starting up for the trip home. How far down depends on many factors from the size and even age of the engine to the temperature of the battery. It would be great if batteries came with little fuel gauges to show how many "starts" were left in there. But they dont. Unless you want to spend few hundred per battery for a battery monitor that tracks the power entering the battery through charging and leaving the battery though use you'll have to do this blind. And even if you wanted to spend the money, the capacity of a battery changes as it ages so that gets tricky too. It used be that cars came equipped with ammeters. With one you could tell the rate at which your battery was charging or discharging. A battery monitor is just a fancy gadget that keeps a constant eye on your ammeter to track the net power left in the battery. 

Now since nobody wants to spend their hard earned gas money on fancy electronics that wont catch them any fish, what's a guy to do? Well it turns out that the voltage of a battery that's not in use can give you a pretty good idea about how much power is available. A "full" battery should show somewhere around 12.5-12.7 volts. But if it's recently received some it could easily read well over 13 volts even if it's not fully charged. Likewise, a "full" battery that just made three failed attempts at starting your F300 could read below 11 volts and still be good for many more starts. While a well rested "dead" battery would show in the 10 volt range or worse. If you are going to judge your battery by voltage, just remember that it should sit unused for 30 minutes or so to get an accurate picture. Note that my Garmin (and I'd assume others) equipment has "low voltage" alarms to gives a heads up that you might be running out of juice.

When you first get in your boat prior to a trip out, before starting the engine or using any heavy loads, you might consider checking the voltage on your batteries to see where you stand. Who knows, that heavy rain might have triggered your bilge pump enough to drain the battery as well as the bilge. While your engine is likely to start, you'd want to make sure you run it for a couple of hours to fully charge the batteries. And yes, bringing a near dead battery back to full charge can easily take hours.

So a dual battery system is a simple fix right? Just put in a switch to select which battery you'll run from and run from the better of the two... or maybe just connect the engine starter to one and all of you accessories to the other and not even bother with a switch? Either way would work great right up until you run one of the batteries dead... and that would happen! If the system was as simple as described, one of your batteries would never get charged. 

The big question about any dual battery system (remember, this is a post about dual battery systems) is how do we keep both batteries charged? The simplest system would be to just tie both batteries together (in parallel) to form a single larger battery: positive to positive, negative to negative. Both would get charged at the same time, but both would also get drawn down at the same time. The good news is that together they would last twice as long. But, you could still run them too far down to start the engine if you're not careful. (With this method it's very important that both batteries are of the same type, size, and age).

To keep one battery ready at all times, we cant have both batteries connected unless we add some smarts to the system. A battery isolator provides the smarts we need. Think of one as replacing that positive-positive connection between the batteries with a switch that only connects the batteries when the engine is running (and the alternator is providing a charge). Now, we can connect all of our accessories to the second battery and only worry about drawing from it when the engine is off. The isolator will separate the two batteries and prevent the accessories from draining the starting battery. This pretty close to ideal. The downside is when the starting battery goes dead there is no easy way to use the accessory battery (often called the house battery) to start the engine. 

Or, we could go with one of those "off - 2 - 1&2 - 1" battery selector switches. The switch will let us select which of the two batteries we'll run. If one doesnt start the engine, the other one might. If we are drifting with the engine off while battery 1 is selected, we'll only be drawing down battery 1. Battery 2 will be ready to get us going again when the time comes. Combined with the battery isolator the selector switch gives us everything we could ever ask for. Using this setup also means it's not necessary to call one battery a house battery and the other the starter battery. Both are used for both purposes depending on the switch position.

When the boat is docked, off is selected. On odd numbered days, I'd start with battery 1. On even numbered days I'd start with battery 2. Short of actually tracking which battery was used on the last trip this method does a great job of keeping the usage of both batteries even. Picking one battery for the day, or switching batteries each time you start the engine or 1 for out 2 for back are all simply variations designed to prevent overuse of just one battery. Switching every time you start the engine, in the worst case, could lead to two dead batteries if you're not careful. I think picking one for the trip and sticking with it till it's dead is safer but might be worth arguing about. Now if bad luck falls upon you and neither battery will start the engine, there's still hope. Select 1&2, cross your fingers, and try again. In a system with an isolator, this the only time I can think of where using the 1&2 position makes any sense. And of course "off" when docked only works if your bilge pump is connected directly to just one battery. 

Do all boats with "off - 2 - 1&2 - 1" selector switches have battery isolators? I dont know. I do know that mine does. I have a fairly new Yamaha F300 that has the battery isolator built into the engine. Do all boats with isolators have them connected properly? Maybe. But as a pessimist I have to doubt it. So how can you tell if your boat has a properly connected battery isolator?. You could follow the wiring or read the owners manual or just take the voltmeter from the tool box and check yourself. With a properly connected isolator and a running engine, the voltage readings at both batteries should be above 13 volts (this indicates charging). If only one battery is above 13 volts, only that battery is being charged. Some fancy isolators make sure that one battery gets a good charge before connecting to the second battery, so you might have to test a couple of times.

What if your boat doesnt have a battery isolator but has an "off - 2 - 1&2 - 1" selector switch? In that case it's up to you to make sure that both batteries get a good charge. This is the only other time I can think of for using the 1&2 position of the selector. I really dont like the idea of moving the selector switch while the engine is running. But without an isolator, there might be no choice. The 1&2 position will have the boat running from both batteries and the alternator will be charging both batteries. The problem is with accidentally hitting the 'off' position of the switch. Bad things are said to happen to the engine's electrical system when the engine is running and the battery is taken out of the circuit. Further, even if you dont hit the 'off' position not all selector switches are "make before break"... meaning that between positions could be the same as off. Is your selector switch "make before break"? Also, dont forget to select just one of the batteries if you stop the engine for a while. Otherwise your accessories will be drawing from both batteries and might leave you without a way home.

Hopefully, I've given folks some ideas about what goes into a dual battery system and what questions to ask about systems they already have or might want. Multiple engines and large accessories (loud audio, inverters powering microwave ovens, fridge) help to complicate things but the same basic questions exists: which battery am I drawing from, how does it get recharged, how long does charging take? Knowing these answers will help you to make the right choices about how you operator your boats batteries.

 

[Angry51]

My Patrol has a dual battery system, it starts on the starter battery, when

it's charged it switches to the aux battery, in other words it's charging two batteries.

If the starter battery is flat you push the big black button on the dash

that joins the two batteries together and whoopee.

The charge does not leak back from 2 to 1.

Would have to lift the bonnet to tell you what brand it is.

Fitted thru TJM.

[Luvit]

I have a similar system in my Prado (Redarc) I have had no problem in my car however, l have heard that VSR Voltage Sensative Relays can be a little unreliable in a boat environment. 

I sure there will be many that have had no problems at all and others that have. 

At least if we give our own experiences then others can decide what is best for their situation. 

 

[benno573]

interesting topic...

having re-wired a yacht that included 2 x starting batteries and a deck of 4 house batteries as well as a wind generator and solar input, there are many many different versions of what is "right".  we went with the "you should be able to charge everything from the engine if required" option which enabled the house batteries to be managed mostly by the wind/solar inputs, however, if a decent run under engine power was on the cards, the ability to switch to charging the house batteries once the starting batteries were completely topped up was a huge advantage. 

My personal preference in a more standard boat would be to have 2 good quality high spec hybrid batteries (i.e. starting and deep cycle) connected in parallel making a bank for both house and starting battery.  If these were each 750-800 CCA and 120AH, this would give ample cranking to start any outboard, and plenty of capacity to run sounders, GPS, lights, fridge etc, as well as simple charging direct from any input of both batteries at all times.  It's a simple appoach (from a simple person) but I personally feel the more bits and pieces you throw in there and expose to salt and corrosion the more that potentially could go wrong, leaving you unable to charge batteries or unable to select a specific battery.

Other things I used to do was to regularly check the resistance of the cables and clean the terminals to ensure they are not corroding and power can transfer to/from the engine with miminal loss.

[Drop Bear]

On 20/03/2019 at 5:53 PM, Angry51 said:

My Patrol has a dual battery system, it starts on the starter battery, when

it's charged it switches to the aux battery, in other words it's charging two batteries.

If the starter battery is flat you push the big black button on the dash

that joins the two batteries together and whoopee.

The charge does not leak back from 2 to 1.

Would have to lift the bonnet to tell you what brand it is.

Fitted thru TJM.

I want one of those. Sounds perfect

 

[Drop Bear]

On 21/03/2019 at 12:30 PM, benno573 said:

interesting topic...

having re-wired a yacht that included 2 x starting batteries and a deck of 4 house batteries as well as a wind generator and solar input, there are many many different versions of what is "right".  we went with the "you should be able to charge everything from the engine if required" option which enabled the house batteries to be managed mostly by the wind/solar inputs, however, if a decent run under engine power was on the cards, the ability to switch to charging the house batteries once the starting batteries were completely topped up was a huge advantage. 

My personal preference in a more standard boat would be to have 2 good quality high spec hybrid batteries (i.e. starting and deep cycle) connected in parallel making a bank for both house and starting battery.  If these were each 750-800 CCA and 120AH, this would give ample cranking to start any outboard, and plenty of capacity to run sounders, GPS, lights, fridge etc, as well as simple charging direct from any input of both batteries at all times.  It's a simple appoach (from a simple person) but I personally feel the more bits and pieces you throw in there and expose to salt and corrosion the more that potentially could go wrong, leaving you unable to charge batteries or unable to select a specific battery.

Other things I used to do was to regularly check the resistance of the cables and clean the terminals to ensure they are not corroding and power can transfer to/from the engine with miminal loss.

I had loose battery connections the other day.... took me 10 mins to notice.... so don't ask me about elec-trickery...

 

[Drop Bear]

On 20/03/2019 at 11:42 AM, Luvit said:

Started another thread as this subject always has many peoples opinions.

I have copied this from another site and it does a good job in explaining different options I think. 

I hadn't thought of 'When the boat is docked, off is selected. On odd numbered days, I'd start with battery 1. On even numbered days I'd start with battery 2' good idea and will use it from now on.

 

 The reason, I suspect, that these threads keep coming up is that there is never a satisfying answer. Most of the answers are correct given the boat they are describing. The problem is that not all boats are wired alike. These answers might describe a boat that is not similar enough to the posters boat to be helpful. To make matters worse, answers often seem to directly contradict each other. Never run on 1&2 vs always run on 1&2? How can both answers be right? While I suspect my answer is too long to be satisfying, I'll try to explain anyways. Now would be a good time to grab a beer.

First, what's the point of having two batteries on your typical single outboard boat? I think the point is to make sure you can start your engine even if one of your batteries goes bad or is run flat by overuse of electronics or pumps. You might have other reasons. If so, ignore everything you are about to read.

For a dual battery system to work it needs to be operated properly. If an owners manual was handy it could shed some light. Blind faith in what the previous owner told you might do the trick. What you did with your previous boat might work as well. Keep in mind that just because it seems to work for you doesnt mean you'll always have the option of switching to a second battery to get you going again. You might be doing it wrong but just never got caught.

You can run a battery pretty far down and still have a good shot at starting up for the trip home. How far down depends on many factors from the size and even age of the engine to the temperature of the battery. It would be great if batteries came with little fuel gauges to show how many "starts" were left in there. But they dont. Unless you want to spend few hundred per battery for a battery monitor that tracks the power entering the battery through charging and leaving the battery though use you'll have to do this blind. And even if you wanted to spend the money, the capacity of a battery changes as it ages so that gets tricky too. It used be that cars came equipped with ammeters. With one you could tell the rate at which your battery was charging or discharging. A battery monitor is just a fancy gadget that keeps a constant eye on your ammeter to track the net power left in the battery. 

Now since nobody wants to spend their hard earned gas money on fancy electronics that wont catch them any fish, what's a guy to do? Well it turns out that the voltage of a battery that's not in use can give you a pretty good idea about how much power is available. A "full" battery should show somewhere around 12.5-12.7 volts. But if it's recently received some it could easily read well over 13 volts even if it's not fully charged. Likewise, a "full" battery that just made three failed attempts at starting your F300 could read below 11 volts and still be good for many more starts. While a well rested "dead" battery would show in the 10 volt range or worse. If you are going to judge your battery by voltage, just remember that it should sit unused for 30 minutes or so to get an accurate picture. Note that my Garmin (and I'd assume others) equipment has "low voltage" alarms to gives a heads up that you might be running out of juice.

When you first get in your boat prior to a trip out, before starting the engine or using any heavy loads, you might consider checking the voltage on your batteries to see where you stand. Who knows, that heavy rain might have triggered your bilge pump enough to drain the battery as well as the bilge. While your engine is likely to start, you'd want to make sure you run it for a couple of hours to fully charge the batteries. And yes, bringing a near dead battery back to full charge can easily take hours.

So a dual battery system is a simple fix right? Just put in a switch to select which battery you'll run from and run from the better of the two... or maybe just connect the engine starter to one and all of you accessories to the other and not even bother with a switch? Either way would work great right up until you run one of the batteries dead... and that would happen! If the system was as simple as described, one of your batteries would never get charged. 

The big question about any dual battery system (remember, this is a post about dual battery systems) is how do we keep both batteries charged? The simplest system would be to just tie both batteries together (in parallel) to form a single larger battery: positive to positive, negative to negative. Both would get charged at the same time, but both would also get drawn down at the same time. The good news is that together they would last twice as long. But, you could still run them too far down to start the engine if you're not careful. (With this method it's very important that both batteries are of the same type, size, and age).

To keep one battery ready at all times, we cant have both batteries connected unless we add some smarts to the system. A battery isolator provides the smarts we need. Think of one as replacing that positive-positive connection between the batteries with a switch that only connects the batteries when the engine is running (and the alternator is providing a charge). Now, we can connect all of our accessories to the second battery and only worry about drawing from it when the engine is off. The isolator will separate the two batteries and prevent the accessories from draining the starting battery. This pretty close to ideal. The downside is when the starting battery goes dead there is no easy way to use the accessory battery (often called the house battery) to start the engine. 

Or, we could go with one of those "off - 2 - 1&2 - 1" battery selector switches. The switch will let us select which of the two batteries we'll run. If one doesnt start the engine, the other one might. If we are drifting with the engine off while battery 1 is selected, we'll only be drawing down battery 1. Battery 2 will be ready to get us going again when the time comes. Combined with the battery isolator the selector switch gives us everything we could ever ask for. Using this setup also means it's not necessary to call one battery a house battery and the other the starter battery. Both are used for both purposes depending on the switch position.

When the boat is docked, off is selected. On odd numbered days, I'd start with battery 1. On even numbered days I'd start with battery 2. Short of actually tracking which battery was used on the last trip this method does a great job of keeping the usage of both batteries even. Picking one battery for the day, or switching batteries each time you start the engine or 1 for out 2 for back are all simply variations designed to prevent overuse of just one battery. Switching every time you start the engine, in the worst case, could lead to two dead batteries if you're not careful. I think picking one for the trip and sticking with it till it's dead is safer but might be worth arguing about. Now if bad luck falls upon you and neither battery will start the engine, there's still hope. Select 1&2, cross your fingers, and try again. In a system with an isolator, this the only time I can think of where using the 1&2 position makes any sense. And of course "off" when docked only works if your bilge pump is connected directly to just one battery. 

Do all boats with "off - 2 - 1&2 - 1" selector switches have battery isolators? I dont know. I do know that mine does. I have a fairly new Yamaha F300 that has the battery isolator built into the engine. Do all boats with isolators have them connected properly? Maybe. But as a pessimist I have to doubt it. So how can you tell if your boat has a properly connected battery isolator?. You could follow the wiring or read the owners manual or just take the voltmeter from the tool box and check yourself. With a properly connected isolator and a running engine, the voltage readings at both batteries should be above 13 volts (this indicates charging). If only one battery is above 13 volts, only that battery is being charged. Some fancy isolators make sure that one battery gets a good charge before connecting to the second battery, so you might have to test a couple of times.

What if your boat doesnt have a battery isolator but has an "off - 2 - 1&2 - 1" selector switch? In that case it's up to you to make sure that both batteries get a good charge. This is the only other time I can think of for using the 1&2 position of the selector. I really dont like the idea of moving the selector switch while the engine is running. But without an isolator, there might be no choice. The 1&2 position will have the boat running from both batteries and the alternator will be charging both batteries. The problem is with accidentally hitting the 'off' position of the switch. Bad things are said to happen to the engine's electrical system when the engine is running and the battery is taken out of the circuit. Further, even if you dont hit the 'off' position not all selector switches are "make before break"... meaning that between positions could be the same as off. Is your selector switch "make before break"? Also, dont forget to select just one of the batteries if you stop the engine for a while. Otherwise your accessories will be drawing from both batteries and might leave you without a way home.

Hopefully, I've given folks some ideas about what goes into a dual battery system and what questions to ask about systems they already have or might want. Multiple engines and large accessories (loud audio, inverters powering microwave ovens, fridge) help to complicate things but the same basic questions exists: which battery am I drawing from, how does it get recharged, how long does charging take? Knowing these answers will help you to make the right choices about how you operator your boats batteries.

 

Good read thanks mate. I think I should leave this stuff to experts.