simple wiring diagram

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fortynine

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I am planning to fit a 2nd battery and have one for starting and one for domestics so I searched online for a simple wiring diagram. How naive. Sure there are lots of diagrams but they are all different. One shows the feed from the alternator to a dual switch then to the batteries for starter and lights etc. In another the feed goes direct to the starter battery and then via the switch to the domestic battery,another has the starter motor connected directly to the alternator.Some have the return in series some directly from each battery and one even showed the positives connected after passing the switch. I am no electrician but I'm sure some of this would not work.
So can somebody direct me to a simple diagram of how to connect the batteries, 1-2-both switch, starter motor and alternator together. Please.
 
Google "The 12V Doctor's Practical Handbook download" and you will be able to download an older edition of this excellent book. You can buy the latest version on Amazon. In it you will find exactly what you are looking for and much, much more. The circuits are hand drawn sketches with good explanations. I highly recommend it. I bought the later edition but the older version is better as it covers more stuff.
 
+1 for Tony Brooks' TB training website

See the index to the boat electrical notes at http://www.tb-training.co.uk/cover.html

The 12 volt Doctors Handbook can be found at http://www.motoren.ath.cx/menus/electrical.php


The simplest wiring scheme for two batteries and a 1,2,both, off switch shown below..........Its one and only merit is simplicity!

Remember never ever switch to "off" while the engine is running. To change the battery selection always switch via "Both"


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http://www.cruisersforum.com/forums/f14/simple-battery-isolator-diagram-107689.html is a link to a real good diagram. I used this on my boat this summer and it worked great. wire the switch alternator directly to the house batteries. I used a Yandina battery combiner to connect the house and the starting battery. IRC it was under $100 us. This allowed me to use the house batteries to start the engine. Should they fail then the starter battery was in reserve. Start battery was always isolated but could be thrown into service with the house batteries or on its own if needed. This was really idiot proof. You just left the switch on house batteries all the time. I tested the start battery every once in awhile. worked a charm. Also b/c the alternator is wired directly to the batteries you avoid any problems with blowing a diode in your alternator when using the battery switch. Here is a link to the combiner I used -- http://www.yandina.com/c100InfoR3.htm
 
Further to my original question I have found a very useful guide on 'e-how' 'How to wire a marine battery switch' It made a lot of pennies drop. May be of use to other confused electrophobes.
 
Seadawg33 said:
. I used this on my boat this summer and it worked great. wire the switch alternator directly to the house batteries. I used a Yandina battery combiner to connect the house and the starting battery.
Click to expand...

What are you trying to gain switching the alternator to the service battery ?

Leaving the alternator on the starter battery is one less job, it means the alternator is always wired to the engine starter battery, not through a second charge system that can fail, loosing engine starting battery charge. Assuming you are not running service battery dead flat, but to 50% then the relay will come in immediately, so no different to charging the engine battery first then the service battery.

Brian
 
I agree with Halcyon. You do not so much need a diagram as an idea of what you are trying to acheive. IMHO the simplest and best way is to treat 2 different systems separately. ie engine battery to starter control panel and alternator with isolation switch. Probably as you have it now but disconnect supplies to domestic services.
Fit a deep cycle battery connected to your fuse panel for domestic services via an isolation switch.
Now connect with a heavy wire the negatives of both batteries.
Now connect the positives of both batteries together via a high current switch.
This switch is operated when the engine is running to provide charge to the domestic battery and is opened when you stop the engine. Provides complete isolation of domestic battery and load from engine battery.
This switch may be operated to provide a jump start if engine battery ever needs help. (old age or neglect).
Now to completely automate the operation you fit a voltage sensing relay between the 2 batteries so domestic batteries is charged when engine is charging but is isolated other wise. Some VSRs will incorporate a jump start connection for emergencies so that the switch battery to batteery is not needed. good luck olewill
 
halcyon said:
What are you trying to gain switching the alternator to the service battery ?

Leaving the alternator on the starter battery is one less job, it means the alternator is always wired to the engine starter battery, not through a second charge system that can fail, loosing engine starting battery charge. Assuming you are not running service battery dead flat, but to 50% then the relay will come in immediately, so no different to charging the engine battery first then the service battery.

Brian
Click to expand...

Halycon
Here is my theory. Wirirng the alternator directly to the house (service?) bank allows the alternator to start charging the batteries that get the most use directly. The way the wiring is laid out I just use the house bank for starting the engine as well as running the house. Should I run the house bank to nothing then all I need to do is to switch over to the starting battery and start the engine. I switched over as a test a couple of times over the summer b/c I wanted to ensure that the start battery was maintaining its full charge. There was never a problem.

The large cable of the alternator is putting the most amperage into the house bank. When it is fully charged it sends any remaining juice to the starting battery. Even if you used the starting battery on a regular basis, which I don't, there is not going to be that much amperage drawn off of it for starting the engine. The house batteries OTOH can be drawn down significantly by a couple days at anchor. The yardina only has a smallish #10 wire to charge the second bank so charging to a severly depleted housebank would take considerably longer then the charge directly from the alternator.

The two best things about this system are 1) it eliminates any chance of blowing the diodes in the alternator if someone should turn the battery switch when the alternator is charging and 2) you don't need to think about it. Just keep the battery switch on house and use it. Should a problem arise with your usage then switch to the start battery.

Charlie
 
Seadawg33 said:
Halycon
Here is my theory. Wirirng the alternator directly to the house (service?) bank allows the alternator to start charging the batteries that get the most use directly. The way the wiring is laid out I just use the house bank for starting the engine as well as running the house. Should I run the house bank to nothing then all I need to do is to switch over to the starting battery and start the engine. I switched over as a test a couple of times over the summer b/c I wanted to ensure that the start battery was maintaining its full charge. There was never a problem.

The large cable of the alternator is putting the most amperage into the house bank. When it is fully charged it sends any remaining juice to the starting battery. Even if you used the starting battery on a regular basis, which I don't, there is not going to be that much amperage drawn off of it for starting the engine. The house batteries OTOH can be drawn down significantly by a couple days at anchor. The yardina only has a smallish #10 wire to charge the second bank so charging to a severly depleted housebank would take considerably longer then the charge directly from the alternator.

The two best things about this system are 1) it eliminates any chance of blowing the diodes in the alternator if someone should turn the battery switch when the alternator is charging and 2) you don't need to think about it. Just keep the battery switch on house and use it. Should a problem arise with your usage then switch to the start battery.

Charlie
Click to expand...

What you are doing, normally using one bank for all purposes and maintaining a starter battery as a reserve , is the favored way in the USA. I think you will find its what Calder suggests in his book.

In the UK the favoured way is to use the starter battery for engine starting and to make it the first priority for the charging system.

Pros and cons of the two ideas have been debated on here before. In the end you just have to accept the differences in opinion.
 
Seadawg33 said:
Here is my theory. Wirirng the alternator directly to the house (service?) bank allows the alternator to start charging the batteries that get the most use directly. The way the wiring is laid out I just use the house bank for starting the engine as well as running the house. Should I run the house bank to nothing then all I need to do is to switch over to the starting battery and start the engine. I switched over as a test a couple of times over the summer b/c I wanted to ensure that the start battery was maintaining its full charge. There was never a problem.
Click to expand...

Charlie

I assume you have a 1,2, both switch ?

The main reasons for the engine/service bank/VSR layout is to maintain a clean power supply to electronics, and a fully charged battery to ensure good engine turn-over. If anchored for 2 days and a low service battery, you get engine starting with no effects to electronics, while if starting from the service bank, the starter will pull the voltage very low causing possible electronic re-sets and generate spikes in the power line.

Charge current should not be effected if you charge the service battery direct, or via relay and engine battery, assuming correct spec cables and relay contacts. As the engine battery is normally not significantly discharged, you get almost instant relay engagement, so quick charge to the service bank, so little difference in charge from either option.

Brian
 
halcyon said:
Charlie

I assume you have a 1,2, both switch ?

The main reasons for the engine/service bank/VSR layout is to maintain a clean power supply to electronics, and a fully charged battery to ensure good engine turn-over. If anchored for 2 days and a low service battery, you get engine starting with no effects to electronics, while if starting from the service bank, the starter will pull the voltage very low causing possible electronic re-sets and generate spikes in the power line.

Charge current should not be effected if you charge the service battery direct, or via relay and engine battery, assuming correct spec cables and relay contacts. As the engine battery is normally not significantly discharged, you get almost instant relay engagement, so quick charge to the service bank, so little difference in charge from either option.

Brian
Click to expand...

Brian,
Thanks for the explanation on the theory. I used that system for many years because it was the way I was taught. The thing I like about the new system that I am using is that I do not have to think (or more realistically don't forget) to turn a battery switch. The way I am wired does not preclude me from using the start battery to start the engine and if we have been anchored for a few days I guess it makes sense to do that but I don't have to worry about electronics on the boat b/c I don't have any.

I'm not sure I agree with you on the charge current but really don't have the knowledge to defend my position with certainty. If someone with more knowledge of electrical theory could step in I would love to expand my knowledge in the area:

1) With the alternator charging directly to the house/service battery larger amounts of amperage can be replaced in the battery when it is more depleted because of a batteries ability to absorb more energy when it is in a greater state of discharge --- Is this true or false.

2) As the battery is charged more and becomes less depleted the battery cannot accept as much charge and thus it takes longer to fill the top 10% of depletion then say the 50% to 60% depletion. --- I am reasonably certain that this is true.

3) With the alternator led to the starting battery. The alternator will quickly replace the energy used to start the engine and then begin to charge the service battery. Because the energy has to transfer from the starting battery to the service battery thru a smaller cable not as much electricity will be able to be replaced as quickly in the rapid absorption phase of charging because the cable that runs from the battery combiner is smaller then that used by the alternator. -- Is this true or false?

Charlie
 
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