Wiring Diagrams

Clyde_Wanderer

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Reposted due to error.
I am looking for basic drawings, one, for a 2 batt system using a 1/2 All/Off switch, as I have only one batt in situe at the moment, but want to install a seperate batt for starting purposes and want to make sure they are connected up properly.
The other diagram I need is to show how a batt level/state meter should be connected up, as I dont have the foggiest about them, but would like to know what is happening while using power/charging etc.
Appreciate any help, even a link to a site which might have such info.
Thanks, C_W.
 

William_H

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High Clyde Have youbought the 1,2,off switch yet. There are better ways to do it.
As for wiring diagram I would advocate that you design it yourself or just wire it up then draw it out for posterity.

The best IMHO is to leave the existing battery wired as is. Presumably with an isolation switch to turn off on departing the boat.

Now mount your new battery and connect the negatives together with heavy starter current capable cable.

Disconnect all your service type loads ie lights instruments from the engine battery circuit and connect to the new battery via an isolation switch. This can be low current like 30 amps capability. More would be better.

OK now you have an isolated battery for services. You need to charge it. This can be done by a switch from the point where the services previously connected to the engine battery circuit (preferable) or from the engine battery itself. to the service battery circuit but on the side of the isolation switch away from the battery.
This switch must be turned on when the engine is running and off when the engine is not running. You may be able to set up a relay that operates off an oil pressure switch to do the job automatically.
Don't use a relay running off the engine power switch cos this will connect the service battery before the engine starts. This will/may melt the relay. A really simple way to do this is witha voltage sensing relay which connects the two circuits together when the engine battery rises cos it is being charged and disconnects when the voltage falls.

Now for emergency start of the engine if the engine battery is dud you can make up a single jump lead to connect the 2 positives together. ie the service battery can boost the engine battery. Or you can wire in a heavy current switch which is only operated in emergencies from one battery pos. to the other. This is a safer option as you can get a spark when connecting the jump lead whicgh can ignite hydrogen battery gasses. It follows that the switch should be as remote as possible from the batteries.

There you have a simpe logical arrangement. You can do similar with a 1,2,off switch but this arrangement leaves the likely hood of both batteries being left connected on both all the time when in use. This means the engine starts on both batteries all the time so you don't know if one is knackered until the other drops dead. It also means the service load can still discharge the engine battery. If you do discipline to use one battery only then you risk alternator damage when you switch to both after starting unless it isa make before break switch. And still a dope might go through the off position. Which may damage the alternator.

You ask about a battery monitor. This can be a cheap voltage indication by led lights or a digital readout. There will be a +ve and a -ve wire which can be connected at the fuse box. It will indicate (perhaps) the condition of the battery and if it is being charged. You would need a switch to connect to the engine battery +ve if you had seperate systems or another monitor.

More sophisticated monitors have an amp meter and measure the current going into the battery or out of it. It records this current in a memory to indicate the cumulative total of charge and discharge.

This is a much better way of checking how the battery is going. But it is still fraught with problems like whether the battery still has the capacity it was made with. (A 50% loss of capacity is not uncommon) and once the battery is near fully charged current going in can be wasted in heat so is not available again for discharge. Fopr all that people love them.
You would need a device designed for 2 batteries or have 2 monitors if you want to include the engine battery although I think it is quite acceptable to forget the engine battery. It should always be fully charged. Thes monitoring devices have a current shunt in (usually) the negative side of the service battery. A shunt is a very low resistance resistor whichdevelopes a tiny voltage when current flows which can be measured to indicate current flow.

I would advocate that you fit an ampmeter for the service battery as a good check of the charging system. If you run the engine just to charge the battery you will see when the battery is getting near charged as the charge current gets to be a lot less to the point where further engine running might seem pointless.

So Clyde from simple to sophisticated it is worth you understanding what you are doing and why. good luck olewill
 

orizaba

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another alternative that i use is poste on a reply to AKELA re batteries/charging, about 2 days ago,simple and effective, not possible for the alternator to blow due to disconnection,you just have to enable switch to manually charge start battery,
i've used the relay type in the past and though an excellent idea i've had problems with relay failure.
 

orizaba

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the isolaters i use are the one with a red removable key /heavy duty used for battery isolation.
connsct the +cable going to your leisure/service battery and the thick charge wire coming out of your alternator onto one post of the isolater switch.
connect another cable from the other post to your start battery.
as has been mentioned before,i am assuming you have an isolater between the start battery and the starter motor,you can connect your charge wire to that as when the engine is running you will have that switch enabled.

when you start the engine you would enable the start battery switch and start as normal,all the charge will be going to your service batteries,after awhile say 1/2 hr enable the charge switch,this effectively connects all your batteries together and provides charge to your start batteries.
the reason for the heavy cables is that they will take all the power from both sets of batteries,which i,ve found useful in the past when the start battery is a bit low and the leisure batteries well charged,if you enable the switch you are effectively jump starting the start battery.
its hard to say what size cables to use as it depends on the distances they have to run, the heavier the better,think jump leads and how hot they can get under load, the cable to the alternator does not need to be as large though as its only a charging wire.
the beauty of this system is that its simple, cheap and effective,there are no electrical components to go wrong,you get no voltage losses and your alternater is connected at all times to a battery bank.
i always carry a spare switch but if it should fail and you don't have a spare you can always bolt cables too one post


this is a further explanation of the system i use
 
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