Alternator Charging Question

[wiggy]

At present I have 2 on/off battery switches that allow me to choose which battery bank to use to start the engine/ run boat electric’s from. i Love the simplicity but need to remember to switch over to the domestic bank once the engine is started and the starter battery has had a bit of charge. If I connected the alternator output via one switch directly to the domestic bank and connected the starter battery via the other switch directly to the starter I could use a B 2 B charger to recharge the starter battery My question is will the get an excitement current to get going if the output is not to the same battery as the starting current?
Am I making this over complicated?
engine is MD2020D.

 

[neil_s]

Yes - I think you're over complicating it. When the engine isn't running - domestic on. When you want to start the engine - start on. When the engine is running - both on. I agree with your preference for simplicity, though!

 

[Refueler]

The alternator doesn't really care where the exciter feed comes from as long as its ~12v ..... because once the alternator starts charging - that feed is countered by reverse voltage taking it to net zero.

So the alternator will start charging ... where you direct the charge is up to you.

 

[[185615]]

Yes - I think you're over complicating it. When the engine isn't running - domestic on. When you want to start the engine - start on. When the engine is running - both on. I agree with your preference for simplicity, though!

The pros and cons of manually switching has been thrashed to death here, not wish to start that again, but I am in full agreement with your reply.
I have for years and never failed to do the switching as part of the start process, its automatic now, manual switching that is.

 

[Refueler]

The pros and cons of manually switching has been thrashed to death here, not wish to start that again, but I am in full agreement with your reply.
I have for years and never failed to do the switching as part of the start process, its automatic now, manual switching that is.

+!

I have the 1-Both-2-OFF switch that gets so much stick from some ... but it works.

I cannot do anything on board if its OFF .. so I need to switch on at least one battery to have any power to anything. To start engine - either will do .. and once started - I know at least one battery is charging - flick one position and both are charging. Yes I have to look to make sure I go correct direction of switch.
But its simple ....

Before I get novels about VSR's and separate switches etc. - I fully appreciate the pro's ... its just not for my old tub ...

 

[PaulRainbow]

At present I have 2 on/off battery switches that allow me to choose which battery bank to use to start the engine/ run boat electric’s from. i Love the simplicity but need to remember to switch over to the domestic bank once the engine is started and the starter battery has had a bit of charge. If I connected the alternator output via one switch directly to the domestic bank and connected the starter battery via the other switch directly to the starter I could use a B 2 B charger to recharge the starter battery My question is will the get an excitement current to get going if the output is not to the same battery as the starting current?
Am I making this over complicated?
engine is MD2020D.

If it's so simple, why the need for your proposed changes ?

 

[[185615]]

+!

I have the 1-Both-2-OFF switch that gets so much stick from some ... but it works.

I cannot do anything on board if its OFF .. so I need to switch on at least one battery to have any power to anything. To start engine - either will do .. and once started - I know at least one battery is charging - flick one position and both are charging. Yes I have to look to make sure I go correct direction of switch.
But its simple ....

Before I get novels about VSR's and separate switches etc. - I fully appreciate the pro's ... its just not for my old tub ...

+1 its the KISS principle Keep It Simple Stupid

 

[pvb]

Yes I have to look to make sure I go correct direction of switch.
But its simple ....

It's not as simple as it could be!

 

[pvb]

If it's so simple, why the need for your proposed changes ?

Simple - it's not as simple as it could be.

 

[PaulRainbow]

Whilst you people are motoring around with the switch set to both, there is a selection of faults that could leave you with two flat batteries. If you are happy having the switch on both, why bother with two "separate" batteries, why not just connect them in parallel and have an on/off switch ?

Simplicity is a battery to start the engine, with its own switch and a battery/s for domestics, with a separate switch.

 

[PaulRainbow]

+1 its the KISS principle Keep It Simple Stupid

There you go, i fixed that for you

 

[[185615]]

Whilst you people are motoring around with the switch set to both, there is a selection of faults that could leave you with two flat batteries. If you are happy having the switch on both, why bother with two "separate" batteries, why not just connect them in parallel and have an on/off switch ?

Simplicity is a battery to start the engine, with its own switch and a battery/s for domestics, with a separate switch.

We prefer a single switch thank you
You wrote all that before about what could? what if?
If ifs and buts were fruit and nuts we would all have a merry Christmas

KISS and make soft shackles

 

[Refueler]

Who says I motor around with BOTH selected unless I want to charge both ? I prefer to decide myself thank you.

I really love how people assume something and then make issue of it.

I have read so much about fit a VSR - then have isolating switch for each battery ... etc. etc.

Any system can have faults and you lose both batterys or one ... so lets leave it at that shall we.

 

[[185615]]

Who says I motor around with BOTH selected unless I want to charge both ? I prefer to decide myself thank you.

I really love how people assume something and then make issue of it.

I have read so much about fit a VSR - then have isolating switch for each battery ... etc. etc.

Any system can have faults and you lose both batterys or one ... so lets leave it at that shall we.

If only.....

 

[Refueler]

If only.....

I know its wishful thinking !

My main boat gets craned in tomorrow ... OH - I HOPE I remember how to operate my crappy 3 way switch .. maybe I should call someone to come sort it all for me ?? Oh Dear I'm all worried now. I know its getting dark out there - maybe I should run out and check it all before tomorrow !!!

 

[Caraway]

I really love how people assume something and then make issue of it.

It's the way.

 

[oldmanofthehills]

Simplicity is a battery to start the engine, with its own switch and a battery/s for domestics, with a separate switch.

Which is no use if engine battery goes flat. Simple but vulnerable unless you have bridge switch as I have added (or third battery plus bridge). I know jump leads will do and I wondered why the boat came with them until engine bat went flat on the grid.

 

[PaulRainbow]

Which is no use if engine battery goes flat. Simple but vulnerable unless you have bridge switch as I have added (or third battery plus bridge). I know jump leads will do and I wondered why the boat came with them until engine bat went flat on the grid.

Given the antiquated, stick in the mud attitude of some in this thread i didn't want to waste too much time fully explaining the system, but you are correct, there needs to be a 3rd switch for emergencies. I've posted it many times:

 

[PaulRainbow]

+!

I have the 1-Both-2-OFF switch that gets so much stick from some ... but it works.

I cannot do anything on board if its OFF .. so I need to switch on at least one battery to have any power to anything. To start engine - either will do .. and once started - I know at least one battery is charging - flick one position and both are charging. Yes I have to look to make sure I go correct direction of switch.
But its simple ....

Before I get novels about VSR's and separate switches etc. - I fully appreciate the pro's ... its just not for my old tub ...

Who says I motor around with BOTH selected

You did, see highlighted text above.

unless I want to charge both ?

And there you go again......

I really love how people assume something and then make issue of it.

No assumptions made, you just said it, twice.

I have read so much about fit a VSR - then have isolating switch for each battery ... etc. etc.

Any system can have faults and you lose both batteries or one ... so lets leave it at that shall we.

Easy to lose both batteries when you use the switch on both, or when you forget which one needs charging, or you don't charge it long enough, or when you turn it the wrong way and blow the alternator diodes, etc, etc, etc

Not so easy with two fully independent systems that just work, with no fiddling around with switches.

You are perfectly free to have whatever switching arrangement you want on your boat, i'm offering the suggestion of a more modern, robust system, as used by every single production boat builder on the planet.

 

[PaulRainbow]

We prefer a single switch thank you
You wrote all that before about what could? what if?
If ifs and buts were fruit and nuts we would all have a merry Christmas

KISS and make soft shackles

So why not just have an off/off switch, with a single battery/bank ?

Why carry lifejackets, flares, VHF, first aid kit, tools etc etc etc

Same as refueler and anyone else, you're free to us whatever system you choose and to use it however you want. The OP is clearly not entirely satisfied with what he has and want to improve it, i'm proposing a simple solution that makes his charging fully automatic (which is what his aim is) and suggesting a more robust switching arrangement. He's also free to take the suggestion up, or not.