Battery switching query

[rgriffiths]

I have just taken charge of a boat that has 1 starter, 3 domestic, 1 alternator and a switch that has 4 positions: Off, 1, 2 or Both. The engine started fine yesterday and I had it running for a few hours.The switch was set at Both and has been all day today. Tonight I tried to start the engine but clearly the battery was drained. I guess this is because of how I had the switch set. It is strange as my meter tells me that the starter battery has about 12.3v.

 

As things are:

 

The cabin lights are on regardless of the switch being on 1, 2 or Both.

With the switch on 1 the starter motor just clicks - no turn over at all

With the switch on 2 or Both the starter motor turns the engine over but really slowly and not enough to start the engine.

 

I have had a quick look and I think that that I should have followed the following:

 

- Have the switch on 1 and start the engine

- Leave the switch on 1 for the first 10 to 20 minutes of running and then switch to Both.

- When you turn the engine off move the switch to 2 for domestic use only.

 

Is this correct? What does this switch do exactly as it doesn't seem to totally isolate the starter and the domestic?

- Leave the switch on 1 for the first 10 to 20 minutes of running and then switch to Both.

- When you turn the engine off move the switch to 2 for domestic use only.

 

Is this correct? What does this switch do exactly as it doesn't seem to totally isolate the starter and the domestic?

[John V]

I can only make an educated guess but....

 

It sounds to me as if the switch is being used as follows ;

 

position one. starter battery connected to alternator

position two. domestic battery connected to alternator

position both. both batteries connected to alternator

 

The domestic battery is connected to the domestic fuseboard hopefully via another isolator.

 

So yes in theory, position one to start engine initially will only charge starter battery

position both while cruising to charge both banks

position two only used if starter battery flat....enables domestic bank to be used to start engine or to charge only the domestic battery

 

I suspect that the engine control panel will still have power to it when the switch is in position 2 but it should be isolated if the switch is in the off position, if this is correct then you should put the isolator switch in the "off" position when the engine is not going to be used.

(Obviously you should not use the off position if the engine is still running as this could damage the alternator)

[Robbo]

It also sounds like your batteries are at end of life and can't supply the current. If you check the voltage whilst trying to start the engine this will confirm.

 

I would budget a complete set of new batteries.

Edited November 15, 2015 by Robbo

[MtB]

It also sounds like your batteries are at end of life and can't supply the current. If you check the voltage whilst trying to start the engine this will confirm.

 

I would budget a complete set of new batteries.

 

 

 

Many a set of new batteries has been purchased because of a loose v belt on the alternator.

[Robbo]

 

 

 

Many a set of new batteries has been purchased because of a loose v belt on the alternator.

I was going on the 12.3v, it's a good voltage and the batteries should be able to turn an engine nicely unless they have no capacity.

[davidc]

Leisure batteries are not designed for stating engines if you use them to many times for this purpose the leisure batteries degrade and will not be powerful enough to turn an engine even if there a re3 of them , but there will still run lights

 

if it was me I would change the switch so only starter battery only starts engine

Edited November 15, 2015 by davidc

[Robbo]

A leisure battery is quite capably of starting an engine, and you'll cause no damage in doing so. There's no internal difference from a starter battery and leisure apart from the capacity and a sticker.

 

Deep cycle batteries like traction batteries shouldn't be used as starter batteries as they can't provide the current, however as these are usually in large banks they should have no problem in doing so either.

Edited November 15, 2015 by Robbo

[MtB]

I was going on the 12.3v, it's a good voltage and the batteries should be able to turn an engine nicely unless they have no capacity.

 

 

Good point. My 24v starter motor starts the engine perfectly well even when the pair of starter batteries are down to 22.0v (11.0v each) at rest.

[davidc]

"In both construction and operation requirements vehicle and leisure batteries are different....contrary to some of the claims made a starter battery performs poorly as a leisure battery and conversely. There is no such thing as a dual purpose battery. A vehicle starter battery is designed to provide an initial burst of power in order to start the engine. By contrast a leisure battery provides a steady flow over an extended period..

[Robbo]

A leisure battery isn't different internally from a starter battery that's the point. It's why we don't recommend leisure batteries for deep cycle use as they aren't built for it.

Edited November 15, 2015 by Robbo

[rgriffiths]

Thanks for all the replies. What I am really asking is what this switch actually does. As hooked up the mains at the moment I had the starter on charge all night (it is a brand new battery by the way), and the engine started straight away. So .... now that the engine is running what do I do with this switch? Is there is method to how it should be positioned for charging?

[bottle]

OFF.. all batteries OFF

 

1. Start battery connected and ability to recharge.

 

2. Domestic batteries connected to boat system but isolated from the start battery.

 

3 Both start and domestics connected together so that the one alternator can charge both.

Only use this position when engine running or in an emergency if the start battery is flat

 

So to start engine, use No.1 when engine running use No.3 (Both). When engine not running use No.2

 

The only problem is your switch may be wired differently ie. No.1 and No. 2 may be reversed.

 

Investigation, wire tracing, will/should solve this.

[nicknorman]

Thanks for all the replies. What I am really asking is what this switch actually does. As hooked up the mains at the moment I had the starter on charge all night (it is a brand new battery by the way), and the engine started straight away. So .... now that the engine is running what do I do with this switch? Is there is method to how it should be positioned for charging?

We can't be sure exactly what this switch does as we don't know how it's wired, and there are a few possibilities. But if you select Both with the engine running, and put it to the domestic battery (2?) when you shut down that will be correct for all configurations I can think of. As mentioned, don't put it to Off with the engine running as this may damage the alternator.

 

For starting it may be necessary to put it to (1) but can't be too certain about that. The key point is to avoid leaving it on Both with the engine shut down, so as to avoid flattening the starter battery.

 

It does however rather sound as though the batteries are knackered anyway.

[rgriffiths]

Thanks Kieth. It is wired as you described (I think). I will try using the method you have suggested. It strikes me that it is easy to forget to switch from Both to 2 when pulling in for the night. I assume there is some clever kit that will manage all this for you.

Thanks Nick. It clearly was leaving it on Both was what caused my starter to drain. I won't do that again!

[bottle]

There are ways of making it 'automatic', that will involve relays and some rewiring.

 

For now, hang a big label on the start/stop, switch/key that says 'switch' or any other phrase you like that will remind you.

[ditchcrawler]

OFF.. all batteries OFF

 

1. Start battery connected and ability to recharge.

 

2. Domestic batteries connected to boat system but isolated from the start battery.

 

3 Both start and domestics connected together so that the one alternator can charge both.

Only use this position when engine running or in an emergency if the start battery is flat

 

So to start engine, use No.1 when engine running use No.3 (Both). When engine not running use No.2

 

The only problem is your switch may be wired differently ie. No.1 and No. 2 may be reversed.

 

Investigation, wire tracing, will/should solve this.

But do not change from one to the other via OFF with the engine running as it could damage your alternator.

[rgriffiths]

All good advice. Seems to be working a treat now switching to Both while running and 2 when moored. Big sign in place as suggested