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Why Engine battery connected to Leisure batteries?


Jay88
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I have cut and pasted this question from another topic of mine as it deviates from the original question:

 

I have noticed that the engine battery is connected to the leisure batteries (see photo) which has raised a few questions..

After scrutinising the boats Electrical System Schematic, it appears the setup from the builder is as follows;

- 2 x 80A alternators with a Sterling A-B charger and a Bat-Bat charger

     *Alternator 1 goes to the B-B charger which connects to the Bow battery and also the A-B charger

     *Alternator 2 connects to the A-B charger which then connects to the Engine battery via the Engine Battery Isolator & the Leisure batteries via the Leisure Battery Isolator   

 

So while the schematic has the engine battery and leisure batteries completely separate, why in reality are they connected? Maybe I'm reading something wrong here? I always thought that the 2 x battery banks should be separate so if the leisure batteries ever die, the engine start battery is still good to go as it's on a different system as such.

 

Thoughts?

 

I would normally take a picture of the boats electrical system schematic and post it here but it's very blurry and wouldn't be clear, maybe I'll do another PPT..

IMG_6712.JPG

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I’m afraid the picture doesn’t really tell us anything as all we can see is a couple of wires disappearing off what is presumably the starter battery.

 

But as a general point, if the starter battery is directly connected to the leisure batteries at both + and -, well you don’t have a starter and a leisure battery, you just have one battery!

 

If this is the case, possibly something failed that resulted in one of the batteries not receiving charge, and the fudge to fix that was to connect everything together.

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The picture shows the engine start battery with its + & - cables connected to the first of 6 x leisure batteries.

 

When we got the boat the previous owner had issues with one of the leisure batteries and bypassed this battery to the other leisure batteries. I can't fathom why this would mean connecting the engine battery to the leisure bank...but maybe this was already set up this way..

 

Anyway the main point is that if I disconnect the engine starter battery when I next replace the leisure batteries, I imagine this would not create any further issues with the current charging setup?

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12 minutes ago, Jay88 said:

Trust me...those cables go to the leisure batteries.

 

You are not being very helpful to those trying to advise. We need to SEE where the cables go because long experience tells us it would be very unwise to trust you or any other low post count member (and a few high post count ones). Not because yoy are untrustworthy but because all too often things have turned out to be not as the poster says they are.

 

It what you say about the connections are true then the bit about engine battery and domestic battery are untrue - as you have been told they are just one big battery bank.

 

Without more information about your charging system we can not say whet the effect of leaving the positive link between banks off will be. Maybe one bank will not get any charge or maybe all will be well. Now tell us about the charging system - how many alternators, any fancy add on charging gismos, and split charge diodes or relays? We may very well then ask you about how they are wired.

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15 minutes ago, Jay88 said:

Trust me...those cables go to the leisure batteries.

 

But that photo hasn't added to what you have said.

Why do you think this is the starter battery? If it has only one positive connection and that leads to the leisure batteries, where is the positive wire to the starter motor?

If we are to help you we need either a full set of photos showing all the relevant wiring and equipment, or a proper wiring diagram.

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I have re-checked the engine starter connections (via multiple videos & pictures I have of the boat as I'm currently not on-board) and can confirm 100% that the engine starter battery ONLY connects to the leisure batteries via the negative black cable..my bad and apologies for the mistake.

 

Soooo re-visiting the electrical schematic, it all makes sense in that the positive engine battery cable goes to the engine battery isolator which in turn is connected to the A-B charger...

 

I suppose this means my question is now mute, it is not one large battery bank. Apologies for the inconvenience!

 

 

 

Edited by Jay88
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40 minutes ago, Jay88 said:

The picture shows the engine start battery with its + & - cables connected to the first of 6 x leisure batteries.

 

When we got the boat the previous owner had issues with one of the leisure batteries and bypassed this battery to the other leisure batteries. I can't fathom why this would mean connecting the engine battery to the leisure bank...but maybe this was already set up this way..

 

Anyway the main point is that if I disconnect the engine starter battery when I next replace the leisure batteries, I imagine this would not create any further issues with the current charging setup?

It would be nice to see a photo that covers the engine battery and first leisure battery and all the connections on them. Otherwise not much point in posting any photos.


But anyway we can only go on what you have posted. It would seem unlikely that someone went to the bother of connecting both batteries together for no reason. As I said earlier, a likely reason is that something went wrong with something and one of the sets of batteries wasn’t getting charged, connecting the batteries together fudged a fix for that. So I would expect that if you separate the batteries again, one set will not get charged. But at least that will allow you to identify exactly what isn’t working as it should, and fix it properly.

 

I suppose it is also a possibility that the duff battery you mentioned, meant that there was insufficient capacity for their needs and so they connected in the starter battery to add capacity.

 

Anyway I think the message has to be yes, disconnect the two batteries from each other, but then check that both are getting charged straight away, BEFORE one of them goes totally flat!

Edited by nicknorman
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51 minutes ago, Jay88 said:

I have re-checked the engine starter connections (via multiple videos & pictures I have of the boat as I'm currently not on-board) and can confirm 100% that the engine starter battery ONLY connects to the leisure batteries via the negative black cable..my bad and apologies for the mistake.

 

Soooo re-visiting the electrical schematic, it all makes sense in that the positive engine battery cable goes to the engine battery isolator which in turn is connected to the A-B charger...

 

I suppose this means my question is now mute, it is not one large battery bank. Apologies for the inconvenience!

 

 

 

Thanks for the apology but your "transgression", was nowhere near what we so often get when we ask for clarification/more info. In any case it was as I suspected, down to lack of experience and now you have gained a bit more experience and knowledge.

 

Your charging system is not typical in that it has an A to B charger and it seems to be feeding the engine battery. As engine batteries with a serviceable engine and serviceable battery spend most of the time fully charged and only have to produce a few Ah to start the engine  (lots of Amps but for a very short time so not many Ah) start batteries normally have little use for any form of enhanced charging gizmo. On the face of it I would expect an A to B to feed the domestic bank because that is the bank that gets most discharged so such devices might help keep it charged. I suspect that once you investigate further you may well find the A to B is not connected to the engine battery unless it is a twin output job and both alternators feed into it. Then it would be used to combine both alternator outputs and the charge both banks independently but its main use would be to charge the domestic bank.

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4 hours ago, Tony Brooks said:

. I suspect that once you investigate further you may well find the A to B is not connected to the engine battery unless it is a twin output job and both alternators feed into it. Then it would be used to combine both alternator outputs and the charge both banks independently but its main use would be to charge the domestic bank.

I think that the Sterling AtoB has two independent outputs - one for the starter and one for the leisure batteries.  If so, and the positive cables from each bank disappear into the Sterling gizmo, all might well be fine in this regard.

 

 

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I have seen a few installations of Sterling AtoB units where the fitter has connected the outputs to the batteries but has omitted to disconnect the original connections between the alternators and the batteries, thus inadvertently connecting both alternators and both batteries all to each other.

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