Battery Monitor installation advice needed please

[Waterloo Sunset]

Hi All

 

I am looking to install a Clipper BM2 solely for my leisure bank, but I am confused about the wiring.  All the negatives on the leisures, 3 off,  and starter are connected together, which I have found is common practice via previous threads on here.  The negative return is currently (pardon the pun) connected to the starter battery.

 

Do I fit the shunt between the negative return and reconnect to the starter battery or should I fit the shunt and the negative return to one of the leisure terminals?  My limited eletrickery knowledge tells me this is irrelevant since the negative's are all linked anyway.

 

Also, along with the 25mm sq. negative return is a ~10mm OD negative wire which appears to be connected to the Sterling Battery Charger for when on landline.  I deduce this since it and a thin red/black wire of bell wire size disappear into a conduit together.  The red/black is definitely connected to the battery charger and a black cable of similar size also connects.  I have no way of testing this as my voltmeter wires are not long enough.

 

The BM2 manual says nothing else should be connected to the negative return/shunt post.  Is this 'other' connection an issue to correct operation of the BM2?

 

Thanks in advance.

[Tracy D'arth]

All the "out" negatives must connect to the same side of the shunt, the other side of the shunt connects to the negatives of the starter and the combined negatives of the leisure bank batteries. There must be nothing connected to the battery side of the shunt other than battery main cables. And therefore nothing else connected to the battery negatives other than the shunt.

[ditchcrawler]

This is a little sketch I did for someone

 

[Tracy D'arth]

3 minutes ago, ditchcrawler said:

This is a little sketch I did for someone

 

I would include the starter battery on the other side of the shunt as otherwise any split charging system will not tell the truth on the BMS.

[Waterloo Sunset]

5 hours ago, Tracy D'arth said:

All the "out" negatives must connect to the same side of the shunt, the other side of the shunt connects to the negatives of the starter and the combined negatives of the leisure bank batteries. There must be nothing connected to the battery side of the shunt other than battery main cables. And therefore nothing else connected to the battery negatives other than the shunt.

I interpreted the "out" negatives as the negative returns so wired it like the image below... Before is at the top, below it the way i re-wired it.  Starter battery on the left, 3 leisures on the right

 

Turned the isolator back on, everything powered up, no bang, BM2 gives a reading so all seems OK.  However, when i turn on the engine (the engine starts at least) the BM 2 still says the leisures are discharging!?!?!

 

 

Edited August 7, 2022 by Waterloo Sunset

[Tracy D'arth]

1 minute ago, Waterloo Sunset said:

I interpreted the "out" negatives as the negative returns so wired it like the image below... Before is at the top, below it the way i re-wired it.  Starter battery on the left, 3 leisures on the right

 

Turned the isolator back on, everything powered up, no bang, BM2 gives a reading so all seems OK.  However, when i turn in the engine (the engine starts at least) the BM 2 still says the leisures are discharging!?!?!

 

 

Thin wires wrong way round on shunt?   Or have you got a neutral some where shorted to the hull?

[Iain_S]

5 hours ago, Tracy D'arth said:

deleted as I dunno how I ended up quoting it!

Move the starter battery negative to the "boat" side of the shunt. Ditchcrawler's drawing is correct

Edited August 7, 2022 by Iain_S

[Waterloo Sunset]

21 minutes ago, Tracy D'arth said:

Thin wires wrong way round on shunt?   Or have you got a neutral some where shorted to the hull?

So move the 10mm OD wire to the other side of the shunt?

21 minutes ago, Iain_S said:

Move the starter battery negative to the "boat" side of the shunt. Ditchcrawler's drawing is correct

Sorry Iain, I know im being stupid but, which wire do you mean with "Starter battery negative"?  The one linking the starter and leisures?

 

EDIT.. Like this?

 

Edited August 7, 2022 by Waterloo Sunset
Add image

[Tracy D'arth]

10 minutes ago, Waterloo Sunset said:

So move the 10mm OD wire to the other side of the shunt?   NO!

Sorry Iain, I know im being stupid but, which wire do you mean with "Starter battery negative"?  The one linking the starter and leisures?

 

EDIT.. Like this?

 

No!    The thin wires to the battery management module.

 

I'm bowing out of this as the op is getting confused. And confusing advice.

[Waterloo Sunset]

2 minutes ago, Tracy D'arth said:

No!    The thin wires to the battery management module.

 

I'm bowing out of this as the op is getting confused. And confusing advice.

Thin wires to the BMS are correct to instructions at both the shunt and on the choc block connecting the BMS to the shunt cable.   I double checked that against the install instructions and cannot see any chance for grounding since we very carefully pulled the cable through the bulkhead and there are no signs of chaffing on the sheath of the connecting wire.

 

Thanks for your help.

[Tony Brooks]

attery.

19 minutes ago, Waterloo Sunset said:

So move the 10mm OD wire to the other side of the shunt?

Sorry Iain, I know im being stupid but, which wire do you mean with "Starter battery negative"?  The one linking the starter and leisures?

 

EDIT.. Like this?

 

 

This diagram will prevent the shunt from showing any charge or discharge for the domestic batteries but would show for the engine battery.

[Waterloo Sunset]

11 minutes ago, Tony Brooks said:

attery.

 

This diagram will prevent the shunt from showing any charge or discharge for the domestic batteries but would show for the engine battery.

SO like this then Tony?

[Tony Brooks]

I think so, although I am still trying to work out what Tract was talking about with a split charging system. This is not saying she is wrong, just that I don't understand. If you have any domestic loads wired earth return they will not be monitored in this diagram, but you should not.

[Waterloo Sunset]

Thanks Tony

 

Now wired up as per.  Interestingly, I can see no evidence of any relay or split charge relay in the engine bay.  This may because the previous owners stayed permanently in a marina and on a shoreline.  There was only 300 hours on the engine when we bought her, despite being a 2007 boat so, perhaps, they relied solely on shoreline for leisure charging?

 

Thank you to all for all your help.

[Tony Brooks]

17 minutes ago, Waterloo Sunset said:

I can see no evidence of any relay or split charge relay in the engine bay. 

 

If you have two alternators you do not need any split charging system, it is only used on single alternator engines. Some split charge components might be used for special purposes on twin alternator boats, but it is far from the nor. 

[nicknorman]

1 hour ago, Tony Brooks said:

I think so, although I am still trying to work out what Tract was talking about with a split charging system. This is not saying she is wrong, just that I don't understand. If you have any domestic loads wired earth return they will not be monitored in this diagram, but you should not.

You didn't understand it because she was wrong. The latest diagram is correct.

If the meter is still reading discharge when its charging, the shunt or thin wires are the wrong way round.