Shunt connecting to loads

[steve yates]

Can I check I have this wired right? it does all work but I wasnt sure about the neg to loads part. I have 2 batteries but only using the bm1 to monitor the front battery. The neg from the front battery went to the neg of the back battery, then a neg cable went from there to the neg busbar in the switch panel.
So I took the neg from the front battery and attached it to the loads end of the shunt, as you can see in the pic.
Is this correct?

 

[Daverw]

Don’t think that’s right, both negatives to one side of the shunt and loads to the other side of the shunt,

 

[PaulRainbow]

It isn't right and at the risk of causing offense, you're making what should be the simplest of installations into something else.

Anyway, you connect the negative from both batteries together, then to the battery side of the shunt. All loads and charging sources go to the load side of the shunt.

With the shunt positive connected to the front battery the BM will only monitor that battery. However, if you're not bothered about the SOC reading (which is usually bollox with a BM1 anyway) you could connect the positive to the common of the 1-2-B switch and monitor the voltage and current of whichever battery is in use.

Still at a loss why you insist on doing it this way. Added gubbins = added failure points, you'll be giving the primary battery a harder life than it should have and your charging will be slower (more capacity = faster charging). You still only have the same capacity however you connect the batteries, you'd be better off with them in parallel and setting a battery alarm.

 

[Tranona]

You really are making life difficult for yourself by not paralleling those 2 batteries - although they are different types and by the looks of it sizes. If you want to use them alternately for your house loads then keep them completely separate. You can only monitor the loads when you are using the battery that the BM1 is connected to.

 

[steve yates]

It isn't right and at the risk of causing offense, you're making what should be the simplest of installations into something else.

Anyway, you connect the negative from both batteries together, then to the battery side of the shunt. All loads and charging sources go to the load side of the shunt.

With the shunt positive connected to the front battery the BM will only monitor that battery. However, if you're not bothered about the SOC reading (which is usually bollox with a BM1 anyway) you could connect the positive to the common of the 1-2-B switch and monitor the voltage and current of whichever battery is in use.

Still at a loss why you insist on doing it this way. Added gubbins = added failure points, you'll be giving the primary battery a harder life than it should have and your charging will be slower (more capacity = faster charging). You still only have the same capacity however you connect the batteries, you'd be better off with them in parallel and setting a battery alarm.

No offence taken paul, I’m learning, slowly. Before I put the shunt in, I had both positives running to the respective 1 and 2 poles on the battery selector, and both negatives connected together, with a cable going to the busbar and the loads.
Thats how the switch is supposed to be setup is it not? And if I turn the selector switch to the both series then both batteries would be in parallel, thats my understanding.
The manual said “
Disconnect the NEGATIVE terminal from the battery and connect to
the shunt as shown on Figure 1.” Which is the diag below, and noting it said not to connect anything else to that battery terminal, I took the bridging cable off the front battery, attached it to the shunt and connected the short cable from the shunt to that terminal instead.


If I read you right, I should have left the set up as it was and added the short shunt cable to the neg terminal, leaving the bridging cable in place, and then removed the cable from the neg bus from the other battery and connected that to the load end of the shunt instead.
Is that right?
By the way, does anyone else only get two thirds of a pic when enlarging the image of the batteries? I cant even see the neg terminals on my ipad except in the thumbnail.

 

[steve yates]

Oh yeah, and I should forget the amphours thing and connect the bm1 pos to the switch so I can monitor voltage and charge in and out of whatever battery is selected?

 

[oilybilge]

Sorry if I'm missing something, but if this is a standard house/starter battery set-up then I'd say Steve's got it right:

 

[Daverw]

The LHD battery shown is the starter battery, it does not show multiple house battery’s

 

[oilybilge]

The LHD battery shown is the starter battery, it does not show multiple house battery’s

Right, just seen on another thread that Steve has two house batteries and no starter. So I was missing something.

 

[mikegunn]

Right, just seen on another thread that Steve has two house batteries and no starter. So I was missing something.

In which case I don’t understand the need for a 1-2-B switch. Such a switch is normally only used where there is an engine start battery involved. As Paul R has written, why make the setup more complex than it needs to be. Simply parallel the two batteries and feed all the neg‘s through the shunt. The switch can be left in the “B” position when in use. Or am I missing something?

Mike

 

[PaulRainbow]

Oh yeah, and I should forget the amphours thing and connect the bm1 pos to the switch so I can monitor voltage and charge in and out of whatever battery is selected?

I would.

You currently have a neg from the front battery to the shunt, leave it as it is.
Remove the cable from the load side of the shunt and connect it to the front battery neg.
Remove the load cable from the other battery and connect it to the shunt load terminal.

Every negative load or charging source must go to the load terminal of the shunt. It's common practice to connect a short cable from the shunt load termainl to a terminal post or busbar, depending on the number of connections. If you only have the load cable and your solar controller to connect, you can connect directly to the shunt.

 

[steve yates]

Thanks paul, I’ll do that today. So if every charging source goes to the load terminal of the shunt, I presume that when I wire in the dual battery solar controller the negative lead to the front battery would terminate atthe the laod end of the shunt, NOT the battery terminal itself?

 

[PaulRainbow]

Thanks paul, I’ll do that today. So if every charging source goes to the load terminal of the shunt, I presume that when I wire in the dual battery solar controller the negative lead to the front battery would terminate atthe the laod end of the shunt, NOT the battery terminal itself?

Yep, nothing else connected to the battery negative other than the shunt.