Fitting a Battery Monitor

[Sailmore Nextyear]

Hi Ladies & Gents,
Has anyone fitted a battery monitor to a Bavaria Cruiser series boat (ours is a 33) 2005.
I have a monitor, and the wiring diagram shows a connection from the switched Load, connecting via the charger, to the unit +ve.
The negative obviously going via the shunt. The negative side is easy.

It's the positive I'm unsure of. Can I connect to the isolater switch? Where I'm guessing the charger Might also connect (But this IS a guess).
Its hard to see how the charger is connected (standard Q Type fitted by Clipper/Bavaria). It's also almost impossible to get to the back of the isolators (Grrr).

Has anyone done this?  Any Ideas?
Ps. may post diagram if I can work out how.

[tiger79]

The important thing with a battery monitor is that the shunt should be the only thing connected to the domestic bank's negative terminal - anything else goes to the other side of the shunt.  There's usually only one positive connection, which should go to the domestic bank's positive terminal, with an inline fuse as close as possible to the terminal.

[Sailmore Nextyear]

Thanks for reply,

Yes the diagram shows the shunt connected to the terminal and all else on the shunts other side, I forgot to mention that.
The fuses are in line between the isolator switch and the battery and I was considering attaching the monitors positive lead to the isolator switch.

I also appear to have put this post in the wrong section. Sorry everyone, I'm new to this forum, may try to move it ...

[tiger79]

The positive connection needs to go to a permanently-on positive, eg the battery positive terminal, as probably shown in the wiring diagram.

[battuta]

Yup, as tiger79 notes, the positive is one of those few things that should go directly only the battery bank (in part to allow the constant trickle flow needed for the monitor to continue monitoring while the boat is left unused).

I installed a Victron on our 2009 B31 a couple of years ago and love it!

-Riyad

[Jeff Jones]

Hi
I installed a NASA BM2 battery monitor that indicates the state of charge of the house battery and also the voltage of the house and also starter battery.

The installation is actually quite simple - it requires the shunt (which reads current flowing in AMPS) be connected directly with the - 0V (minus terminal) of the house battery, this way all energy flowing in and out of the battery is monitored.
By removing the battery -0v wire and connecting it to one side of the shunt, make up a short cable from the shunt to the -0v battery terminal you know don't need to worry the you might be bypassing something.

The display wires connect on either side of the shunt with a secondary + wire connect to the starter battery to display the start battery voltage only as well as the house battery volts / current discharge or charge and estimates how much charge is in the house battery.

The BM2 or most other battery monitors - read the voltage and current and then calculate / estimate the state of charge of the house battery... in a %

I use this as an indicator and "guide only" of what going on with the boat electrical power.
They are also other factors that have an effect on how accurate these types of power meter are - temperature, how big the loads are and the condition of and how old the battery is.

I have installed these meters on both the boats I have owned, they definitely help me knowing what's going on and much better than just a volt meter.

I hope the photos assist you

[tiger79]

The installation is actually quite simple - it requires the shunt (which reads current flowing in AMPS) be connected directly with the - 0V (minus terminal) of the house battery, this way all energy flowing in and out of the battery is monitored.
By removing the battery -0v wire and connecting it to one side of the shunt, make up a short cable from the shunt to the -0v battery terminal you know don't need to worry the you might be bypassing something.

However, the photo shows that you have something else connected to the battery's negative terminal...

[Jeff Jones]

yes well spotted, I had all the power off and needed some tunes whilst working (it was the radio supply).

[MarkTheBike]

Jeff, why did you choose the BM2 over the BM1? I was under the impression that a BM1 would be more than enough (unless you're running air-con++)...

Just curious.

[Jeff Jones]

Air Con - I wish    it was to cover the charging currents mainly..

The original house battery is protected with a 125A HRC fuse so I sized all the components to suit that as a minimum.

I think DC Shunts are a weak link in the electrical system by nature (with a very small volts drop across) - personally, I prefer to run them well within the rated size (from industrial experience)

With the 200A shunt, the connection terminals are a bit more robust than the 100A. Springer's battery cables are original 95mm2 singles so quite hefty anyway

I have just installed a larger 115A alternator for a future planned increase in house battery size, the recharging is where the largest current are going to be seen.
I hope after the house battery upgrade (size unknown at this point maybe 450Ahr) I think then id be pretty close to 100A even for a short time. 

there wasn't much difference between the 100A and 200A models was about £15.00 from memory.

[MarkTheBike]

Thanks for the info, Jeff. I've just bought a BM1 as I've got a couple of 140aH AGMs, topped up by the standard alternator on an MD2030D. Apart from the winch, I don't have anything that draws anywhere near the 100a so am within limits. I tend not to use the fridge so it's mainly instruments and lights (slowly being replaced with LEDs).