Nasa Bm-1

[tigger_b]

Hi,

I have a 2005 Beneteau 331 with what I understand to be 'normal' Beneteau battery selection / isolation arrangements - i.e. separate Neutral, Starter and Domestic isolators. I am thinking about fitting a NASA BM-1 to monitor my domestic battery condition, however I am a little concerned how it will react to switching in & out of the starter battery. Will it confuse the smart calculations it is meant to perform and render them inaccurate? Does it recognise a reduction in the bank capacity when the engine is finished with and the starter battery is isolated? Does anyone have first hand experience and do you rate the monitor? Any help or advice gratefully received!!

Thanks,

Simon

 

[Jackdaw]

I installed the on all three of our firsts (235, 260, 36.7). They work very well and are very well regarded. It will monitor voltage on both the house and starter batteries, but only track consumption and remaining charge on the house, as this is the one that is shunted. In practice it works very well. You enter the amp hour capacity of the house bank and via the shunt monitors consumption and give hours remaining at current rate. We love them.

 

[tigger_b]

Fantastic, thanks for the help...

 

[tigger_b]

Having just thought about reply from Jackdaw, does anyone know how the BM-1 handles a second battery connected in the domestic circuit? If the shunt is on the negative off the first battery, will it read the combined capacity of the two if the total amp hour value is entered into the monitor?

 

[Jackdaw]

Tigger,

Via the shunt, the BMW-1 reads the draw on ALL batteries active at the time based on your battery switch. This is normally just your house. The current BMW-1 has a dedicated sense wire to connect to your starter battery to monitor voltage. If you think about it, it's all you need there. If the voltage is good, you only need it for a few seconds.

 

[Philip_Oceanis 361]

This is how I have connected it to my Beneteau Oceanis 361.

 

[tigger_b]

Thanks again.

@Philip_Oceanis 361 - forgive my lack of understanding on this, does your sketch match this one (below) that I found on the NASA website? Once the shunt is in the negative circuit, does it detect the whole battery bank with the engine battery switched in? Apols if some of this falls into the 'daft question' category!!

SRB

http://www.nasamarine.com/prodimages/one_battery_wiring1.pdf

 

[Philip_Oceanis 361]

Thanks again.

@Philip_Oceanis 361 - forgive my lack of understanding on this, does your sketch match this one (below) that I found on the NASA website? Once the shunt is in the negative circuit, does it detect the whole battery bank with the engine battery switched in? Apols if some of this falls into the 'daft question' category!!

SRB

http://www.nasamarine.com/prodimages/one_battery_wiring1.pdf

As you can see I have one negative for both services and engine (probably common to most boats) but they way the shunt is connected measures only (hopefully!) the services batteries.

 

[Jackdaw]

Here is the way NASA recommends wiring. I would run each battery negative to a ground buss to be AYBC compliant. Note that if your unit has 5 wires as shown below (and not 4) it is a newer design and can monitor the starter with the addition of a simple wire.