Calling BM1 battery monitor owners, a couple of questions-

[cliffdale]

With a Raymarine setup the radar is automatically powered up to standby when the plotter is switched on and you have to remember to switch it off.

I have just had fitted a new Raymarine plotter and radar. My radar does not automatically switch on when powered up. I have to press the 'page' menu and choose the radar and switch on from here. It then has to warm up and I wait for it to count down before I can use Tx.

Thanks for the replies, I am ordering the BM1 and will see how I get on with it.
Cliff

 

[prv]

If you are on a swinging mooring or on long passages I can see that the more accurate SOC given by the SG may be very valuable. But if you are routinely charging from shore power you know your battery is fully charged when you leave

Ah, maybe that's why I like it. I have a marina style pontoon mooring but no power, and I rarely visit places where you can plug in a cable. In fact at the moment the boat doesn't even have a shore power charger fitted, though I keep meaning to get one. The only charging is from the alternator, and a "full" charge only when motoring a very long way which is rare for me, so it's vital to have something that tracks the batteries rather than needing to be periodically reset to a known "full" state.

Pete

 

[RogerG]

Just to clarify, the BM1 doesn't have to be set to a known full state, but to the maximum battery capacity. It will then calculate from various factors such as voltage, current drain, charge, puekerts etc what the SOC is. To enable it to maintain a fairly accurate SOC indication, it is wise to reset the max battery capacity to a lower level over time, to allow for the natural reduction of total capacity.

In my own experience as a 24/7 liveaboard, that is about 20% per annum.

Roger

 

[PeterR]

Just to clarify, the BM1 doesn't have to be set to a known full state, but to the maximum battery capacity. It will then calculate from various factors such as voltage, current drain, charge, puekerts etc what the SOC is. To enable it to maintain a fairly accurate SOC indication, it is wise to reset the max battery capacity to a lower level over time, to allow for the natural reduction of total capacity.

I like my BM1 a lot but although what you say is true the NASA manual admits the most accurate starting point for assessing battery condition is from a known full charge after a prolonged period of trickle charging. If after that the total amp hours read zero no adjustment is necessary if there is either a significant plus or minus number of amp hours showing it is only sensible to zero the instrument.

The manual also admits that the the instrument will show a significantly lower remaining capacity after a few minutes discharging than it did when it was still charging and ascribes this to the characteristics of battery chemistry. I have no idea whether the SG does any better in this respect.

 

[RogerG]

To the best of my knowledge, I understand that all SOC readings including the SG require a settling time after charge. It was described to me as being like pouring a pint of beer and waiting for the froth to die down to see how much is in the glass. I think the correct battery term is surface charge.

Roger

 

[noelex]

To the best of my knowledge, I understand that all SOC readings including the SG require a settling time after charge. It was described to me as being like pouring a pint of beer and waiting for the froth to die down to see how much is in the glass. I think the correct battery term is surface charge.

Roger

The surface charge will have no effect on most battery monitors. There is no need to wait after charging to read the SOC.

When trying to estimate SOC from voltage alone, even with a smart voltage gauge like the SG this is not true. The weakness of the SG is that it has no knowledge of the current into or out of the battery.
The BM-1 is a proper battery monitor, but it uses an very unusual system to measure the SOC. This avoids it having to make some complex calculations, and avoids the user having to input values on battery efficiency etc that they might not understand. but my feeling is the SOC display does not work quite as well as other battery monitors.

While the SOC display is helpful a battery monitor will give you a lot more information than this.
Knowing how much current devices are consuming is very helpful in reducing power consumption. Dim the chartplotter screen and you can instantly see and measure the reduction in power consumed. Angle the solar panel and see the benefits. Know when the engine charging current is dropping down. Look in the morning at how much power you used last night. For this information you need a battery monitor and you will find it invaluable even if you never look at the SOC.

 

[RogerG]

I haven't got the electrical knowledge to agree or disagree on your surface charge comment, but I do completely agree with all your other points and certainly wouldn't want to be without my B1, a great piece of kit

Roger

 

[mcframe]

Perhaps you could change your set up to have your radar on it's own switch?

All my switches are the toggle type, up for off, down for on, I have two different switch panel and the chart plotter is on it's own at the chart table.

Bling it up!
My fridge has it's very own big silvery toggle with a red led in the end.
(Err, it was cheap in Halfords)

Next-highest current-drawing is the Webasto, which obviously also has it's own "not on the panels" switch. Plotter is on "Instruments" and VHF & stereo share "VHF".

I thought the panel on an Oyster at LIBS a couple of years ago was quite cool - I've got no "Engine room CCTV" nor "WIFI Repeater" switches ;-)

 

[snooks]

I thought the panel on an Oyster at LIBS a couple of years ago was quite cool - I've got no "Engine room CCTV" nor "WIFI Repeater" switches ;-)

See, when my engine room is easily accessible I have no reason for CCTV in there, I can also hear that everything is running smoothly on deck...That's how advanced the Sadler 32 really is.

I do however have a wifi repeater, but that comes on with my chart plotter....It's on test at the moment and has to go back to Digital Yacht