Strange Nasa BM1 problem

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pieter2

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I have installed a new Nasa BM1 on my service battery, exactly as shown in manual. I also use a Ctek batteryloader, directly connected to the poles of the servcie battery.
With all main switches off (not any electrical device working), the Nasa shows a continous discharging of 2,1 A. When I put on the backlight of the NASA BM1 (illum), immediately the discharge falls down to 0 or 0.1 !!
So it looks like the BM1 only shows the right values with the backlight on.
Anyone who knows the answer to that?
Pieter
 
pieter2 said:
I have installed a new Nasa BM1 on my service battery, exactly as shown in manual. I also use a Ctek batteryloader, directly connected to the poles of the servcie battery.
With all main switches off (not any electrical device working), the Nasa shows a continous discharging of 2,1 A. When I put on the backlight of the NASA BM1 (illum), immediately the discharge falls down to 0 or 0.1 !!
So it looks like the BM1 only shows the right values with the backlight on.
Anyone who knows the answer to that?
Pieter
Click to expand...

What is a CTEK batteryloader? There is nothing in Google by that name. :confused:

If you mean battery charger I have a couple of questions.

1) Was the charger switched on - i.e. connected to the mains or had it been switched on recently before you noticed the 2.1A discharge?

2) Have you taken any measurements with the CTEK disconnected from the battery?

Also, why did you not connect the CTEK to the load side of the shunt so that the BM1 can measure the charging current?

Does the BM1 read correctly (as far as you can tell) in all other situations?
 
pieter2 said:
I have installed a new Nasa BM1 on my service battery, exactly as shown in manual. I also use a Ctek batteryloader, directly connected to the poles of the servcie battery.
Click to expand...

After installation, did you set the residual current reading to zero with everything switched off, as detailed in the manual?

Also, the only connection to your negative battery post should be the Nasa shunt. Everything else, including your Ctek charger, should connect to the other side of the Nasa shunt.
 
Sorry for the bad English. It is a battery charger.
1) Wheter or not the charger has been connected to the main does not change the 2.1 discharge. Of course when it is connected it start to load the battery and this is shown at the BM1
2) I havent checked the situation when the charger is disconnected from the battery yet. I will do so next weekend.
3) The BM1 does show the charging of the battery.

The 2.1 discharge really seems to be a constant error. All discharges due to electrical equipment is shown correct when I subtract the 2,1
 
pieter2 said:
. . . .The BM1 does show the charging of the battery.
Click to expand...

That's good (although it does mean the charger is not connected directly to the battery poles as you stated in your OP :).

pvb said:
After installation, did you set the residual current reading to zero with everything switched off, as detailed in the manual?
Click to expand...

2.1A is a large offset. IIRC, the offset on my BM1 when first installed was 0.1 or 0.2A. Also, turning on the light should not reduce the amps :confused:
 
Playtime said:
That's good (although it does mean the charger is not connected directly to the battery poles as you stated in your OP :).
:
Click to expand...

I really DID connect the ctek directely on the poles of the battery! And the BM1 displays a charging situation when the ctek is switched on. I suppose that would be as expected because the BM1 'reads' the battery.
As I understand from you, the ctek should be connected with the loading pole of the shunt.
Perhaps this is the reason of the strange response on turning on the backlight ?

Connecting the ctek to the loading point of the shunt. Wouldn't this harm the ctek when the alternator would start loading when the motor is running?
 
pieter2 said:
I really DID connect the ctek directely on the poles of the battery! And the BM1 displays a charging situation when the ctek is switched on. I suppose that would be as expected because the BM1 'reads' the battery.
As I understand from you, the ctek should be connected with the loading pole of the shunt.
Perhaps this is the reason of the strange response on turning on the backlight ?

Connecting the ctek to the loading point of the shunt. Wouldn't this harm the ctek when the alternator would start loading when the motor is running?
Click to expand...

If the CTEK is directly connected to the battery poles then the BM1 is not measuring the charging current from the CTEK. The current can only be measured by the BM1 if it goes through the shunt. Therefore the charger should be connected to the load side (not the battery side) of the shunt.

If the BM1 "displays a charging situation" when the CTEK is charging then it can only be registering the increase in voltage. If the current reading changes then it is another symptom of the original problem.

If you connect the CTEK to the load side of the shunt, the alternator, when charging, should not harm the CTEK.

Have you tried zeroing your no load amps, as suggested by pvb? If not, then this would be worth a try, although, as I said in my previous post, 2.1A is a high offset to start with.

Other than the above I have no further suggestions, I'm afraid.
 
Playtime said:
Have you tried zeroing your no load amps, as suggested by pvb? If not, then this would be worth a try, although, as I said in my previous post, 2.1A is a high offset to start with.

Other than the above I have no further suggestions, I'm afraid.
Click to expand...

Thanks a million for all the answers!
Next weekdend, I will disconnect the ctek from the poles. Then I will check the BM1. When all is working ok, I will connect the Ctek to the shunt.
If all of this does not work, I will disconnect the BM1 ;)
I will inform you about results
 
I have a NASA BM1, correctly fitted slavishly following the manual, and it shows a constant discharge of .1W

It only works as a vague comparison guide as to battery state better or worse, and has to be displaying all the time 24/7, which even with a tiny draw seems abit counter-productive.

I am deeply unimpressed; next time I'll spend more.

The same goes for my windspeed & direction unit, the first one failed after 11 months and NASA refused to honour the guarantee, I was daft enough to replace it and the next one lasted about 18 months.

I didn't actually want a wind instrument anyway, the first one was a gift to me, so now I do without.
 
BM-1

The backlight draws about 10mA. This current is supplied through the red wire and returned back to the battery through the black wire. If the black wire is not properly connected then the return will pass through the white wire which is one of the shunt sense wires. It only takes 50mV accross the sense wires for the display to read 100A. So even a few mA through
the sense wire will cause a problem.
Check all the connections. Make sure the terminal screws are tight and on the wire rather than the plastic sleeve. The offset is caused by stray voltages generated in the sense wire
(white and yellow wires) terminals and should never be more than 0.1 to 0.2 Amp. It can, of course be ballanced out but if it's as high as 2amp then there is something wrong and ballancing it out should not be attempted.
I've had my unit several years and find it invaluable.
 
@crossbones: This really sounds logical, it should have been the solution I was looking for!
However, this weekend I have checked everything over and over and it looks like that I everything is exactley according to the manual. Also the Ctek is connected in the right way.
There are just two things I am not sure of:
1) the shunt is connected with the battery and the earth (black wire) of the motor. Is that ok?
2) I have a Bosch relais for switching off the service battery for starting. Would this effecte the BM1?

I think this problem is harder to solve than expected. I suppose I will have to start measuring. Could someone tell me what and how to measure in order to understand th problem a bit more? Please keep it simple, I am not electro-technical.
 
BM-1

The shunt should connect directly to the negative battery terminal. All the wires that were on the negative terminal should go to the other end of the shunt. The black/white wire goes to the battery end of the shunt and the yellow wire to the other end.
Have you tried to ballance out the residual current. If you have moved it a long way ( I don't know how far it can be moved) then it could confuse the issue. I suggest you measure the voltage accross the shunt sense terninals and note what current the BM-1 reads. You will need a voltmeter that can read down to 1mV. Many of the cheap multimeters around are excellent and have a 200mV range which will do this.
Let me know the results and perhaps I can help. If you could post a circuit diagram of how it's wired or photo's of the installation that may show the problem.
Best regards.
 
Happy newyear to all!

Sorry for the very very long delay in my answer. I hope you all are still reading this.
I have measured (finally) the sense wires:

With backlight off:
yellow-black : 0,3
white-black: 0,3
white-yellow: 0,00

With backlight on:
Yellow - Black: 1,20
White- Black: 1,20
White - Yellow: 0,00

So, still the main problem is that with backlight ON I have a current of approx 0 on the screen and with the light off it shows a cuurent of approx 1,7 (This is now, after some disconnecting and connecting again.
Temperature is about 3 degrees at the moment.
Voltage on battery is 12,7 / 12,8 according to the multimeter as well as the Nasa battery monitor.

Who may help me with this?

Pieter
 
This doesn't relate directly to your problem, but I have found that theh 'zero offset' drifts quite alarmingly with ambient temperature. I don't know if this a general problem or if my BM-1 is faulty in this respect. The net result is that if the boat has been left for several weeks (with all battery loads definitely disconnected, and no conceivable charging source (swinging mooring; no wind gen or solar panels).....the BM-1 is likely to be showing cumulative AHr reading of anything from say 50AHr discharge to 50AHr charge. Either would be ludicrous and the battery voltage is healthy around 12.7v.

I too consider the small but continuous drain by the BM-1 unnecessary and now disconnect it when not expecting to use the boat for a week or more.

Vic
 
With backlight off:
yellow-black : 0,3
white-black: 0,3
white-yellow: 0,00

With backlight on:
Yellow - Black: 1,20
White- Black: 1,20
White - Yellow: 0,00
Click to expand...

Are these voltage readings between the wires mentioned?

If so i think you must have it wired incorrectly!

Check with the wiring diagram http://www.nasamarine.com/prodimages/one_battery_wiring1.pdf

It must be wired exactly as shown in the diagram.
 
Last edited:
pieter2 said:
Happy newyear to all!

Sorry for the very very long delay in my answer. I hope you all are still reading this.
I have measured (finally) the sense wires:

With backlight off:
yellow-black : 0,3
white-black: 0,3
white-yellow: 0,00

With backlight on:
Yellow - Black: 1,20
White- Black: 1,20
White - Yellow: 0,00

So, still the main problem is that with backlight ON I have a current of approx 0 on the screen and with the light off it shows a cuurent of approx 1,7 (This is now, after some disconnecting and connecting again.
Temperature is about 3 degrees at the moment.
Voltage on battery is 12,7 / 12,8 according to the multimeter as well as the Nasa battery monitor.

Who may help me with this?

Pieter
Click to expand...

Hi Pieter

Happy New Year.

I thought you must have solved this one back in September. :)

It looks from the above measurements as though the white and yellow wires are connected together (to one end of the shunt) and the black wire is on its own at the other end of the shunt. This would be incorrect according to the wiring diagram in VicS's post. By the way are the measurement in mV and not volts?

Can you check your wiring and circuit diagram again - it could be that the wiring loom you were supplied with from NASA is wrong.
 
Last edited:
Everything is connected exactly as in schedule. Yellow and white are not connected.
The - connector of the battery is connected however with the - connector of the starting battery as well as the - wire of the steeringmachine.
Would this be a proble?
 
pieter2 said:
Everything is connected exactly as in schedule. Yellow and white are not connected.
The - connector of the battery is connected however with the - connector of the starting battery as well as the - wire of the steeringmachine.
Would this be a proble?
Click to expand...

In that case, everything is not "connected exactly as in schedule"! The only thing connected to the negative terminal of the service battery should be the BM1 shunt, as it clearly shows in the diagram.
 
pieter2 said:
Everything is connected exactly as in schedule. Yellow and white are not connected.
The - connector of the battery is connected however with the - connector of the starting battery as well as the - wire of the steeringmachine.
Would this be a proble?
Click to expand...

If you are convinced that the wiring is exactly as per the published wiring diagram then I can only conclude that there is a fault (colours reversed, maybe) in the NASA wiring loom.

The shunt should be connected to the negative terminal of the services battery (assuming you have a separate starting battery) and everything that was connected directly to that terminal should be connected to the OTHER side of the shunt.
 
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