Strange Nasa BM1 problem

Where it says "no other connection must be made to this post" It means no other connection !

Connect the other battery and any other equipment like this

scan0058.jpg
 
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pieter2 said:
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

Pieter
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Firstly, VicS is absolutely right with his wiring diagram above. If your wiring is different to this then that is the first thing to correct.

Secondly, I believe (somehow) that the white and yellow wires are connected together, otherwise how do you explain the zero voltage between them, and a measurable voltage in the other combinations.

Could you possibly take photos of your battery, shunt and connector wiring if you are convinced otherwise.
 
Secondly, I believe (somehow) that the white and yellow wires are connected together, otherwise how do you explain the zero voltage between them, and a measurable voltage in the other combinations.
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Quite and how do you explain the voltage difference between the white and the black when they should be connected together at one end!
 
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VicMallows said:
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.
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Err, I'd have thought that is entirely normal - until you get 5 mins of charge or 5 mins of draw, then any reading (effectively of battery voltage) is suspect - IMO that's a "feature" of the batteries rather than the monitor.

[edit] Someone else may me correct me, but I wouldn't be surprised if 12.6-12.8v on the battery would explain the difference.
 
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mcframe said:
Err, I'd have thought that is entirely normal - until you get 5 mins of charge or 5 mins of draw, then any reading (effectively of battery voltage) is suspect - .
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Disagree. The Nasa BM-1 is a cumulative up/down counter of the Amps flowing through the shunt integrated over time. If nothing is flowing through the shunt the counter should remain at zero.

There is another form of battery monitor on the market (name forgotten, but SNOOKS was keenly advocating it quite recently) which apparently DOES work on the principle of the battery voltage characteristic as 'learned' in relation to previous charge/discharge cycles. Essentially a refined version of the way many of us have always roughly estimated our battery capacity by observing the rate of fall of battery voltage.


(Edit: I am refering to the AHr charge/discharge reading only; I agree the perecentage-charge bar graph is not meaningful untill after some charge/discharge .....but I consider it pretty useless anyway).

Vic
 
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Playtime said:
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.
....
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So, Could I take a chance by switching wires and using the yellow as white and visa versa?

(I will check the other thing about connecting the start battery first)
 
VicS said:
Where it says "no other connection must be made to this post" It means no other connection !

Connect the other battery and any other equipment like this

scan0058.jpg
Click to expand...

Thanks! That is clear. My Nasa booklet does not mention that there should be nothing connected with the shunt at the service battery side (see picture), but I will have the connections changed.
 
pieter2 said:
Thanks! That is clear. My Nasa booklet does not mention that there should be nothing connected with the shunt at the service battery side (see picture), but I will have the connections changed.
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You are right it is not made clear in the instruction book !


Regarding swapping the white and yellow.
There is not enough information to know exactly which wire does what.

If the white and yellow are the sensing wires then swapping them will make it read charging when discharging and vice versa.

The black and yellow wires might be the sensing wires ... I cannot tell from the diagrams.

No harm will come from swapping them though.

BUT please check the wiring at the connector block at the instrument end of the cable again. Make sure yellow is connected to yellow, white to white and black to black.

It is difficult to believe that Nasa has sent an instrument out with the wiring muddled up!
 
I am still thinking about this.

You say
With backlight on:
Yellow - Black: 1,20
White- Black: 1,20
White - Yellow: 0,00
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If it is wired correctly the black and white wires will be connected together at the shunt. If they are connected together you cannot get 1.20 between them but you do! Therefore the black and white cannot be connected correctly.

You should get the same reading between the white and yellow as you do between yellow and black! But you dont !

Check all this wiring again!
 
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VicS said:
You should get the same reading between the white and yellow as you do between yellow and black! But you dont

Check all this wiring again!
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The White and Black are crimped into a single crimp at the shunt end. Have we considered the possibility that one or other is not actually making contact with the crimp? I would certainly be remaking the crimp at this stage.

(all this would be so much easier if we had a circuit for the internals of the BM-1 !!)

Vic
 
I just came back from checking wires and voltage again. I have registered all wires. I would need some time to draw the schedule, but at least then we have all information.
For now:
All connections are according to schedule. The only thing that might be wrong is that the start battery + is connected with the domestic battery +, so - indirectly- with the 'wrond side of the shunt.
I will change that later.
But all the rest is according to the schudule. Indeed the black and white are connected with eachother in one 'crimp'
I also checked the voltage with the backlight off (I do this at the terminal block near to the BM-1 display):
With the multimeter set on 2000:
yellow-red : 12,7
white-red: 12,7
black-red: 12,7
With the multimter set on 200m:
yellow-white: 0,0
yellow-black: 0,30
white-black: 0,3

I wil put post the schedule as soon as I have it ready. As well as some photo's.

kind regards
Pieter
 
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pieter2 said:
The only thing that might be wrong is that the start battery + is connected with the domestic battery +, so - indirectly- with the 'wrond side of the shunt.

I wil put post the schedule as soon as I have it ready. As well as some photo's.

kind regards
Pieter
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Do you really mean battery + above? :rolleyes:
If you do mean + (positive or red), then you have a bigger problem than just the BM1. :eek:

Vic Mallows suggestion above re the crimps is worth investigating.

I look forward to seeing the 'schedule' (wiring diagram?) and the associated photos. Until then I have nothing further to suggest.
 
The only thing that might be wrong is that the start battery + is connected with the domestic battery +,
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The start battery positive should not be connected to the domestic battery positive if you want a separate engine starting battery

It begins to appear that you do not have a separate start battery at all. It appears that you have two batteries connected in parallel to form a single battery bank.
They would be connected directly positive to positive and negative to negative.
You would then be using that combined bank for all purposes.

However the BM1 is designed to monitor a separate domestic bank so ideally requires the two batteries to be separated ss shown in my earlier diagram. The domestic circuits being supplied, as I indicated, from the battery which is being monitored and the engine starter circuit being supplied directly from the starter battery. ( the connection on the left hand side which I did not label)

Once separated in this way you will require some split charging system. A diode splitter or a VSR, or perhaps something like a Driftgate X-split, unless you have a fancy charging controller such as a Sterling Alternator to Battery charger with two separate outputs.

However I look forward to seeing some diagrams of you system as it is at present.


Regarding the black and white wires, I too would suggest checking that crimp connection to make sure they are properly connected to each other.
 
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Dear all,
My BM1 is working sice three years, it is correctly wired and tested in long sailing trips. It appears exactly the same problem showed in this post. With all loads disconnected current is 0A (drift is corrected in the set menu) and when the light is on the current grows until 3A (charging).
I do not not why. I hope somebody found any solution.
Happy 2011 to all falks
 
VicMallows said:
Over what sort of time does the current 'grow' ? I will then check mine to see if anything similar. (I vary rarely use the backlight so may not have noticed if it is an inherent design problem).

Vic
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It spent 10-20 seconds to reach 2.9 - 3.0 A (charging). All loads off. Charger off.
My instalation: One domestic bank (460 Ah) and an starter (100 Ah). A very usual instalation.
After switch light OFF current goes quickly (5-10 seconds) to 0A.
Hope this help.
Cheers
 
Don't know if it helps but we've fitted two of these and in both cases, we never saw any difference whether the backlight was on or off. I know of people who've had troubles but this always seems to be down to having something connected to the wrong side of the shunt. I'm thinking that may be pieter2 has a faulty instrument. Have you been in touch with NASA to see if they've seen this fault before?
 
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