BM-1 Funny Readings

[WiseOwl]

Hi

 

I recently installed a NASA/Clipper BM-1 battery monitor as we have no solar panels or hookup and wanted to ensure the batteries were not being run too low. 

 

I followed the instructions and the montior worked great. Until I had to move it, which involved disconnecting it, I have also disconnected the batteries.

 

For some reason now... when the engine is RUNNING the percentage goes passed 100% and it says time to discharge, also shows it discharging up to 45A an hour!?

 

Then when you stop the engine, it seems to go back to normal again. Apart from the high charge percentage. Has anyone had this issue, is there anything I can do? Reset etc?

 

Photos attached (engine running), hope this helps.

 

Thanks

WiseOwl

 

 

[Glynn]

Mine did similar once, I contacted them & they advised putting a load on it for a while.

[Robbo]

Sounds like you’ve connected the shunt connections the wrong way round

Edited December 27, 2018 by Robbo

[WiseOwl]

4 minutes ago, Glynn said:

Mine did similar once, I contacted them & they advised putting a load on it for a while.

Cheers Glynn. I actually did try this - I stopped the engine and turned on every appliance until it was reading a draw of 5amps. I left like this for a while but as soon as we started the engine again... crazy readings!

[WotEver]

Just now, Robbo said:

Sounds like you’ve disconnected the shunt connections the wrong way round

Yes, the two small wires from shunt to display are swapped around by the sounds of it. 

[WiseOwl]

7 minutes ago, WotEver said:

Yes, the two small wires from shunt to display are swapped around by the sounds of it. 

 

9 minutes ago, Robbo said:

Sounds like you’ve disconnected the shunt connections the wrong way round

Thanks both.

 

Do you mean at the shunt itself? The wiring is definitely correct at the terminal rail (choccy block).

 

I did move the shunt the other day, I did this so I could properly mount it.

 

To do this I had to use a negative wire from a different battery, maybe this other battery has other connections. Sorry I have only just noticed on the drawing it says no other connections to that terminal! Potential oops!

 

[TheBiscuits]

4 minutes ago, WiseOwl said:

I did move the shunt the other day

Have you reinstalled it backwards?

 

From your diagram, I think the "Yellow" end of the shunt is battery side, not load side where it should be.

Edited December 27, 2018 by TheBiscuits

[WiseOwl]

21 minutes ago, TheBiscuits said:

Have you reinstalled it backwards?

 

From your diagram, I think the "Yellow" end of the shunt is battery side, not load side where it should be.

 

Photo attached of how I have it at the moment. Which looks correct to the diagram I think!

 

 

[WotEver]

What are all those other wires on the battery negative post?

 

One connection and one connection only to the battery - the shunt. All other wires, yes all of them, yes even that one, and the starter negative... yes all of them, go to the other side of the shunt. 

[WiseOwl]

1 minute ago, WotEver said:

What are all those other wires on the battery negative post?

I honestly have no idea! I will find out, I guess this could be the issue?

[WotEver]

Just now, WiseOwl said:

I honestly have no idea! I will find out, I guess this could be the issue?

Without any doubt. 

[TheBiscuits]

Just now, WiseOwl said:

I honestly have no idea! I will find out, I guess this could be the issue?

Just stick them on the yellow end of the shunt after isolating the battery.

[WotEver]

However many batteries you have in your domestic bank, they should have their negatives connected together and wired to the black & white end of the shunt. Every other negative connection should be connected to the yellow end of the shunt. Including the starter battery negative. 

 

 

Edited December 27, 2018 by WotEver
Clarity

[WiseOwl]

2 minutes ago, TheBiscuits said:

Just stick them on the yellow end of the shunt after isolating the battery.

Okay great, I will give that a try soon! Thanks for your help all

[Tony Brooks]

While we are at it.

 

1.It is not 45 amps an hour, its 45 amps. Amps is an instantaneous reading. If you did   discharge at 45 amps for one hour you would have discharged the batteries by 45 Amp Hours (45Ah).

 

2. If you believe anything about hours left or percentage charged that meter is telling you it is most likely to do the opposite of what you installed it for - it will encourage you to destroy your batteries.

 

3. Use voltage and time to know when o recharge. Briefly recharge as full as is reasonable every day and fully at least once a week but the more often and fuller the better. When the voltage with nothing running hits about 12.2 to 12.3 its time to stop discharging and recharge.

 

4. For a full recharge keep charging until the voltage is above 14.2 volts and the current (amps0 is less than about 1 o 2% of the battery capacity so 4 x 110 Ah batteries = 440 Ah, keep charging until the current is around 5 to 7 amps.

Edited December 27, 2018 by Tony Brooks

[WiseOwl]

Now working properly - thanks everyone!

 

The battery with the negative shunt connections had other connections as well, I moved them to the next battery, no more crazy readings when running.

 

Thanks

WiseOwl

[WotEver]

I give up!

[TheBiscuits]

3 hours ago, WiseOwl said:

Now working properly - thanks everyone!

 

The battery with the negative shunt connections had other connections as well, I moved them to the next battery, no more crazy readings when running.

 

Thanks

WiseOwl

No No No No No!

 

The only negative connection to your battery bank should be the shunt.  1 cable, to the Black/White end of your shunt.

 

Anything else MUST be connected to the yellow end of the shunt.  I don't care what the manual says or what Fred three boats down says - if it's not connected to the opposite side of the shunt from your battery bank, you have wasted your time and money installing the monitor.

 

Moving it to another battery is both wrong and stupid.  If it's a negative it goes on the Yellow end of the shunt.  No ifs no buts no maybes...

[1st ade]

7 hours ago, TheBiscuits said:

Moving it to another battery is both wrong and stupid.

Unless "the other battery" is the starter battery which is wired (correctly) to the Yellow end of the shunt?

[Detling]

even if it is the starter battery, the route charge current from the alternator will take is alternator -ve to engine -ve  then to the starter battery -ve and then via the link to the domestic battery -ve. If the OP has just the 2 batteries and now has disconnected the starter -ve from the domestic -ve he will no longer charge the domestic battery from the engine.

 

On 27/12/2018 at 15:42, WotEver said:

However many batteries you have in your domestic bank, they should have their negatives connected together and wired to the black & white end of the shunt. Every other negative connection should be connected to the yellow end of the shunt. Including the starter battery negative. 

THIS is CORRECT

 

 

 

 

[WiseOwl]

Im a little confused with this apoligies. I thought I had followed everything right, I mean the BM-1 now works spot on again, and yes everything charges fine.

 

In the photo I attached showing the shunt, you could see other negative connectiosn to that pole of the battery, meaning its on the white/black side. I moved them to the yellow side, which I thought was the same as moving them to the next battery. As this is where the cable with the yellow wire goes.

 

Sorry for the confusion but I am happy with how it is working now.

 

Thanks

Jamie

[WotEver]

If ‘the next battery’ is the starter battery then it’ll work.