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NASA BM 1 Install


JamieM23

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Hi all, sorry to jump on this but you guys seem to know what you are on about. 
 

I have just installed a NASA BM1, I have 2 110ah batteries connected in parallel (connected neg to neg), wired up correctly with NO other negatives on the batteries part from the wire to the black and white side of the shunt. 
 

When everything is turned off the battery is displaying discharge of 0.01amps and when charging it goes pass 100% (to roughly 105%). 
 

I have a 100w solar panel installed (it’s giving me 0.4amps of charge due to living in Yorkshire with crap weather this time of year). The neg from the solar is also Connected to the yellow end of the shunt. 
 

Should the neg from both battery’s be connect to the black and white end of the shunt or connected together with one wire going to the black and white end? 
 

Is all this right? Have I done something wrong. 

 

Thanks in advance everyone.


 

Edited by JamieM23
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Others will be along to correct me if I have it wrong but my understanding is that the batteries connect -be to -ve, and then a cable from one of those -ves to one end of the shunt, and anything else connects to the other end of the shunt. I don't know about the yellow / black and white end of the shunt, but the instructions should tell which of those colour combinations should connect to the batteries.

 

Hope this helps, but see what PinappleGuy has said, he types quicker than I do!!

 

Oh, and ignore the percentage SoC value, it'll start off as vague and quickly become total rubbish!

Edited by Col_T
Edited to add SoC comment
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I certainly find that the SoC reading responds correctly to changes in the capacity value that I set. Like others I tend to ignore it in favour of looking at the actual current; instead I use it backwards. With the engine still running and the charge current being down to a low value consistent with the batteries being fully charged, I then adjust the setting of the capacity value until the SoC reads 100%. The value that I have set then tells me the actual capacity of the battery bank.

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Thanks everyone. 
 

I just wanted to confirm that I had done it right and to confirm that both my battery’s are connected in the right way:

 

neg to neg to shunt (on the black and white end) 
 

What caught my eye was the 0.1 discharge when everything was turned off at my PMS 3H. I would have thought it would have been zero but then thinking again the BM1 is powered (on perm live) and so is the display for the heater so I’m guessing that’s where the 0.1amps is going. 
 

I also got worried when I saw the SoC at 105%, I didn’t want to over charge and damage the batteries. I have set the BM1 to 220ah via the engineering mode. 

thanks again all. 


 

 

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26 minutes ago, JamieM23 said:

Thanks everyone. 
 

I just wanted to confirm that I had done it right and to confirm that both my battery’s are connected in the right way:

 

neg to neg to shunt (on the black and white end) 
 

What caught my eye was the 0.1 discharge when everything was turned off at my PMS 3H. I would have thought it would have been zero but then thinking again the BM1 is powered (on perm live) and so is the display for the heater so I’m guessing that’s where the 0.1amps is going. 
 

I also got worried when I saw the SoC at 105%, I didn’t want to over charge and damage the batteries. I have set the BM1 to 220ah via the engineering mode. 

thanks again all.
 

 

0.1A is too much just for the current used by the BM1, by a factor of at least 10. Not sure about the heater display but it sounds like you need to adjust the zero.

Edited by nicknorman
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45 minutes ago, nicknorman said:

0.1A is too much just for the current used by the BM1, by a factor of at least 10. Not sure about the heater display but it sounds like you need to adjust the zero.

Possibly there are a couple of other loads that are ‘always on’ such as the solar controller and maybe a permanent live feed to the car radio as well as a Webasto that is powering the heating controller.  I would check the current with a multimeter before adjusting the zero.

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