One for the electrical gurus (1 Viewer)

[MikeandCarolyn]

We have 2x80w solar panels and a NASA BM1 Battery Monitor-last year we had 1x110Ah battery and whether on EHU or solar we would get a reading of 105% when battery was fully charged.If on solar this would usualy be achieved by 10.00 hrs regardless of how low it went by bedtime.
Now we have 2x110Ah batteries and every thing else is the same.On EHU we get a reading
of 105% as before,but on solar it only goes up to 85% and stays there. Today,in bright sunlight,I was getting 20.2 volts from the solar panels. I switched the TV on and ran it till I was getting 70% charge on the BM1 then switched it off and the % climbed back to 85% in about 15 mins but didn't go any further.
Why this anomaly in readings ?

Mike.

 

[pappajohn]

i could be talking bo//ox Mike and im sure someone will say so but....

i think it may be down to the type of solar controller you have.

PWM or MPPT

PWM isnt as efficient as MPPT and may be struggling to charge your 220ah battery bank to full capacity.

just as a standard battery charger will usually only charge to around 80%/85% i beleive the PMW is about the same.

worked fine with one 110ah battery as it only had half the work.

as an afterthought.....do you need to set any parameters into the BM1 ?

 

[MikeandCarolyn]

i could be talking bo//ox Mike and im sure someone will say so but....

i think it may be down to the type of solar controller you have.

PWM or MPPT

PWM isnt as efficient as MPPT and may be struggling to charge your 220ah battery bank to full capacity.

just as a standard battery charger will usually only charge to around 80%/85% i beleive the PMW is about the same.

worked fine with one 110ah battery as it only had half the work.

as an afterthought.....do you need to set any parameters into the BM1 ?

It is a PWM controller and I have set 220Ah as the capacity in the BM1- It was in the back of my mind that by increasing the number of batteries I was giving the system more work to do. Think you've cracked it-hopefully

Mike

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[Geo]

Yes John he should re calibrate the BM1 to his new system using known fully charged batteries
Geo

 

[MikeandCarolyn]

I had discussed the problem with Sunshine Solar and told them I suspected that the controller I had was not performing properly-they sent me a replacement today which I have installed with the same results-I now see that they also sell a MPPT controller and claim a 30% increase in efficiency for it !! Why didnt they suggest that earlier Grrr.

Mike