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russinthecascades avatar image
russinthecascades asked

BMV History - very little data recorded, why?

I've had a BMV-712 monitoring 4 x 100Ah AGM batteries for 3 years and very few of the history parameters have been recorded - can anyone tell me why? For most, if not all of the time, the SOC has not been accurate with voltage readings. As the batteries are failing I've done 2 load tests taking the voltage down to mid-11v and the SOC was still in the 70 percentiles. I understand cycles not being recorded as the SOC never reached 65%, but what about last discharge, average discharge, time since last full charge? I read the manual, but it doesn't go into detail on how the parameter are derived; if there are any published resources that help explain, I would appreciate a link.

Main components: BMV712, Smartsolar 100/50, Multiplus 12/3000 120-50. I'm replacing the AGM's with 3 x 100Ah LiFePO4 batteries and want to make sure I do a better job on the initial setup. Thanks

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BMV Battery Monitor
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3 Answers
cklio avatar image
cklio answered ·

Hi Russ,

I believe VRM only records about 6 months of logged data if I remember correctly. I think outside of that you have to pay for a premium service to have all the data stored on their cloud servers.

It does look a bit peculiar that there was no last discharge. As that would implicate this is your first time using these batteries. Perhaps go into the battery settings, and take a SC with 'expert' options and see some of the settings. Did you set it to default AGM settings? Sometimes battery monitors require you to enter in how many AH that your bank has. If entered incorrectly it might lead to these issues...

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Matthias Lange - DE avatar image Matthias Lange - DE ♦ commented ·
The VRM portal has nothing to do with the question.
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Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

Last discharge is 0 because you might be synchronized right now.

Average discharge is 0 because you don't have any cycles because a cycle is only counted if the SOC gets lower than 65% and then change back to 100%.

Time since last charge is 0 because you might be at 100% at the moment.

What are your current settings?

https://youtu.be/mEN15Z_S4kE

https://youtu.be/4ReljfO3k6M

https://youtu.be/yMJ_vzB2avE

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russinthecascades avatar image russinthecascades commented ·

Current settings are:

BMV712: Current threshold - 0.10A

Smartsolar 100/50: Max charge current - 50A

Multiplus 12/3000 120-50 120V: AC1 input current limit - 20A; Current limit overruled by remote - On; Dynamic current limit - Off; Charger current - 90A

Thanks for the video links. I've watched "How to set up BMV Battery Monitor..." numerous times in the last few weeks and changed some parameters due to his advice. I'll need to study the other two, as they are new to me.

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Matthias Lange - DE avatar image Matthias Lange - DE ♦ russinthecascades commented ·

Please make screenshots of the settings, the BMV has more settings than just the current threshold.

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russinthecascades avatar image russinthecascades Matthias Lange - DE ♦ commented ·

Some screens probably aren't relevant... thanks for your time and advice.

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The Low SOC relay - off is hidden - currently at 52%

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Matthias Lange - DE avatar image Matthias Lange - DE ♦ russinthecascades commented ·
Try to increase the "charged voltage" and lower the "Tail current" a bit.

Maybe the BMV is synchronizing to 100% to early (due to low PV charging currents; this should be explained in the video).

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kevgermany avatar image kevgermany ♦♦ Matthias Lange - DE ♦ commented ·
@russinthecascades also increase charged detection time, depends a lot on your weather, but 15 mins might be a better starting point.
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russinthecascades answered ·

I wish I had more time to play with these settings with the failing (failed) AGM batteries. But as I mentioned in the first post, I'm trying to understand settings so I optimize the replacement LiFeP4 batteries. The batteries have arrived, so over the next few weeks I'll be doing some major changes to the electrical system.

What I find odd is the BMV using 65% SOC as the cycle counting point. Why doesn't the BMV use charged and discharged Ah? Most of the time my DOD is only 20-35% before solar recharges. Those events could be tallied to make a more accurate cycle figure...

Thank you for the explanations and links to videos; it was very educational and much appreciated.

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