question

rod-evans avatar image
rod-evans asked

MPPT 100/50 charge controller and BMV700 Battery Monitor

First off, let me clearly state that I'm a total moron when it comes to matters of electricity and electronics. Perhaps I should also mention that all the installations I'm about to refer to were done by Victron accredited installers. Historically, about 4 years ago, I had a 12/1600/70 inverter installed in my house to cover daily electricity cuts of up to 5 hours, and this worked perfectly for the appliances I wanted to keep running during those power cuts. Of late, however we are now experiencing power outages for 18 hours daily, so I decided I needed a solar solution as back-up to keep the 2 X 12v 200Ah batteries charged during daylight hours. This was done 2 days ago, but according to the battery monitor readings, the reserves keep dropping, which, to my addled brain indicates that the solar panels (3 X 265W) are not charging the batteries? My question is this: Is there a possibility that the MPPT 100/50 charge controller isn't doing its job, and if it is, why doesn't the battery monitor indicate an increase in storage levels?

charge controller compatibility
5 comments
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

klim8skeptic avatar image klim8skeptic ♦ commented ·

You don't mention which Mppt you have. If is a Smartsolar version download the Victronconnect app onto you phone and have a look at the history. If you have a bluesolar version you will need a BT dongle, or a ve direct to usb adaptor.

0 Likes 0 ·
rod-evans avatar image rod-evans klim8skeptic ♦ commented ·

Ahhh ... ok, thanks for the info. It's a bluesolar controller, so I'll need the dongle. As a matter of interest though, is there a reason why the monitor doesn't show an increase in storage levels. I've just noticed that the controller has moved from the 'bulk' led to the 'absorption' led (solid blue light, not flashing). In other words, why the necessity for an additional widget to see what's happening in real time, when I already have one in place that should show me the current status of the battery bank?


0 Likes 0 ·
klim8skeptic avatar image klim8skeptic ♦ rod-evans commented ·

I like to know how many kWh my array has produced (my energy consumption.) I also like to look at the charts/stats to see what charge states/times the battery has charged up to for each day. The history also records batt min/max voltages which can be useful for diagnosing system problems/battery warranty.

A dongle/usb is also useful for firmware updates.

Read Murray's post also.

0 Likes 0 ·
Murray van Graan avatar image Murray van Graan commented ·

Do you have a wiring diagram or pictures of how the charge controller connects to the battery monitor/battery bank? It is possible that the charge controller was connected downstream of the battery monitor, which could explain your situation

0 Likes 0 ·
rod-evans avatar image rod-evans commented ·

To the best of my knowledge, this is how the setup is currently wired. Prior to the solar panels and the MPPT controller being installed, the Battery monitor was working perfectly, showing the discharge during power outages, and recharge during the times when either the grid was supplying power, or when I was running my generator.

0 Likes 0 ·
wiring.jpg (51.4 KiB)
2 Answers
Paul B avatar image
Paul B answered ·

The Neg wire from the Solar controller should go to the LOAD side of the shunt.


Thats why its not showing any incoming amps


Also I would recommend that you change the solar Panel array to a series connection, (as long as the total O/C voltage does NOT GO OVER 100 volts) its a bit tight on a 100 volt controller you really should have a 150volt unit (if you do change the MPPT go for a SmartSolar 150/50 unit)

anyway if you can you may get some more output out of your panels on cloudy days and early mornings and late afternoons if you go to series connection . However in your case you can only do this if each panels Open circuit voltage is UNDER 30volts or you change the controller.


if each Panel is above 30 volts and you want to keep the current controller then leave the Panels connections AS IS.


Suggested



1563717493261.png (160.8 KiB)
1 comment
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

rod-evans avatar image rod-evans commented ·

My mistake, I think the panels are in fact connected in series, because when it was all explained to me when I purchased the 'upgrade', the technician mentioned that the parameters were 'on the edge'

0 Likes 0 ·
rod-evans avatar image
rod-evans answered ·

Thank you Paul B, much appreciated. Again, being totally clueless in these matters, my logic tells me that power from the solar panels is going INTO the controller, and OUT to the batteries. Does this mean I need to disconnect the negative wire from the battery (where it is now) and connect it to the LOAD side of the shunt instead?

4 comments
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Paul B avatar image Paul B commented ·

Yes as per the attached wiring diagram that I modified for you

0 Likes 0 ·
rod-evans avatar image rod-evans Paul B commented ·

Gotcha, I'll go and do that now, as my skill levels can just about handle that operation. Any safety procedures I should take prior to disconnecting/reconnecting? I don't want to break anything.


0 Likes 0 ·
Paul B avatar image Paul B rod-evans commented ·

turn the inverter off just so that no high current is flowing

0 Likes 0 ·
rod-evans avatar image rod-evans Paul B commented ·

Done. Thanks again Paul. There was no immediate change, with the monitor reading 62% after almost a full day of bright sunlight. Because our power generally only comes live at around 22:00Hrs, having been cut at 05:00 Hrs, I figured it would be a good idea to fire up the genny for a couple of hours to ensure the battery reserves didn't drop below 50%. After some 45 minutes, I went to check the status, and the batteries showed up at 100%, so I'm pretty confident that I'm going to get the correct readings from now on. I'll keep an eye on the monitor throughout the day tomorrow, and hope to see the reserve at a constant 100%. I'll also check with the installer to establish whether the panels are connected in series, or parallel. Once again, thanks so much for your valued input.

0 Likes 0 ·

Related Resources

Additional resources still need to be added for this topic