question

vicky avatar image
vicky asked

Smart Solar 100/50 minimum consumption when sun is gone ?

I need to replace an entirely broken 12V offgrid system of a remote northern cabin in real cold climate. The new setup is: Smart Solar 100/50 & BMV-712, Panels 2 x 250Wp, Batteries 2 x 6V AGM DeepCycle 190Ah. So far the old system was shut off during the winter period where there is twilight for 4 hrs only. (Batteries fully loaded , then disconnected for 6 months). Now I am wondering if it would make sense to leave the System powered up so the Batteries would be at least kept alive. However I did not find any clear information if the Smart Solar's self consumption of 30mA is always the same or if will be less if solar power is gone. Appreciate any information and hints how to keep the batteries alive.

MPPT Controllersoffgrid
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3 Answers
prairiecamper avatar image
prairiecamper answered ·

Hi

Not quite the same system as yours, however a lot of similarities! An RV with 2 - 75 watt panels and another 2 -75 watt to be installed and a victron 100/30 solar charge controller and 2 - 6 volt GC lead acid batteries. My battery monitor is a wired shunt type trimetric Bogart engineering. I leave the system active year round in a cold climate as well, ( +40 to -40 C ) This is the 3 rd winter in operation and the performance is great! The batteries are still in good shape, the drawback for me is the solar panels are flat on the roof and when it snows I have to clean the snow off. Recently I was away for a week with the panels covered and when I checked the history on the victron the battery voltage was still 12.15 volts. I remove all the parasitic loads from the trailer with a battery dis-connect. If you have any slope on your panels snow probably won't be a problem I suspect your batteries should be trickle charged just fine. hope this helps somewhat. Can't answer question re: smart solar power self consumption.

Don

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snoobler avatar image
snoobler answered ·

6 months of AGM stored after being FULLY CHARGED in very cold climate will likely only lose about 10-20% of their stored charge and sustain little to no ill effects; however, keeping them topped off is better.


You can confirm the self-consumption by measuring it with a dc clamp ammeter.


Even if it pulls .03 all the time, 190Ah/.03A = 6333 hours or 263 days. That assumes you get no solar ever, which might occur if they're covered in snow for > 130 days (50% discharge level on battery).


Note that my computations ignore temperature effects on battery capacity.


The SmartSolar and BMV would need to be in a VE.smart network to ensure the MPPT gets the appropriate battery temperature for compensation.


Unless the panels would be completely covered in snow for weeks at a time, I would lean towards leaving the system active.


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vicky avatar image
vicky answered ·

@Prairiecamper @snoobler Thanks guys, very helpful answers. As soon as I am on site again I'll do the measurements.

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