MPPT 100|20 and battery low voltage

DIY
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1

Hello,
I have a Victron SmartSolar MPPT 100/20, connected to a BIG Pro Solar DC EFB 12V 110Ah C100 battery.

For the last days, I have the following metrics:

Day Yield Consumption
-9 190 50
-8 170 20
-7 150 130
-6 310 200
-5 170 200
-4 150 200
-3 280 120
-2 330 190
-1 280 210
0 90 190

For a total:

  • yield: 2120Wh
  • consumption: 1510Wh

But this morning the voltage was too low and the appliance, I am connecting, shut off.

Am I misconfiguring the controller?

Or am I misunderstanding how the entire system works?

Thanks

2

@power46 There is a lot more to it, e.g. lead acid voltage drop under load, charge and roundtrip efficiencies etc. Maybe spend some time reading up on the various aspects as you also don’t discharge lead acid chemistries below 50% which all should be factored in when sizing a system.

3

Thanks for the message.

But how do I measure the discharge percentage?

The controller only shows the battery voltage.

4

A properly calibrated battery monitor can provide a lot of useful information such as SOC based on the power in and out of the battery and even approximate time-to-go. The Ah in and out it how you measure it. Have a look at the range of monitors here. If you have e.g. a LifePo4 with a bms and bluetooth, it is another way.

5

Sorry, for the late reply.

What I find very strange is that the controller shows a very greedy approach.

Consider the case the battery has very low voltage in the morning, even if there is sun for all day, most of the energy yield is done for a short period (2-3 hrs, battery voltage up to 14.6V), then it sort match the solar power to the load.

If I attach more load the solar power jumps up to compensate.

In a way the controller never really full charge the battery.

I am not sure if it is a configuration issue, now I have:

  • Battery voltage: 12V
  • Max charge current: 20A
  • Charger enabled: true
  • Battery preset: User defined
  • Absorption voltage: 14.6V
  • Float voltage: 13.5V
  • Equalization voltage: 15.2V
  • Automatic equalization: false

Should I trigger a manual equalization?

Thanks

6

Have a look at the screen same as below for your setup to better understand things.

image
image1640×2211 315 KB

7

I am sorry, I am not following.

The table in the opening message was from the VictronConnect App History.