MPPT solar power battery charging

31 Jan 2010
Posted by Laptop Junction

MPPT is a recent development in the world of solar power technology. MPPT gets upto 30 % more power from existing solar panels. Although MPPT was first applied in large grid solar power systems, the technology now finds it way into consumer market. Here’s a real example of MPPT in the Machine.
 

MPPT solar power battery charging

MPPT means Maximum Power Point Tracking – a technology designed into a new generation of solar power battery chargers. In simple terms the technology ‘tracks’ or ‘follows’ the maximum power point for a solar panel. MPPT is not a mechanical tracking device to position the solar panel perpendicular to the sun – it’s about the electronics / firmware in a solar battery charger.

  IVT MPPT Solar battery charger - SolarLadeRegler
  The IVT MPPT solar battery charger
Just as maximum HP peaks at specific amount of rpm’s for car engines, the same applies for solar panels – but that’s how far the analogy goes. The maximum power point (MPP) for solar panels shifts by the amount of sunshine captured by the solar panel.

In analogy with a car engine, a MPPT solar battery charger acts like an automatic gear box. Keeping the engine running at the optimum RPM it delivers maximum output. Now for a solar panel the sun is the fuel – captured energy varies with the time of day, clouds and solar panel temperature – requiring constant adjustment for optimum performance.

Conventional (PWM) solar power battery chargers manage the state of charge of the battery regardless of the maximum power point of the solar panel. Consequently, the battery ‘pulls’ the solar panel output away from it’s optimum. This is especially true when a battery is discharged. Basic measurements with a simple solar cell phone charger also showed this effect.

Ipad Mini on Solar Power
 

MPPT solar battery charging in action

The machine is equipped with a IVT MPPT Solar Battery Charger charging a 24 Volt 230 Ah (5.5 Kwh) AGM type battery bank. It’s produced by Innovative VersorgungsTechnik GMBH in Hirschau Germany.
 

  Inside the IVT MPPT Solar battery charger controller - SolarLadeRegler
  Inside the IVT MPPT solar battery charger. The MPPT controller chip sits on the back side.
Bottom right a standard 25 Amp car fuse. Above the fuse relay for switching the load on/off.
On top the gray temperature sensor lead next to the load switch. To the left the connector for the remote panel


The MPPT charger logs it’s operating parameters to a 2 Gb SDCARD.
 

IVT MPPT Solar battery charger SDCARD output IVT MPPT Solar battery charger remote display panel
The IVT MPPT solar charger remote control panel with the TEXT output on the SDCARD


Below the MPPT voltage trend on an average sunny / cloudy day in winter time in southern Europe
 

  MPPT solar battery charger voltage and current trend
MPPT Solar battery charging graph created from logged IVT data


Solar panel output voltage runs freely and peaks at 37 Volt while battery voltage averages just around 26 volt. The current from the solar panel is just below the battery charge current which peaks at 5.2 Amps. Round 2pm in the afternoon the AC mains battery charger was connected causing a jump to 28 volts. 15 minutes later the MPPT solar battery charger shuts down because of high battery float voltage.

The maximum logging rate is 1 measurement / 10 seconds and drops to a lower rate when there’s no change to report. Measurement (sampling) accuracy isn’t mentioned in the manual but values seem to roughly match.

The IVT MPPT solar battery charger, replaced a STECA PR2020 – a classic PWM multi-stage solar battery charger. The IVT MPPT charger allows solar panel voltage to run more freely, regardless of battery voltage.
 

MPPT battery charging observations

Most striking for MPPT solar charging are voltage levels at high and low solar panel output.

1)    When output is high, solar panel voltage moves towards battery voltage.
2)    When output is low(er), solar panel voltage can move up more freely.

Specially 2) shows the advantage of MPPT– in less ideal conditions there’s more power compared to classic solar battery charging.

In case of 1) the ideal situation would be a loss-less connection between Solar panel and battery – meaning battery voltage would be equal to solar panel voltage. However a small voltage drop can be expected, specially at high charge currents.

Peak solar panel power on 4 January 2010 was 156 Watt of which 137 Watt was converted to charge the batteries. The conversion efficiency at that moment was 156 / 137 = 88 % which is an average score. Consequently the IVT consumed about 19 Watts.

Accuracy of the digital measurement samples yet has to be confirmed by a future measurement with an external voltage trendmeter like the Fluke Scopemeter 123.
 

MPPT solar battery charging backgrounds

MPPT performs better in conditions when it’s needed the most;

-    When the battery is discharged
-    During cloudy, dusty or smoggy days
-    During partial shading of the panels

Conditions where solar panels perform worse:

-    When panel temperature is high
-    When solar panel is partial shaded
-    When solar panel angulation towards the sun is off
 

More about solar power technology

MPPT solar chargers in the UK

Similar MPPT solar chargers in the US:

MPPT Solar chargers in Germany

 

Solar power information



Website Innovative VersorgungsTechnik GMBH in Hirschau

Read about Swiss made portable solar power

From China cheap 180 Watt Solar panel

A simple solar cell phone charger

 Good MPPT solar charging article

 

 

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