Solar Power

A rough dump of various links and aspects of doing a solar power generation.

  • real time radar imaging of cloud cover in Berlin

Real world test between mono and polycrystaline panels

Panels + Controllers

This looks like the solar panel mentioned in the review:

MPPT vs PWM: Fast comparison for off-grid solar: Really good buyers guide to solar controllers:

Review of flexible panels shows they do not work as well as the glass mounted panels. This is because the heat distribution is uneven and the cells can overheat and become damaged. The reviewer says that this can mean they die within 5 years of use

Note that one commenter did cast doubt on some of the overheating issues saying it happened due to circuitry:

``` Lance Alpuerto 1 year ago I agree that the inability to dissipate heat would cause failure of the panels or at least reduce its performance. Ambient temperature does account for a large portion of heat, but what is being show at 0:46 is from circulating current due to individual receiving different amounts of radiation, thus different currents. It has more to do with internal interactions rather than environmental temperatures. Also, this is an issue flat panels share, so his statements aren't technically true. It just happens more often with flexible panels because how they are being used. ```


This is a company in the US that makes large battery arrays with used batteries

Using solar in Europe

Northern mainland Europe gets an average of 3.3 hours of sunshine per day. When taking in to account 30% loss due to inefficiencies in the solar system this means you could generate 231Wh per day on average for each 100 Watt panel.

This means that if you wanted 2 days of backup power for moderate usage of electronics such as laptops and phones you would need a 90 Amp hour lead acid battery.

DIY foldable panels

Outdoor Housing

German Solar Manufacturers


AGM batteries can only be drained down to 12.3V which is 50%, 10.5v is 100%:


If you take a lead acid battery cycles by how much you drain as a percentage

  • 20% Full - 250 cycles
  • 50% Full - 500 Cycles
  • 80% Full - 1,200 Cycles

### Powering an Apple computer from 12v AC

### Understanding C ratings on Lead Acid Batteries

Understanding the right voltage of a PV and Battery

``` The Victron MPPT is a buck DC to DC converter. It reduces the higher PV side voltage to the lower Battery side voltage. It can’t boost the (too low) voltage from a PV panel in order to begin charging a battery. Working at up to 98% efficiency the MPPT can accept any PV side voltage up to its maximum PV input voltage limit. This varies with the Victron models between 75V and 250V and is clearly printed on the unit itself, and all associated documentation.

On the battery side, it is the battery which sets the system voltage. The MPPT takes the panel voltage and converts it to a charging voltage which is higher than battery voltage in order to get current to flow into the battery, the voltage is reduced, the current goes up, and the power remains the same. But the battery chemistry will be dragging that MPPT voltage down at the DC bus level, and that electrical work is going into the battery chemistry to charge it.

Once the battery is full, and reaches a target voltage, the MPPT will adjust its voltage conversion to maintain a pre-set float voltage which is still higher than the battery voltage at rest – but not high enough to provide a significant current flow …which avoids the battery becoming overcharged.Bulk, Absorption, Float… Solar charger output voltage depends on where the connected battery is in its charging cycle (bulk, absorption, float) – the voltage of each stage being pre-set by battery charging algorithm employed by the MPPT. (The target voltage for each step can also be user-defined.)

In the case of a nearly empty lead battery at 11.5V the MPPT begins work by ‘Bulk’ charging with as much power as it can get from the solar panel(s) (unless a lower current-limit has been set) until it reaches the absorption voltage of 14.4V.

The MPPT will only begin charging when there is sufficient solar radiation to cause the PV panel voltage to rise 5V above the Battery voltage. After that condition has been met it will continue charging as long as the PV voltage remains at least 1V higher than the Battery voltage (or until the battery is full).

In the example above: The MPPT will begin charging when the panels provide around 16.5V …and will need a minimum of 12.5 V rising to 15.4V to continue charging.

When planning your installation you may find it helpful to use this ready made solar charging calculator to choose suitably sized equipment.

Common Mistakes

When connecting the inverter to the charge controller ‘DC load’ terminal, check in the charge controller data sheet whether this terminal is powerful enough to provide the input current to the inverter. Otherwise, connect the higher power inverter directly to the battery bank. In such a case, you will render the charge controller’s function that prevents the battery from overdischarging useless.

State of Charge for Lead Acid


solar-power.txt · Last modified: 2020/11/02 10:36 by earth