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DIY emergency power system - a field report

Instructions for a simple DIY emergency power supply using PV

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The storm disaster in NRW (Germany) has shown that the fears of many scientists can quickly become reality. Within hours, entire regions were cut off from the outside world. I myself was in the crisis area, as my parents and many friends from my school days live there. It is impossible to describe the picture on the ground.

I will show some Instructions for a simple DIY emergency power supply using PV (Using standard and long lasting items)

The storm disaster in NRW (Germany) has shown that the fears of many scientists can quickly become reality. Within hours, entire regions were cut off from the outside world. I myself was in the crisis area, as my parents and many friends from my school days live there. It is impossible to describe the situation there.

In the area i was, there was relatively little support from THW (THW is a Governmental Organization in the field of civil protection and is based on the voluntary commitment of dedicated people) and the fire brigade, especially at the beginning. There was no electricity, no water and no telephone. Due to the failure of the mobile phone network, the battery of many mobile phones ran out much faster than usual, as mobile phones in these situations search for available networks with maximum power. This was also the case with my parents. We as a society in western Europe are used to everything working and we have become dependent on it. This is called the vulnerability paradox and is one of the main arguments for protecting critical infrastructure.

Even when the mobile phone networks were partially working again, many still could not make phone calls because of the empty mobile phone batteries and the lack of electricity. In addition, of course, without electricity there was hardly any light and young parents had the problem of getting baby porridge or milk for the children warm due to the lack of alternative cooking options.

Emergency generators are a possibility, but these require fuel, maintenance and without regular test runs according to Murphy's Law "of course" do not work especially in an emergency. I myself was able to stay afloat with a power bank and solar panels with USB output. However, I already had the idea of setting this up more professionally and robust solution. The idea of a solar-based emergency power supply with battery buffer was born.

Of course, such systems can be bought ready-made, but some of them cost over 1000 euros as a kit and are still not portable. So something for mobile use was needed. The following goals were defined:

  • Battery storage (No Lipo), easy to obtain
  • Charging of USB devices
  • 230V system for everyday use (bottle warmer, light, etc)
  • 12V output for chargers


I deliberately decided against lipos because they are more difficult to secure and, depending on the quality of the lipos, have a higher fire risk. You can get a car battery on every corner and, in the worst case, you can also remove it from a defective vehicle on site.

To stay mobile, I wanted to use only one solar panel. It should also be a monocrystalline module, as this has a better energy yield. But this is only a question of price and taste. It works just as well with the much cheaper polycrystalline modules. I had a 45 Ah car battery in the cellar for a long time. So the goal was defined and I went looking for individual parts in the basement lab.

Note: Electrical work should only be carried out by qualified, skilled persons!

The assembly is relatively easy and can be done in two hours. The cost was around 320 euros. If you adapt certain things (box for installation, other solar panels), you can even get under 250 euros.

  • 1 × Car battery In my case a Varta starter battery, 12V, 45Ah, 400A)
  • 1 × 12V to 230V inverter at least 300 Watts (no Name China Model used)
  • 1 × 12V socket (a cigarette lighter from the car)
  • 1 × Solar inverter As a Set "Offgridtec® basicPremium-M 80W"
  • 1 × Solar panel

View all 8 components

  • 1
    Battery Placement

    In order to prevent the battery from slipping, a precisely fitting base plate was cut from chipboard. This has a recess for the battery so that it can no longer slip. Of course, this has to be cut to fit the user's box (if you use another one then me).

  • 2
    Connect PV and Battery

    The next step was to connect the electricity. All cables were already included in the PV set I used. When using your own cables, please ensure that the cable cross-sections (10 mm) and fuses are suitable (maximum 15 cm away from the battery). I connected the cable to the solar panel first. Plus to plus, minus to minus. Since high currents flow, please tighten them firmly. I have not yet connected the solar panel (this has special quick adapters). Next I connected the battery. A 20A fuse must be installed in the positive cable (included in the PV set). Again, plus to plus, minus to minus. This fuse should not be plugged in! There is a danger of a short circuit.

  • 3
    Adding the Solar inverer

    The230V invertermust not be connected directly to the solar inverter. The 230V inverter must be connected directly to the battery. My inverter came with 2 cables that could not be connected directly. I shortened them, re-crimped them and then connected them directly to the battery. A fuse was also installed directly in the positive cable of the battery.

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