+<p>
+<a href="https://www.amazon.de/gp/product/B07RLQH5TR/ref=ppx_yo_dt_b_asin_title_o07_s00?ie=UTF8&psc=1">Single sided prototype PCB is used</a>.
+</p>
+</div>
+</div>
+
+<div id="outline-container-sec-4" class="outline-2">
+<h2 id="sec-4"><a id="ID-65d68227-4bf2-4c4f-b4d3-c390bc6a9c34" name="ID-65d68227-4bf2-4c4f-b4d3-c390bc6a9c34"></a><span class="section-number-2">4</span> Main board</h2>
+<div class="outline-text-2" id="text-4">
+<p>
+This is logically main board because it appears to be central hub that
+connects all components. It also houses 2 <a href="https://www.amazon.de/gp/product/B072MQYJ93/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1">adjustable DC-DC Step Down
+voltage converters</a>.
+</p>
+
+
+<figure>
+<p><img src="main%20board/main%20board,%201.png" class="img-responsive" alt="main%20board,%201.png">
+</p>
+</figure>
+
+<p>
+High-level schematic of entire device:
+<img src="main%20board/schematic.png" class="img-responsive" alt="schematic.png">
+</p>
+
+<p>
+As seen from schematic, ~30 volts DC from transformer board is routed
+into first step-down converter that reduces it to about 15V. Reduced
+voltage is then directed to <a href="#sec-5">Current limiter circuit</a>. Current limiter
+loses about 2 volts. Now we have current and voltage limited power at
+about 13 volts. This power is used to charge connected 12V Lead-Acid
+battery. Also the same power is routed to <a href="#sec-7">connector terminal</a> to be
+consumed by connected devices.
+</p>
+
+<p>
+As seen from this schematic, device is not meant to provide high
+current for long periods of time. Instead it gets comparatively
+limited current to charge the battery and feed devices with low
+current requirements. Occasional current spikes are backed up by
+battery that stays in use-changing mode.
+</p>
+
+<p>
+Also about 13V output voltage is approximate and depends on connected
+battery charge level.
+</p>
+
+<p>
+Second Step-Down converter reduces voltage even further to quite
+precisely 5V DC. This resulting voltage is also routed to <a href="#sec-7">connector
+terminal</a>.
+</p>
+
+<p>
+Both 13V and 5V lines are also routed to <a href="#sec-6">indicator panel</a> for
+monitoring.
+</p>
+
+<p>
+There is single on/off switch. In off position, it disconnects battery
+and transformer from the system effectively powering everything down.
+</p>
+
+<p>
+On schematic above, some wires are annotated with numbers from 1
+to 13. This corresponds to output pins on the board.
+</p>
+
+
+<figure>
+<p><img src="main%20board/main%20board,%202.png" class="img-responsive" alt="main%20board,%202.png">
+</p>
+</figure>
+</div>
+</div>
+<div id="outline-container-sec-5" class="outline-2">
+<h2 id="sec-5"><a id="ID-afc22d23-9bc4-421c-9cac-e0ce34bd36bc" name="ID-afc22d23-9bc4-421c-9cac-e0ce34bd36bc"></a><span class="section-number-2">5</span> Current limiter</h2>
+<div class="outline-text-2" id="text-5">
+<p>
+Schematic:
+<img src="current%20limiter/schematic.png" class="img-responsive" alt="schematic.png">
+</p>
+
+<p>
+Simple LM317 based current limiter is used. I used 4.7 ohm
+resistor. It provides about 265 milliamps of current. See <a href="http://www.reuk.co.uk/wordpress/electric-circuit/lm317-current-calculator/">calculator</a>.
+</p>
+
+
+<figure>
+<p><img src="current%20limiter/current%20limiter,%201.png" class="img-responsive" alt="current%20limiter,%201.png">
+</p>
+</figure>
+
+<p>
+Thermal paste below and UV hardening glue on top is used to attach
+LM317 to the heatsink. There is also jumper-like solution on top
+right. This is handy to attach multimeter tap to verify/monitor
+current during initial device calibration.
+</p>
+
+<p>
+If attached battery is really empty, significant voltage drop can
+occur in LM317. Heatsink is needed to dissipate that power.
+</p>
+
+
+<figure>
+<p><img src="current%20limiter/current%20limiter,%202.png" class="img-responsive" alt="current%20limiter,%202.png">
+</p>
+</figure>
+
+<p>
+Note: resistor gets hot too.
+</p>
+</div>
+</div>
+
+<div id="outline-container-sec-6" class="outline-2">
+<h2 id="sec-6"><a id="ID-c9a69490-f920-4a31-b32e-b101bfc3d01b" name="ID-c9a69490-f920-4a31-b32e-b101bfc3d01b"></a><span class="section-number-2">6</span> Indicator panel</h2>
+<div class="outline-text-2" id="text-6">
+
+<figure>
+<p><img src="indicator%20panel/indicator%20panel,%201.png" class="img-responsive" alt="indicator%20panel,%201.png">
+</p>
+</figure>
+
+<p>
+Basically 2 digital DC voltmeters and main on/off switch.
+</p>
+
+
+<figure>
+<p><img src="indicator%20panel/indicator%20panel,%202.png" class="img-responsive" alt="indicator%20panel,%202.png">
+</p>
+</figure>
+
+<p>
+Download:
+</p>
+
+
+<figure>
+<p><img src="indicator%20panel/indicator%20panel.png" class="img-responsive" alt="indicator%20panel.png">
+</p>
+</figure>