SolarPi experiment 2: Finally something that works
1. Lead Acid is far cheaper, though its bigger and heavier than LiFePo. 12V @12Ah is only $35 from a brand-name (<a href="https:&#x2F;&#x2F;batteryinthecloud.com&#x2F;products&#x2F;ps-12120" rel="nofollow noreferrer">https:&#x2F;&#x2F;batteryinthecloud.com&#x2F;products&#x2F;ps-12120</a>), and closer to $25 from no-name brands on Amazon.<p>2. Modules to charge LeadAcid are so cheap, they don&#x27;t even make them. This specified PS-battery hsa a 13.5V to 13.8V &quot;standby&quot; voltage, meaning that 13.65V from the Solar Panel is all you need to have a UPS. Connect the 13.65V source from the Solar-panels to the + and - leads of the 12V battery, and volia. You get 13.65V when solar is available, and 12V from the battery when the solar cuts off. The end. Isn&#x27;t that easy?<p>3. Grid-tie should be similarly easy, though I don&#x27;t have too much experience with it myself. IMO, buy a professional AC-&gt;DC converter, probably at 19V or some other suitable voltage and then get a DC-DC buck converter to go from 19V to 14.35V, and then a diode (0.7V dropoff) to hook up to your batteries in parallel. You&#x27;ll also need a diode in your Solar-panels cause you don&#x27;t want your Grid-tie system &quot;charging your solar panels&quot; (that&#x27;d probably create a fire and&#x2F;or damage them...).<p>Hobbyists should NOT deal with main-power themselves, but there&#x27;s a gross-many number of AC-to-DC converters available from $10 to $40.<p>4. Don&#x27;t battery balance. Just buy bigger batteries. If 12Ah isn&#x27;t enough, buy a 20Ah battery. If 20Ah isn&#x27;t enough, buy a 33Ah battery, etc. etc. The limit is whatever you&#x27;re comfortable with (the bigger batteries give more current which can be more dangerous)