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<\/a><\/p>\nhttps:\/\/www.digikey.com\/schemeit\/project\/shunt-regulator-LDU34M83021G\/<\/a><\/p>\n You will need a heat sink big enough to dissipate the excess energy from the solar panel. The piece of sheet aluminum seems to be enough for the 5W solar panel I am using to charge a 12V 7AH SLA battery.<\/p>\n There are pros and cons to this design. Pros: simple, no vampire drain, inexpensive. Cons: it does not cut the battery off when it runs low, you need to watch that, you will need a big heat sink if you have a big solar panel.<\/p>\n Update:<\/p>\n I needed to build another one of these and decided to use a bipolar transistor. Even though the one I built using the above design has worked well for many years, my concern is that the Vgs turn on voltage may not be consistent from MOSFET to MOSFET. So I used a MJE3055T instead. The 3055 is a bit cheaper and the turn on is based on the .7 V turn on of a bipolar junction. It has worked well, and it ends up the wiring is exactly the same. Bipolar transistors require more current to drive, but if you use a 5W zener, you should be fine for most things the 3055 can handle.<\/p>\n https:\/\/www.digikey.com\/schemeit\/project\/shunt-regulator-npn-2DB09QO501AG\/<\/a><\/p>\n","protected":false},"excerpt":{"rendered":" 12 volt sealed lead acid batteries are very useful for many applications, but many charge controllers put a small drain on the battery. Once this drain has emptied the battery, it will be ruined if not immediately recharged. But with … Continue reading <\/a><\/p>\n