Zero Vampire Drain SLA Battery Charge Controller

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 a charge regulator that does not put a drain on the battery, it can store for months and still hold a decent charge.

So I put together a simple shut regulator to test out the concept. So far it has been working well. I can leave it in the garage for months at a time, and grab it for camping trips, etc.

https://www.digikey.com/schemeit/project/shunt-regulator-LDU34M83021G/

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.

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.

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