I have designed a simple DC UPS for my network equipment (Modem,Router and RPi). It uses 12v 5AHr Lead acid battery and an Arduino to control the 3 stage charger based on LM317. I haven’t build it yet, want to correct/improve from your valuable suggestions.
Feel free to ask/suggest anything, i really appreciate it.
The old circuit didn’t worked as expected, here is a revised one.
- Vin is ~18v DC (may be from an old Laptop charger)
- Vout can be anywhere between ~11v and ~18v
- TWO LM317. One is wired as Constant current charger, and one as a constant voltage charger + floating charger.
- Activate relay for CV/Float charging.
- The CV charger (~14.4v) function is enabled by default when relay is on. A high input at “FC” will enable float charging (~13.8v)
- AVR can monitor the Battery voltage from “V1”.
- Battery charge current can be measured using Instrumentation Amp AD620.
- It has a HD44780 LCD display, and a button to turn on back-light.
- During a power outage, the load will be switched to battery without interruption.