. i am thinking using battery to power up my arduino uno. but arduino needs stable voltage.
is it possible that i use rechargeable battery to power up it. and program the mcu itself so that when the battery voltage decreases, the mcu will charge it using ac power.? it's like a loop.
You can certainly use rechargeable batteries to power Arduino.
The problem is RE-charging. Most NiMH and especially LiPo batteries don’t like to be recharged in series very many times. Lead-acid can be charged and occasionally “equalized” with a higher voltage.
A small 6V lead-acid (like in some emergency lights etc) might work. You’d need to:
- Use a relay to turn a 12V charger on and off.
- Monitor the battery voltage to set end-of-normal-charge
- Monitor temperature for correction if the temperature varies a lot
- Periodically charge to 14.5V or so to “equalize” the 3 internal cells.
Some small 6V / 12V line powered battery “maintainers” might work OK.
And there are small chargers for 2 LiPo (about 7.4V) that charge the cells separately.
Let us know what you end up doing…