- Not sure what the Arduino has to do with it. I gather you are switching on the basis of the presence of 5V from some sort of Arduino, but not obvious what the overall project design is. Always nice to know what you really wish to do.
- A lead-acid or "gel cell" is float charged at 13.6V, not 14.4. Your circuit does not show the regulator for such float charging.
- Somewhat strange way of using the 500 ohm current limiting resistor in the emitter circuit. If you are using extra transistors as inverters (but "4000" series CMOS gates would do that with no static current draw) then you might as well use a "constant current" circuit.
- Would not FETs do a better job if you are concerned about current consumption?
- 100k resistor at 5V - something of the order of 50 µA (microAmps). This is significant why?