Get rid of the inverter; optimize your battery's stored energy better find means of powering your electronics with direct current (DC).

Most Electronics device operate with direct current (DC), however because electricity from the mains supply is in alternating current (AC) form, these devices are connected to the mains, the device manufacturer includes a power supply circuitry to step the mains supply (AC), down to a much more lower voltage (usually) and then convert the stepped down AC to DC.

Inverters waste energy when converting energy stored in batteries in DC form to AC (which most electronics are connected to) the wasted energy in the conversion process will better serve in giving additional operational time for your electronics.