Car Battery Charger | Will the battery stay charged if you have an inverter in your car with a battery charger hooked up (no key on)

4 Responses to “Will the battery stay charged if you have an inverter in your car with a battery charger hooked up (no key on)”

1. Ally

   If both electrical appliances are 100% efficient, it might work. But in practise, they are probably only about 25% efficient at best.

   Energy is lost as heat, sound etc. So the battery would eventually run out.

2. Kes

   If the inverter is plugged into the cigarette lighter, it may remain energized with the ignition switch on or off depending on whether it is part of one of the switch circuits. If the inverter is connected to the battery while a charger is also connected to the battery, retaining charge could depend on whether the load on the inverter is larger or smaller than the capacity of the charger. A trickle charger might not work.

3. itsbob1

   The first answer said it all.

4. basteve721

   Your saying that the battery charger is charging the same battery which the inverter is connected.

   Nope, won’t last. Both the inverter and the charger contributes losses to the battery.

   P(bat) – P(Inv) – P(Chrg) + P(Chrg_out) = -P(bat_drain)

   You can figure this out by looking at the rating plate of each of the devices Inverter & Batt Chrgr.

   Invrtr: Input power = 1200watt, Output power = 1000watt Net loss is 200watt.
   Charger: Input is 1.2amp at 120V = 144watt, Output is 10amp at 12V = 120watt, Net loss is 24watt.
   The total Net power loss is approx 224watt.

   Depending on how well the battery was originally charged up and the reserve rating of the battery I would guess it would last about 12 – 16hr before the Inverter shuts down.

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