Thread: Question on Inverter draining battery when turned off

I've let my car sit for as much as three weeks in the winter with the inverter on with a 5 year old battery and there was no prob. The drain the inverter puts on a battery is parasitic. Probably slightly more than the radio memory. I've never seen a persons battery die just from the inverter being on.

So would it be safe to keep the Inverter button on and the Xbox button off when the car is turned off, or do I need to turn the inverter button off too when I turn off the xbox along with the car?

Originally Posted by PapaPrem

So would it be safe to keep the Inverter button on and the Xbox button off when the car is turned off, or do I need to turn the inverter button off too when I turn off the xbox along with the car?

Be careful - Your xbox is probably pulling some current too. I can't see this being too much of a problem if you drive everyday, for 30minutes to an hour.

You may want ton invest in a power-meter. I think thinkgeek used to make one. You plug it between your xbox, and your wall. It measures the power consumption rate, so you can determine if your xbox is a current hog when powered off.

Originally Posted by KyleYankan

Be careful - Your xbox is probably pulling some current too. I can't see this being too much of a problem if you drive everyday, for 30minutes to an hour.

You may want ton invest in a power-meter. I think thinkgeek used to make one. You plug it between your xbox, and your wall. It measures the power consumption rate, so you can determine if your xbox is a current hog when powered off.

I just ran a search on thinkgeek and didn't find one. I also looked in the gadgets and electronic goodies. Nada...

Your'e right. It must have been on one fo the thinkgeek-like vendors? computergear maybe? I'll look through the magazine stack later tonight.

The easiest power meter device like you describe that I have used was called the Kill-A-Watt. It is made by Bits limited.

However, devices like these generally give you watt numbers and will not measure trickle currents to a small enough scale that will allow you to guage how much draw an idle inverter will make to the battery or how much draw your xbox will use from the AC outlet when powered off. For that, you just need an ammeter (or multimeter) which can measure draw down in the milliamp range. A load of less than 1W (which will not be indicated by the kill-a-watt and similar) is enough to affect your car battery significantly over a couple of weeks.

To calculate this time, measure the idle current Let's assume you measure 250mA. Divide it by 1000 to get the amps.. ie 0.25A in this case. Then divide the amp hours of the battery by this number to get the hours of time your car will survive while off.. ie if you have a really nice high capacity optima yellow top with 120Ah of capacity you do 120/0.25 meaning that a constant 250mA load will kill that battery in roughly 480 hours or 20 days. Note that it will probably be longer or shorter due to a number of factors such as the load not being constant, the battery not being at its full charge, etc. But in any case you can easily see that even a comparitively small current draw has a pretty big effect. If you find that your inverter and xbox draw 500mA or something from the battery and you have a 60Ah battery, that's going to kill your battery in less than 5 days! If you don't have a deep cycle battery and don't drive your car every day, running the battery very low like that will shorten your battery's lifespan by a tremendous amount.

In the long run, a custom DC-DC power supply for your Xbox will probably be a better route than mucking with the inverter. It seems expensive, but compared to the cost of the inverter itself plus the cost of replacing the battery needlessly soon, it may not be such a bad investment.