No Batteries Available ?-How to Check battery health on MacBook Pro early 2011

A few days ago, I went on vacation and unplugged power cable from my MacBook Pro 13' early 2011 and then I got back home, the battery was not detected by OS and didn't charge. I then understood that I had automatic startup configured and the laptop did power ON next morning then I was not at home. The battery was discharged completely.

I tried to restart, to power down and unplug power cable, I also tried to did SMC reset, but that didn't work.

What's the most reliable way to check the health status of the battery? - I want to replace it, but I want to be completely sure that this is the battery, and not something else.

Battery is about 3 years old and about 250 cycles.

The battery icon is the same as below:

UPD1:

I did run AHT and it returns the following error code:

4xxx/1/40000000: "Battery"

I plan to perform extended testing as well later today to see if any other errors appear, but it looks like the culprit of the issue is battery.

The battery Condition now is Replace Now.

The status changed after I unplugged power cable for a couple of days and then I plugged the cable and the laptop started, the battery status changed to Replace Now.

I will shortly check it with another battery and perhaps replace the old one.

UPD2:

I've tested my MacBook with similar working battery and it did detected the battery and worked fine and this is the good news. On the other hand I now need to have the battery replaced.

UPD: Eventually, I now have replaced battery and it all looks OK.

The laptop is running smoothly either connected to AC power or on battery.

All the information you get from fancy 3d party is already in your system (that is where they get it from anyway).

Open your About This Mac, more info, system report and find Power:

It will tell you all about your battery.

It looks like this on my system:

Normally the Battery will keep a small reserve charge to be able to report its status to the computer. In your case somehow it was sucked dry completely :)

The good news is it is the battery, since your SMC is working and everything else is working based on the message "Replace battery". That same message was probably run all the time during your vacation, till the battery was exhausted to the level were the battery build in chip did not have enough power to talk to your OS. As for what caused that drain? did you leave your computer in a sleep mode ?

Looks like your battery is dead, go get a new one.

Depending on where you live you need to get a new one from Apple or you might find cheaper batteries from a 3rd party vendor.