Have you ever let AA batteries sit inside of your tv remote control and forget about changing them... then find out that you really need that remote but when you go to replace the batteries you find a mess because the batteries were wayyyyy past their life cycle?? That's pretty much the same thing that's going to happen except on a bigger scale. I can't answer this question and say that nothing bad will happen (sometimes a bad battery with a lot of current provided to it will get so hot that it will explode!) but more than likely -- no. These units are designed as an offline UPS (you can read more here: http://psihq.com/products/ups-systems/)
so there will not be steady current going through the battery all of the time.
My sincere advice - if you're done with the UPS then unplug it from the wall and recycle the battery; then you can store your UPS for later use. Remember, it's against the law to throw batteries away, you must recycle them! Well... in the States anyway.
If you would like pricing on a new UPS, we can offer pricing better than any big box store (walmart, bestbuy, etc...). Contact me whenever & in whichever way is easiest for you:
Daniel • [email protected]
• Power & Systems Innovations • 800.260.2259 • www.psihq.com