[gundam91]

I have a PurePower 2000 conditioner. I had purchased this used during my house remodel, so it had been sitting in the storage for over a year. When I first plugged it in, it would not work. Based on discussion with PurePower, I found out that there are 6 batteries inside the unit, and because it had been unplugged for so long, the batteries would no longer retain the charge. Once I replaced all of them with a new batch, the unit was working fine.....for about a month. The batteries are the type you find in computer UPS units. My understanding is that the unit is charging the batteries continuously, and it is essentially supplying power through the batteries.

The last time I had the system up and running was on 7/4. On 7/7, when I tried turning the unit on, it did the usually self-check, then shut down immediately. Upon closer inspection, I noticed that everything seems to be normal, except the output voltage has dropped from the usual 120V to 96.0V. Due to the low output, the unit automatically shut down. I opened up the unit and unplug and replug all the batteries just to make sure the connections are tight. But no use.

I've sent an e-mail to PurePower, but I wanted to see if someone might be able to answer my question. What would cause the output voltage to drop? Could the problem be that one (or more) of the batteries is dead?

How would I check each battery to see if it is working correctly? I have a volt meter, but could use some guidance on how to use it. The batteries are all 12V. Do I check each battery to see if voltage is OK? Or do I check something else?

Thanks,

[Speedskater]

First you turn the unit OFF and unplug it from the wall outlet.
Then set your meter to DC Volts and the 20V or greater range.
Next measure one battery at a time.  It should read over 12 Volts.  (often about 12.7 V)
You can check your meter by reading your automobile's battery,  it should have about the same voltage.

[gundam91]

The batteries are chain linked and then connected to the unit. I assume I should disconnect the batteries from the unit, and remove the cables linking the batteries first before measuring?

[Speedskater]

If the batteries are wired as a series circuit (that is the "plus" terminal of one battery is connected to the "minus" of the next battery) then nothing needs to be disconnected.

But be careful the total voltage is about 75 Volts DC. 

If the batteries are connected in some other type of circuit, then some wires will need to be disconnected.