Back-UPS XS 1200 staying on battery, acting oddly when battery disconnected

[Anonymous user]

Model: BX1200

Serial#: JB0611022850

My unit had a failed battery and had not been in use for a few months. It was unplugged during that time, but the old battery was still in the unit. I recently purchased a new battery pack, which was a duplicate from the same vendor as the last battery, and installed it. I let the unit recharge overnight.

After plugging in the unit and powering it up, the green "On Line" light flashes, then the yellow "On Battery" light comes on solid, then the green light goes out and the unit starts beeping, as if there is no power.  I have tried setting the sensitivity adjustment to "Low" with no difference in behavior.

As a little sanity check, I disconnected the battery and powered it up. I expected the green light and the red "Replace Battery" light to come on, as described in the manual, but this is not what happens. Instead the green light flashes for about 3 seconds, then the green light goes out and unit enters a pattern:

• the yellow light comes on for about 1 second
• the yellow light goes out (all lights are out) and the fan runs for about 1 second
• the fan stops and the green light flashes very quickly
• the cycle starts again.

I really don't think I have bad power in my house, and the unit has functioned well for years prior to this.  Is this potentially a problem with the batter pack, or a problem with the unit itself?

Edit:

This video shows the same behavior. https://www.youtube.com/watch?v=lioxJe0UdxY

Several users report that the sensitivity adjustment was useless, but that replacing a Mosfet N-Channel Transistor fixed it.

[BillP · Accepted solution]

Hi,

Try to reset the unit

To do this, follow the below procedure; 

1: Disconnect any attached load.

2: Unplug the UPS from the wall socket.

3: Disconnect the UPS' internal battery.

4: Push and hold the "On" button on the UPS for 5 seconds

5: Reconnect internal battery.

6: Plug UPS in to known good power source.

7: Turn UPS on.

[Anonymous user · Accepted solution]

Following the reset procedure did not result in any change. Still seeing the same symptoms.