How do we remove the battery from ETN 5110 UPS Systeem

No fires with Nickel Cadmium batteries. April 1998 Technology

It's a guess, but all phones have intelligent charging. The phone is treating your new battery the same as the old one and is reducing or turn off charging one it reaches the Mah of the old battery.

It sounds like it is working, so don't worry.

AliExpress appear to sell the batteries as well as here

https://batteryclerk.ca/products/replacement-battery-for-nokia-bls-2n-bls-4-bms-2s-bps-2?variant=16405452455979&utm_source=googleshopping&utm_medium=cse&gclid=CjwKCAiA-dCcBhBQEiwAeWidtfZjoRRddz783McYHwGJObfykZhJFDgPzoPkP5g3ppFp1mxI7AKhIxoC0d0QAvD_BwE

https://www.aliexpress.com/w/wholesale-nokia-5110-battery.html

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learn that when you have black out.
the batteries TAKE OVER< and are huge stress on any battery like this,, and when the lights (AC power) turned the UPS tries to charge said batteries and are now bad.
time for new batteries, or let it beep for 24hours and hope the batteries can recover.
the manual tells you how to see if the batteries are bad and with errorcodes, on all UPS made. RTM read the manual first.
no 2 UPS are the same , unless are.
the first is battery voltage under charge, if too low that means
a cell in 1 battery is shorted. as the LOVE TO DO.

Without the exact model number, it is difficult to best assist you. Perhaps I suggest you give Eaton a call:
Toll Free: 1 800 843 9433
International: +1 919 871 1800
E-mail: [email protected]
You can view the manual here in the documentation tab:
Eaton 9355 UPS (if this is the model you are referring to).

check and flip the reset button
if it still is faulty have it repaired or replaced

If there is no alarm silence button. Most likely the unit have develop some internal fault

I believe you will find that your battery is either dead or shorted.

Replace the batteries. A lot of the smaller UPS systems won't start or restart if the batteries are bad.

I recommend that you call Eaton (the manufacturer) service line: 800.356.5737. Here is the product page for the 3105: http://powerquality.eaton.com/Products-services/Backup-Power-UPS/3105.aspx?cx=3 You can also send an email:[email protected]

The front plate beneath the digital read out slides down to expose the battery bay area....
Here is a digital copy of your manual for future reference.

GOOD LUCK AND PLEASE RATE THIS POST!!!!

You probably need to replace the battery. Here is the product page link: http://powerquality.eaton.com/Products-services/Backup-Power-UPS/5110.aspx?cx=3 There's a PDF for the manual.