How to test which battery is bad (internal or external?) on a Smart-Ups XL model
All models with an "XL" suffix, All Serial Numbers
You can test the external batteries simply by performing a self-test on the UPS. A self-test can be performed either through the PowerChute software (under the diagnostics menu), or simply by pressing and holding the test button on the UPS for 5 seconds.
If the battery packs were added correctly when first installed (through hyperterminal, for example), the UPS becomes aware of the entire battery charge, runtime, and condition. Instructions for adding external battery packs to a Smart-Ups XL unit can be found in the Knowledge Base document titled, ""Adding external battery packs to a Smart-UPS XL.""
For example, if the replace battery light comes on the UPS it is indicating either a bad internal battery or bad external battery. The only way to find out which battery went bad is to perform a self-test with no external batteries attached. If the replace battery light does not come on with zero external batteries attached, you know the issues lies within one of the external battery packs. Now, try attaching external batteries one at a time, performing a self-test after each one you add, until you determine which battery needs to be replaced. Visit https://www.apcc.com/support/upgrade.cfm for your replacement and upgrade options."