Re: Maintenance on UPS

Additional Comment re: Replacement of Batteries.

Batteries work as a team. Depending on your UPS there are a number of them in series (meaning they all carry identical current but may not have exact voltages) and sets (or strings) of these are often connected in parallel. These then have identical voltages (as a set) but may or may not carry the same current. Why do you care? Because if you only replace SOME batteries, the newer ones, being fresh, will provide more current and hold a higher voltage. The old ones will not hold voltage as well and may require additional charging compared to the new ones. But they are all connected together (in most UPSs) so they ALL get charged, need it or not. This has two detrimental affects: 1) Wasted electricity and additional heat, and 2) The new batteries get abused and their life shortened. This can cause battery swelling and resultant problems replacing them. In extreme cases UPS failure can result. Just recycled a big APC unit last week that died from this very abuse. Batteries in the unit were dated all over the last four years. Some had swelled to 20% larger than their original size ruining the battery cases as well. Worse than all that, the UPS dumped power completely to the data center it was feeding causing a full day outage.

Replace your UPS batteries as a full set.

Reminds me of the old man and his oil filter "You can pay me now, or pay me later."

- Larry "DrFranken" Bolhuis

On 6/13/2011 9:56 AM, rob@xxxxxxxxx wrote:

Does your maintenance cover batteries if they fail? Maybe. However, if
the battery fails during an outage during a critical time how much does
that downtime cost you? Would it be less expensive to just replace the
batteries on your own dime during a scheduled downtime? Does your
maintenance cover a "preventive maintenance" replacement upon a
recommended schedule (like, perhaps every third year) or does it only
cover replacement upon failure?

We have a rack with a large quantity of batteries. When they test down to
a certain level we replace them all. Saving some money to have the UPS
fail at an awkward time is penny wise and pound foolish - IMHO.


Rob Berendt