So they didn't have a bypass switch? As long as we are talking about
UPS's no one should had one and not have a bypass switch.

JMHO,

Chuck

-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx
[mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of DrFranken
Sent: Monday, June 13, 2011 10:29 AM
To: Midrange Systems Technical Discussion
Subject: 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

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