[ale] OT: APC wattage

Jim Lynch jwl at sgi.com
Wed May 7 09:09:20 EDT 2003


That is excellent advice for lead-acid batteries in general. 
Discharging them beyond 50% will decrease their life significantly. 
I've read where flattening a lead-acid battery twice will pretty much
make it useless, but I have no practicle experience.  I talking with
people who live on battery power (long time cruisers, sail and power)
they all agree the 50% is a golden rule never to be broken.  Dead
batteries for them are sometimes a serious problem.

Gelcell bateries used in most UPS units fall into the lead-acid
category.

Jim.

Dow Hurst wrote:
> 
> My experience has shown me that if you expect to run off your batteries
> for long enough to start really heating the battery that you should get
> a large enough UPS to not use more than 50% of the available wattage.
> So, a 450VA APC SmartUPS will certainly keep my SGI O2 with external
> SCSI CDburner alive for ten minutes, maybe 15 minutes.  However, the
> batteries will have overheated and started to degrade.  When I had 90%
> of an APC capacity used in one situation, the battery literally melted
> it's case and deformed significantly.  So I always try to ride around
> 50% of UPS capacity for my load when on battery.  The batteries will
> last longer that way too!
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