[time-nuts] Oncore battery backup

EB4APL eb4apl at cembreros.jazztel.es
Thu Apr 7 00:34:50 UTC 2011


I did the same to extend the back up time of a couple servers, I used 2 
car batteries because the UPS runs on 24 V.
But be careful, aside for the live battery connection (I couldn't figure 
it out and learned that in the rude way, 220 V here), you can go into 
another problem: some UPSs, mainly the cheap ones intended for backup a 
PC lack the power dissipation capacity to run more than the internal 
battery discharge time, about 10 minutes at full load.  If you connect 
an external battery to extend this time the power transistors can be 
cooked.  I always wondered why these UPSs were not offered in several 
time ranges with the same power rating and this is usually the reason.
Some time ago I used several UPSs manufactured by HP in a project and 
they had provisions for connecting external battery packs.  They  had 
the dissipation department well designed.

Ignacio, EB4APL


On 06/04/2011 20:25, Murray Greenman wrote:
> Why not just put a bigger battery in your UPS? I have a couple of old
> ones, and they run just fine with an old car battery, and thus give me
> many hours of backup for my Trimble/Nortel GPSDO.
>
> Just be careful though - in some UPS units the battery is live to the
> mains! The APC ones seem to be OK.
>
> Murray
>
>




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