[time-nuts] Oncore battery backup

paul swed paulswedb at gmail.com
Wed Apr 6 20:41:54 UTC 2011


Well some good comments about the UPS ability to handle the heat from
running for a long time. Absolutely true. The charger does not deliver
enough current to effectively charge the battery set if its larger then the
original design. As such the battery life is effected up to 50% and
certainly the operating capacity. They build these things cheap as they can
to preserver sales margins and a average life of 2 to 3 years. Regulation of
the charge voltages/currents to optimize SLA life is sloppy.
Don't get me at all wrong. A cheap ups and 2 X batteries should do something
and at the costs they want these days, its pretty amazing actually. Heck
have you seen the cost for a good set of sla batteries these days? I do not
mean homedepot been on the shelf dead for 3 years either.
There is one other reasonable approach. Been around for years and pretty
sure its on the web for the 3801. Essentially float a battery set across the
24 volt input with a good grade charger. This is pretty much how HP does
there RB and CS standards. You do not have the inefficient up conversion
costs of a UPS. Thats exactly how I run my FRS in the basement and on 2 X 14
amp SLA batteries and get around 12 hours as I recall. And thats not killing
the batteries. Bad idea at what they cost these days.
By the way I drop the distribution divider chains and such when I go to
battery Even the leds.
Regards
Paul.

On Wed, Apr 6, 2011 at 4:21 PM, Jim Lux <jimlux at earthlink.net> wrote:

> On 4/6/11 11:25 AM, 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.
>>
> The other thing is that some UPS's have a thermal limit on how long they
> can run (e.g. 20 minutes before they melt)... suitable fans might help (as
> opposed to having it in a dust filled box under your desk)
>
>
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