[time-nuts] OT Gel Cell question

Brian, WA1ZMS wa1zms at att.net
Mon Jul 28 21:03:46 EDT 2014


At the risk of adding fuel to the fire, I'd like to chime in and then will
go quiet.

Based on my first-hand day-job experience:
The consumer UPS units I have seen seem to run the float-voltage on Gel
Cells
at the very high-end of the cell's spec.  The goal appears to be to get the
battery
back to full terminal voltage and do it fast. That way the next AC mains
drop out
can utilize the full capacity of the Gel Cells.  The long term downside is
that the
cell would rather float at about a volt less or so and thus the life of the
cells are
reduced rather sharply.  Great for the UPS vendors; they get to sell
replacement
cells!

If one enters the 10kW and up category the game changes and the UPS vendors
take
much care to use a multi-stage charger system to get bulk charge into the
cells, but
not to float or "top off charge" the cells too much.

Enter the modern AGM-I and AGM-II cells and it becomes a grey area that I am
not
well educated about.  I asked for hard data from the battery vendors, but
the answers
were mixed at best.

Blunt answer I see is:
Do not treat flooded lead acid the same as Gel nor as AGM-I nor AGM-II.
And ALWAYS use temp sensors for best performance!

My 2 cents in the RF/Telecom World.

-Brian, WA1ZMS

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of paul swed
Sent: Monday, July 28, 2014 8:17 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] OT Gel Cell question

Elio
Oh man I have seen the amp hour magic also.
Thought maybe I was just getting older batteries. We have major home chains
in the US that batteries sit around for quite some time as measured by the
dust on them. So I was thinking that was the case.
Regards
Paul.



On Mon, Jul 28, 2014 at 6:50 PM, Elio Corbolante <eliocor at gmail.com> wrote:

> In my previous work I was developing UPSs: I can confirm that in the 
> last years the quality of the typical gel batteries has declined.
> What once was 7Ah batteries now are sold as 9Ah ones!
> And 5-6Ah ones are sold as 7Ah... :(
> One of the best way to identify the "quality" of sealed batteries is 
> to weigh them: the heaviest have the highest capacity (and in general 
> are also the best because the producer didn't spare on materials).
>
> _       Elio Corbolante.
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