I talked about this earlier today, but my message disappeared along with
a second message. Neither made it to the list at all. So out of three
messages sent, so far only one made it to the list. Let's see if this
one makes it.
All UPSs have a problem when trying to figure out what float voltage to
use since the correct voltage varies with temperature, amongst other
factors. Some UPSs use a low-tech way to avoid the problem. They use a
standard current-limited constant-voltage charger, but after float
charging the battery for a couple of days they disconnect the charger.
Too simple! They then monitor the battery and recharge as necessary.
This simple trick can double the life of the battery because it
eliminates the continuous overcharging that uses up the very limited
amount of water in the cell.
Ed
On 7/28/2014 7:03 PM, Brian, WA1ZMS wrote:
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-boun...@febo.com [mailto:time-nuts-boun...@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 <elio...@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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