Re: Unused Li-ion battery pack

On Sun, 04 Oct 2009 11:02:14 +0800, who where <noone@xxxxxxxx> wrote:

Rhetorical question: Why don't UPS manufacturers use a decent
charging circuit in their SLA-backed UPS's?

Many years ago, I accused APC of intentionally setting the charger in
some models to prematurely destroy batteries and create hazardous
conditions (bulging, leaky, and overheating batteries). Specifically,
the early APC 1400RH 4ru model was the major culprit.
<http://www.LearnByDestroying.com/pics/home/apc1400.jpg>
It has 4ea 12V 7A gel cells in a series-parallel derangement. We had
about 35 of these installed at various installations, all of which
rapidly ate batteries. Eventually, these UPS's were removed when it
was found that the batteries had bulged and leaked so much that
extraction was impossible. I ended up with most of them and tried
redesign the charging circuit. APC was totally uncooperative. I
don't want to go into the details, but eventually APC released a
totally new 1400RH model, with a slightly improved charging circuit.

During this adventure in frustration, I learned a few things about UPS
charging philosophy. The customers want the batteries to recover as
fast as possible after being run for a while. That's because power
outages tend to come in clusters, like during a storm. Fast recharge
is an important requirement. Given the choice of long battery life
and fast recharge, most customers will choose fast recharge. More to
the extreme, when faced with the possibility of killing the battery
just to get it charged quickly, most customers will accept the cost of
a new battery pack rather than risk any additional server downtime.

So, rather than a modern staged charging system, that tapers off near
the EOC, and is intentionally easy on the battery, the typical UPS
battery charger is designed to get as close to 100% of charge as
quickly as possible and never mind going into overcharge. That
results in dramatic changes in EOC threshold with aging batteries,
connector losses, manufacturing variations, etc. Basically, you can
have long battery life, or fast recharge, but not both.

My current guess(tm) is that UPS charging circuits are designed first
for fast charge and secondarily for maintaining as close to 100%
charge as possible. Both of these are detrimental to long battery
life, so the charging is selected for a "reasonable" battery life of
about 3 years (depending on model).

Some of my previous rants on the subject:
<http://groups.google.com/group/sci.electronics.repair/msg/e99a0f155fc198c0>
<http://groups.google.com/group/sci.electronics.repair/browse_thread/thread/cf5ea1e3f3a01d4f/>

--
Jeff Liebermann jeffl@xxxxxxxxxx
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
.

Relevant Pages

  • Re: Unused Li-ion battery pack
    ... the early APC 1400RH 4ru model was the major culprit. ... Given the choice of long battery life ... and fast recharge, most customers will choose fast recharge. ... Bulk charge recovery is achieved under the CL phase, ...
    (sci.electronics.repair)
  • Re: TECH: Replacing a Nickel-Cadmium Rechargable Battery
    ... It will depend on the charging circuit. ... The simplest and cheapest way to charge a NiCad is the C/10 method. ... the Amp-Hour capacity into the battery. ...
    (rec.games.pinball)
  • Re: HF 20% Off Coupon. Ends 2/27
    ... battery is rejuvinated; they keep charging. ... resister in series with the positive wire from the charging circuit ... charge the battery, but this could probably be overcome with a SPDT ... Many years ago I used a "wall wort" to make a trickle charger with a switch to open the circuit and add a resistor inline for my 40+ year old garden tractor. ...
    (alt.home.repair)
  • Re: Voltage stability in old truck
    ... >> the charging circuit. ... >> At the very least your voltage regulator should be smoothing out any ... >The battery is connected straight to the charging circuit so running off the ... You replace the old regulator with a new solid state regulator. ...
    (sci.electronics.repair)
  • Maximum safe continuous charhe current NiMH Batteries
    ... I am busy designing a AA NiMH battery charging circuit, ... However to meet IEC 60950 I believe we ... Does anybody know what the maximum charge ...
    (comp.arch.embedded)