For discussion of batteries and chargers.

39 responses total.

Has anyone used the UDQ-9000 Charger/Conditioner for "ALL packs"? I've
seen one briefly, but am not sure how it connects to any battery pack.

Nope.  But I am looking for a really good charger that will handle a wide
variety of batteries.  Mostly NiCad but also NiMH and lead acid.  Pulse
chargers were suppose to be good.

I bought a Maha version of what I describe in #1. It is for radio
battery packs - not individual cells - but will charge batteries
put in series in a separate holder, bewtween 3.6 and 12 volts. It
is interesting as it determines the makeup of the pack (# of cells),
and then charges to that at ca. .6 A and then drops to a trickle
charge of 0.06 A. The hardware adjusts to the battery terminals
on most packs. 

That sounds like a pretty aggressive charge rate for smaller battery
packs.  A 600 maH pack is usually charged at about 1/10 of the maH
rating, putting the charge current at about 60 ma.  Perhaps the newer
cells can take it or, with it being a smart charger, can cut back on
the current such that the life of the pack is not adversely affected.
I don't think my 250 maH pack would like it.

Probably not. The charger is meant to provide a rapid recharge in
one to a few hours, rather than the slow 1/10 mah criterion, which
can take 10+ hours. (Corrections: the Maha unit works with packs
between 4.8 and 12 V, and the final trickle is 0.04 A.)

The main enemy of NiCd batteries is heat.  If you can keep them from getting
too hot, they'll take fairly fast charge rates.  (The problem is if you
don't cut back the current when they hit full charge, they'll heat up pretty
fast.)

The Maha charger has a "magnetic temperature sensor" to place on the
battery pack to protect from overcharging (heating). No other specs
are given for it. I'm a bit skeptical of the design, as the wire to
this sensor is very thin (1.3 mm) and seems subject to damage.

I was charging a gel cell (nominal 12 V, 2.4 Ah) with an unintelligent
charger. When I checked on it a couple of hours later it was running at
about 0.12 A, but ca. 2 cc of liquid (and bubbles) had leaked out of one
of the cell-plugs. It was, of course, acid electrolyte (it had even
'dissolved' a nylon tie that held the battery in a case). Does this mean
anything in terms of the condition of the battery - or its future
prognosis? (I have two of these batteries - the other charged OK and ended
at 0.04 A when I quit. Voltage checks after resting showed 13.27 V from
the "good" one, and 13.20 V from the one that leaked.) 

Gell cells that leak acid under normal charging conditions (Amp capacity /
5 or 10) are not healthy.  I'd discharge them through a constant load (12 v,
250 mA light bulb) to about 11v and measure the lapsed time to see how much
energy they actually hold.  You may be able to recover some capacity by
putting them through a few charge / discharge cycles.

What is the nature of the possible "disease" that causes the leak? I
presume it is H2 forcing out electrolyte. What would cause too much
H2 to form in one cell and not recombine? 

I'm not sure, but I've noticed a tendancy for gel cells to "swell" when 
they fail.  I've been replacing batteries in some of the APC UPS's here 
at work, and sometimes they've swelled up enough that it's almost 
impossible to slide them out of the case.  Haven't seen one that had 
leaked acid yet, though...mostly they're ones that have lost the 
ability to hold a charge due to old age.

I suppose if a  cell became fully sulfated, the only effect of charging
would be to generate hydrogen. I think I'll try Klaus's suggestion, and
see what the capacity is now.

Re #12: That would make some kind of sense.  I've found that a bad lead-
acid battery will often appear to have a reasonable terminal voltage, 
but it's just a "surface charge" and will drop sharply when put under 
load.  I don't recall now if the voltage measurements you gave earlier 
were under load or not.

Unloaded.

The most common failure I see in UPS applications is dehydration.  The
chargers in most UPS's do no do a good job of float-charging and boil off the
water with time.  They hardly ever go through a discharge cycle either.  The
times I've seen one or two cells in a battery boil off electrolyte is when
all the cells within the battery are no longer of equal capacity.  Some come
up to charge sooner that others, etc.  There are equalization procedures for
wet cells but I don't know how they would apply to gel cells.  It  might be
a good idea to go to the web site of the Co. the made your battery and see
what they have to say.

Re #15: I agree about the chargers, but don't see how the lack of 
discharge cycles would shorten the life.  Aren't discharge cycles bad 
for lead-acid batteries?  The useful lifespan of the battery in an APC 
UPS seems to be around four or five years.

(Of course, with the way Detroit Edison neglects the outskirts of town, 
my UPS batteries at home have gone through *several* deep discharge 
cycles in the last year.)

I have now done what Klaus suggested in #9.

I discharged the battery through a bulb drawing 0.23 amperes. The
voltage dropped pretty linearly for several hours and then dropped
precipitously. When I caught it the batter was at 9.8 volt, a little
less than Klaus suggested. The total discharge was 1.1 Ah.

This is nominal "12 V, 2.3 Ah"  battery. What is the connection between
the nominal Ah rating and the actual capacity? Does it having a capacity
of only 1.1 Ah mean the battery is half-dead (so to speak)?

I then recharged the battery at 0.052 amperes for about 20 hours, when
the cell voltage (under charge) was 15.2 volts (I wasn't able to check
when it went through 13.8 V). The current did  change a bit over the
charge cycle, especially at the  end when it was 0.035 A. Integrating
the current over time I estimate a total charge of .. 1.1 Ah. 

The conclusion seems to be that the battery now has only half the
nominal capacity, but all the cells in the  battery appear to be
similar with nearly equal capacities. 

I don't remember how amp-hour capacities are calculated, but it assumes 
a certain discharge rate.  (To use an extreme example, a 30 amp-hour 
battery will probably not supply 120 amps for fifteen minutes, because 
of the higher heat losses under heavy current demands.)  At a low 
discharge rate I'd expect to get fairly close, though.  How close you 
can expect any one battery to be to the nominal depends on the 
manufacturing tolerances.  I did a project once that involved testing 
deep-cycle lead acid batteries under load, and saw variation of 20% 
between different batteries of the same type from the same manufacturer 
for one brand, and less than 10% for another.

I suggested a 250 mA discharge rate because it was about 1/10 th of the amp
hour capacity.  The capacity is deratted according to load current but that's
something that specified by the manufacturer.  The capacity is usually rated
at 1/10 to 1/20 th of the rated capacity.  You may want to try it at 115 ma
and see what you get.

You've got a point there. The fact that charging the battery took 1.1 Ah,
the same as was obtained on discharging it, only means that that was the
effective capacity at 0.23 A. I know the effective capacity is lower at a
higher discharge, but hadn't thought it would be a factor of 2 lower using
the 10-hour rule for discharge.

I agree.  I have a feeling that your batteries are not in the best of shape.
Perhaps a few charge / discharge cycles will bring them back.  Only one way
to find out, however.

Re #17: I  neglected to mention that with charging at 0.052A, there
was no electrolyte release, even though I was "overcharging" for a
while. 

Sounds like a goner to me.

Actually, it sounds "OK" to me. What makes you say it is a "goner"? It
holds its charger very well.

I misread that, I thought you said there was electrolyte release.

So much for bbsing while only 1/2 awake.  :)

hmmm.....

back in NJ I used to have my computer connected to commerical power with
only a surge protector between me and the grid.

Well, I'm now in Kalamazoo and I noticed that when the refrigerator which 
came with the apartment turns on there is a noticably drop in voltage.
specifically my monitor will flicker. I'm sure its not good for my Hard 
drive either, though I haven't had any spontanious reboots yet.

typically the nominal voltage is 120.6, which drops to 119.6 as soon as 
the refridge starts then settles back to 120.0.....and then back up to 
120.6 VAC when the refrige stops running... (I'm not sure how accurate 
this is because I was using a digital multimeter).

Well...today I went to Bestbuy and picked up the cheapest APC UPS....I 
really wasn't too concerned with the uptime....I just wanted something
that would smooth out the voltage spikes and dips.

Anywho, after unpacking it, you have to connect the battery to the UPS. So 
I open up the bottom of the battery case, and to my suprise the battery 
that came with my UPS is identical in Voltage and Amp hour rating and size
to my Yuasa lead acid gel cell I use with my ham radio. 

This got the little cogs in my head spinning.

I could probably connect these two batteries in parallel to double the up
time...but wait....why stop there? I could buy two more batteries and 
quadruple my up time. Anyways...why bother with puny gel cells, I could
probably buy a deep cycle marine battery...and have at least an hour up
time.

other than voiding my warranty...can anyone tell me if i'm overlooking
something?

well anyways, now I don't have to worry about buying a seperate gel-cell
charger. :)

You're not overlooking much.  The charging current drawn by an empty battery
might overwhelm or overheat the UPS charging circuitry, which might be
something you could fix with better heatsinks and a cooling fan.  I can't see
longer runtime being a problem, although expecting higher output current
wouldn't be a good assumption.

Another question is whether you really need the longer runtime.

I have a cheap UPS on my server that gives me 20 minutes.  (There's no
monitor on this machine, hence the long runtime.)  I've found that's
sufficient to ride out most outages -- and living on Carpenter Road, I
get a *lot* of outages.  Most of them are between ten seconds and five
minutes in length.

I would need long runtimes from a UPS if I were doing unattended number
crunching. However the only such I do is running SETI in the background,
but that isn't disturbed by being terminated. I've been happy to just have
enough time to finish a short operation and shut down, when the power
fails, or ride out a brief power outage.

re#27

interesting that you mention that...

I went to Circuit City yesterday and near the entrence where all the rebate
certificates are on display...I noticed a consumer safety recall for certain
APC models....I went home and checked the serial# and model# that were
affected, and mine happends to be one of them...

from their website: http://www.apcc.com/rely the problem is "Potential
Overheating and Fire Hazard"...

According to http://www.cpsc.gov/cpscpub/prerel/prhtml03/03068.html
" APC has received six reports of units overheating resulting in the melting
of the unit's outer casing and three reports of minor property damage...."

They said they will send me a new one and will include (I'm guessing) a
pre-paid cartoon for me to ship the defective one back.

Looking over all the products at the cpsc.gov website, I'm starting to wonder
how many products that are recalled and no one every hears about. I'm guessing
its quite a few. Maybe they figure if you didn't fill out the warrenty card
that comes with most products they are free of an liability, because they have
no way of contacting you....I should probably fill out my warrenty cards from
now on....I would have never know about this if I hadn't gone to Circuit city.

From having worked in the consumer electronic industry, I can reccomend
not filling out your warranty cards, at least right away.  Most reasonable
sellers will exchange your product, if it "dies" in the first 30 days, or
so.  But if you've already registered your product with the manufacturer,
they can't.

Besdies, as you can see from looking at the cards, most of them are used
for marketing research.  (Of course nothign says you have to fill that info
out on their cards.)

Yeah, I used to send them in, then I realized they only wanted them so
they could send me junk mail.

Most devices work fine until they are obsoleted - which could be
pretty quickly - so one doesn't experience any benefit from having
the warranty. But I send them in anyway, and haven't noticed much
junk mail as a result. I think that may be because the companies also
are obsoleted so quickly. 

Seriously, most of it is for marketting research.  They want to know
market shares, and crap like that.

I know they tell you not to do this, but does anybody regularly 
recharge Alkaline batteries in NiMH chargers?

I have an energizer battery charger....and I want to get a few
more uses. What do you think is a safe time to charge?

oh...I should mention; on the back of the charger it 
says for AAA batteries it charges at 2.8V at 50mA

I haven't used a NiMH charger for this, but have used an NiCd charger
before.  It doesn't work all that well, since alkaline batteries aren't
meant for rechargeing, and the chemistry will only take so much.

They will not charge back up to their full potential, and charge to 
a lower percentage each time.  They also will start to leak at some
point.

Overall, you'll get about four recharges out of them, with the last
one not lasting at all.

You can't recharge alkaline batteries - the chemistry does not permit it.
What passes for "recharging" is actually depolarization, which rearranges
some of the chemicals a bit to get back a little more service. Recharging
also produces gas....and it could explode. I don't bother, but getting
a little more time might be useful in some circumstances.

I've never felt like it was worth the risk that the recharged batteries
would leak in the device I tried to use them in.  Alkalines aren't
*that* expensive, and if you're going through a lot of them you're
probably better off with NiMH batteries.

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