That has been my point in this thread. You don't expect a good battery
to gas when charged by a well suitably controlled charger.
Batteries can go without topping up for years. Hence the OP's experience
is out of kilter with mine.
I can assure you it isn't due to recombination catalysts.
I'm not sure that is true. I've just bought 3 traction / cyclic spec
'gel' batteries (not wet / flooded) that are VRLA and gas whilst being
charged during the balance phase (you can hear them doing so quite
It is good that stationary flooded cells gas to some degree when in
the last phase of their charge to prevent electrolyte (and therefore
charge) 'stratification' as the rising bubbles help mix the
I agree. My EV didn't have recombination cell caps and so did require
regular distilled water adding and when left unattended for a long
time, most of the cells dried out to some degree. ;-(
Cells do gas not only when charged but when being discharged and that
includes when they are self-discharging. If the OP's battery is only
25% of it's original capacity and whilst it is still functioning, I
wonder if it's self-discharging more than the other batteries he's
comparing it with? <shrug>
Cheers, T i m
Complex charge regimes usually have an equalisation charge phase where
the intention is to 'overcharge' the battery so it gasses, hopefully
undoing some of the sulfation and mixing the electrolyte. It's done as a
separate process to absorption and float charging.
Given the quantities of water the OP says the battery has been
consuming, even a complete self-discharge wouldn't cause 50ml to
disappear from each cell.
<snip> >> It is good that stationary flooded cells gas to some degree when in
As do the most basic transformer based chargers.
That would be a big *hope* IMHO.
Yes, that is a positive side effect of 'overcharge' gassing.
Yes, if you break down the phases logically with say a 'Smart' charger
but still happens with a basic charger (to varying degrees, depending
on the terminal battery voltage and the charge / current and voltage
etc), during the end of the absorption phase (the last 10% of the
<snip> >> Cells do gas not only when charged but when being discharged and that
I agree. The 8 x Crompton 6V x 200Ah traction monoblocks I was running
in the EV would take that (each) and more if I left the checks for a
bit too long (weeks rather than days) but I'm not sure even they would
lose that (each) when the car was not being used. However, when left
for a couple of years unused, even these large and fairly new
(compared to the OP's battery) batteries lost enough electrolyte to
expose the plates. If I checked them again now, all the cells are
probably bone dry. ;-(
Now, that is either from evaporation or the plastic battery cases
being gas-permeable to some degree (as is much plastic) and it's (the
water) simply leaving as gas (H2O)?
Cheers, T i m
On Fri, 17 Nov 2017 19:24:05 +0000, newshound wrote:
Even assuming a capacity of 20AH, that's still only 25% of its original
Quite frankly, I think, at a mere 25% of capacity, the battery is well
and truly "Shagged". I used to run two banks of 'revived' ex-pabx
batteries for about a decade before the cells finally became too
thirsty to justify the cost of distilled water and the energy to keep
Although there was plenty of space beneath the plates, the paste in the
plate grid structure had eventually disintegrated enough to form a
significant layer of debris in the bottom of the cells where it could no
longer provide its original function as plate anode material and, if not
actually shorting the plates, it was certainly increasing the self
discharge leakage rate (hence their thirstyness). I'd had a good ten
years worth of service out of 'My Freeby' by then so finally decided to
call it a day and weighed them in for scrap (along with a collection of
similarly buggered SLAs and car batteries).
One thing to note with SLI batteries is that they're totally unsuited to
use as UPS battery packs. It took 3 expensive lessons before I finally
realised this. Mind you the first lesson was over ten years prior to the
last two and only involved a single car battery connected to a 4A rated
13.8v CB radio mains PSU rather than the strings of 4 used with an APC
SmartUPS2000 just a few years ago.
It seems that the continuous float charging 24/7 at 13.8v per car
battery is what does them in after just 6 months or so of UPS service.
When used for their intended purpose (Starting Lighting Ignition), they
thrive quite happily on their regimen of 14.2v intermittent charging and
brief bursts of 100 plus amps starting loads along with the various
accelerations associated with accelerating/braking and sideways G forces
generated when negotiating corners and tight bends. It seems the 'rough
mechanical handling' keeps the electrolyte nicely stirred up and
homogenised preventing a deleterious density gradient in the electrolyte
that otherwise builds up when wet cell batteries are used in a fixed
I reckon there was still more than 50% capacity in those car batteries
by the time they became a maintenance liability and an unnecessary drain
of charging power demand on the UPS. I have a theory that by sacrificing
some some 5 or 10 percent of usable capacity by reducing the float
charging voltage to 13.5v per car battery instead of the "standard 13.8v"
normally used by APC UPSes, I might be able to get a better than 5 year
service life. However, I haven't had the heart to put this to the test so
it remains just a theory.
Getting back to your 'battery mystery', I'd say you're simply dealing
with a battery that's long gone past its Best Before Date and is well and
truly ready to be weighed in.
 When I discovered them in a decommissioned PABX, the battery had been
disassembled into individual 125AH Tungstone cells and simply left
standing for Ghod knows how many years. I picked the best 12 cells out of
the 25 that had been left in a completely discharged state to haul back
to my basement radio shack and connected each one to a basic 4A 12v
battery charger via a current limiting 21W 12v indicator lamp until the
almost pure water finally became reactivated with the electrode bound
acid and the lamp started to glow before rigging a string of 6 at a time
to let me connect them directly to the battery charger (doing this for
two bank's worth).
Having revived them sufficiently to be charged as 12v batteries in the
conventional way, I then rigged up a dummy load made up of three 0.3 ohm
100W resistors in series and boiled a few bucket's worth of water
discharging them after each charge or reverse charging cycle until I was
satisfied I'd restored them to as good a state as I could. It seemed I'd
managed to get the capacity of each bank to circa 100AH at the 200 hour
discharge rate - just over a week's worth running the 1.05A load from my
VHF packet radio station setup.
Yes it is certainly shagged from an automotive viewpoint, but it gives
me a month or so of "free" lighting at the stables. And of course unlike
a UPS this isn't in any way a critical application, I normally have a
spare ready to go.
<interesting stuff snipped>
On Sat, 18 Nov 2017 01:56:26 GMT, Johnny B Good wrote:
APC "Smart" UPS's do cook their batteries. I only have a little one
(750 VA) and it used to kill a pair of 12 V 7 AHr SLA's in 3 to 4
The last failure was of the "What's that funny smell?" "Seems to be
under the desk" "Ouch the UPS is rather hot":
I then reduced the charge voltage and fitted a fan. UPS now reports
around 30C internal temperature instead of the 40 odd before. This
was in Mar 2014, We've had a few short mains glitches recently that
the UPS covered, previously that sort of thing would have alerted me
to kanckered batteries. Guess I need to give it a real test though,
may be later.
Voltage is everything in charging a Lead Acid battery. Also, the higher
the temperature the lower the ideal float charge voltage.
Anything more than 13.8V continuously applied is going to shorten the
life of the battery.
On Sun, 19 Nov 2017 12:31:09 +0000, Fredxxx wrote:
Some ought to tell APC. I dug out the datasheet for the batteries,
the charge voltage was way above what it should be for the
temperature of the batteries, for bulk rate let alone float!
Not that APC UPS chargers have bulk and float rates...
On Mon, 20 Nov 2017 10:32:56 +0000, Andy Burns wrote:
Yes, there is that factor too but, in my case, that can't explain the
short life of SLAs and the even briefer life of two sets of cheap 36AH SLI
batteries with the APC SmartUPS2000 acquired 2nd hand without a battery
module (it's a split design and I only got hold of the inverter half sans
battery case). The unit was set up in my basement shack, wired up to a
set of four 12v SLAs in parallel with a set of four car batteries on the
shelving below the UPS itself. The basement temperature rarely got above
18 deg C in summer and no lower than 8 to 10 deg C in winter.
Excessive temperatures are a proven deleterious stress on batteries of
every type, primary and secondary cell types alike but is even more so
with LA batteries subjected to an unremitting constant voltage float
charging regimen. However, in my case it seems an unremitting 13.8v per
12v SLA and/or car battery alone was sufficient of itself to shorten
battery service life. Excess temperature simply didn't apply in this case.
As well as overcharging *for* their batteries. :-(
In my limited experience of other, admittedly old brands of UPSes, the
use of 13.8v per 12v battery pack was a universal practice. Today, I
would hope a more intelligent charging scheme other than utilising the
dumb constant 13.8 volt charging of SLAs is being used with the current
crop of UPSes.
Although the likes of SmartUPS2000s and SmartUPS700s have extremely
complex circuitry with microprocessor control of the sinewave inverter
and its mains conditioning for over/undervolt events as well as dropouts,
the battery charging circuits are about as basic as you can get
(essentially a constant voltage supply).
It seems there's ample opportunity to improve on the basic battery
charging management system of old with today's modern UPS kit. Whether an
extra percent or two of the total manufacturing cost has been diverted to
battery management with modern commodity UPSes to improve battery life or
not, is something I'm not aware of since I've not shopped for new UPS kit
It might pay me to check out the adverts for new UPSes to see whether
any models are boasting of such improved battery care. I might get a hint
as to whether reducing the classic 13.8v setting to a mere 13.5v would be
the best way to go with my existing UPSes.
My experience with charging a 2nd hand 12AH SLA just once a year to
maintain it in good condition by leaving to sit at its 12.7 volt resting
voltage for over 11 months of the year, rather implies that a setting of
13.5v per 12v SLA would provide an improvement with just a small
reduction in autonomy compared to a brand new, not yet shagged, battery
that's slowly dying a death from being relentlessly subjected to the full
13.8 volts typically used by APC and others to maximise their advertised
autonomy times on a brand new set of not yet shagged out batteries. It
pays to keep in mind that advertising is the art of lying by omission.
They can but not always. I can't help feeling they would help
themselves if they ran the fan at low speed to increase airflow, even
when there wasn't a mains problem.
A couple of years ago I posted a very similar photo of a Yuasa Y7
battery bulging after being used in an APC UPS
However the Y7 range are designed as alarm panel batteries, they produce
NP7 batteries for UPS type applications.
I found the "secret" commands to adjust the float voltage (perhaps with
hints from you or someone else here) and set out to adjust mine, only to
find they were already bang-on.
As noted above, mine has a fan, but only uses it when it's covering a
mains problem. Quite annoyingly it runs it for the daily spikes of a
couple of seconds around midnight when "something" at the substation
adjusts for over-voltage.
On Sun, 19 Nov 2017 13:44:55 +0000, Andy Burns wrote:
My little one doesn't come with a fan. I hi-jacked the SNMP(?) card
slot space and fitted a PC slot exhaust fan along with a speed
Complain to your DNO. Ours (Electricity North West) takes complaints
about the supply quite seriously, especially if you have data to back
up the complaint. A regulator shouldn't spike as it changes and
"around midnight" (*) strikes me as a bit odd as well. I wouldn't
expect load variation to be that consistent, weekday/weekend being
different at the very least.
(*) 2359 +/- 20 mins?
OK, it's not a spike, rather the times of day that the UPS goes into and
out of buck mode, due to over voltage.
I plotted a chart in a spreadsheet of the time of day the overvoltage
starts and ends over the last year, the main periods are roughly 6am to
9am and 9am to midnight. I didn't look at weekday/weekend variations.
When I was a datacomms guy we had some X.25 kit in a remote site that
seemed to be regularly 'locking up', roughly the same time each
Long short, we put a mains voltage monitor on it and found a large
spike on the cabinet PSU and that coincided to when the cleaners came
in and plugged 'Henry' into the cabinet power strip. ;-(
Cheers, T i m
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