My regulated charger normally tapers to a fraction of an amp. On this
battery, it will stay at 2 amps indefinitely. Most car batteries will
settle at 12.6V when fully charged. This battery settles at 12.3.
I don't have a hydrometer. Could diluted electrolyte cause this problem?
Fully charged it has to saturate to 13.3 with 12.8 being full, I have
an older charger I opened and found a voltage set screw and adjusted
it. What is indefinatly at 2a for a day? 12.6 is to low and will
sulfate and ruin a battery. www.batteryuniversity.com
Don't they say to bring it to 14.4-14.7 to be sure of a full charge and
I was measuring the voltage after stopping the charge and running the
lights 15 seconds, which is supposed to be equivalent to letting it sit
I've left it at 2 amps up to 48 hours at a time.
Was the voltage measuered with the lights still on ?
Without a load on a battery it is difficult to tell anything just by the
voltage. They will usually measuer close to the normal voltage unless the
battery is very bad and not just weak.
"battery looks old" - might be a symptom?
(How old is the battery, asked twice already)
Anti-Freeze, you can test electrolytes <sp> with a VOM (meter
reading), battery acid is different.... I'm guessing.
Your battery is sulphated and will have a reduced output. Adding acid
Take it to a good auto parts place that has a battery conductance
tester (generically known as a Midtronics tester). If it passes that
test it is good. If it fails that test you are running on borrowed
time - get rid of it.
Why do you think there is a problem? Does the battery crank the
engine well? (This test is not as good as it might be since so many
cars start immediately now, less than a second of cranking, but if
yours takes longer, it's a good test.)
Normal full charge is 12.6, so 12.3 is low. Of course one of my
meters has a separate scale for checking battery voltage from the one
for measuring other voltages in the 20 volt range. Have you tried
your meter on another battery known to be good and fully charged?
Always worth doing.
Get someone to measure the voltage why you are cranking the engine.
Take off the coil wire to the distributor if you have to. If the
voltage doesn't fall much, the battery's good, but I forget how much
is not much. I think if it stays above 9 or 10 volts, you're in good
shape. Less in cold weather.
They certainly won't all be dilute, unless somehow electrolyte was
spilled out of all of them.
Have you even checked the water level yet? As my brother puts it,
"Check your erl and your bachery?"
www.batteryuniversity.com page 13. 12.6v is the minimum and not
where you should charge to. A full charge should be much higher at
around 13.3 to soak the cells. My cars over years and chargers go to
about 13.3v normaly. If new batteries sold are not fully charged they
may never reach 100%.
I just got a free battery from SEARS because they did not do this,
and did a bait and switch on oil. I stopped pay on a ck, they filed
charges, The Atty General said I was justified in not paying. Free
battery - free Mobil One, from your friendly Independantly owned Sears
It depends what you mean by "their charge". 12.3 is too low. When
the connections between the cells were available for voltage
measurement, one could measure the voltage on each cell. Are 5 of
them at 2.1 and the sixth way too low? Maybe. Are all 6 cells at
2.05? Frankly, I doubt it. You probably have a bad cell. A
hydrometer would find it, and I think it is worth the money to have
one and to learn something. When I buy things I keep them forever and
my hydrometer is probably 40 years old now, so the cost of the item
isn't that important. (Unless you are short of storage space.)
A bad cell might have shorted plates. It's more complicated than the
explanatory drawings. There are maybe 6 plus and 6 minus (or more)
plates in each cell and they alternate. This maximizes the power
available for a given size battery. But it also means cells can short,
a plus plate can touch a minus plate, and I don't think there is
anything you can do about it, because the access hole is so small.
I once had a battery that only shorted when it was pretty hot. If I
drove a half hour in the summer and turned off the car, the battery
wouldn't work for 30 or 60 minutes. Fortunately for me it only cost
me one short taxi ride and one bus ride back to figure this out. By
the time we went to dinner and back, the battery was cold enough and
the car started. I went home and it started the next day too and I
went and got a new battery.
The charger voltage can be 13.3, to force the recharging of the
battery, but the battery itself, when disconnected from the charger,
will never show 13.3 volts.
Look at figure 3 on the very page 13 you site,
State of charge in % 100% Open Circuit Voltage 12.65 volts.
That's just a little over the 12.6 volts I said.
I don't think many people in this thread were commenting on the
charger voltage. I have two chargers and last measured their voltage
10 or 20 yerrs ago. Say it is 13.3. As the battery approaches 12.65,
ays it's 12.5 volts, subtract that from 13.3 and that leaves only 0.8
volts to force the last bit of recharging into the battery to be
charged. The other 12.5 volts of the charger only serve to
neutralize, to counteract the 12.5 volts of the battery.
Just like stuffing anything, it takes effort.
BTW, same chart points out that even when a car battery is 75 percent
discharged, it will still have have 95 percent of its voltage, 12.05
volts**. Twelve sounds like it's almost 12.6 and people might imagine
that a battery with 12 or 12.3 volts is nearly charged.
**WE went over the arithmetic on this when I took high school
chemistry, and it's pretty simple and clear once you see it done. It's
not black magic that the voltage continues to a much higher percentage
of normal than the perecentage of charge is.
Chicago is the home of Sears, and when I lived there, I went to Sears
a lot. The first time was just after my brother had given me his '65
Pontiac, in the summer of '67, the newest car I had owned, but it had
a bad battery. (The dealer said he had replaced the battery,
regulator, and alternator each twice, but they never fixed the car,
and when the 2-year warranty was up, they refused to do any more.)
So my brother gave me the car when he went to Viet Nam, and I took it
to Chicago, and then to Sears, and said I wanted to buy a battery, and
the service guy said, Do you want our free two thousand point
multi-check, and I said, "Not really. I just need a battery." and he
said "It's free. You ought to take it", so not wanting to argue with
the guy, I let him test the car, and he found a bad connection between
the positive battery cable and the starter motor solenoid stud. He
took off the cable, scraped it with a knife on both sides and put it
back. And the car worked fine thereafter. The dealer, out of
business less than 4 years after I got the car, I think spent too much
time replacing big boxes at the end of the wires and too little time
looking at the wires that connected the boxes. I was very impressed by
It did happen that everytime I left the lights on for more than an
hour, again the car woudn't start, even with a jump. I used to crawl
under the car, remove the nut, clean the cable end with a knife and
put it back togehter. By the second or third time this was too much
work, too dirty and time consuming, so I just reached down, grabbed
the cablen, and twisted it around the solenoid stud. 10 degrees or
less was enough to make the car start.
I thought about replacing the battery cable--there must have been
something different about it, but I learned not to leave the lights
If five cells charged normally and one was .3V low, that cell would be
discharged, and I would not expect the charged battery to run the lights
and start the engine normally.
If one cell had serious leakage, I would expect the battery voltage to
drop to about 10.5 within a week. It stayed at 12.3.
I'd like to know more about the arithmetic. It seems to me that if the
voltage of a certain chemical reaction were 2.1, a 6-cell battery
measured with a 10 megohm meter should read 12.6 whether 1% charged or
Neighbors kept calling me when their battery ran down. It seemed to be
the regulator built into their Delco alternator, and I couldn't find the
problem. One day they phoned when their car wouldn't start at the post
office. I happened to touch the positive battery cable and it started.
They'd had somebody replace their starter and the cable wasn't
tightened down at the starter.
Everything had always looked good idling in their driveway, but I guess
sometimes on the road the loose connection would confuse the regulator.
My neighbors called me a fool for not fixing their car sooner. They
considered me their fool because I helped them for free.
Wikipedia says a fully charged cell should be 2.10 to 2.13. It says the
voltage will go down as the charge goes down but doesn't say why.
Alkaline cells are different. A cell that reads 1.45 open may not have
as much life as one that reads 1.35 open. I don't know what causes
It appears that once a nickel cell has been off the charger awhile, its
no-load voltage won't vary as its charge is used up.
It would work find in the driveway without being touched, so I think at
certain engine speeds the connection was vibrating in a way that
confused the regulator.
The ones with the battery moved in a couple of years ago and immediately
became best friends with the ones with the starting problem.
It's not important what you would expect.
An OPEN or high resistance cell will make it so the lights don't light
and the starter doesn't crank properly.
A fully shorted cell is like that cell just isn't there at all - it's
been "jumpered out" - but a fully shorted cell would mean the voltage
(open circuit, no charge being applied) would be 2.1 +/- volts low -
so insted of 12.6 you would have 10.5
10.5 volts from a fully charged 5 cell battery WILL crank and start a
car. When cold, cranking voltage van drop to 9.6 volts and still start
Because a cell can be PARTLY shorted, it can reduce voltage by less
than a full cell - it may still crank the engine if it is not too
cold, and lights will still work - but your capacity will be quite
Like I said before - the ONLY way to know if today's low maintenance ,
sealed, or semi-sealed batteries are any good is to test them on a
"midtronics" type battery tester.
They can test a battery with less than 30% charge remaining with an
accuracy of somewhere around 95%.
Caveat - the midtronics will NEVER give a false "bad" test - but has
been known to say a battery with an intermittent open intercel
connector was good - ONCE.
Put a good load on it, then test it again, and it fails. I've had that
experience and it is not good when a customer is told the battery is
just fine, and then the car can't start to leave the lot!!!!!
A load test, as recommended by some others, is ONLY accurate if the
battery is fully charged - and there is some question whether this is
the case on this particular battery/vehicle.
If a cell drained through leakage between plates of a couple of amps or
so, I would expect fairly high resistance from watery electrolyte. I
say that because if a battery goes flat (leaving lights on, for example)
it won't accept much charging current at first.
If a cell were nearly drained, I might see more than 12V with no load,
but I would expect less than 10.5 with the lights on.
When the battery kept drawing 2 amps from the charger, the first thing I
did was check for a shorted cell with a voltmeter.
If 6 cells will feed a starter 10 volts, 5 cells would feed it only about 8.
I think a battery with partial shorting could work fine shortly after
charging. I disconnected the battery to get rid of the 30ma drain from
the van's equipment, then checked the battery a few days later. The
voltage was the same.
I once had a battery like that.
This battery holds its charge and handles the starter load very well, so
I wouldn't tell the owner to buy a new one yet.
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