If you are looking for the smoking gun, you have found it. The battery has not been getting a good charge for who knows how long. The battery, left in a partially discharged state for even a few weeks would have sulfated. That battery may still take a charge, and appear okay, but it has lost CAPACITY. The somewhat low voltage measurements after charging indicate exactly that.
There is so much misinformation in this thread (about lead acid storage batteries as used in autos) it's hard to know where to start.
A typical auto battery these days has six cells each, nominally, 2 volts.
Hence such systems are called 12 volts systems. Actually 14 to around
11.8 volts!*Some boats, heavy trucks and some military vehicles and some aircraft have 24 volt (and occasionally 32 volt) systems. Back in the 1940s six volt systems were common. Although European vehicles, generally, have always been 12 volt. But leave that aside.
But the voltage across each cell, also assuming they are all in good and equal condition and therefore the whole battery, will vary over fairly narrow limits.
Measuring the voltage of standing battery without load is not necessarily a good indication of the state of the battery.
You cannot say something such as; 14 volts =3D 100%y charged, 13 volts =3D
75% charged, 12 volts =3D 50% charged ........... etc. And unlike a propane tank/cylinder you can't weigh the battery to see how much is in it! :-)Also one bad cell in the series of six can spoil the battery. The bad cell (or cells) either can't pass the electric current through, or is itself sufficiently deteriorated to not output (i.e. turn chemicals back into electrical current). Low temperatures can aggravate the ability of the battery to reproduce the electrcity that has been stored in it.
High temperatures including overcharging** can also cause damage and cause lead sulphation. That's when the battery cells start losing their ability to store electrcity chemically and reconvert it back to electrcity when demanded!
Given that voltage is not an indication of how much capacity the battery has remaining nor does it indicate the capability of the battery to do the heaviest job of all 'Cold Cranking' of a cold engine in winter.
Measuring voltage with of a good or bad battery outside the vehicle is not a good indicator. .
Any battery will most likely show on a voltmeter alone (Which draws a few thousandths of an amp) something over 12 volts immediately after being taken off the charger or immediately after the auto engine engine stops!
However with a reasonably accurate voltmeter it is is possible to measure the battery in operation in the vehicle and get some idea of a) Is it being charged b) Is it capable of providing small amounts of electrcity and also regulate the output of the engine alternator. c) Crank the engine to start it.
a) Maximum voltage should be around 2.3 to 2.4 volts per cell. So 6 x
2.35 =3D 14.1 volts. So charging voltage should be around 14 volts. b) A reasonably charged battery with engine idling but not actually charge will probably be around 6 x 2.0 to 2.15 volts per cell. So that around 12 to 13 volts. urn on a few lights, with engine idling a good battery should maintain 12 volts. c) Cranking; this is not so much a matter of voltage. Not only will the battery voltage drop as the battery puts out, for very short time, the up to 100 amperes of current needed to operate the starting motor, there will also be voltage drops in the wiring, the starter switch and starter solenoid/relay etc. The voltage might drop to say 8* volts and then recover immediately the internal combustion engine starts and starter disengages.Here are some practical voltages for lead acid cells used in large installations where the cost is many thousands of dollars per battery string and they must power critical systems, sometimes for 8 up to 24 hours.
A) Recharging: 2.3 to 2.4 volts per cell. (May depend on slight differences and whether North America or European administration).
B) Floating: In service but neither charging of discharging, just waiting with a full reserve, 2.15 to 2.17 volts per cell.
C) Discharging: For very long periods while battery supplies 'all it's got', 2.0 volts per cell.
D) As the last percentage of the battery capacity is used the voltage will then tail off rapidly; how quickly depending on the load at that point. Lights will be dimming etc. voltage will drop to 11.0 volts and below.
The six cell (auto service) equivalents for these are; A) 13.8 to 14.4 volts. B) 12.9 to 13.0 volts. C) 12 volts D) Voltage tails off .............. nothing left.
If battery is charged normally for a normal time period (not overcharged) then allowed to stand for say 10 to 24 hours and then shows around 11.3 volts it is most likely useless!
However a friend who is a mechanic took an old uncharged car battery out of a scapped vehicle to his to his cabin and hooked it up to an old car radio, probably quarter of an amp? And was surprised that it had enough chemical action to run the radio for most of the summer!
As Herb says above, some chargers will automatically time or adjust the charging. Others will just grind away (for a week or more) pushing current into an already fully charged battery. That merely heats up the battery and if severe can cause battery to sulphate; which may/ will reduce it's life and usefulness.
One can charge a dead battery for ever and it will not come back to life. Strengthening the acid, unless some has been spilt is not advisable, it won't make battery any 'stronger'. Water may/will evaporate, especially in heat and depending on type of battery may need to be 'topped up', with chemically pure-clean distilled water.
Yup, and unless they say it's only good to use for table salt, I save them and use them on the applicances around here that have starters. Genset, lawn tractor, etc.. They can get quite a bit worse and still run for years on those! Got 5 more years out of the last one on the genset before it started to crank slowly.
Cheers,
Twayne
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 differing voltages.
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 a car.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 reduced.
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.
Poly-fuses are getting pretty cheap these days and are used for a lot of those applications. It's like a conductive wax thet melts when it gets hot - and doesn't conduct when melted, but when it cools it reforms and conducts again.
That is NOT the exact explanation of how it works. Note I said it is LIKE - so don't bother flamong me if you happen to be an electronics wizzard.
That is what is known as a "shorted" cell. And it is not sulphate, necessarily. It is "active material" which is spongy lead and lead oxide.. When a battery is dead, both plates are basically lead sulphate (pbS04) and the electrolyte is basically water. Fully charged the electrolyte absorbs the sulphate, becoming H2S04 leaving one plate pb and the other pb02.
Maintenance-free batteries resist high charging voltages better than conventional ones, and 15V can be appropriate. (I think the appropriate voltage can be higher in cold weather. Modern regulators figure that stuff out.)
In my car, I made a panel meter using a cheap movement, diodes, and resistors. The needle swings 90 degrees between 11.8 and 15 volts. It may serve better than an ammeter. Before I start, when I turn the key I expect about 12.6V. After I start, it shows what the alternator is doing. If it's not over 14 by the time I get home, I know I haven't been driving enough to keep the battery charged and I'd better use a charger. In winter it's often at 15.
I don't understand the chemistry, but it shows me if a battery is charged. Different authorities may give slightly different figures.
You've been pretty well on the mark so far - but you missed it here. A fully charged battery will NEVER sulphate as all the "sulphate" is in the acid. Discharged batteries sulphate.
This is the classic result of "sulphation" All the "sulphate" is in the lead and can't be driven back into the electrolyte. (to turn the water back into acid)
You are right.
Strengthening the acid will make the battery put out more voltage - for a very short time - but will certainly not fix it. It WILL make the Hydrometer read closer to what you want it to read - but that's about all. The plates are still very close to uniform in composition - PbS04 A total waste.
MOST of them even have a MidTronics tester!!
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.
You don't get it. The cell is SHORTED. By definition, a short is a VERY LOW resistance. The watery electrolyte has absolutely nothing to do with it.
And how did you do that? On TarTops you COULD check cell to cell with a voltmeter with high accuracy. On monoltyhic hard tops that is pretty difficult.
Have you taken the battery in to have it tested on a Midtronics tester?
If not, you know NOTHING.
Not necessarily - depends on the resistance of the "shorted" cell.
You think wrong my friend. A battery with a shorted cell, or a partly shorted cell will NEVER work FINE. It MIGHT kinda sneak by, but that is all.
That's up to you - but if the battery voltage is consistently low SOMETHING is wrong. It COULD be your voltmeter, you know. Not likely, but possible.
For more than you probably want to know about batteries:
You just said it was "an open or high resistance cell." I thought by "high resistance" you meant a slow internal drain.
It's easy if you read the numbers on the meter. If you have one shorted cell, you'll see about 10.5V.
You've introduced the concept of partial shorting. They're all like that. I believe a new conventional lead-acid battery on the shelf will drain in a month or so at room temperature. (Maintenance-free batteries drain more slowly.) New batteries have "partial shorts" and most work fine.
Thanks, it looks like a gold mine.
I see you can expect 1000 starts if your battery is typically at 60% charge and 13,000 starts if it stays at 100%. That's why I made a panel meter to alert me when my battery needs topping off.
I'll see if the site leads me to a chemical explanation of why voltage works as an indicator of the state of charge.
If you nhave a totally dead battery you will too, or if you have several partly shorted cells. But you are right, GENERALLY a battery that is down roughly 2 volts AND STILL CRANKS AN ENGINE has a shorted cell.
No, new batteries do not have "partial shorts" they have self discharge, which is "normal" but it won't drain in a month. A GOOD lead acid battery will hold about 80% charge for 6 months. A "pure lead" battery = no calcium or antimony, will hold a LOT longer than that. A Hawker Genesis EP has a "shelf life" of almost 3 years.
That's simple - the electrical potential difference between dislike materials. Lead to lead oxide is 2.15 volts, more or less. Between lead sulphate and lead sulphate is 0 volts. The percentage concentration of lead sulphate difference between the plates indicates the level of charge and the potential difference between the plates.
A totally dead battery won't show 10.5V with the lights on.
What would be the point of trying to crank the engine? If five good cells cranked it one day, they might not do it the next. Under a big load, they could produce less than 8V.
All batteries have electrical leakage within the cells.
which is "normal" but it won't drain in a month. A GOOD
On the shelf, a typical car battery will be down to 80% in 12 days at
100F, 30 days at 80F, and 100 days at 50F. A particular model may discharge faster or slower.That's lead-tin stored at a cool temperature. Are they practical?
Car manufacturers use batteries intended to start the vehicle after two weeks parked. If you disconnect the battery, the time you can park and still get started varies from 1 to 6 months, depending on the temperature and the model of battery.
Why does the acid concentration change the 2.15V between lead and lead oxide? Is there a table somewhere? Does temperature affect it?
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