Battery state of charge

[Marc]

It's annoying to be asked questions that wouldn't need to be asked if you had read the previous answer(s).
http://www.uuhome.de/william.darden/carfaq4.htm#remove
Read section 4.3

[sagaboy]

Voltage State of Charge
12.6+ 100%
12.5 90%
12.42 80%
12.32 70%
12.20 60%
12.06 50%
11.9 40%
11.75 30%
11.58 20%
11.31 10%
10.5 0%

The voltage reading is fine ONLY if the batter is new or relatively new otherwise the reading are quite meaningless because as the battery gets older and due to sulfating on the plates the reading will show 12.6+ volts non-floating charge but in actual fact the battery may only have 20% or less stored charged.
And further more 12.6+ may not be the true indication of a fully charged battery because it all depends on the quality of the acid used by the manufacturer hence some fully charged batteries are 12.5+ for example: sealed maintenance free battery will have 12.9+ due to manufacturer using thicker acid (I believe it is to slow down the evaporation of water).
The most effective way to ensure a battery will live up to its intended life of at least 48 months or more (my battery is on its 7th year and still going strong) is to install a battery desulfator to prevent the sulfate forming on the plates.

[sagaboy]

I just learned only a couple of days ago that a battery "Voltage State of Charge" is not a reliable indicator of the battery condition, for example you can have an indication of a fully charged battery of 12.6v but due to sulfating the battery is unable to store sufficient current.

One of the best way to check battery condition is to use a hand held battery tester like the Bosch Bat 110 tester to check the battery ability to deliver sufficient CCA {cold crank amp). The back of the Bosch battery tester will show a list/types of battery and their ability to deliver ?CCA when new.

Most cars requires 400CCA to crank the starter but I noted just 250CCA was sufficient to crank our old VW on a summer day, not sure if 250CCA will be sufficient on cold winter days.

[Ol'fogasaurus]

I had a battery that was sufficient for the 1776 I have but, to make a long story short, when I converted over to an 091 the battery did not have enough juice to turn the 091's starter. At first it fired OK but some time later the engine would barely turn over or not do anything. Since it was a used transaxle and starter I thought it was a starter problem so almost $200 later for a new starter... no change.

I finally took the battery down to a battery shop as my tests showed it to be OK. After charging then running a draw/load test the battery was not capable of dealing with the draw needed for the 091 starter. Since the battery was several years old I sprung for a new deep draw battery of the correct CCA and so far I haven't had any problems.

The trouble with the charts is that they don't always take into consideration battery condition. You can have a battery that will only take a surface charge but will show the voltage listed in the charts. After starting the engine, an AMP gauge will show a normal charge (13.8 +/-) to refill the starter's draw but then the needle quickly drops down to normal run charge (quicker than it would normally do with a good battery) usually indicating that a surface charge (or low water in the battery) is all that the battery is capable of handling. (sorry about bring up the AMP gauge bit again but that is what I grew up with)

Lee

[Marc]

Seems like as good a place as any to point out that you can use your test voltmeter to check a conventional, unsealed battery for a "dead" cell.

http://autorepair.about.com/cs/electric ... 303a_2.htm


"The individual cells can also be tested with a voltmeter.

Take a coat hanger and make two lead extensions about six inches long and attach them to the meter's test leads.

Touch the positive lead to the positive terminal and stick the negative lead inside the cell next to it.

It should read about 2.1 to 2.3 volts.

Now insert the positive lead in the first cell and the negative lead in the second cell.

Proceed down the line until you get to the last cell. Here you will put the positive lead in the last cell and the negative lead on the negative terminal.

All the cells should read the same, or within 0.2 volts.

If one reads 4.0 or more ...(or)... you get a very low reading or a zero reading ... the battery is no good."


You can skip the coathanger extensions and simply insert the tip of the test lead probe into the electrolyte (it only needs to make contact with the liquid, no need to touch the plates) ...but of course you'll want to rinse them off when you're done

[Ol'fogasaurus]

Marc is correct on this.

There are ways to prolong a battery besides keeping a trickle charge on it such as flushing the battery (I will not tell you how though as it can be dangerous). I have long been told not store the battery on a concrete floor but have a non-conductor between the bottom of the battery and the concrete; I have used wood blocks before but apparently this may not be true any more: http://www.snopes.com/autos/techno/battery.asp.

The reasons I was told for not putting it on the concrete for long periods of time is not what Snoops says other than in one paragraph but it has been so long that I forget the reasons now but the migration feels correct: "...These days, the problem of car battery electrolyte seepage and migration has been all but eliminated. Says battery manufacturer Yuasa, "Nowadays, containers are made from a solid plastic that does not allow any current to flow through it, so the batteries do not discharge, even if they sit in a few inches of water." (Snoops above where it talks about old battery cases)

I was also told to pull the battery out of the car for long periods of non-use. It still sound reasonable and it is good for the use of a trickle charger and checking the cells regularly.

A hydrometer is also useful and not expensive, for testing cells on a non-sealed battery; works well with cell testing like Marc described with a meter.

The older non-sealed batteries had open straps between the cells but guess it is safer this way.

Several years ago I found you could get a battery with an 8/9 volt post plus a 12 volt post but doing a search trying to find a 3 post 12/9 (or volt battery I could only find a 16 volt/12 volt battery with three posts. In the old days we just put a screw into the proper strap and used that when converting a 6 volt car with a 12 volt engine so the 12 volt starter could be used.

[Marc]

I remember when I was kid and the family got its first 12V car (a `57 Chev wagon)...Dad had a perfectly good 6V trickle charger and was too frugal to buy a 12V, so he drove a sheetmetal screw into the center strap and when the battery needed charging he'd do it one half at a time
When VW introduced the dealer diagnostic computer in the early `70s, factory-installed batteries all came equipped with a center tap which allowed the voltage of each half of the cells to be compared during electrical testing - the theory being that in all likelihood only one cell would go bad at a time, so a failing battery could be detected without measuring all six individual cell voltages.

If the concern were over the battery discharging via the conductivity of the battery case and the concrete floor, cars would all need to have insulated battery boxes - steel is a much better conductor than concrete! It's the moisture which might be present on a concrete floor that caused the problem, and a modern plastic-cased battery isn't even affected by that.

"However, this legend is historically based in fact. The first lead-acid batteries consisted of glass cells that were enclosed in tar-lined wooden boxes. A damp concrete floor could cause the wood to swell, breaking the glass inside.

The Edison cell (i.e. the nickel-iron battery) that preceded the rubber-cased battery was encased in steel. Those that weren't isolated in crates would discharge into concrete quite easily. Later battery cases used primitive hardened rubber, which was somewhat porous and could contain lots of carbon. A moist concrete floor combined with the carbon in the battery cases could create electrical current between the cells, discharging them.

None of this is a problem with modern batteries — safe in their hard plastic shells. In fact, concrete is generally an excellent surface on which to place a battery bank. The electrolyte in a battery sitting on an extremely cold floor with very hot air around it could stratify, causing damage from sulfation; whereas concrete provides good thermal mass to buffer any temporarily extreme temperatures in the battery compartment."

http://www.homepower.com/articles/solar ... s-concrete

It's still a good idea to NOT set a battery directly on the floor, but it's for the floor's sake in case any acid leaks onto it.

[Ol'fogasaurus]

"When VW introduced the dealer diagnostic computer in the early `70s, factory-installed batteries all came equipped with a center tap which allowed the voltage of each half of the cells to be compared during electrical testing - the theory being that in all likelihood only one cell would go bad at a time, so a failing battery could be detected without measuring all six individual cell voltages."

Never seen or heard of that before... interesting. If you do a search on batteries using 12 volt and 8 or 9 volt the hot rod guys are still talking about tapping the battery. I will still try to see if I can find where I saw the three post battery at. Heading to the dunes tomorrow so it might take a while.

Thinking back (my short term memory is going to heck and long term memory takes a long time to come through ), when batteries were under the floor board, hanging down by the frame rail. the battery was usually located under the driver's feet. The main reason for pulling the battery was for any acids that could be vented out. Many of the caps did have vent holes, was to protect from gas build up and to protect the underside of the car from the acids outgassing even though the floorboard access cover in that area were usually wood but there was fairly thin metal all around it with a doubler ring supporting the access hole. Probably why the cars of that period rusted out so fast on the driver's side. The door seals/gaskets, windshield wiper seals, the center hood vent seals, windshields, etc. were known to dry out quickly and leak also.

Lee

[Marc]

Never seen or heard of that before...

I mispoke, the center connection on those OEM batteries was for an electrolyte level sensor in one of the cells - it may have also been able to convey the cell voltage information but that's not what they represented its primary function to be. The point of the extra wires going to the solenoid and battery cables was to allow the inference of charging/cranking current (from the measured resistance between the points and their instantaneous voltages during testing) to eliminate the need for lifting up the back seat for a proper test/inspection when the car was in for routine service. The system was introduced late in the `71 model year and its use was quietly abandoned later in the decade, but not until it had undergone progressive refinements which allowed checking the ignition timing with the computer too. About the only use for the diagnostic plug anymore is as a point where you can tap into the lighting circuits (for trailer lights) or to repurpose some of the wires for the connection of gauges, thus avoiding the need to pull new wires through from the cabin.

[Dale M.]

So much information and some of it just a myth....

http://www.batteryfaq.org/

Dale

[Ol'fogasaurus]

What part Dale. I can't see most of the URL you posted. There is an awful lot of information there and where I am their site keeps jumping around making it hard to follow especially when you don't know what part of it is covering what you think was posted wrong. I know you were into electricity as an occupation but I am kind of at loss to know if I posted wrong information or what.

Lee

[Dale M.]

Nothing on FAQ site is wrong.... Just some myth posted on this SITE....

Read whole FAQ, enlightenment is wonderful...



Voltage 52.08 for whole stand (battery string of 24 cells), each cell 2.17 (+/-) volts... 500 amphour...for 8 hours...

These are what power your land line telephone systems...

Dale

[Ol'fogasaurus]

As I said, I am on a limited use site now and reading all that isn't possible; it will take all the time I have available. Please reiterate what part I posted that was said wrong; I will learn and correct it if I miss-spoke. Also remember, not everything you find on the web is true .