Battery state of charge

Post by **david58** » Thu Dec 07, 2006 6:18 pm

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%

MNAirHead · Post by **MNAirHead** » Fri Dec 08, 2006 6:48 am

Is this with the car running or turned off?

Post by **david58** » Fri Dec 08, 2006 7:02 am

This is with the engine off. The battery ideally should be dis-connected from the electrical system, because you are checking the battery and nothing else in this test.

MedicTed · Post by **MedicTed** » Fri Dec 08, 2006 5:24 pm

Actually, a 12V battery should give 13.6V.

Post by **david58** » Fri Dec 08, 2006 8:36 pm

MedicTed wrote:Actually, a 12V battery should give 13.6V.

When should it?

BATTERY CONSTRUCTION

Lead acid batteries used in the RV and Marine Industries usually consist of two 6-volt batteries in series, or a single 12-volt battery. These batteries are constructed of several single cells connected in series each cell produces approximately 2.1 volts. A six-volt battery has three single cells, which when fully charged produce an output voltage of 6.3 volts. A twelve-volt battery has six single cells in series producing a fully charged output voltage of 12.6 volts.
Go to this URL: http://www.progressivedyn.com/battery_basics.html
I see 2.1 x 6 = 12.6

MedicTed · Post by **MedicTed** » Sat Dec 09, 2006 6:48 am

I can only tell you what practical experience has shown. It is certainly possible that I am incorrect. It would not be the first time in my life.

Post by **Leatherneck** » Sat Dec 09, 2006 6:52 am

What about the optima dry cell batteries, I already bought one, but anybody have any negatives about them. And are they the same as the wet cell voltage state of charge?

MNAirHead · Post by **MNAirHead** » Sat Dec 09, 2006 7:29 am

Negatives are theat they are not servicable and cost more $$$$

We only install gel batteries in commercial equipment now they're affordable.

MedicTed · Post by **MedicTed** » Sat Dec 09, 2006 4:58 pm

There is one big point in their favor. No acid to cause your battery tray to rust out.

Badbugtwo · Post by **Badbugtwo** » Sun Dec 10, 2006 6:25 am

David58bug wrote:
MedicTed wrote:Actually, a 12V battery should give 13.6V.
When should it?
…I see 2.1 x 6 = 12.6

David58bug is correct, a fully charged battery will be 12.6 volts. Now the charging system voltage is another story! It will definitely be higher!

Post by **Marc** » Thu Dec 14, 2006 9:59 am

Leatherneck wrote:What about the optima dry cell batteries, I already bought one, but anybody have any negatives about them. And are they the same as the wet cell voltage state of charge?

Essentially. The table David58bug posted is still a good guide (there are slight differences between batteries, so it's not gospel in any case).
A fully charged "12V" lead-acid battery will read about 13.2V before the "surface charge" is removed (done by applying a small load, ~15A, for a minute or so...conventional batteries will self-discharge to this level just from sitting for a day) after which it will read around 12.6-12.7V.
When charging your Optima, don't exceed 10A (5A is better) or ~8 hours. Don't use a charger that puts out over 15V, and if it starts to hiss take it off charge and let it cool down.

www.autoshop101.com/forms/hweb4.pdf
http://www.optimabattery.co.uk/english_ ... torial.htm

sagaboy · Post by **sagaboy** » Tue Jan 02, 2007 8:08 am

Normally at what % point of charged should we consider replacing the bug battery or at what % point of discharged before it stop cranking the starter?

Post by **Marc** » Tue Jan 02, 2007 9:18 am

The replacement decision would be based upon the results of a load test. With the battery fully charged (if it hasn't set idle for 12 hours after charging you should turn on the headlights for 20 sec or so to knock down the "surface charge") a resistive load is applied to draw current at ½ the Cold Cranking Amp rating (or other testing current spec if labelled) for 15 seconds. At the end of that time the voltage should still be over 9.6V (at 70°F) and the specific gravities should not differ by more than .05 cell-to-cell....that's the "short" answer - more here: http://www.uuhome.de/william.darden/carfaq4.htm#remove

Normal starter current can vary depending upon the model of starter and just how hard the engine is to crank over (compression ratio, oil viscosity, ambient temperature, etc. are factors)...for the sake of argument, let's say it's 175A. Even a cheap group 42 battery should have a CCA of 400 or so (good ones are 500-600) so any battery that passes the load test shouldn't have any trouble cranking the engine.

sagaboy · Post by **sagaboy** » Wed Jan 03, 2007 7:35 am

So.... it means that even though the battery state of retained charge capacity is at 12.06 V 50% "after 12 hr set idle" and as long as it can crank the starter--we can continue to use it. If this is the case does a leaky battery put a strain on the alternator trying to charge it to full storage value?

sagaboy · Post by **sagaboy** » Thu Jan 04, 2007 8:06 am

Are the values "after 12 hrs set idle" or that it is normal for any good working 100% 12.6+ charged battery to start losing it charge after 12 hrs?
RE:
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%