Tip & How-To about Cars & Trucks

Automobile battery and charging system


Most automobile batteries are lead acid which should have a standing voltage of about 12.6V fully charged at 70 degrees F. To test a battery first it must be fully charged. If fully charged a good battery will stay above 9.5V while cranking engine. Most part stores will charge and test batteries, starters and alternators. To be sure your alternator is properly charging start the engine and turn on the headlights and blower fan to add electrical load. Voltage should be over 13.2V at idle and under 15V with a known good battery. If not check the larger wire bolted to the back of the alternator for loose connection and continuity to the battery. If ok check fuses. If all are present and check good most likely the alternator is bad and needs replacement, although it is possible on many modern automobiles to have a powertrain control module (PCM) be the problem as they serve as the voltage regulator. Most late 90s and newer GM and Chrysler do. If all else fails have a professional check it to be sure. Hopefully this will answer the questions of many. Good luck ??.

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w crank


An unloaded reading of 10 Volts on a 12 Volt car battery is considered dead. There are 6 cells in a typical lead acid (car) battery - each provides 2 volts. They are internally connected in series to provide 12 volts on the + and - posts. If one is cell shorted out - you'd see 10 volts if fully charged. Trickle charge the battery for 24 hours and measure voltage again. If 12 volts, bring it to be load tested. that will tell you the true state of the battery.

Apr 22, 2014 | 1994 Chevrolet S-10

1 Answer

Alternator


Vehicles: any failing to keep its battery charged.

A vehicle unable to charge its own battery has one of 4 problems:
(a) alternator failure
(b) voltage regulator failure
(c) battery failure
(d) wiring problem between battery and alternator/voltage regulator.

One most modern vehicles (including 2002 Lexus RX300 - 2WD and AWD), the voltage regulator is an integral component of the alternator and is not separately serviceable.

In the US, one can get a free "charging system diagnosis" from the popular auto parts chains: AutoZone, Advance Auto Parts & Pep Boys. You needn't remove any parts from the car to get this diagnostic, since they can attach a diagnostic meter to the charging system in the parking lot. This diagnostic aid will tell you exactly which component has failed - battery, alternator or voltage regulator.

In case the vehicle is immobile, one can DIY (do it yourself) the diagnosis.
(a) inspect the wiring for corrosion/loose connections/loose connectors/etc.
(b) check alternator belt/pulley - if drive belt is properly turning the alternator pulley (no slippage/misrouting/etc.), then the mechanical tests are complete, and you'll need to continue testing the electrical performance of the charging system components.
(c) first component to test: battery
DIY test 1: remove battery from car and put battery on a 120VAC automotive battery charger and charge it fully (or just check it in the car with motor off, since the car's charging system is a type of automotive battery charger).
test parameter: a fully charged lead-acid automotive battery should read 12.45 volts on a VOM/DMM
DIY test 2: disassemble battery out of car after driving it to one of the auto parts chain stores (Advance/AutoZone/Pep Boys) for a free battery test. These testers will test the battery under load, which is not possible with just a DMM.
(d) if wiring is good, and battery tests good under load, then
the failed component is the alternator/voltage regulator - by process of elimination.
(e) DIY test 3: direct alternator/voltage regulator test (car must start and idle successfully to perform this test)
Start the car, and put a VOM/DMM across the terminals of the battery. Since the car is running, you'll be reading the output voltage of the alternator and not the output voltage of the battery. The acceptable ranges for alternator/voltage regulator output are:

ALTERNATOR CHARGING VOLTAGE

Most alternators that are charging properly should produce a voltage of about 13.8 to 14.2 volts at idle with the lights and accessories off. Always refer to the vehicle manufacturer's specifications. Many Asian vehicles, for example, have higher charging voltages of around 15 volts.

When the engine is first started, the charging voltage should rise quickly to about two volts above base battery voltage, then taper off, leveling out at the specified voltage.

The exact charging voltage will vary according to the battery's state of charge, the load on the vehicle's electrical system, and temperature. The lower the temperature the higher the charging voltage, and the higher the temperature the lower the charging voltage. The "normal" charging voltage on a typical application might be 13.9 to 15.1 volts at 77 degrees F. But at 20 degrees F. below zero, the charging voltage might be 14.9 to 15.8 volts. On a hot engine on a hot day, the normal charging voltage might drop to 13.5 to 14.3 volts.

Here are the full specs for installation of the 2002 Lexus RX300 alternator - you may be able to check these specs yourself (with a torque wrench), or pass them along to your mechanic.

Note: the VIN 8th digit should be "F" for the 2002 Lexus RX300 (2WD & AWD)

2002 Lexus RX300 (2WD and AWD) - 3.0L Engine, VIN "F" SFI DOHC

Alternator

Drive belt. Tension the belt to 170-180 lbs. for a new belt or 95-135 lbs. for a used belt.
Adjusting alternator lockbolt. Tighten the bolt to 13 ft.-lbs. (18 Nm).
Alternator pivot bolt. Tighten the bolt to 41 ft.-lbs. (56 Nm).

Glossary of acronyms
--------------------------------
DIY = do it yourself
DMM = Digital Multimeter
DOHC = Dual Overhead Cam
SFI = Sequential Fuel Injection
VOM = Volt Ohmmeter

References
----------------
How to test a Car Alternator - todayifoundout.com

Alternator & Charging System Checks - aa1car.com

Dec 26, 2011 | 2002 Lexus RX 300

1 Answer

battery


For a battery to be good and operational, you need 3 things: Voltage, Cold Cranking Amps, and good cells.
A fully charged battery will have at least 2.1 Volts per cell. So, a 12V battery should read 12.6V to be fully charged. Before you can proceed any farther, the battery will need to be charged fully.

A "load test" will need to be performed to determine if the battery has enough energy to start your vehicle. Cold cranking amps (CCA) is the amount of energy the battery supplies at 32 degrees. This test can be performed with a hand held load tester that can be purchased at a parts store, or performed by a technician at a shop. Batteries lose their ability to supply CCA's when they begin to age or the lead material on the "plates" begins to sluff off.

If you are able to remove the battery caps, a specific gravity test can be accomplished with a hydrometer. This is a glass tube with a bulb on top for suctioning acid into the tube, which in turn will float the hydrometer. Fully charged batteries will float at 1.265 specific gravity. Each cell needs to lift the float at least at 1.265. If one or more of the cells fails to lift the float at all, it can be determined that that cell is dead.

If any of the above tests fail, the battery is considered defective.

To clean a battery, a mixture of water and baking soda can be used. Also, remove the cables from the terminal posts and clean with a wire brush. Remove all crusty buildup. Posts should be shiney as well as the inside the battery cables.

Dec 11, 2011 | 1998 Toyota Corolla

1 Answer

I need a new battery for my 1986 Oldsmobile ninety-eight regancy sedan. fully loaded. what type of battery would i need?


Attributes Battery BCI # : 75
Battery CA @ 32 Degrees F : 775
Battery CCA @ 0 Degrees F : 630
Battery Height : 7 1/4"
Battery Length : 9 3/4"
Battery Posts Type : Side Post
Battery Reserve Capacity : 90
Battery Voltage : 12 volt
Battery Weight : 33 lbs.
Battery Width : 7"
Wet or Dry : Wet
A lead acid battery with the fallowing specs
group 75



Attributes Battery BCI # : 75
Battery CA @ 32 Degrees F : 775
Battery CCA @ 0 Degrees F : 630
Battery Height : 7 1/4"
Battery Length : 9 3/4"
Battery Posts Type : Side Post
Battery Reserve Capacity : 90
Battery Voltage : 12 volt
Battery Weight : 33 lbs.
Battery Width : 7"
Wet or Dry : Wet
Attributes Battery BCI # : 75
Battery CA @ 32 Degrees F : 775
Battery CCA @ 0 Degrees F : 630
Battery Height : 7 1/4"
Battery Length : 9 3/4"
Battery Posts Type : Side Post
Battery Reserve Capacity : 90
Battery Voltage : 12 volt
Battery Weight : 33 lbs.
Battery Width : 7"
Wet or Dry : Wet
Battery BCI # : 75
Battery CA @ 32 Degrees F : 775
Battery CCA @ 0 Degrees F : 630
Battery Height : 7 1/4"
Battery Length : 9 3/4"
Battery Posts Type : Side Post
Battery Reserve Capacity : 90
Battery Voltage : 12 volt
Battery Weight : 33 lbs.
Battery Width : 7"
Wet or Dry : Wet

Feb 27, 2011 | 1986 Oldsmobile Regency

2 Answers

There is steam and a strong egg smell coming from the battery. What is the problem?


This is a high charging on the battery, as it is overcharged . this can be failure of the alternator rectifier or the regulator.
so use a voltmeter and confirm the voltage range to rectify the fault.
A high charging of this nature can damage the battery in the long run.

Sep 25, 2010 | 2006 Chevrolet Avalanche

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