Battery/Alternator check

From: "RG" >
To: "Ralph" >
Subject: Fw: How to test Battery/alternating testing
Date: Saturday, November 27, 2004 9:48 PM


----- Original Message -----
From: "Ackerman" >
Newsgroups: alt.autos.lexus
Sent: Sunday, November 07, 2004 6:28 PM
Subject: How to test Battery/alternating testing


|I thought I'd layout the procedure to check your battery and charging
| system. First, the battery has to be fully charged. Then take a voltage
| reading, which should be about 12.5 volts. Next start the engine and the
| voltage reading should go to 14.5 or so. This tells you the alternator is
| putting out. The last question is whether it is putting out sufficiently.
| So, turn on the headlights and see if the voltage stays about 14.5. If
so,
| the charging circuit is OK.
|
| Next you need to verify whether there is drain back from the battery when
| the engine is off. To do this, disconnect one of the battery terminals
and
| place an ammeter in series with the battery terminal and the removed
cable.
| There may be an initial surge of current, but should quickly stabilize to
| less than 50 milliamps. Make sure you close the car door and have all
| lights off. On some cars this reading can be as high as 80 milliamps, but
| any higher than this will cause a dead battery after a few days. If
higher
| you need to remove fuses one at a time or check for leakback through the
| alternator. Sometimes something as simple as a trunk light switch can
cause
| the problem.
|
| Lastly, you need to check the battery to see if it can hold a charge and
| whether it can provide enough power to start the engine. To do this,
again,
| the battery must be fully charged. Take a voltage reading (should be
about
| 12.5). Disable the engine so it will not start. This is best done by
| removing the fuse for the fuel pump. Crank the engine for 5 seconds (use
a
| watch). Wait 15 seconds and do again. Repeat this several times. You
| should be able to do this 10 or more times before the battery goes dead.
If
| it fails sooner, the battery is defective (assuming you don't have
excessive
| current draw problem with your starter).
|
| Lastly again starting with a fully charged battery, disconnect either
| battery terminal. Take a voltage reading. Wait 12 hours and read again.
| Repeat this for two days. The voltage should no drop more than.1 volt.
| Reconnect the battery and crank the engine. If it cranks, battery is OK.
|
|
| John Ackerman
|
|
|