Israelq95

I recently replaced my battery as it was leaking already and had a hard time during cold starts to turn on my car. I checked voltage with the off and battery was still good with specs but after turning it on I checked voltage with the new battery and still read the same thing as my old one with a total of 13.3 to 13.5 volts. What do you guys usually see as a norm when you check for the alternator and battery

MikeFig82

iTrader: (13)

Dang funny thing. I'm checking voltage on my new 3 day or so battery. I'm getting 14.2 volts idle no load cold engine. I'm curious what everyone is seeing. Now car is @ operating temp idle no load I'm getting 13.75V.

I was getting like 13.5v with load before on a bad battery. Idle without load it was 13.2V.


With headlights, fog lights, and A/C on.

Israelq95

I'm getting 13.5v with a load. Gonna try without a load later today but if it's near 13.7 or 13.8 the alternator is still good right? Normally I like seeing 14 but I dont think I'll get near with the new battery could be my alt is slowly going.

MikeFig82

iTrader: (13)

You should be testing at around 2000 rpms. Most alternators do not provide maximum output at idle.

INSPECT CHARGING CIRCUIT WITHOUT LOAD
HINT:
If a battery/alternator tester is available, connect the tester to
the charging circuit as per manufacturer’s instructions.

1. (a) If a tester is not available, connect a voltmeter to the charging circuit as follows.
   1. (1) Disconnect the wire from terminal B of the alternator, and connect it to the negative (−) tester probe of the ammeter.
   2. (2) Connect the positive (+) tester probe of the ammeter to terminal B of the alternator.
   3. (3) Connect the positive (+) tester probe of the voltmeter to terminal B of the alternator.
   4. (4) Ground the negative (−) tester probe of the voltmeter.
2. (b) Check the charging circuit as follows.
   1. (1) With the engine running from idling to 2,000 rpm, check the reading on the ammeter and voltmeter.

Standard amperage: 10 A or less
Standard voltage: 13.2 − 14.8 V

INSPECT CHARGING CIRCUIT WITH LOAD

1. (a) With the engine running at 2,000 rpm, turn on the high beam headlights and place the heater blower switch at ”HI”.
2. (b) Check the reading on the ammeter.

Standard amperage: 30 A or more






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MikeFig82

iTrader: (13)

I found this on the LS forums, as it's describing what I saw testing my battery this morning. On my old GS400 if I remember correctly I would get around 13.5v idle with loads, and never had to replace the alternator. I did replace the battery as preventive maintenance. For as I didn't know how long that battery was in there.


"5 Years ago, when I first purchased my 01 LS430 it had 98,000 miles at the time. A year or so later I decided to purchase a battery. I did not know how old it was with certainty, and here in Florida, it's always a good idea to replace a battery every 3 years as that's about the life of them. Many claim they get double that life span, but I don't like being a hero. I measured my Alternator output at that time after installing the battery, and it read 13.4 volts at the battery fully warmed up. Since then, I have never once had a problem but did investigate with a multimeter to find the following results. When the car starts up cold in the morning, the output is around 14.1-14.2. Gradually, as it warms up and I watch it over 10 minutes or so, it will drop to 13.6 or so. . I check the battery at the terminals with the car off and it usually reads 13+ after I shut the car down. In the morning when cold at the battery may read 12.5-12.6. I was told by a tech, that as the battery reaches it's peak charge, the alternator puts out less voltage, In addition, when I park my car for a few days, I place a CTEK 3300 charger on it, and it usually goes to green within a few hours which tells me it's close to fully charged. I don't mind getting a new alternator, but everything seems to show my battery is in healthy condition and I've never had a problem starting the car. I'm not convinced that our alternators should be constantly showing over 14 volts even over a long period of time driving."