Battery? Alternator? (1 Viewer)

[dizzidave]

Battery? Alternator?

My wifey took my truck in while I was gone to get warranty corrosion protection on the frame. While it was at Toyota, they said my battery failed their test. My truck has been fine so I wasn't worried about it. Yesterday it took 3 key turns to get her started which was unusual.

Took it to get tested and they say battery is fine, just needs to be charged. Isn't that what the alternator is supposed to do?

What are your ingenious opinions?

Thanks.

 

[Jacket]

The alternator supplies the charge, and the battery needs to hold it. (stating the obvious).

If it took 3 turns, and your battery was bad, it should have trended toward not starting (like the cranks getting weaker each time). In other words, but the 3rd crank you'd be nearly dead and it wouldn't start. So I don't think a 3 crack start is indicative of a dead or dying battery in and of itself. The dealer may have been trying to sell your wife a battery......

Do you have a volt meter? Start up the truck and give it a test. If you touch the main (red) positive wire coming from the alternator (and the black pin to the battery ground), it should measure around ~14 volts. Then touch the red battery post and it should measure ~12 volts. If it's less than 12 volts, test it after 30 minutes of driving. Is the battery now at 12-12.5 volts? That would be one good indication that it's charging or keeping a charge.

 

[dizzidave]

The battery was at 12.53 volts when I had it tested. I believe it was from the red. There was no other volt number given on tag the machine printed out.

There was no weakening during the cranking, that's why I was thinking perhaps it was an alternator issue. I guess if I see dimming lights and other weird things I'll know it's the alternator.

Thanks

 

[dizzidave]

Oh and no on the volt meter, but dang I should by now. My electrical skills be weak sauce so I haven't dabbled in the super easy electrical realm yet.

 

[Duane]

Checking voltage on the battery posts should be fine.
When running the voltage should be at least 12.8 and maybe even up to 13.8 or so depending on the voltage regulator. This would show an alternator putting out a correct voltage.

When shut off then you should see 12.5 volts or so on the battery posts.

Most batteries are sealed now so i think about all they test is a quick load test for battery voltage drop. This can show weak as well if your battery isn't fully charged and/or you have poor battery post connections.
I use one of these testers myself. About a $35 touch.
Not certain on the time to recharge a battery but a 10 minute trip across town isn't going to do it likely either. I would put a charger on it for 6 hours to get a good charge on it then try it.