I recently replaced my battery since the dealer said my old one has only 225 cranking amps, and this is their solution to why my car died while driving. I used the multimeter and it gave the following readings with the new battery:

Before crank: 12.61
During crank: 10.8-11.4
After crank: 12.8

Those numbers are kinda low compared to my family's 3 other cars. Another note is that after crank the voltage reading doesn't stay put but slowly change between a low of 12.6 to a highest of 13.6, in both direction. I notice with 3 other cars the voltage reading after crank stays very much put and only fluctuate by 0.05 at most.

I also measured the voltage directly from the alternator output and got 13.3 while idling and at 2k rmp it goes up to 14.2 volt. The idling number also change slightly but not as much at the battery terminal.

Do the above numbers reflect an aging alternator? I've drove a couple of times with a total of 30 miles since the new battery.

 

The after-crank reading is too low. These voltage readings are useful measurements but they don't tell the whole story. For example, they don't tell you if you have pure direct current or if there is a "ripple" of alternating current superimposed on the direct current. The ripple could indicate a failed diode in the rectifier circuit inside the alternator.

Some auto parts stores offer a no-cost charging system test. This is done with an electronic tester and takes only two minutes. Please have this test done.

 

Sorry to bring back an old thread but this one relates exactly to a question I have.

In my case, I'm planning on taking my family in our '95 Maxima 650 miles to Maine, in August, but want to be sure to have no battery/alternator problems as the alternator is the original and the last time the battery was changed I don't know off-hand.

So I had recently bought a multimeter for troubleshooting other issues in the Maxima, and wanted to test the voltage readings for the battery with it.

I set up my camera next to the battery to record the readings, and here's the way it shook out:

Before crank: 12.65, with lights on 11.93
During crank: dipped to 8.54
After crank: 14.31

My question is do I need to worry about the fact it dropped to 8.54 when it cranked? The car starts right up and is even easier to start since putting new belts and a new pulley in recently, though I'm not sure that is related.

I read the follow-up post to this one and he suggested getting the charging system tested at an auto-parts store, as it is free at some of them.

Should I just leave well enough alone? I read in another thread that sometimes you can replace one part in the charging system and then others will fail in a snowball effect, like the starter and alternator.

Thanks in advance, for any replies!

 

nah those are good readings. i get 13.4 after crank so 14.4 is awesome. if it doesn't have trouble starting you're good go for the trip man!

 

Thanks for the speedy reply. I just looked at the clip again and the initial voltage is higher than I first posted, 12.65 vs. 12.4 originally posted, and the final voltage after it starts is 14.3 - 14.31, rather than 14.4 as first posted.

We make lots of little trips in the city without driving enough for the battery to recharge fully so that's one of the concerns I have before going on a long trip.

 

The voltage while cranking is not good. Your battery is having problems producing all the current (amps) that the starter needs. Probably sediment is building up in the battery and is beginning to touch the plates, causing internal shorts. As long as the car starts quickly and does not have to crank for a while, you can squeak by. But when the weather turn cold, or something happens and you have to crank the engine, that battery won't start the car.

Take the car to a place that will do a load test on it and be prepared to hear them tell you the battery is no good.

 

I normally read over 14volts while running. With the engine off it's just over 12volts. You seem to be reading good.

 

The battery may be beginning to fail unless you had your lights on as well while cranking to give you such a low reading.

 

Starting the vehicle takes a lot of current so I can believe a drop that low while cranking. Also, a dead battery can still read 12 volts if it's dead

 

Soo, to bring this OT for a second, where you planning on visiting up here?

 

Friends of our family have a cabin on a lake up there, and my wife and 7-year-old son went last year while I was in Europe for a school trip (MBA finale). This year we are all going (our new baby and me included), so we're driving. My wife doesn't know where in Maine it is b/c last year they flew in and got picked up, by our friends.

We're actually debating whether the Maxima is big enough for all the gear we'll need as a family, now that there is a little one (@9 months old). I may end up renting a van after all. I don't drive the Maxima much anymore b/c I bike or walk to work, so truthfully, I want to drive it. Plus, I have done a lot of maintenance and it is riding great again.

 

Nice. Well enjoy your trip up here. I live about 20 minutes outside of Augusta.

 

Upon further investigation, my battery was last replaced in Feb, 2007 and it was manufactured in Aug, 2006, which makes it almost 6 yrs old. It's an AC Delco 5-yr 35 series battery with 540 CCA. I'm probably going to get an external charger and a new battery and then put in a new one, before we go on our trip. Even though my test results with the multimeter showed adequate voltage, I think the amperage must be reduced, because I've noticed that sometimes the power seat motor won't move as fast when the car if off, and then when I start the car, it works the way it is supposed to.

 

Have it tested. During crack voltage can not got lower than 10V. If it does then your battery is going bad.

 

Replace the battery my man....no need to risk being stranded.

 

I got a new one at Autozone yesterday, a Duralast gold with 750 CCA, a 3-yr replacement warranty and a 96-month lifespan. I'm sure the 3 grades of Duralast they sell are all pretty close in quality but I guess I paid extra for the warranty.

One less thing to worry about...

On a side note, I went to Pep Boys Saturday to look at batteries and talk to someone about whether I needed to charge the battery before putting it in, and he was clueless. He had told the customer ahead of me that none of the batteries they sell were charged, and so I figured I must need to buy a charger. When it was my turn to ask for help, I asked about a "trickle-charge" type charger so I could charge it slowly, and he had no idea what I was talking about.

When I went to Autozone yesterday the guy that helped me was a big help and knew what he was talking about. He said most parts stores sell the batteries charged. He checked the old battery and it definitely needed to be replaced.

In my own experience, the only times I've ever bought a battery were while the car was being serviced so I knew nothing about them prior to doing a little homework here on the .org!

 

New batteries may not be 100% fully charged when you buy them but they are close enough so that connecting a battery charger is not necessary. The car's alternator will charge the battery up all the way within a half hour or so.

I think that you've figured out that the guy at Pep Boys shouldn't be selling car parts.