Charging/Battery Issue, not sure what to do next. Help!

Maintenance/Repairs
1

Ok, so here is the problem about 6 months ago, my alternator died just after buying a new battery which, I didn’t notice until the battery had been discharged to 0.

I replaced the alternator, charged, the battery and everything is good, right?

Well no, I’ve noticed the battery seems to discharge really fast. I don’t know if this is because I damaged the battery or I got a bad battery, but like if I leave a door open for like 20min, the battery goes from full charge (12.9v) to like 12.1, sometimes not enough juice to even start the truck.

So I took the battery back to the auto store and got them to test it. They put it on their tester and came to the conclusion the battery is totally fine, no issues at all.

Last night I had it on a trickle charger all night, (2-8amp auto mode) this morning I went to start the truck and it couldn’t even crank, I had to boost the truck and then even though It was running, the truck died a few minutes later because the battery hit 0 again.

I know its not an alternator issue because my multimeter is showing 14v when idling, also it isn’t taking charge from a trickle charger either. I can presume if it was the alternator, the battery would charge fine off the trickle charger.

Is this battery just ruined or could it be some other issue? I don’t want to buy a new battery and just ruin that too? I’m not sure how to further test it? A cranking tester shows ~900 cranking amps but I just can’t keep the battery voltage up. If I hook a booster battery on, the truck comes to life normally so I don’t think its an issue with the starter system. Could this be a grounding issue? (I tested the ground coming off the battery and it seems to work fine, same with the ground by the alternator) Or is it just as simple as this battery is done and the store is lying to avoid a warranty claim?

Thanks for any help. This is on a 2007 Yukon Denali.

2

If the vehicle has the side mount battery cables, peel back the rubber cover of the positive battery terminal and check for corrosion.

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Tester

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3

Hm, unsure, I can try cleaning it, the positive side is certainly dirtier than the negative side, but it doesn’t took super corroded? Should I consider replacing that part fully? (note the red/blue wire is just a multimeter) (Also that multimeter is currently showing 14.6v coming off the trickle charger which is also connected)

I’d also add that if I pull the trickle charger off, the multimeter is showing 12.9v, that is less than an hour after the battery was so low that it could even crank. When it does charge it seems to charge really fast, but also discharge really fast. I’m assuming a corroded terminal would explain charging issues or connection issues to the truck, but it shouldn’t explain the battery going from 12.9 to 12.1 in like 20-30min just off a few cabin lights on unless there is some sort of parasitic drain but if I turn off those cabin lights, it stops draining and if I do a parasitic drain test I don’t see any evidence of parisitic drain.

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4

what is your definition of “no evidence of a parasitic drain” . . . ?

and how long are you leaving the dmm hooked up?

some modules take quite awhile to go to sleep

50 milliamps or less is my definition of “good”

2 Likes
5

When you replaced the alternator, did you recharge the battery before starting the engine? It is easy to damage a new alternator by overloading it with a discharged battery.

It is rather difficult to damage a battery via a charging cycle.

6

Using a multimeter to check for current when the vehicle is off.

7

Yeah the battery was fully charged when I installed the new alternator.

8

You have only partially answered my question

How many milliamps of parasitic draw are you measuring?

9

It fluctuates between about 40 and 50 milliamps when I have it connectedI left it on for about 5 min. Though one thing I wonder about is whether I may have parasitic draw on some accessory that doesn’t turn on right when reconnecting the battery, is that a thing?

Like say some accessor only comes on after driving for a bit, gets stuck on, drains the battery but as soon as I disconnect the battery to attach the multimeter, it shuts off and doesn’t come back on again until I drive it again?

10

Thank you

The numbers you mentioned are indeed very acceptable, imo

The reason I asked what you consider acceptable is because I’ve known MANY people, including some fellow mechanics, who considered very high numbers to be okay

For example, I know a middle-aged professional guy who’s been a professional as long as I have, who for some bizarre reason considers a 500 milliamp draw to be well within normal parameters

Okay . . . back to it

When you set up the dmm, are you waiting for the draw to settle down and then setting it up to record min/max over the course of a few hours?

you aren’t leaving some kind of usb charger constantly plugged in, are you?

11

I just clamp it on and leave it for a bit. If I put the key in and turn it to accessory, it jumps to well over 200 and the when I remove the key again it settles back into that 40-50 range.Though I am noticing eventually it drops really low. Like after 10min my DMM is reading under 10. I just walked back out as I had left it on while responding to you and its sitting at 5.5 right now.

Note: Voltage is reading at 12.7

No accessories plugged in and everything is off.

thanks so much btw!

1 Like
12

It certainly sounds this simple. However, I wouldn’t use the word “lying”. The store-level employee has nothing to lose by returning your defective battery and issuing a warranty replacement. This sounds more like incompetence (on the part of the store employee) than a concerted effort to not honor the warranty.

You see, it is mathematically impossible to fully charge a discharged car battery, which was too low to even crank the starter, in one night. The problem is that the battery has a very low capacity, so it accepts a “surface charge” fairly quickly, but when you attempt to draw significant current (e.g. start the engine), the “surface charge” quickly drains away.

The problem is that to a low-skill big-box parts store employee, there’s limited understanding of how batteries work. Such a person might honestly believe that if they charge a battery for a few minutes or a few hours, and the voltmeter shows a certain voltage, then it’s a good battery. However, that is simply not true. One can offer other examples of this phenomenon, such as laptop batteries and power tool batteries which often charge to “100%”, based on voltage, for the entire functional life of the battery, however as the battery ages it has less capacity, and each charge provides less runtime.

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13

Each of our battery cores must have test results attached for the battery distributor. Some techs would test an old “spare” battery to obtain a failed test report.

If the battery distributor sees a number of clean batteries on the return pallet, he will begin to perform battery tests to see if they match the attached reports.

If the shop or store has $2000 in rejected battery claims each week, will the store clerk still have nothing to lose?

As for the OP observing the battery voltage dropping from 12.9 to 12.1 volts, this is probably due to the battery being under load at the time; ignition on or doors open. The battery voltage must be measured with no load to assess state of charge.

14

This is correct; the doors were open in the situation I described. Which means cabin lights are on. But I’ve never had a battery go from freshly fully charged to can’t even turn the crank while I leave the doors open as I load for a trip before.

Based on what you are saying it sounds like the battery is bad and that is likely not some other issue with the vehicle? Not sure how I can convince them to take it back on warranty, but more than anything at this point, I just want my truck reliably working again but I don’t want to just go buy another brand new battery only to ruin it having it go to 0 a few times.

15

I see, this makes sense, so maybe this is a limitation of my trickle charger as well? Because it charges up to what it thinks is 100%, then stops, there is no “setting” on it to change that. Is it possible that its only charging it to that surface charge and then I never get past that point?

How would I go about figuring out if the battery is just charged to the “surface” level or all the way to capacity?

And yes, thats exactly what they did, they put it on this big battery tester thing and were like: “See 12.6v”, its fine. Then he went and got a crank tester, Did a crank test and it measured 900 cranking amps, so he was like: “Ok also fine”. I was standing there while he did it.

So I put the thing back in the truck, drove home, stuck it on the trickle charger, then the next day went to fire the truck and it wouldn’t crank. Voltmeter read 12.0. When I stuck the booster on it, the truck fired up instantly.

16

Sounds like the starter failed. What is the battery voltage at the battery while the ignition is in the start position? If more than 11 volts, the starter should crank the engine.

Next, what is the battery voltage at each connection on the starter while cranking?

17

It starts just fine when the battery is at 12.6, or if I have the booster hooked up. I’d also note that when the battery dies the truck clock resets, I lose all my settings such as radio channel, interior temperature, etc. The same as if I had disconnected the battery.

Another example, I just drove to the store and back. The battery was at 12.6 to begin with, the truck started instantly. It is about a 1.5 miles each way. I know thats not enough time for the alternator to fully charge the battery, after I got home the battery was at 12.45.Is that normal? That seems like a lot of drop for 2 starts? (This was after about 18 hours hooked up to the trickle charger set to 8amp) (Also the truck’s battery gauge read 14v the entire time)

I will have to jack the truck up and try take a DMM reading on the starter maybe tomorrow, its not super easy to get to on that truck but I really don’t think its the starter as the truck fires up perfectly if I’m connected to the booster battery.

18

There may be a problem with the battery current sensor in the vehicle.

https://www.carid.com/sf-pl-mpn/pid-0-mmyid-1572-ofmpnid-4482442631.html

Tester

1 Like
19

If the battery appears to lose its charge in a short amount of time while parked, it seems there is a poor/intermittent connection somewhere.

20

Thanks, ordered one, they are cheap. :slight_smile: