Intermittent charging problem

Lfd49 · May 6, 2021

I recently had to change out the original battery in my 2013 Silverado. Since then, it has had a chaffing problem, I brought it to a shop that repairs/rebuilds alternators and such and he noticed that the original 130A alternator was “burned up”. He replaced it with a rebuilt 160A alternator and it worked for about 4 days then I noticed the volt gauge going to roughly 15V on start up then steadily dropping in the first 5-10 miles of driving, down to 12.5 V. I know these are accurate values because I put my own tester on the system when I saw the gauge. I returned to the shop and he bench tested the replacement alternator and it passed just fine. He decided to put a second one in just in case, with the same results. I took the truck to a Chevy dealership and was told(after two days) and $157 , that “this was a normal swing and that it was the system not charging when it wasn’t needed”. I’ve driven almost everything over 42 years and never saw a volt gauge behave like this. Anyone else having this issue? Thanks for reading.

Sharpz · May 6, 2021

I am curious why he put a bigger alt in? Why not the original? The belt tensioner when wore can cause this issue too. At this point it would just be throwing guesses out there. If were my truck, I would take it back to where they replaced my original and ask them to put the size alt back in that came out, unless of course you are running more then normal things such as an inverter or something like that.

Lfd49 · May 6, 2021

He didn’t have a 130A on the shelf, and I asked him if it would be possible to install a larger one.

Lfd49 · May 6, 2021

Added, also, he has been in business for 30+years rebuilding electrical equipment for the fishing fleet down here as well as automotive.I have no reason to doubt him, he’s done work on my vehicles in the past.

Lfd49 · May 6, 2021

Also, I am interested in installing an inverter as I have a small handyman gig and it would be convenient to have power to the back of the truck.

Sharpz · May 6, 2021

So since you trust this mechanic, I would recommend getting your belt tensioner changed, as well as a new belt. If that doesnt fix your issue, return the tensioner and put your old belt on the shelf in case something happens to the new one. These alts have a built in regulator so the chances of two being bad are slim to none. I would normally say listen to the dealer, but I dont agree with them on the volt drops. If that were true, it would do it when the truck was new too, not after parts are changed.

The only thing I can't attest to though is that you are running now 30 more amps on your new alt vs your old alt. I suppose giving that the output is more, the alt doesnt need to work as hard to keep up with the electrical items running on your truck. You could test this by turning the key on turning the headlights on high beam, fan motor on high, radio on, basically everything your can get on. Wait about 5 few minutes without starting your truck, let the battery drain a little, then start the truck. If your gauge shows charge and stays that way, it would be a good indication that the dealer is right. Eventually the battery will charge and the alt will do as the dealer says and not charge until needed. If you experience the drop immediately then I would say to go ahead and change out that belt and tensioner.

Edited May 6, 2021 by Sharpz

It's Tim · May 6, 2021

1 hour ago, Lfd49 said:

noticed the volt gauge going to roughly 15V on start up then steadily dropping in the first 5-10 miles of driving, down to 12.5 V.

Normal.

Charging varies according to need.

garagerog · May 6, 2021

7 minutes ago, It's Tim said:

Normal.

Charging varies according to need.

Yep, controlled by the ECU, been that way since 2005. With a newer, good battery the voltage drop will be observed much sooner than an older, tired battery.

bubbanbrenda · May 6, 2021

Mine does this too, but it's by design it's reducing the output of the alternator once the battery is topped off. It done in the name of fuel economy by way of reducing the load on the alternator, but I doubt it makes that much difference.

Lfd49 · May 6, 2021

Thanks, I have a friend here that has a 2013 Sierra 1500. Basically identical to my truck, and he has never seen it happen to his.

hollywoodsle · May 6, 2021

Battery Load Management

The vehicle has Electric Power Management (EPM) that estimates the battery's temperature and state of charge. It then adjusts the voltage for best performance and extended life of the battery.

When the battery's state of charge is low, the voltage is raised slightly to quickly bring the charge back up. When the state of charge is high, the voltage is lowered slightly to prevent overcharging. If the vehicle has a voltmeter gauge or a voltage display on the Driver Information Center (DIC), you may see the voltage move up or down. This is normal. If there is a problem, an alert will be displayed.

The battery can be discharged at idle if the electrical loads are very high. This is true for all vehicles. This is because the generator (alternator) may not be spinning fast enough at idle to produce all of the power needed for very high electrical loads.

A high electrical load occurs when several of the following are on, such as: headlamps, high beams, rear window defogger, climate control fan at high speed, heated seats, engine cooling fans, trailer loads, and loads plugged into accessory power outlets.

EPM works to prevent excessive discharge of the battery. It does this by balancing the generator's output and the vehicle's electrical needs. It can increase engine idle speed to generate more power whenever needed. It can temporarily reduce the power demands of some accessories.

Normally, these actions occur in steps or levels, without being noticeable. In rare cases at the highest levels of corrective action, this action may be noticeable to the driver. If so, a DIC battery voltage and charging message displays, it is recommended that the driver reduce the electrical loads as much as possible. See Battery Voltage and Charging Messages and Driver Information Center (DIC).

Battery

This display shows the current battery voltage. If the voltage is in the normal range, the value will display. For example, the display may read BATTERY 13 VOLTS. Your vehicle's charging system regulates voltage based on the state of the battery. The battery voltage may fluctuate when viewing this information on the DIC. This is normal.

Been doing it since new. This is straight out of the owners book.

swathdiver · May 8, 2021

On 5/6/2021 at 7:12 AM, Lfd49 said:

I’ve driven almost everything over 42 years and never saw a volt gauge behave like this. Anyone else having this issue?

Look up RVC, Regulated Voltage Control and EPM, Electronic Power Management. It is normal and is what kept your original battery alive for so long.

See page A18 in this guide:

https://www.gmupfitter.com/files/media/photo/487/2013_LD_ElectricalPickupsChassisCabs_100713.pdf

The whole thing is worth a read too. What motor is in yours?

Edited May 8, 2021 by swathdiver

Lfd49 · May 8, 2021

Thanks for the info, I have the 5.3 flax fuel

Sharpz · May 8, 2021

5 hours ago, swathdiver said:

Look up RVC, Regulated Voltage Control and EPM, Electronic Power Management. It is normal and is what kept your original battery alive for so long.

See page A18 in this guide:

https://www.gmupfitter.com/files/media/photo/487/2013_LD_ElectricalPickupsChassisCabs_100713.pdf

The whole thing is worth a read too. What motor is in yours?

That is good to know. What I cant figure out is when I had my 2010 2500 HD I never once saw the voltage gauge move below 14. I bought it with 320 miles on it. It had the 6.0 in it.

swathdiver · May 8, 2021

1 hour ago, Sharpz said:

That is good to know. What I cant figure out is when I had my 2010 2500 HD I never once saw the voltage gauge move below 14. I bought it with 320 miles on it. It had the 6.0 in it.

Well, it might have been unplugged. The sensor goes around the battery cable just inches off of the battery and if disconnected will run the alternator at full capacity like the old days.