How to hook up a battery charger on a 2018 silverado

[zeke1883]

You know something like this used to be a non issue, but anymore on these new vehicles, they complicate the shit out of stuff.  How the hell do you hook up a battery charger to top off your battery while it is still in place under the hood?   Do you hook it to the post on top of the battery??  Do you hook it to the cable at the back of the battery next to the firewall?  I have my charger on that top post but it doesn't appear to be taking a charge according to the meter on the battery charger.

 

[zeke1883]

I am not sure why suddenly my battery seems to have taken a big dump.  It used to show around 14 volts on the gauge in the dash, and now it is down closer to 12, and I'm a little concerned about it.   Especially since I am going on vacation and it is going to sit for a week and not be used.

[calgator73]

What is your battery voltage? What kind of battery charger are you using?

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[calgator73]

Don't trust the gauge

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[zeke1883]

Battery charger is a 2 amp/6amp charger I think I got at sears.  There is no brand name on it.  When I am driving, I have a cigarette lighter deal that fits in a cupholder and monitors battery voltage, and I know for a fact that used to go to about 14 volts while driving, it now never goes above 12.6V.   voltage across battery is 12.6v.  How can you tell if it is charging?

[zeke1883]

I just went out and started it up, the gauge in the dash was at 14 volts, as i started driving it through the subdivision it dropped down to 12v and stayed there.  Doesn't matter how fast I go, it doesn't look to me like it is working correctly.

[damnthetorpedoes]

These trucks have on demand alternators, so the battery isn’t always being charged while driving. It is normal to see the voltage change as you are seeing. I believe there is more information in the manual about it. GM has been doing this for over 10 years. 

[txab]

^^^^This. Explained in the OM.

 

Battery condition is best diagnosed through load testing

Edited June 24, 2018 by txab

[redwngr]

Put the charger away.

 

The computer is controlling the rate of charge -- not just a simple regulator like in the past. 

It'll issue a message if intervention is necessary.

 

It also monitors loads and ambient temperatures and will adjust the truck idle speed if necessary, in multiple steps - again depending on loads and state of charge.

Edited June 24, 2018 by redwngr

[cdh027]

Yep, I thought my brand new 2018 Denali HD's charging system was shot because it would drop to 12.6 volts. Back in the day, 12.6V would mean your alternator is shot and not charging. Not so with the new computer controlled charging.

[zeke1883]

So to answer his original question... How do you hook up a charger to the battery? 

 

[64BAwagon]

Many of the late model GM trucks have a tab under a red sliding cover on the positive post of the battery, thats the easiest place for the positive. The negative will often be uncovered and readily accessible OR the truck may have a ground post on the fender near the battery. 

You should also check if your truck has an AGM battery. The charging volts is slightly different than a lead battery and most older chargers dont have an AGM setting. Old chargers will still charge the battery but not at an optimal rate.