Battery Voltage Increases During Coasting

[Markevolt]

Ok guys, teach me something. I've been watching the battery voltage on my 2018 TourX DIC. Driving around it hovers at about 12.5 volts BUT when I coast downhill or to a stop light, it can increment up to 14.8 volts (I'm not braking). This is messing with my 50+ years of driving because I'm expecting voltage to go up when the engine rpm is up, not the other way around. What's going on ?

 

[MelsRegal]

Computer controlled charging system. If your trying to maximize mpg, reduce charge load on engine, recharge when not stepping on the gas.

 

[Markevolt]

Thanks for the explanation but, should I assume that if the battery is below some threshold, it will charge until it reaches a usable level, while stepping on the gas ?
The alternator "system" must be giving some amperage back to support the cars normal function, right? That's why I'm seeing a base line to 12.5v.
Do you think all this was built into the Opel version before the Buick badging?
Take care.

 

[Hunter Mike]

The charging strategy has been around for a while now in GM vehicles. As MelsRegal mentioned, it's a fuel-saving measure to help with CAFE regulations. Watch your voltage after a cold start and you will notice it stays around 13.5V for about 10 miles +/-, depending on the state of charge. The battery module communicates with the rest of the modules in your car to decide its strategy. It's important when hooking up a charger to NOT hook it directly to the battery terminals...use the jump-starting posts as shown in your manual.

GM owned Opel so everything they did up until the PSA sale would have been built into their platforms.

 

[Markevolt]

The charging strategy has been around for a while now in GM vehicles. As MelsRegal mentioned, it's a fuel-saving measure to help with CAFE regulations. Watch your voltage after a cold start and you will notice it stays around 13.5V for about 10 miles +/-, depending on the state of charge. The battery module communicates with the rest of the modules in your car to decide its strategy. It's important when hooking up a charger to NOT hook it directly to the battery terminals...use the jump-starting posts as shown in your manual.

GM owned Opel so everything they did up until the PSA sale would have been built into their platforms.

Thanks for the info.
It was nice that they put jumping and charge connection points available. The battery on my 2018 TourX is encased and not to convenient to get to.
How about a float charger hook up ?
Not directly to the battery either ?

 

[Hunter Mike]

Correct. The battery monitor keeps an eye on incoming and outgoing current. If you're using alligator clips just hook it to the + connection under the red cover, and the ground on the left strut tower. I wired mine permanently to the adjacent positive connection on the power distribution center, just follow the connection from the + battery terminal if you want to do this. Ground goes to an existing nut on the strut tower.

I had my charger on overnight and was full this morning. My voltage was 12.5 from the get-go.

 

[G-111007]

I have the Battery Tender Plus that puts out 1.25 amps and it took 24 hours to go solid green, the first time I tried it. Subsequent charges take about 8 hours to go from the 80% condition (flashing green) to solid green. I also have a Tender Junior that I use for free standing / un-installed batteries that aren't supporting any monitors, like the TourX.
My Honda CRV drives me nuts because of the off-hours ongoing testing and purge cycles it goes through.
I also installed the SmartStopStart module. That "feature" drives me nuts. They did a modified unit for me because the remote start procedure just locked the doors twice.
Take care.

 

[Markevolt]

Correct. The battery monitor keeps an eye on incoming and outgoing current. If you're using alligator clips just hook it to the + connection under the red cover, and the ground on the left strut tower. I wired mine permanently to the adjacent positive connection on the power distribution center, just follow the connection from the + battery terminal if you want to do this. Ground goes to an existing nut on the strut tower.

I had my charger on overnight and was full this morning. My voltage was 12.5 from the get-go.

Just so I understand your charger connection point, if I remove the cover to the positive end of the battery, there's about 5 heavy power terminals. The positive battery stud connection has a metal tab that comes up to the top of that distribution bar and there's a red 18ga. wire on a ring terminal attached.
Is that where your talking about?
Can't tell what that connection is but its a solid connection to the positive battery post.
All the high current connections run under the fuse panel adjacent to the positive jumper tab. No contact points there.
Thanks, I'll leave you alone now 😎

 

[Hunter Mike]

Since I thought it would benefit others, I started a how-to on installation

How to: Battery Tender hardwiring

 

[Markevolt]

Since I thought it would benefit others, I started a how-to on installation

How to: Battery Tender hardwiring

Too bad the 12v accessory plug in the console doesn't stay alive. We could use that without lifting the hood all the time. 😎

 

[BoostedRegal2.0]

All you have to do is rewire the 12v accessory plug to a constant power source. 😉

 

[G-669521]

All you have to do is rewire the 12v accessory plug to a constant power source. 😉

Easier said, than done. 😎

 

[Markevolt]

All you have to do is rewire the 12v accessory plug to a constant power source. 😉

You got my couriousity going -- the 12v accessory outlet in the back of the TourX is alive but the console outlet is only hot when the engine is running.

 

[Markevolt]

Since I thought it would benefit others, I started a how-to on installation

How to: Battery Tender hardwiring

Maybe you'll see my comments to BoostedRegal but I found that my 12 volt accessory outlet in the trunk stays hot when the car is off. Console outlet turns off.

 

[BoostedRegal2.0]

You got my couriousity going -- the 12v accessory outlet in the back of the TourX is alive but the console outlet is only hot when the engine is running.

Just connect the new wire into the fuse that is for the rear outlet on the fuseblock using a fuse tap. You can find out which fuse is for the rear 12v outlet in the owners manual

 

[G-51283]

Just connect the new wire into the fuse that is for the rear outlet on the fuseblock using a fuse tap. You can find out which fuse is for the rear 12v outlet in the owners manual

OR....use the 12 accessory plug that plugs into my Deltran Battery tender. So many options. 😁

 

[BoostedRegal2.0]

Isn't that under the hood though? Markevolt wants an option so he doesn't have to lift the hood to access the 12v outlet, so that's why I said to rewire the console outlet for constant power.

 

[Markevolt]

Ease of use, convenient and obvious, is the goal. It's too crude but have you seen the inlet they use for ambulances and fire trucks? They can't miss it when they get in the rig.
So, a 12v accessory plug probably from Deltran, and the float charger can live in the trunk (even where the spare should be) with the 120v plug out the tailgate.
Toss the plug in the back and away we go. Thanks guys for all the conversation. 😁✋

 

[landsharkmz3]

The charging unit plugs into the wall. I don’t want to leave my door open, close the door seal over a wire, or drape wires over an open window. I park so the garage door is less than 12” behind the hatch. The hood is the most convenient location. Only question now is if I take the extra effort to extend the wires to the grill and arrange it to connect without opening the hood, but also be discrete.

 

[D2R]

The charging unit plugs into the wall. I don’t want to leave my door open, close the door seal over a wire, or drape wires over an open window. I park so the garage door is less than 12” behind the hatch. The hood is the most convenient location. Only question now is if I take the extra effort to extend the wires to the grill and arrange it to connect without opening the hood, but also be discrete.

I wonder if our cars are equipped with active grille shutters.