Charging question

[MattMPA]

I freaked out when I was using my scanguage and it shows my battery was at 12.x volts.

I took my ScanGuage out. I had one in my 2005 Excursion almost since new. (And another SG. that was in a few different cars over the years)

I had a problem with the alternator in the Excursion that was later tracked to a connector. It left me stranded at one point, so I was carefully watching the voltage once we thought the problem was corrected.

When I checked the voltage at the battery...both with the engine running and not....I found the ScanGuage was displaying at least a full volt less than was at the battery. A technician friend mentioned that often an item plugged into the OBD port will show less voltage than is accurate.

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[Cobra Jet]

Are you all running stock battery’s. I started with stock but after a few of them I went to a optima which was not much better. now I run 355cca U1 battery’s x2. I’m thinking about adding a third for over 1000cca

Had issues with an Optima?

I have a post on here somewhere - I just replaced the Optima Red Top in my 1994 Cobra - after (15) years of use. Replaced it with another Optima Red Top, maybe I'll get another 15 out of the new one... LOL

 

[Johnnybee]

"This does work. The manual also says leaving the car locked and untouched for 8 hours works as well. I did the procedure and left the car for the 8 hours anyway as well."

One more time - they are two different things. The 8 hours with the car locked tells the system the battery's state of charge; the BMS reset tells the system that the battery is new.

Yes, on re-reading that section of the manual it does only refer to state of charge. However, interesting that this section is speaking to the replacement of the battery, and speaks of the BMS, but does not indicate a requirement to reset the BMS. Anyone just relying on the manual would replace the battery, let the car sit for the 8 hours, and then perform procedure to relearn the idle and fuel trim strategies, without doing the BMS reset.

 

[Vlad Soare]

How much the alternator charges the battery is written into the tune. You tune how much voltage it makes at what temperature and at what fuel demand

As far as I can see, only a small part of the charging strategy is managed by the PCM. There's just a dependency on the fuel demand and the inferred battery temperature in the tune - and quite a coarse one at that.
The supplied voltage is controlled much more finely than that. It depends on the current state of charge, on the age of the battery, on the recent charging history, on the type of battery, on the engine load or lack of it, and perhaps on other things as well. And I see nothing of the sort in the tune. I believe all of this is handled by the BCM.

 

[Cory S]

Are you all running stock battery’s. I started with stock but after a few of them I went to a optima which was not much better. now I run 355cca U1 battery’s x2. I’m thinking about adding a third for over 1000cca

Why would you need 1000CCA? You can start a coyote with 300CCA no problem.

Or are you looking for more reserve with key off?

 

[DougS550]

This may be silly question but I need to ask.ive been,pretty much housebound,and wanted to check battery on,my 19 gt.so start the car and see voltage is 13.9
I figure when, had got my battery would be charged by letting it run at idle for an hour,just like if do in my old gtos.wrong,.after 2 --30 minutes idle runs battery its at 13,5v,so then say I'll go for an hour drive on highway and keep rpm around 4k.well did that,still 13.5v. So is there an optimum rpm while driving the car that would allow alternator to charge battery was 4k too high.car only has 2k miles and was driving it once a week,and voltage on gauges would always be around 14.thanks for any advice as always.

Hi. I would recommend to first, fully charge your battery. Test the Cells (If it has removable Cell battery acid Fill Caps) for proper hydrometer electrolyte readings. With Engine Off and No Load on car electrical system, a serviceable battery has a resting voltage of approxamately 12.6 VDC. Then start engine and let run at idle. Turn All accessories to "ON", HI Mode, AC Fan on High, Headlights to High Beam, Seat Heat on if you have it, then check to see what your battery voltage is reading at idle. Then Raise the RPM to About 1500RPM and check Battery voltage accross terminals again. If its above like 12.5 your charging system is good. Most older cars would be charging at max level like 13-14VDC under all conditions buit not ours. Your car will regulate the required voltage accordantly. And Yes, Lock your car when not in use, even when parked in garage. If car is not used regulary, use a Good Trickle Charger to keep the battery serviceable. Good Luck

 

[Jackson1320]

Had issues with an Optima?

I have a post on here somewhere - I just replaced the Optima Red Top in my 1994 Cobra - after (15) years of use. Replaced it with another Optima Red Top, maybe I'll get another 15 out of the new one... LOL

15 years ago optima was a whole different company. Those batteries lasted forever. Now not so good

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