New LV battery behavior

[Twilloo]

Today is the first time I have ever seen this happen. I have a volt meter plugged in the 12 v receptacle thinking this would be handy due to all the LV charging problems that have been documented. I have a select with job 2 production. Every day when I take off in car I see the voltmeter is always 14.8 with car running and I know that is ok but today I started off and I see 13.5 and after a few minutes of driving I see 13.0. This is new behavior. I stopped car and restarted and it went to 14.8 and then again started declining to 13.0 after a minute or 2. I could be wrong but it seems that anytime I have had the mme on it showed 14.8 or very close to that and after I am stopped with car off it usually shows 12.8 or so if nothing is on. Am I starting to have a LV charging problem? I will put a voltmeter on the battery after taking off covers and see if maybe it is just the plug in voltmeter that is off. I might add that today was about the same temp as it has been recently in the mid 30's. Also I have continually kept my charge between 60% and 90%. My garage never gets below 50 degrees. Thanks for any help.

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[Bryan_GTPE]

I suspect this is actually good news. If it reads 12.8 when off, then it’s fully charged and holding well. It sounds like you are driving enough that the LVB is staying charged and not drawing much from the HVB. This to me indicates that the charging system is working as designed and the LVB updates that Ford made are improving the situation.

 

[macchiaz-o]

12.8V is fine. Remember too that you are measuring the battery under load (computers are on, lights are on, accessory ports, etc).

 

[Logal727]

Yeah, normal, battery doesn’t need to be charged since it’s charging properly.

 

[Twilloo]

12.8V is fine. Remember too that you are measuring the battery under load (computers are on, lights are on, accessory ports, etc).

I realize that 12.8 is fine but it has always read 14.8 while driving at least every time I have looked at it.

 

[dtbaker61]

I suspect this is actually good news. If it reads 12.8 when off, then it’s fully charged and holding well. It sounds like you are driving enough that the LVB is staying charged and not drawing much from the HVB. This to me indicates that the charging system is working as designed and the LVB updates that Ford made are improving the situation.

pulling down to 13.0 while under heavy load would be 'normal'. I'd bet this voltage sag happens as the e-heat comes on.... so, as long as the LV is > 12.4 when sleeping you are in great shape. I wouldn't worry unless you see 11.9 when MME is 'off'.

 

[macchiaz-o]

I realize that 12.8 is fine but it has always read 14.8 while driving at least every time I have looked at it.

I wouldn't worry about it.

It's fine.

Besides, if your charging system isn't working optimally, what is your recourse until an actual fault condition occurs? Until then, enjoy your awesome car.

 

[hawkeye3point1]

I realize that 12.8 is fine but it has always read 14.8 while driving at least every time I have looked at it.

I am using an OBD monitor and the Carscanner App. and have observed a similar reduction in the 12V system, after a period of time. This is actually better for the LVB and indicates that the car is reducing DCDC converter output as the LVB SOC increases.

 

[Twilloo]

pulling down to 13.0 while under heavy load would be 'normal'. I'd bet this voltage sag happens as the e-heat comes on.... so, as long as the LV is > 12.4 when sleeping you are in great shape. I wouldn't worry unless you see 11.9 when MME is 'off'.

forgot to mention, I turned off all the load, nothing but on, no heat

 

[SpaceEVDriver]

If you're reading 14.8 V, you're not reading battery voltage, you're reading charger voltage.

This table shows a temperature-dependent typical bulk stage charging voltage (from the charger) for a 12V wet cell lead-acid battery that's used cyclicly. You want the charging to happen around 25C when possible.

Battery Temperature	Charge Voltage per cell	Charge Voltage
-20 °C *	2.6	16.02 to 16.56
-10 °C *	25.1	15.66 to 16.2
0 ° C *	2.45	15.3 to 15.9
10 °C	2.41	14.94 to 15.54
20 °C	2.37	14.58 to 15.18
25 °C	2.35	14.40 to 15.00
30 °C	2.33	14.22 to 14.82
40 °C	2.3	13.86 to 14.46
50 °C	2.26	13.5 to 14.10

 

[Twilloo]

If you're reading 14.8 V, you're not reading battery voltage, you're reading charger voltage.

This table shows a temperature-dependent typical bulk stage charging voltage (from the charger) for a 12V wet cell lead-acid battery that's used cyclicly. You want the charging to happen around 25C when possible.

Battery Temperature	Charge Voltage per cell	Charge Voltage
-20 °C *	2.6	16.02 to 16.56
-10 °C *	25.1	15.66 to 16.2
0 ° C *	2.45	15.3 to 15.9
10 °C	2.41	14.94 to 15.54
20 °C	2.37	14.58 to 15.18
25 °C	2.35	14.40 to 15.00
30 °C	2.33	14.22 to 14.82
40 °C	2.3	13.86 to 14.46
50 °C	2.26	13.5 to 14.10

Thank you. I understand charger voltage but it just seems that anytime I was going down the road in mme and I looked at the voltmeter that it read 14.8 or very close to that and now it starts off there and quickly goes down to 13 volts. I just have never seen this before after owning for just a month.

 

[Mach-Lee]

The charging voltage will decrease as the battery gets warmer. You will notice it as outside temps increase or parking in a heated garage. Normal behavior.

 

[SpaceEVDriver]

Thank you. I understand charger voltage but it just seems that anytime I was going down the road in mme and I looked at the voltmeter that it read 14.8 or very close to that and now it starts off there and quickly goes down to 13 volts. I just have never seen this before after owning for just a month.

As others said, if it drops very low (below about 12.0V), that *might be* an issue. If it starts at 14-ish and drops quickly to 13-ish, that's entirely expected.

 

[mkhuffman]

Thank you. I understand charger voltage but it just seems that anytime I was going down the road in mme and I looked at the voltmeter that it read 14.8 or very close to that and now it starts off there and quickly goes down to 13 volts. I just have never seen this before after owning for just a month.

If you remain concerned, I recommend getting a OBDII scanner and the Car Scanner app. You can monitor the LVB while driving using the app, and then review the data later after your trip is finished. You can also monitor the LVB while the car is off, but keep in mind that will put a strain on the LVB. I did it a few times just to verify the car was maintaining the LVB properly, but would not do it on a regular basis.

Here is the scanner I use:
https://www.walmart.com/ip/VeePeak-...d-Compatible-1996-Cars-Light-Trucks/954799575

 

[JimmyMachE]

I looked at the voltmeter that it read 14.8 or very close to that and now it starts off there and quickly goes down to 13 volts.

Answer is simple: the LVB is at optimal 90% SOC, so is not charged anymore. It is maintaned at 90% with 13V and very small charge current.

In CarScanner you can see that fluctuating charge currect (amps) and the LVB %SOC. Without these other values it is rather hard to understand the fluctuations in charging voltage of the LVB.

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