AC Delco 12V MME 50 Ah, Chevy Spark, Cadillac Battery

[louibluey]

What? Why are are anyone talking about CCA on an _electric car_ with nothing to crank? A battery with a high CCA is a much more fragile battery which is why all other applications that does not require high amps will use batteries with a low CCA. CCA is the number of amps the battery can supply in 30 seconds in serious freezing temperatures with a voltage > about 7V, it has absolute no meaning for an EV.

The 12V battery in an electric car has no use other than
1) Powering on the relay for the high voltage battery to enable DCDC regulator if the high voltage battery is completely discharged.
2) Providing backup power after a collision for locks, hazard lights, emergecy call system, airbags, etc.

All the other features are provided by the DCDC regulator. Any faults or dicharging of the 12V battery is a result of a failure of the charging system/DCDC regulator, which runs 24/7 connected or not connected, running or not running, or an actual failure in the battery itself. Putting in another battery with a high CCA but tiny fragile electrodes (almost like pieces of paper in an ICE startup battery). The most common reason for 12V ICE start batteries to fail is mechanical breakage of the electrodes. Parts of the electrodes breaks and falls to the bottom of the acid which at some point shorts out the cells when they get stuck between the cells. The lost part of electrodes results in inbalance between cells, causing overcharging of broken cells and undercharging of other cells, causing evaporation of water, causing even more damange. This is simply why we do not want the fragile high-CCA batteries in our EVs, they are just made for one single purpose, but not for what we want, which is a stable 12V source which can be constantly charged.

The BMS for 12V battery is pretty simple stuff.. charge with a set max voltage until no current flows. Thats how to detect if a lead acid battery is charged. The voltage is calculated based on battery temperature, battery chemistry and the required state of charge. There is no counting of amps or cell balancing involved like in lithium battery charging. The battery negative terminal is isolated from any load with the current sensing in series to detect the current to and from the battery. There is no battery life estimation or anything in lead acid batteries. Partially because the number of Wh a lead acid battery can deliver is not really possible to estimate in the first place, it is very dependent on the current draw and temperature. The charge voltage (100%) does not change as the electrodes starts to generate crystals.

Good information, thank you for taking the time to write your thoughts. As noted above, most of us are looking for a bit higher Ah, however we take note at your caution of fragility, interesting. Nobody has discussed CCA before your post so far as I know, but, your cautionary notes are heard. Several of us have quite a bit of EV experience, so EVs and 12V bus load are well understood, at least by practical experience. Many of us are engineers, although only some are in the automotive industry.

On BMS, we are reverse engineering based on LIN data, CAN data, and direct voltage measurements under various conditions. It is definitely a crowd sourced effort coming at the question, How well does MME do at maintaining the 12V LVB? from some very different angles and approaches.

Some of the incentives for these efforts include MME with dead LVB, flat LVB, and three or four+ different LVB warnings, which include, for example, MME sleep, deep sleep, warnings to service your LVB, replace the LVB, etc. In many situations, many of us believe that some of the warnings are bogus, where the LVB is okay.

However, clearly there are some LVB problems, obvious ones where a 12V LVB must be jumped, to possible LVB problems while driving which cause MME to complain, and sometimes stop running. That is another reason, or possibly the main reason for this interest in MME LVB care and feeding.

For me, it is mostly a learning project. I barely knew what LIN stood for before, and now I am learning about LIN master, LIN slave, types of LIN frames, and how to decode them. It is like a community college course in auto mechanics. The CANedge2 LIN monitor from CSS Electronics in Denmark was relatively costly for a hobby project, but less than tuition for most formal courses. Example from today.

Sponsored

 

[phidauex]

How is the battery holding up? Any odd SOC values or vehicle complaints? Mine has now thrown "12V Battery Fault - Service Soon" three times in the last month (May 2021 build). I'm going to try a full manual charge and recondition, but thought I should start looking for replacement options as well.

I know I should probably take it in for warranty, but honestly doing the work in the evening after the baby is in bed is so much easier than driving it to the dealer, figuring out how to get home, shuffling cars, etc... For a $500+ problem I'm definitely taking it in, but for a $150 problem I'm inclined to just get it done myself.

 

[louibluey]

How is the battery holding up? Any odd SOC values or vehicle complaints? Mine has now thrown "12V Battery Fault - Service Soon" three times in the last month (May 2021 build). I'm going to try a full manual charge and recondition, but thought I should start looking for replacement options as well.

I know I should probably take it in for warranty, but honestly doing the work in the evening after the baby is in bed is so much easier than driving it to the dealer, figuring out how to get home, shuffling cars, etc... For a $500+ problem I'm definitely taking it in, but for a $150 problem I'm inclined to just get it done myself.

Fine until tonight (1/10/22) when I got the 12V battery, service soon message. I went out and unplugged, then reconnected the BMS LIN monitor so I get a stand alone file for tonight through tomorrow when I get chance to read and graph the voltage and soc data. Supposed to be -6F by morning, high tomorrow 11F, so should be a good test of cold weather too (unheated garage).

MME was plugged in L2 since just after noon when I moved it to the driveway for a while. I guess I woke it this evening, when I opened the frunk to reset the LIN monitor, otherwise I will leave it alone through tomorrow morning, then have another look. Guess I better move the fob away and turn off the phone Bluetooth for a better test.

I really think a lot of the 12V warnings are bogus, but it will be interesting to see the soc curve. It is possible Ford needs to keep improving the way they are monitoring and charging the LVB. So, how much is faulty monitoring and alarming vs. faulty LVB maintenance routines is still TBD.

 

[phidauex]

Fine until tonight (1/10/22) when I got the 12V battery, service soon message. I went out and unplugged, then reconnected the BMS LIN monitor so I get a stand alone file for tonight through tomorrow when I get chance to read and graph the voltage and soc data. Supposed to be -6F by morning, high tomorrow 11F, so should be a good test of cold weather too (unheated garage).

MME was plugged in L2 since just after noon when I moved it to the driveway for a while. I guess I woke it this evening, when I opened the frunk to reset the LIN monitor, otherwise I will leave it alone through tomorrow morning, then have another look. Guess I better move the fob away and turn off the phone Bluetooth for a better test.

I really think a lot of the 12V warnings are bogus, but it will be interesting to see the soc curve. It is possible Ford needs to keep improving the way they are monitoring and charging the LVB. So, how much is faulty monitoring and alarming vs. faulty LVB maintenance routines is still TBD.

Interesting, thanks for the feedback. Sounds like something is odd with either the alarming or the maintenance routines. Hopefully it is just alarming and that the car is overly sensitive to 12V issues because of the known severity of them. On the other hand that could result in a boy who cried wolf situation with 12V alarms.

I'll keep going with the reconditioning of mine and see how it goes.

 

[louibluey]

Interesting, thanks for the feedback. Sounds like something is odd with either the alarming or the maintenance routines. Hopefully it is just alarming and that the car is overly sensitive to 12V issues because of the known severity of them. On the other hand that could result in a boy who cried wolf situation with 12V alarms.

I'll keep going with the reconditioning of mine and see how it goes.

Almost forgot, Fordpass has been complaining that it wanted to do an OTA, but I turned off OTA updates. At around 5pm, I relented and turned OTA back on. I think the 12V warning was this evening around 8pm. So, I need to pay special attention to the end of the last record and look at what happened to soc after I turned OTA back on. It will be interesting to see if there was any significant drain in those three hours. Of course MME should just run the DC/DC converter, but maybe it doesn't during some part of an OTA? People have speculated that OTA might be the cause of a lot of these 12V warnings / problems, looking forward to looking through some data tomorrow.

I have had no 12V warnings since I changed the battery (12/29/21), until tonight.

 

[Astraea]

Fine until tonight (1/10/22) when I got the 12V battery, service soon message. I went out and unplugged, then reconnected the BMS LIN monitor so I get a stand alone file for tonight through tomorrow when I get chance to read and graph the voltage and soc data. Supposed to be -6F by morning, high tomorrow 11F, so should be a good test of cold weather too (unheated garage).

MME was plugged in L2 since just after noon when I moved it to the driveway for a while. I guess I woke it this evening, when I opened the frunk to reset the LIN monitor, otherwise I will leave it alone through tomorrow morning, then have another look. Guess I better move the fob away and turn off the phone Bluetooth for a better test.

I really think a lot of the 12V warnings are bogus, but it will be interesting to see the soc curve. It is possible Ford needs to keep improving the way they are monitoring and charging the LVB. So, how much is faulty monitoring and alarming vs. faulty LVB maintenance routines is still TBD.

Just curious what the outcome of this was. Not sure if you saw from other posts or not but my car is in a bad way with the LVB and any potential fix to my ongoing problem is helpful to look into. Any update or information you have after this experiment is infinitely helpful! Thanks you. ?

 

[Brown1000]

Fine until tonight (1/10/22) when I got the 12V battery, service soon message. I went out and unplugged, then reconnected the BMS LIN monitor so I get a stand alone file for tonight through tomorrow when I get chance to read and graph the voltage and soc data. Supposed to be -6F by morning, high tomorrow 11F, so should be a good test of cold weather too (unheated garage).

MME was plugged in L2 since just after noon when I moved it to the driveway for a while. I guess I woke it this evening, when I opened the frunk to reset the LIN monitor, otherwise I will leave it alone through tomorrow morning, then have another look. Guess I better move the fob away and turn off the phone Bluetooth for a better test.

I really think a lot of the 12V warnings are bogus, but it will be interesting to see the soc curve. It is possible Ford needs to keep improving the way they are monitoring and charging the LVB. So, how much is faulty monitoring and alarming vs. faulty LVB maintenance routines is still TBD.

@louibluey any update on the info you found out? How's the battery holding up? Thanks

 

[louibluey]

@louibluey any update on the info you found out? How's the battery holding up? Thanks

I have been running the Cadillac battery for some months now. I got one or two more FordPass 12V service warnings, but I know them now to be mere announcements that MME charged the 12V battery in some conditions (I forget off hand if it was L2 plugged in or not, it's in my previous posts).

Work took me away for a while, so I stopped plotting the LIN bus 12V data, but no actual 12V LVB problems, none.

 

[CzarR]

Hi, I am curious if I can add a XS Power XP750 Supplemental 12-volt battery for an external car amplifier. XS power is also AGM so does it help.

 

[snowdoggie]

As you are approaching almost 3 years of the replacement how did everything turn out? Also would the 26R size be the same as the LN1 size?

Sponsored