If the battery is left barely charged, it builds up sulfates on the plates. It basically reduced the size or capacity of the battery because the lead isn't exposed to the acid. So you can charge it to 12.6 V but it discharges too quickly due to reduced capacity. Sometimes the battery can be revived by hitting it with a high amp charger which removes some of the sulfates, but it will never be as good as it was.
I could easily be wrong here, but on the bad batteries, I think individual cells were soft shorting so instead of 6 cells at 2.13V, you basically had 5 at 2.13v. Sulfating can cause this, but poor manufacturing was more likely the culprit. You'd easily spot this with low voltage so I doubt this is the case for you.
Heat is also the enemy so make sure to have the blanket on the battery. My LS had the battery in the trunk and those lasted 8 years without any attention. AGM batteries are more susceptible too so I need to get a insulating blanket on mine.
I hooked my 5A battery tender up but it basically was in maintain mode after a couple minutes. The car sat long enough it should have updated the state of charge but it was at 71%, and 74% after 45 minute drive. Whole thing is beginning to really irritate me because when the battery is full, the car audibly turns over faster. Its not confidence inspiring to hear its not as fast as I know it can be, and the cold winter is right around the corner. The stupid BMS also encourages sulfating as a result of its strategy. Add in trunk modules and touch screens staying on and here we are with 1 year battery life.
I may charge directly to the negative battery post with my jumper pack, then verify its good with the Tender, and reset the BMS again. AND put target charge to 100%.
I replaced my battery yesterday with the FoMoCo battery BXT-99RT4A for $150. It's only 8" across vs the 11" for the H6 (48) AGM. It's only got 390 CCA, compared to the 760 from the H6 battery.
The BXT is for the Hybrid. Costco couldn't even find a cross reference for it.
I asked the service writer at the Ford dealer about the BMI and resetting it with a Scan tool. He said there was not necessary for cars built before 2020 or 2021. I put a trickle charger on while I was replacing the battery, just in case the war stories were correct that we'd lose radio settings, idle settings and so on. That seems to have worked, but can't tell if it was necessary or not. Next did the 5 head light flashes and 3 brake pushes. Within a couple of seconds after that I heard mechanical sounds from the engine bay. Not sure if it was just the brakes or something else. No indications on the dash, as we don't have the 12 volt battery warning.
According to this video about Ford BMS resets you can flash your headlights 5 times and then your brake peddle 3 times. There are a number of videos confirming this. Not sure if it works with the hybrid though.
I had to alter the url so it wouldn't bring up the whole youtube screen >>> https:// www.youtube.com/watch?v=VEDKsKEetMg
In our case, the dealer assured me they reset the battery age. However, at 18 months I tried the folklore sequence (which escapes me now) and did manage to get a dashboard confirmation of BMS reset.
I also read that hitting the Lock button twice (horn beeps) will cause the vehicle to deep-sleep it's modules sooner than just pressing Lock one time. We'll see if that changes anything.
Thank you for the additional insight. Will post some data after another day of logging values from the smart charger's display.
The question I have is why this Motorcraft MAX battery is considered "toast" after less than two years? Systemic charging issues, or is a bad batch of batteries also involved?
I busted out the laptop and my obd link (wired usb adapter forscan approved for programming modules) and noticed a couple things. While I reset my BMS when I put the new AGM battery in last year, I didn't update the battery type. It was still set to the original. Another setting is that the car targets just 80% rate of charge. I use my car for 45 minutes and it was not charging it to 80%, it was sitting around 70%. Maybe it waits to a certain threshold before charging or it has to sit deep sleep for 8 hrs to update? Anyway, I updated the battery type and set the target charge to 90%. I will charge it with a battery tender, then remove it and let the car deep sleep for 8 hrs (locked, and no interaction for 8 hrs including nearby key fob) so BMS can account for the fresh charge.
I did reset the BMS which is not desirable as now the car thinks its a new battery when in reaility its a year old. Its probably not the end of the world. The car is always trying to disable the alternator to gain MPG and these charging issues are the result, in combo with trunk modules and stuff having parasitic drains. I'll try 95% target next after watching this a while, and finally go to 100 if i don't see problems. My car is not start/stop equipped, but these charging targets, parasitic drains, and poor battery quality are the main causes behind those systems disabling.
Speaking of the BMS, I just watched a YouTube video about replacing the battery. Guy was talking about needing the BMS reset after installing the new battery. Wonder how many are doing the rest?
I'm getting the "System Off to Save Battery" message. After the message a loud click. Either side of the speedometer are blacked out. Figure it's about time. It's been in for around 6 years and 53,500 miles.
Going to give them a call and see if they are capable of the BMS rest.
Group Size: H6 (48) AGM $179.99*
I just picked up the H6 battery from CostCo and it is too big. The tag on the Hybrid FoMoCo battery i BXT-99RT4.