Auto start/stop fix ?

[daver401]

2023 XLT FWD 2.0L ECOBOOST ENGINE 760AMP AGM BATTERY
After 6 months (12,000+ miles) Auto s/s quit working so took to dealer and got 'battery is low, not driving enough'. Told auto s/s quits working when battery goes below 80% charged (12.5 v per another thread, 12.73 is fully charged). Took back in for battery draining issue and left overnight so dealer could see how much battery dropped overnight per their suggestion. Instead, the next day they did the tail lamp recall, charged battery, and said working fine. They also did Battery Sensor Reset. Page 319 of my 2023 owner's manual says this is for when you install a new battery. (Battery was not replaced.) Does this set a new fully charged battery voltage value for the BMS?

I Immediately went to auto parts store to get a voltmeter to see charge state, but store was out. Went to my mechanic (AAA certified and AAA recommended) and he said he could really dig in to find where the draw was. In less than 10 miles from the dealer my mechanic tested the battery, and it was only about 55% charged, but auto s/s was still working. I left truck in shop for 6 days for him to really troubleshoot. Temp was -20 outside, so I wasn't going anywhere, and shop kept Maverick inside entire time. Multiple load and drain tests and also Parasitic Draw test. Monitored on meter and scope with memory and readout.

SHOP RESULTS: While maverick was sleeping something woke up and got a 1 amp draw for 30 seconds and then went away before he could find the module that woke up. AND he asked, How do you park the truck? Seems if you lock the doors and take the keys out, you have a 1 mAmp draw and if you leave it unlocked and keys in, you have a constant 5 mAmp draw on the battery. Possibly the biggest thing he did at the end was a 'software update', but we never know what that update was really about. I did rerun the Battery Sensor Rest after I knew it was fully charged.

End of story: Maverick has been working fine since. I also left the headlights on when parked to drain the battery lower to insure the 'auto s/s not working due to vehicle charging' came back. Learned much more - these are just the highlights.
When the auto s/s quits working I now know the battery is below 80% charged. I shut off the auto s/s when in town on short trips via the console switch. During all this the Maverick never failed to start, but still got a small 1A battery charger to better top of the battery.

Also got on google and did a search for automotive digital voltmeter and ordered one that has a digital readout and just plugs into the cigarette lighter.

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[Packer Bill]

You made some interesting statements. For the AGM, I thought 12.9 volts is full charge and the EFB (I have this in my Mav) is 12.7 volts. Also the BMS limits the battery to 80% charge and when the discharge level is 70%, the auto stop/start is disabled.

So far, for me, I I trickle charge to a full charge once a week. This is the only thing that works for me.

 

[Red Pepper Maverick]

I for one don't like the Auto S/S. I had a 2019 Ford Ranger and basically disabled the AS/S by plugging a night light into the rear AC receptacle behind the passenger seat. It kept the AS/S from activating for almost 5 years on the Ranger. I tried it on the Maverick and sometimes it would disable S/S and sometimes it wouldn't. I know with the Ranger if the light was plugged in the AC outlet the system would keep the engine running. It may require more current draw with the Maverick than it did with the Ranger. I may have to experiment with other night lights.

 

[Bob The Builder]

Indeed, 12.8 - 13.0 is considered full charge for an AGM battery. My A.S.S. now works great since I had the factory defective battery replaced under warranty.

Important to note is the fact I do not drive all that much, maybe 50-75 miles a week locally mostly, and the A.S.S. always works.

 

[Red Pepper Maverick]

I for one don't like the Auto S/S. I had a 2019 Ford Ranger and basically disabled the AS/S by plugging a night light into the rear AC receptacle behind the passenger seat. It kept the AS/S from activating for almost 5 years on the Ranger. I tried it on the Maverick and sometimes it would disable S/S and sometimes it wouldn't. I know with the Ranger if the light was plugged in the AC outlet the system would keep the engine running. It may require more current draw with the Maverick than it did with the Ranger. I may have to experiment with other night lights.

I think the problem I was having with the night light not 100% disabling S/S was it being a night light it probably wasn't lit all the time. It is a night light after all. On my Ranger I think it stayed dark enough for the light to be lit all the time, maybe not so much for the Crew Cab Maverick. I put tape over the sensor to be sure the light would stay lit. It seems to work now. No more annoying S/S for me. Easy fix if you want to disable S/S without having to push the button every time.

 

[B2000]

We had a long discussion about this before and I think the 70% charge figure is right- below that no S/S function and the battery management system only charges to 80% so you have a small window for it to work.

If I charge mine using a battery tender it works for a day or two but that is it. I also don't put a lot of miles on mine. I have had no problems starting or with any other functions.

 

[Packer Bill]

I changed my battery charge level to 95% with ForScan. I also installed an AGM battery. This solved my battery issues.

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