Auto Start Stop Staying Off!!

[Mscdman]

There is also a battery state-of-charge parameter (apart from just Voltage, although you can kind of infer that if your Voltage is being kept high for long durations that it's trying to recharge that back up) that you can't see on the dashboard that feeds into if ASS is enabled or not. This is what usually causes it to just randomly stop, especially if you do a lot of short trips (and when the battery charges itself back up, or you put it on a charger, it randomly decides to come back).

Along with a long list of things that can shut it off - here's a list one guy compiled (this was from F150 forum, but I can't imagine it being a lot different)

Steering Wheel Manuevering
Battery Charging
Cabin Climate unsatisfactory
Ambient Climate isn't Moderate
Selected Gear (4x4)
Selected Mode (Sport, Baja, Mud)
Windshield Defrosting
Primary Seatbelt not fastened
Door Ajar
Incline / Decline too Steep
Elevation exceeds 11,000 ft
Insufficient Brake Vacuum
Normal Operation (if you stop, then proceed without exceeding 3MPH then Auto Stop Start is still disabled)
Engine Temperature
Trailer Connected
Selected Manual Transmission
Hill Decent Control Active

Thanks. So if I see in my gauge while driving that the voltage stays high (what’s high?) then that is a sign that the battery is low?

I do take short trips to and from work but don’t drive it often or put a lot of miles

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[Brian_B]

Thanks. So if I see in my gauge while driving that the voltage stays high (what’s high?) then that is a sign that the battery is low?

"Normal" is anywhere from low 12's to low 15's. Anything over 13 is charging at some level. Most people will notice it seems to get stuck at 14.9 or 15.3 or something - which is high charge. It's normal for the Bronco to do that immediately after starting, or while coasting, but it probably won't typically be doing that for too long while just on cruise control going down the highway.

Most of the time - the BMS does it's job and the battery is working fine. So most of the time, whatever the charge is doing on the Bronco, that's what it's supposed to be doing. If you think the charge is low - best thing you can do is put it on a charger over night and let it catch back up (be aware, with the BMS there is a special way you should hook up a charger/maintainer, and you should use one that is rated for AGM-type lead batteries).

Since almost everything on the Bronco is electric, short trips with it can actually leave it without enough time to recharge off the alternator. This happens frequently in my wife's Bronco Sport, for instance, where most of her trips are a mile down to the bus stop and back for the kid. A few weeks of that, and the battery just never gets a chance to get caught up, so we have to put it on a charger about once a month.

The first sign of an undercharged or failing battery is ASS just kinda stops working out of the blue. A lot of people don't even notice it for a while. The next sign is that your vehicle will start to enter Deep Sleep often - once is a sign you should definitely get it on a charger and get it charged back up. If it keeps doing it after that - that's your sign for a new battery before it finally just craps out on you somewhere.

And I would be negligent if I didn't also mention - there have been a few people where they change the battery out, and that replacement also fails quickly - those folks needed a new alternator or had another wiring issue that was putting a constant drain on the system (older RSE powered sliders seemed to be a common culprit). That doesn't seem to be common, but there has been more than one case of that around here. Just something to be aware of. You should get a few years out of a battery on a properly working system.

 

[Mscdman]

"Normal" is anywhere from low 12's to low 15's. Anything over 13 is charging at some level. Most people will notice it seems to get stuck at 14.9 or 15.3 or something - which is high charge. It's normal for the Bronco to do that immediately after starting, or while coasting, but it probably won't typically be doing that for too long while just on cruise control going down the highway.

Most of the time - the BMS does it's job and the battery is working fine. So most of the time, whatever the charge is doing on the Bronco, that's what it's supposed to be doing. If you think the charge is low - best thing you can do is put it on a charger over night and let it catch back up (be aware, with the BMS there is a special way you should hook up a charger/maintainer, and you should use one that is rated for AGM-type lead batteries).

Since almost everything on the Bronco is electric, short trips with it can actually leave it without enough time to recharge off the alternator. This happens frequently in my wife's Bronco Sport, for instance, where most of her trips are a mile down to the bus stop and back for the kid. A few weeks of that, and the battery just never gets a chance to get caught up, so we have to put it on a charger about once a month.

The first sign of an undercharged or failing battery is ASS just kinda stops working out of the blue. A lot of people don't even notice it for a while. The next sign is that your vehicle will start to enter Deep Sleep often - once is a sign you should definitely get it on a charger and get it charged back up. If it keeps doing it after that - that's your sign for a new battery before it finally just craps out on you somewhere.

And I would be negligent if I didn't also mention - there have been a few people where they change the battery out, and that replacement also fails quickly - those folks needed a new alternator or had another wiring issue that was putting a constant drain on the system (older RSE powered sliders seemed to be a common culprit). That doesn't seem to be common, but there has been more than one case of that around here. Just something to be aware of. You should get a few years out of a battery on a properly working system.

Great info!! Thanks! I have my battery hooked up to an AGM rated trickle charger now but I have it hooked right up to the battery terminals. Is that wrong?

 

[Brian_B]

Great info!! Thanks! I have my battery hooked up to an AGM rated trickle charger now but I have it hooked right up to the battery terminals. Is that wrong?

That is in fact incorrect.

You can see the BMS hanging off the negative battery terminal - that little black box on the negative terminal. It's kind of hidden underneath the green arrow in this pic.

(I'm stealing an image from another post here)

If you hook the negative directly up to the terminal, you bypass the BMS and it can't see the battery charging - so it won't reset the amp-hour calculation (battery life).

You need to ground to the chassis, or to that tab over to the right/along the upper bolt for the main cable. That puts the BMS in the loop and then it can see, and correctly count, the amps going back into the battery and keep the battery life calculation accurate.

 

[Mscdman]

That is in fact incorrect.

You can see the BMS hanging off the negative battery terminal - that little black box on the negative terminal. It's kind of hidden underneath the green arrow in this pic.

(I'm stealing an image from another post here)

If you hook the negative directly up to the terminal, you bypass the BMS and it can't see the battery charging - so it won't reset the amp-hour calculation (battery life).

You need to ground to the chassis, or to that tab over to the right/along the upper bolt for the main cable. That puts the BMS in the loop and then it can see, and correctly count, the amps going back into the battery and keep the battery life calculation accurate.

Ok so then attach negative to the tab with yellow arrow?

 

[Mscdman]

I just moved it to that tab with the yellow arrow but it was sitting for a few hours on the negative terminal itself (incorrectly). Have I ruined anything?

 

[Mdozier]

No harm. You provided voltage across terminals that always have voltage across them. You just didn’t include the BMS intelligence in the loop. Including the BMS adds the system into the charging process; good for protection of the battery, the electronics and the rest of the system and updates the BMS with the battery charge status.

 

[helifino16]

I had a "Charging System Error" that was introduced by trying to turn off the ASS with ForScan. Everything checked out - Alternator and Battery, so I just enjoyed the ASS being disabled for a while (this was finally corrected by Ford Service). I ended up getting the harness that plugs in behind the dash to have it remember whatever I leave it set. So, I can actually turn it back on with the button if desired. For the few $$, I think this is a better solution than mucking around with ForScan to try to get it turned off.

 

[BadlandsA51]

There is a menu selection under the fuel economy menu for ASS that will tell you why it’s not shutting the engine down. It doesn’t include all the reasons why it’s not working, but the most common reasons.

 

[sundaeman]

Coincidentally my auto start/stop has been staying off lately. I've just been haplessly enjoying it for the last couple of days. Button and gauges show off.

 

[Brian_B]

No harm. You provided voltage across terminals that always have voltage across them. You just didn’t include the BMS intelligence in the loop. Including the BMS adds the system into the charging process; good for protection of the battery, the electronics and the rest of the system and updates the BMS with the battery charge status.

Exactly correct

 

[Keerplunk]

If your Battery hits either 75% or 70% charge the Auto start/stop is shut off, it if gets lower you will start to receive ford pass notifications saying your bronco is going into deep sleep and suggests you drive longer. I drove from CA up to UT and it only started working again on the return trip. 500 miles for it to charge enough and reset.

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