Dead Battery, Advance Auto Says Bad Alternator on 2020

[dtech]

Most modern AGM charging systems - be it the ones in the vehicle or an external battery charger have a certain degree of charging intelligence built into them and they will always maintain a margin of safety as it pertains to charging voltage limit. So factors like ambient temperature or even a sensing of actual battery temp, and they will allow for more voltage depending on the SOC, as a battery approaches full SOC resistance increases and this is what can raise the battery temp so again logic is built to reduce the allowable charging voltage.
How many on here have experienced or even heard of an AGM battery failing due to outgassing ? I never had. So short term levels above 15v under certain conditions is not going to damage the battery. It took a very long time to convince the uniformed and skeptics on here that disconnecting the BMS and therefore reverting to a fixed charging voltage is not going to fry the battery.

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[dtech]

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While we are talking about BMS, I do not understand the need for a clutch on the alternator. It is quite easy to vary the alternator output by simply modulating the stator input voltages, lowering the stator field voltages lowers the alternator output voltages, and the parasitic drag from the alternator. Remove all voltage and the alternator is effectively an idler pulley. The clutch seems redundant.

Can someone tell me what I am missing?

Well possibly you are missing that Ford pretty much copied what I believe BMW originally developed . The clutch can reduce wear on the belts, pulleys and alt bearing, other than that I don't know.

 

[got3fords]

That is Ford's eco-BMS at work. I only saw the 15+V when BMS was active, and I was coming to a stop or off throttle. On a freshly charged battery at 100% SOC, I have seen 12.4v charge rate, which is undercharging the battery. I only saw the 15+V when battery SOC was at or below the 70%-75% threshold.

While we are talking about BMS, I do not understand the need for a clutch on the alternator. It is quite easy to vary the alternator output by simply modulating the stator input voltages, lowering the stator field voltages lowers the alternator output voltages, and the parasitic drag from the alternator. Remove all voltage and the alternator is effectively an idler pulley. The clutch seems redundant.

Can someone tell me what I am missing?

It's not really a clutch, it just free wheels in one direction, like a bicycle's crank. It supposed to prevent backlash.

 

[dtech]

It's not really a clutch, it just free wheels in one direction, like a bicycle's crank. It supposed to prevent backlash.

From my engineering days - I believe that fits the definition of an "overunning clutch"

 

[harringtondav]

Yeah, but that would add fifty cents to every alternator - can't have THAT!!!

I replace the 'alternator' in my daughter's 2007 Sebring due to bearing squeal.
I shopped for the best AM price. All had it listed as a generator. I checked the tech manual. ...yep, generator.

 

[harringtondav]

It's not really a clutch, it just free wheels in one direction, like a bicycle's crank. It supposed to prevent backlash.

AKA an overrunning clutch. Early - and maybe current-automatic transmissions used one to hold 1st gear torque. It spun freely as higher trans speeds ran away from it.

 

[got3fords]

From my engineering days - I believe that fits the definition of an "overunning clutch"

Ah, indeed!

 

[Frenchy]

Unless disabled for some reason, the BMS is always at work.

 

[harringtondav]

Unless disabled for some reason, the BMS is always at work.

Apparently. My Ranger sits fallow in the garage this time of year, sometimes for a couple of weeks.
When I get into it there is a display notice about some sort of battery saver mode.
Always plenty of cranking juice, but the battery is now 5+ yrs old. ....time to make that battery/alternator multimeter check. ....or just wait until it struggles and give it a 50 amp boost jolt from my charger. Then replace it.

 

[Frenchy]

Apparently. My Ranger sits fallow in the garage this time of year, sometimes for a couple of weeks.
When I get into it there is a display notice about some sort of battery saver mode.
Always plenty of cranking juice, but the battery is now 5+ yrs old. ....time to make that battery/alternator multimeter check. ....or just wait until it struggles and give it a 50 amp boost jolt from my charger. Then replace it.

At that age I would replace

 

[conductor]

So while mine was never dead, i definitely saw a lot of time spent with ~14.8v going into the battery per my Ford Performance tuner. Finally swapped it out for a fresh one, and quickly saw the voltage levels return to normal. My keyless entry door sensors work again! But now my auto up/down switch for the drivers window isn't doing the auto part, so i'll have to whip the laptop out i think.

One thing i will say tho... Ford did NOT make getting the battery in and out a very easy task, and maybe this is exclusive to the Lariats, but man there are a lot of things connected to the terminals... and naturally i didn't want to take them all off for fear of not getting them back in the correct place. Had to go in and out at an angle, which is not the easiest thing to do with how tall trucks are these days (just ignore the fact that it was me who added the taller tires and leveling kit).

To reset your windows just Google on it , I did and I fixed the auto up down on my 2020 Ranger in a minute .

 

[harringtondav]

At that age I would replace

I know. But I'm a bit of a tight a*s procrastinator. Heck, I might be able to squeeze a few more months out of it. ....and hope it dies at home in the garage.

 

[rang19ca]

You're probably not saving any money by putting off the battery replacement. Pricing are always going up for some reason.

 

[TJC]

FWIW, I have had a voltmeter on the dash in my 21 Ranger for over 3 years. Can't say I have ever seen 15.1 volts but first start in the morning it is not unusual to be at 15.0. it will drop back down to low/mid 14s pretty quickly. After a long drive it is not unusual to see it at 12.9 volts.

f you voltmeter is feeding off a 12v socket in the cabin, you need to add 0.2v to whatever you see to get an accurate reading of the voltage flowing into the battery.

 

[TJC]

Well possibly you are missing that Ford pretty much copied what I believe BMW originally developed . The clutch can reduce wear on the belts, pulleys and alt bearing, other than that I don't know.

Thanks for the explanation. It is not used to regulate voltage, but to save wear on the belts and bearings. Consider me "educomated" !!

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