Maximizing Battery Life

[RangerBill]

Learn something new every day!

Nice 99 (?) Ranger BTW!

It was a 1994 that I had till 2019 when I bought my new Ranger. I bought it in 1994 and sold it in 2019.

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[Big Blue]

Lots of good discussion on the alternator clutch. I not convinced it has any thing to do with the BMS.

What it does is allow the alternator to spin faster than the drive pulley when the engine slows down when going off throttle or coasting. It will never let the alternator go slower than the drive pulley. This takes load pulses off the drive belt with rapid changes in engine speed, such as during shifts.

As someone with an engineering background. I too, like @TJC would like to see a flow chart of how the BMS works. This regenerative charging thing really makes no sense to me. Especially if it is the reason for keeping the battery in an under charged condition, which it obviously doesn’t like. I cannot believe it gains that much fuel economy to be worth the effort for the average driver.

 

[moorejl57]

Lots of good discussion on the alternator clutch. I not convinced it has any thing to do with the BMS.

What it does is allow the alternator to spin faster than the drive pulley when the engine slows down when going off throttle or coasting. It will never let the alternator go slower than the drive pulley. This takes load pulses off the drive belt with rapid changes in engine speed, such as during shifts.

As someone with an engineering background. I too, like @TJC would like to see a flow chart of how the BMS works. This regenerative charging thing really makes no sense to me. Especially if it is the reason for keeping the battery in an under charged condition, which it obviously doesn’t like. I cannot believe it gains that much fuel economy to be worth the effort for the average driver.

Your not alone. My interpretation of the "regen charging" is that normally for fuel economy, the alternator is lightly coupled to the engine (via pulse width modulation?) during normal driving and then it is fully coupled during deceleration increasing loading and charge rate. I am guessing that disabling the BMS allows the alternator to always be fully coupled. If I actually understood how the whole things works, I would likely disable the BMS in Forscan and get the ASS disabled as a bonus.

 

[Bsthroop]

Your not alone. My interpretation of the "regen charging" is that normally for fuel economy, the alternator is lightly coupled to the engine (via pulse width modulation?) during normal driving and then it is fully coupled during deceleration increasing loading and charge rate. I am guessing that disabling the BMS allows the alternator to always be fully coupled. If I actually understood how the whole things works, I would likely disable the BMS in Forscan and get the ASS disabled as a bonus.

The risk there is that with BMS/ASS disabled with Forscan there is no charge regulation so it stays at 14.7 volts and can damage the battery. I don't believe there is a one size fits all solution since disconnecting BMS may be fine for occasional drivers but may overcharge for heavy use vehicles.

 

[TJC]

Hmmm, Maybe we put a multi channel O'Scope on the alternator I/O and watch what's happening in real time, driving.

It has been 42 years (1982) since I last used an O'scope on a daily basis at work. Moved from HW engineering and testing, to SW and AI development work in 1983.

I still remember the principles, but I'd have to read up on scope operations manual and get my hands on the Ford schematics before even attempting that.

I am not even sure what's where anymore in modern trucks. How much of the voltage regulation is in the PCM (or some other system controller) vs internal to any part of the voltage regulator (that may still be) internal to the alternator.

Life was a whole lot simpler with a conventional charging system.

The more complex the plumbing, the easier it is to stop it up.

 

[TJC]

The risk there is that with BMS/ASS disabled with Forscan there is no charge regulation so it stays at 14.7 volts and can damage the battery. I don't believe there is a one size fits all solution since disconnecting BMS may be fine for occasional drivers but may overcharge for heavy use vehicles.

I have not found this to be the case when I disconnected the BMS sensor. My charge voltage varies with the battery SOC and ambient temperature. Drops down to 13.8 - 13.9 range all the time if driven long enough. In the heat of summer I expect it to drop a bit more. I see it start to drop in as little as 10-15 miles.

If your battery is at a low SOC, you may never see the charge voltage drop. It takes quite a while to charge a lead acid battery to a high SOC! If your battery is in a weakened state, the charge voltage may never drop in 10-30 mile trips.

I may plug it back in and disable ASS/BMS in Forscan to see how the system behaves. I believe that Airline Tech tested both and found the behavior identical.

 

[Big Blue]

Your not alone. My interpretation of the "regen charging" is that normally for fuel economy, the alternator is lightly coupled to the engine (via pulse width modulation?) during normal driving and then it is fully coupled during deceleration increasing loading and charge rate. I am guessing that disabling the BMS allows the alternator to always be fully coupled. If I actually understood how the whole things works, I would likely disable the BMS in Forscan and get the ASS disabled as a bonus.

I believe the clutch is strickly an overrunning clutch. There is no electrical control of it. If there was slippage in it to control voltage it would be a huge wear issue.

The output voltage of the alternator is regulated by the voltage applied to its field coil. Actual RPM of the alternator has a reatively small affect on it output voltage. Besides it runs in a fairly narrow rpm range. Under hard acceleration is the only time it sees higher RPMs and that is when the PCM would reduce voltage to reduce load.

I could see the PCM increasing voltage output during off-throttle situations to increase load to add to to engine braking and get some added charging. Just seems like a rather trivial amount of savings at the cost of battery life.

 

[airline tech]

Thanks for the Video, that video and another article is what I based the boost charge on, so now I am second guessing and think that when the truck is in deceleration - the clutch is mechanical device and via spring tension within the pulley creates the couple and decouple advantage.
The pulley free spins, that is a known fact.

Once I saw the video above, it leads you to believe that the momentum of the spinning tire keeps the pulley spinning at a faster rate so if this is the case it would be a friction-based boost (like a windup toy) sort of
or
The PCM knows the engine is in Decell mode, through engine RPM readings and combines that with the VSS sensor to trigger a higher boost voltage from the alternator by using the regulator.
So, this makes more sense as the BCM and PCM know what the battery voltage is and knows when the boost charge is needed and combine this control with the free spinning pulley produces the boost.

So, I can accept the free spinning pulley producing the boost and understand it, but the question remains is actually how the boost is maintained throughout the coasting effect until you reach a full stop. I was lead to believe it was all done within the pulley, but now question it and it appears there is more to it than the pulley itself.

 

[Big Blue]

I have not found this to be the case when I disconnected the BMS sensor. My charge voltage varies with the battery SOC and ambient temperature. Drops down to 13.8 - 13.9 range all the time if driven long enough. In the heat of summer I expect it to drop a bit more. I see it start to drop in as little as 10-15 miles.

OK, if you have the BMS sensor disconnected, how is the system detecting SOC and adjusting charge voltage to it? Isn't that what the sensor is for?

 

[dtech]

The risk there is that with BMS/ASS disabled with Forscan there is no charge regulation so it stays at 14.7 volts and can damage the battery. I don't believe there is a one size fits all solution since disconnecting BMS may be fine for occasional drivers but may overcharge for heavy use vehicles.

Also disagree with saying there is no charge regulation, the ecm has a voltage regulation system, bms just adds additional functions to it, 1.5 yrs of bms being disconnected hasn't killed my battery, in fact I believe it's extended it lifespan.

 

[TJC]

So, I can accept the free spinning pulley producing the boost and understand it, but the question remains is actually how the boost is maintained throughout the coasting effect until you reach a full stop. I was lead to believe it was all done within the pulley, but now question it and it appears there is more to it than the pulley itself.

I infer the same, but I do not understand how the increased resistance from a over charging alternator does not rapidly decelerate a free spinning clutch. The alternator will act like a brake on the free spinning clutch. There has to be more to this puzzle.

 

[Bsthroop]

I infer the same, but I do not understand how the increased resistance from a over charging alternator does not rapidly decelerate a free spinning clutch. The alternator will act like a brake on the free spinning clutch. There has to be more to this puzzle.

The clutch does not appear to have anything to do with charging, only helps smooth the belt operation. The system senses coasting from speed sensors and engine load and excites the alternator to a higher charging voltage until the engine is under load again, utilizing the coasting energy.

 

[dtech]

OK, if you have the BMS sensor disconnected, how is the system detecting SOC and adjusting charge voltage to it? Isn't that what the sensor is for?

It would measure soc via the same electronics in the voltage regulator module that is used when you hook up a batt tester or vohm. At one time rectification and voltage regulation was integrated into the alternator, now it's found in the ecm, probably because of stuff like regen can be added. SOC awareness and voltage regulation is basic to any device that has a rechargeable batt- cell phones, laptops, etc. So the voltage is likely measured from the smaller positive cable that typically runs from the batt to the alternator, but one would need a charging system schematic to be exact.

 

[Big Blue]

So, I can accept the free spinning pulley producing the boost and understand it, but the question remains is actually how the boost is maintained throughout the coasting effect until you reach a full stop. I was lead to believe it was all done within the pulley, but now question it and it appears there is more to it than the pulley itself.

The problem I see with this is the pulley is not free spinning, it is locked to the motor through the belt. The alternator is allowed to spin faster than the pulley but never slower. This means that when the motor slows down the alternator can spin faster than the pulley until the load on it slows it back down to motor speed. Which I don't think would be very long. Especially if the PCM jacks up the field voltage, causing it to make more charging voltage. The clutch just takes the shock of the initial speed change off the belt like the video talks about.

Again I think the clutch really has nothing to do with the regerative charging. It is simply the PCM jacking up the alternator output voltage, causingore load, while the motor is not being used to power the vehicle and the enertia of the vehicle is back-driving the motor (engine braking).

Since we believe the BMS knows the battery SOC. Why does it need to leave room for the regenerative charge? Couldn't it just not boost the voltage if the battery didn't need it?

Or am I just over thinking this and being logical.

 

[dtech]

The problem I see with this is the pulley is not free spinning, it is locked to the motor through the belt. The alternator is allowed to spin faster than the pulley but never slower. This means that when the motor slows down the alternator can spin faster than the pulley until the load on it slows it back down to motor speed. Which I don't think would be very long. Especially if the PCM jacks up the field voltage, causing it to make more charging voltage. The clutch just takes the shock of the initial speed change off the belt like the video talks about.


Regen converts mechanical energy from vehicle drivetrain to electrical energy via the alternator, to use this energy it has to be stored somewhere, hence the bms limits batt soc and this energy is stored in the battery then alt load can be reduced, batt drawn down and the cycle repeats itself. Similar to how evs do it.

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