Although in fairness, it won't just be the current from the starter that the alternator ha to replace after a cold start. In a diesel there will also be the glowplug current and in both cars there will be fuel pump, ventilation fan, injectors, heated rear screen etc plus whatever natural discharge to replace since the last time the car was started. However, I agree these are likely to be relatively trivial.
Smart charging alternators.
- Thread starter Burnerman
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Although in fairness, it won't just be the current from the starter that the alternator ha to replace after a cold start. In a diesel there will also be the glowplug current and in both cars there will be fuel pump, ventilation fan, injectors, heated rear screen etc plus whatever natural discharge to replace since the last time the car was started. However, I agree these are likely to be relatively trivial.
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Plus the central locking last time the car was locked, constant drain and then opened again.
Even if the time is doubled, it's still far less than people think.
Even if the time is doubled, it's still far less than people think.
It's all to eek the last 0.1mpg or milligram of emissions regardless of the battery longevity and production cost (to the environment).
Same as all these 0 weight oils, terrible for the engine but better for MPG..
They had to design a new style of battery to take the abuse of all these SMART charging strategies and Stop Start.
When towing I have to have headlights on low beam (puts the car into "normal" charging mode).
Same as all these 0 weight oils, terrible for the engine but better for MPG..
They had to design a new style of battery to take the abuse of all these SMART charging strategies and Stop Start.
When towing I have to have headlights on low beam (puts the car into "normal" charging mode).
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Honda 2016 i-dtec (oiler.) Need to keep battery up and systems running somewhat.
Drive to end of road, turn up hill, engine under load, 12.0V !! (DVM reading from auxillary socket), hit the level hilltop back off slightly on loud pedal, 15.2V.
And so it goes on, load engine - Volts drop to just about battery level, engine on over run - up go the Volts. Guess we'll have to tow the begger up the hill with the 'do-it-all' 'Note' oiler - then 'overrun' back.
"...charge harder during a brief period of deceleration without sacrificing fuel economy or
overcharging the battery. In fact, when there’s a greater alternator load on the engine during
deceleration, that load contributes to engine braking—something that’s good for brake pad
life as well. Think of this as a mild form of what hybrid vehicles do with regenerative
braking..."
During the drive I thought about adding electrical load, side lights perhaps, but sort of reasoned the alternator output may just increase enough to cover the extra load with little or nothing extra for battery charge. Maybe I am wrong perhaps the system only has two operating modes high or low output ? I expected smooth gradient low to high... Maybe the battery is knackered !! Car was virtually off the road for 8 months, so 20 miles/wk did not do it a whole lot of good. Surprised at the DPF not causing any probs.
Very tempted to unplug the 'smart' sensor at the battery -ve terminal... It is said that the system defaults to - No Stop / Start, and a standard(?) 14.2V alternator output (I bet the Honda is different !) - Some guy did this with Porsche and (he said) Mercedes... Here he is :-
https://www.youtube.com/watch?reload=9&v=x9UML_jDKL0&feature=youtu.be
Short journeys - shouldn't pose a risk of overcharge - should it ?
Not using s/s wouldn't require battery to only be at 80% - would it ?
Not gonna experiment under lockdown - last thing I want is car off road - No local dealership access at present.
It is theoretically a clever system - but not brilliant in execution - A bit like everything else nowadays.
-0-
Drive to end of road, turn up hill, engine under load, 12.0V !! (DVM reading from auxillary socket), hit the level hilltop back off slightly on loud pedal, 15.2V.
And so it goes on, load engine - Volts drop to just about battery level, engine on over run - up go the Volts. Guess we'll have to tow the begger up the hill with the 'do-it-all' 'Note' oiler - then 'overrun' back.
"...charge harder during a brief period of deceleration without sacrificing fuel economy or
overcharging the battery. In fact, when there’s a greater alternator load on the engine during
deceleration, that load contributes to engine braking—something that’s good for brake pad
life as well. Think of this as a mild form of what hybrid vehicles do with regenerative
braking..."
During the drive I thought about adding electrical load, side lights perhaps, but sort of reasoned the alternator output may just increase enough to cover the extra load with little or nothing extra for battery charge. Maybe I am wrong perhaps the system only has two operating modes high or low output ? I expected smooth gradient low to high... Maybe the battery is knackered !! Car was virtually off the road for 8 months, so 20 miles/wk did not do it a whole lot of good. Surprised at the DPF not causing any probs.
Very tempted to unplug the 'smart' sensor at the battery -ve terminal... It is said that the system defaults to - No Stop / Start, and a standard(?) 14.2V alternator output (I bet the Honda is different !) - Some guy did this with Porsche and (he said) Mercedes... Here he is :-
https://www.youtube.com/watch?reload=9&v=x9UML_jDKL0&feature=youtu.be
Short journeys - shouldn't pose a risk of overcharge - should it ?
Not using s/s wouldn't require battery to only be at 80% - would it ?
Not gonna experiment under lockdown - last thing I want is car off road - No local dealership access at present.
It is theoretically a clever system - but not brilliant in execution - A bit like everything else nowadays.
-0-
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I'm sure it will be fine - just enjoy the fractionally better fuel consumption and environmental performance! If the smart charging system had felt that the battery was low, it would have charged going up hill. These systems have pretty complex strategies but the priority is to be a battery charging system. Maybe try leaving your headlights on for a few hours and then try the same test. My bet is that it will charge going uphill. The fact that it didn't suggests to me, that your battery is excellent health and that starting the car didn't take enough out of it to make the system want to charge it immediately. It felt happy enough that it could wait for some over-run.
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It depends how long a battery has been left discharged for, starting a car and it will take maybe a minute or so to put that back in, but leave a car for a month running even very small things like the radio back up, and to put that back in takes a long time, with a battery left on a caravan for 6 months put that battery on a smart charger with max 3.8 amp output and after just 15 minutes it has dropped to next stage of 3 amp, that stage will likely take a lot longer maybe 8 hours before it drops to 0.8 amp stage, and that stage may run for days before it drops into final 0.1 amp stage.
The point is the longer the sulphur has been on the plates the harder it gets and the longer it takes to put that sulphur back into the electrolyte.
There is a problem with the charger reporting fully charged, it can go into the final stage prematurely, and if you watch you will see it keeps returning to previous stage. This is typical
the battery is nearly fully charged, but that last little bit takes an age, possibly days, and if it is not completely charged next time it is harder to complete the charge. Once those peaks have stopped then the battery will recharge each week much faster, keeping it in tip top condition.
But with a modern car it seems putting a smart charger on the battery can mess things up, if the car is being used daily then each junction the engine will stop and restart, but leave it unused for just a week and the stop start stops until battery fully recovered, it can some times take a few days of 20 miles a day before the stop start resumes.
I have asked the question about using a smart charger on a car with computer controlled charging, and it seems each time I ask, I get a different answer, so I don't know which is the right answer.
We had the battery changed on the Jaguar XE as being faulty, it would just sit there and do nothing, after the battery was changed no more starting problems which seems to point to the battery, but that old battery we took to use in the caravan, and a good 18 months latter that battery seems to hold charge and work A1. It will sit on the smart charger for weeks showing 13.4 volt, and take it off charge and put it back on charge 3 weeks latter and it is back to showing 13.4 volt within an hour. Off charge is shows around the 12.6 volt after 3 weeks, so not sure if there was really anything wrong with it other than being sitting on a car sales forecourt for a few months.
If the car starts I will not touch the battery, if the car fails to start likely charge for at least a week. Other batteries the charger does its rounds, once one battery has been charged for a couple of days it goes on the next one. So once the restrictions are lifted they are all ready to role, and any runs required are done in the Jaguar XE in the hope they will be enough to keep it in good order.
As to the link to https://www.powerstream.com/car-battery-faq.htm as you read down the questions and answers you get
This answer is incorrect, as when a battery charges the electrolyte level increases, so topping it up before charging can result in it over flowing, as soon as you see one item you know is incorrect, you have to question the rest of the answers.
The point is the longer the sulphur has been on the plates the harder it gets and the longer it takes to put that sulphur back into the electrolyte.
There is a problem with the charger reporting fully charged, it can go into the final stage prematurely, and if you watch you will see it keeps returning to previous stage. This is typical
But with a modern car it seems putting a smart charger on the battery can mess things up, if the car is being used daily then each junction the engine will stop and restart, but leave it unused for just a week and the stop start stops until battery fully recovered, it can some times take a few days of 20 miles a day before the stop start resumes.
I have asked the question about using a smart charger on a car with computer controlled charging, and it seems each time I ask, I get a different answer, so I don't know which is the right answer.
We had the battery changed on the Jaguar XE as being faulty, it would just sit there and do nothing, after the battery was changed no more starting problems which seems to point to the battery, but that old battery we took to use in the caravan, and a good 18 months latter that battery seems to hold charge and work A1. It will sit on the smart charger for weeks showing 13.4 volt, and take it off charge and put it back on charge 3 weeks latter and it is back to showing 13.4 volt within an hour. Off charge is shows around the 12.6 volt after 3 weeks, so not sure if there was really anything wrong with it other than being sitting on a car sales forecourt for a few months.
If the car starts I will not touch the battery, if the car fails to start likely charge for at least a week. Other batteries the charger does its rounds, once one battery has been charged for a couple of days it goes on the next one. So once the restrictions are lifted they are all ready to role, and any runs required are done in the Jaguar XE in the hope they will be enough to keep it in good order.
As to the link to https://www.powerstream.com/car-battery-faq.htm as you read down the questions and answers you get
This answer is incorrect, as when a battery charges the electrolyte level increases, so topping it up before charging can result in it over flowing, as soon as you see one item you know is incorrect, you have to question the rest of the answers.
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That makes an assumption that because its an 80amp alternator, it will push 80amps back into the battery, which is wrong. Given a charging current, the batteries voltage will rise rapidly, alternators limit voltage produced, so the current input will rapidly be much less than the 80amps suggested.
Not arguing; just interested.
When, then, does an 80A alternator produce that 80A?
Would that not be when the battery has been replenished?
They only produce 80A when there is demand from lights, cooling fan and etc. for that amount of current.
Even a 3amp charger will bring a batteries voltage up to the limit quite quickly, which then severely limits the current input.
Long ago I designed and built for myself a fancy 60amp pulse charger, so as to be able to quickly able start my cars with flat batteries. The full current, even at 14.5v would rapidly decline to just a few amps. The only way to increase the current flow was to increase the output voltage limiter.
Remember the commercial garage fast chargers? They used to output at 60v to rapidly force current into a flat battery.
Ok.
Are you saying that the example in my link will take 27 (80/3) times as long as it states? 27 x 8 seconds = 216 seconds.
What, then, would be the Amperage at 14.5V for an alternator?
I had a look at our Ford, the SMART alternator control is handled via the Body Control Module (BMS sub system).
It calculates the "best" charging strategy based on battery age, battery State Of Charge, estimated battery internal temperature, estimated load from all devices etc.
All good until you tow a caravan and want your fridge to stay cold on a long journey!.
For us putting the headlights on forces the car to revert to "normal" alternator operation.
The other side of the coin is Load Shedding, the car will start to turn off all non essential systems when the car detects alternator failure.
I would genuinely like to see real world results in MPG and Emissions between "normal" and "smart" control.
The 216 seconds is rediculous, because it is based on 80amps - the full output rating of the alternator, which is a ridiculous assumption to make - it would be much less than than.
I cannot state a current delivered by the alternator, because the it would decline rapidly once the engine started. I would guess at it being at most 20 to 20amps, but only for around 3 seconds, it would decline rapidly from that value to maybe 2 or 3 amps at 216 seconds.
Usually, it is accepted that is takes a at least 20 minute run, to replace the current consumed from a battery, by a cold start. It takes many hours of running, to bring a near flat battery up to a full charge.
If the link has done the calculation at 80A and you say it might be only 3A then it will take 27 times longer.
So, how long does it take to replace the 600Amp-seconds draw?
So, does it start off at 80A?
Why 3 seconds? Why 2 or 3A at 216 seconds.
...but as per my first query, that cannot be the case.
If your battery is flat and you run it down the hill, it will then start on its own much quicker than that.
If your drive to work takes 15 minutes and later 15 minutes home then the battery would continually drain - not to mention all the other draws previously listed.
A stop/start car in London would rack up hundreds of necessary recharging hours after a few miles.
How long does such a car take to cease its stop/starting?
Why 2 or 3A at 216 seconds? because the battery voltage rapidly rises to oppose the flow of current. The current flow graph declines very rapidly over a short time, unless the voltage is increased.
I fail to see the relevance of your comment about running the car down a hill to start it.
That's correct, a 15minute run per day with no decent longer run at the weekend usually means eventually a flat battery.
Stop/starts are specially designed for the purpose. I understand they use a special design of alternator to improve restart efficiency - much better than a starter motor.
You do not seem to be answering my questions. It's fair enough if you don't know; no one else seems to either.
My link is the best I have.
To replenish 600 Amp-seconds will take 600 Amp-seconds so if the alternator is only at 3A then it will be 200 seconds - not 13 miles (originally stated) nor 15 minutes.
It obviously depends how long eventually is but I have not found that to be the case.
So, it doesn't take 15 minutes to replenish the battery.
My link is the best I have.
To replenish 600 Amp-seconds will take 600 Amp-seconds so if the alternator is only at 3A then it will be 200 seconds - not 13 miles (originally stated) nor 15 minutes.
As I said, if you go out in the morning and the car won't start because the battery is 'flat' and you run it downhill to start it, then after much less than 13 miles or 15 minutes the battery will start the car.
You said 15 minutes would replenish the battery.
It obviously depends how long eventually is but I have not found that to be the case.
Not sure I understand that.
So, it doesn't take 15 minutes to replenish the battery.
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