Focus Mk2/2a Charging Discussions

[Tdci-Peter]

The Mk2/2a is getting on a bit now. But many are still giving good service. battery charging, Alternators and so-called Smart charge remain complex and often puzzling areas, and maybe even more so in cars that have reached the "mature" stage of their life!

I have read a great deal about the infamous smart charge system, and much of it is conflicting, confusing, or sometimes downright wrong. One problem is that on these cars, and other Ford models of similar age, the alternator is controlled from the PCM (aka ECU or ECM). This part is provided by other companies, and is likely to be largely programmed by them, with specifications provided by Ford. And each engine has a different PCM. My 1.8 (Lynx) has the VDO / Seimens / Continental fuel injection system, and the PCM is part of that. It is very likely there will be significant differences in detail, as to how the charging system works on PCMs from different suppliers.

In principle, the smart charge system is a simple & cheap modification to a standard alternator. A standard alternator has an inbuilt regulator, that energises the field winding with a PWM signal. This is an efficient way to control the alternator output, which would otherwise rise with rpm. Cutting back the current in the field winding reduces the output, to match the rpm & demand. The regulator must do 2 jobs, regulate the voltage for the best battery charging voltage without over-charging it, and limit the output current to protect the alternator from overload. So there is already a way to PWM modulate the field current & a way to measure current.

All Ford had to do was request an extra connector be fitted, which gives access to both the field PWM directly, and the current or load signal. And for there to be a way that signals on this connector can over-ride the internal regulator, and control the field PWM directly. Then the PCM can take over control. It knows a bit about demand, as it can interrogate the BCM (aka GEM or Passenger Fuse Box) to find what is switched on, and it can measure battery voltage, temperature and time since start, etc. So, in principle, the PCM can manage the battery voltage better than the alternator itself can.

As I do not know much detail, with any certainty, about how it really works, and in response to a request from a member, I have done a quick Forscan data run on my 1.8TDCI during a cold start. It does show a few details of how the charging system responds to heavy loads.

This shows the starting. The green voltage line dips as I turned off the ignition briefly to initiate a new glowplug cycle. (Ignition needs to be on to set-up and start getting data in Forscan, but it survived the ignition off dip ok, The PCM does not power down for quite a few seconds after ignition off) During the glowplug on time (orange line), voltage dipped to a low of about 10.7v, then slowly recovered as the plugs heated up. The plugs did switch off when the glowplug LED went out. During cranking, voltage dropped to 9.2v.  As the engine fired up, the glowplugs came back on again. Voltage rose to about 13.2v over the next 10 seconds. 

Over the next few minutes, I tested varying loads. Heated rear window & mirrors, Headlights, Main Beam, & vent fan on full. On applying one heavy load, voltage dipped to about 12v, then recovered to near 13v. But applying both heated rear window and main beam dropped the voltage to 11.7v, and it did not recover until the load was reduced. Glowplugs were still on at this time. The lowest I recorded was 11.4v, with the 3 above loads on.  With no load except basic ignition & glowplugs, voltage did get up to about 14.2v. After about 150sec. of being on, glowplugs turned off. After this the lowest voltage with all loads above was 12.7v, and the unloaded voltage was 14.2v to 14.3v.

Note that the Forscan voltage is not exactly the battery voltage. It will be measured inside the PCM, and voltage drops in cables between the battery and the main fuse box will have a small effect on the readings. Loaded voltages will be a little lower at the PCM than at the battery. Maybe 0.1v to 0.2v.

For keen Forscan users, the complete file is below. You will have to change the .TXT extension to .FSL after downloading it, for Forscan to be able to read it. I can't upload .FSL files directly!

start-gp.txt

[unofix]

Thanks for that investigation @Tdci-Peter, it was something I have been meaning to do for sometime but never got around to. Your voltage dropping to 9.2V during cranking is right on the boarder line. Is your battery getting a little old, or is it just a bit low on charge ?

As you probably already know, the alternator is 3 phase with a rectifier pack. On some makes this is a controlled bridge which gives the means to limit the available current, as well as by adjusting the excitation field. 

When the 'smart control' fails for whatever reason, the alternator will default to just being a standard unit, and charge the battery at approx 13.6V

Like me you you will have noticed the many people who are complaining that their heated front screen is not working, and that they feel the alternator has enough output to keep it powered. Given that the load of many front screens is 60A it's little wonder that with the many other demands on the electrical system in the cold weather that without a good fully charged battery the screen is sometimes not available.

[Tdci-Peter]

1 minute ago, unofix said:

Is your battery getting a little old,

It is a top quality Bosch 5 year job, but is now 4 years past its warranty period! And it had been sitting for a week. So I am not surprised it is a bit low! I am beginning to wonder about its starting capability, but it has fired up after the usual first couple of compressions so far this winter. The first really cold sub-zero days might be a test for it though.

I would think that even with a new, fully charged battery, if the demand exceeded alternator capacity, voltage would still drop to below 12v, though not by much. The glowplugs & cranking effort would have taken any "surface charge" off the battery, and 20 or 30A of discharge current should then get the voltage below 12v.

When I tested my glowplugs, I think they drew about 60A (total) cold, dropping to about 30A as they heated up.

I am not sure what alternator capacity would be at idle. I somehow doubt if it could deliver its full nameplate amps. About 2/3rds of it would be my (wild) guess.

I do not recall hearing about controlled output rectifiers, but can believe it. It seems a bit of a cheap and nasty way to control output, I guess they just use SCRs. These can only (without some very fancy circuits) operate at the phase rotation rate, once they are on, they stay on until the ac voltage from the stator coil reverses. So the output will be very lumpy. But it might be cheaper or easier, especially a decade or so ago, when good power MOSFETs cost an arm and a leg, while beefy SCRs were dirt cheap.

 

[Tizer]

It's a pity FORScan does not allow you to monitor the current as well on that car, its a lot more useful than the voltage. Here are my observations for the different system on the Mk4 which may be of interest to you or anyone else.

Here is a snapshot of my petrol engined car during cranking when it was nearly new. The scale on FORScan only goes to -127 amps and the battery was almost at its hobbled 80% SOC.

 

Immediately after starting the net current is usually in the high teens to high 20's with the voltage in the 13's for a few seconds before gradually reducing to its normal 0 1,2 0r 3 amp net charging range, often pulsed. The voltage goes to its normal 14.8 within a few seconds after starting. When charging in one of the modes other than conventional then the current can be higher, maybe 5 or 6 with the voltage dropping to the low 14's. Sometimes the voltage goes to 14.9 with very low current in one of the other modes too.

According to FORScan, on my car switching on accessories doesn't make the slightest bit of difference to the net current or voltage after things have settled down, which is very quickly after starting, and nor does driving on the motorway, it charges exactly the same as it does at Idle. Coasting down a hill doesn't change it either.

When the ignition is switched on there is a current draw of about 8 amps, double that if the HVAC and Auto lights are on. It is the same when the engine is shut down. The voltages are about 11.9 ignition on before a cold start and 12.6 when switched off after a run. 

Maybe if people waited for 10 seconds or so before using their heated screens and HVAC on a cold morning then they might work every time. That is what I have always done and I have never had a problem with the screen not working.

On the subject of Glow plugs, it must be an emission thing, not a starting one. I had a Rover with the old L series engine and a Distributor Pump. These engines only had Glow plugs on 3 cylinders and they only came on when the temperature was well below 0. That car started no problem with no pre-heating right up to when I scrapped it at 17 years old and 280,000 miles on the clock. 

[troy45]

There’s quite a bit of information on the smart charging system if you’re able to access the ETIS info for the charging system. Think there are sites that cover it outside of Ford channels but I can’t find the link at the moment.

Things like the alternator charging being turned off during initial cranking and engine start-up to lower the load, then at times the AC being turned off if the system decides that’s needed.

I had to dig into all of this when I had charging issues early this year, turned out the factory remanufactured alternator I’d fitted and less than a month old had failed 🙁

[Tdci-Peter]

20 hours ago, Tizer said:

It's a pity FORScan does not allow you to monitor the current as well on that car, its a lot more useful than the voltage.

That is not entirely the fault of Forscan, it is the car! These older cars do not have the current monitoring device (battery Monitoring Sensor) fitted to the battery. I suspect the alternator itself can measure current, and the Alt-Mon signal from the alternator to the PCM may well be that current, but there are 2 problems there: Alt-Mon is displayed on Forscan in % (it is a simple PWM waveform), with no hard & fast way to decode it to Amps; Also the alternator current is not the battery current, you have to know all the load currents to work that one out. The software in the car faces the same problems, it has to estimate load currents, so after-market add-ons, mods and faulty parts will make those estimates incorrect. So this generation of smart charge was never going to be capable of the fine control of charging current that you get on the Mk3 and later Foci, and other contemporary Fords.

It is interesting to hear about how accurate charge current control can be with the BMS. Though there are still assumptions and problems, particularly relating to SoC (State of Charge). This is critically dependant on battery condition, and that is a variable that remains way beyond the capabilities of any sensors or software to make accurate estimation about. Hence the huge number of topics on problems with Stop-Start systems and the like, which tend to rely on these SoC estimates. Replacing useable batteries at 50% (or less) of their potential life is most certainly not a good approach, in my books anyway, to get some fancy software add-on to work!

20 hours ago, Tizer said:

On the subject of Glow plugs, it must be an emission thing, not a starting one.

I think that is partly right, but noise and driveability may also be improved by using the glowplugs after starting. My engine sounds like a bag of nails for the first minute or two after a start at about 5C or below. It is not that clapped out, since when I first start it after an oil change, with no oil in the filter, there is no real change of engine sound when the oil pressure LED goes out, which is something I often had on previous cars. The Common rail direct injection system relies on very fine oil droplets and tiny pilot injections to smooth out and speed up the ignition of the fuel, making the engine quieter. But the cold cylinders must result in delayed, and rather violent ignitions. The plugs may reduce this effect quite a lot.

When I first had this car, I discovered the glowplug fuse had blown, probably before I bought it. It was fine through Autumn without the plugs, it was only the first few sub-zero starts that alerted me to a potential problem, and found the fuse was open circuit. So it will, as you say, start without them down to quite low temperatures, but can be a bit rough.

 

[Tizer]

1 hour ago, Tdci-Peter said:

It is interesting to hear about how accurate charge current control can be with the BMS. Though there are still assumptions and problems, particularly relating to SoC (State of Charge).

According to the info I have for my car type the BMS is supposed to accurately set itself when the engine has been off for several hours with the parasitic drain is less than 100 mA. That is true to a certain extent, sometimes after a long run the S/S does not work, but it does the next morning. FORScan does show the SOC going up throughout a journey though. The BMS Sensor has been upgraded and the new one is being fitted under warranty I believe when people complain about their S/S.

On the subject of switching accessories on, I checked this morning by switching my heated window on at Idle and for a second the current and voltage dipped slightly before going back to where they were and staying there.

The only car that I have driven with an Ammeter on the dash was my fathers old Taxi. That was an indirect Diesel engine, so needed glow plugs and was before PCM's were used and the readings looked like what I see on FORScan.. They start very high before settling down to not many Amps, so the old Alternators must have been capable of doing their job albeit with a lot less power demands than modern cars.   

[Salas]

Hello sir, 

I had same problem and solve it. 

You have to connect RC to li to check the pcm är not the failure. 

After that you have to replace the harness to the charge regular connect.