Wagen

Smart for two ALTERNATOR START STOP MHD

21 posts in this topic

I have problem with alternator star stop. 

 

Remove alternator and put back, and now not work, nost start engine. 

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Did you disconnect your battery before doing this swap...???   IF not I bet you accidentally shorted the positive lead and fried it.  ooops....IF not then check all grounds near or associated with the starting system....maybe even check SAM module and ECU connections for corrosion.....again disconnect battery first and do not touch anything metal on pins or bend pins trying to clean corrosion off them, there are capacitors that will be charged up in your ECU that will discharge and cook the unit.....expensive mistake.....just saying.

 

Also welcome to the site, many helpful folks here who'll chime in soon I bet.....enjoy....

 

Edited by Willys

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1 hour ago, Wagen said:

Of course i am disconnect battery... Do you somebody know what i can do now? 

 

Some ideas? 

Hmmmm....?   Did you look at any of the things i suggested...?

 

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i have no experience with MHD system on smarts but maybe the starter wires got jostled and now there is a bad connection on starter?

 

am I right that you are saying it wont crank over at all now after changing the alternator?..

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Of course i am disconnect battery... Do you somebody know what i can do now? 

 

Some ideas? 

10 hours ago, Willys said:

Hmmmm....?   Did you look at any of the things i suggested...?

 

Yes, all grounds is ok... From ecu to alternator. Everybody told me is this alternator bad, and every smart have peoblem with this part. 

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That item itself isn't usually problematic, so "everybody" is wrong. Its actually fairly rare for that to fail. 

 

The usual problem is with the mounts, which are threaded into soft alloy.  The massive tension on the belt means that over time the mounting holes elongate and the whole things shifts so the belt no longer runs true, the belt shred itself, and the engine overheats and cooks itself causing terminal damage.  Smart have released no less than 6 "fixes" for this, including steel inserts that mount in place of the original mounting holes, but none of these fixes work reliably.

 

Has this unit been bench tested and is known to be good? Why was it removed in the first place?

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6 hours ago, Chopper said:

That item itself isn't usually problematic, so "everybody" is wrong. Its actually fairly rare for that to fail. 

 

The usual problem is with the mounts, which are threaded into soft alloy.  The massive tension on the belt means that over time the mounting holes elongate and the whole things shifts so the belt no longer runs true, the belt shred itself, and the engine overheats and cooks itself causing terminal damage.  Smart have released no less than 6 "fixes" for this, including steel inserts that mount in place of the original mounting holes, but none of these fixes work reliably.

 

Has this unit been bench tested and is known to be good? Why was it removed in the first place?

Hmmmm....?   Just wondering why is it the alt and not the starter that is the issue here?   Was the battery dead? IF so , then yes it 's the Alt. not charging the system enough to get starter to start....but if tested good then it has to be something else? Was the belts all on and in good condition? IF so then it's something else..?  Hmmm....why such massive tension on a charging belt? Why does it require any more tension than a normal engine...I do not know, just asking?  I dislike the whole idea of a vehicle stopping and then restarting just for the few seconds sitting at a traffic light.  Can this be tuned out of it? If so I'd be doing so..?  Just a bunch of stupid questions and suggestions from someone who hasn't experienced one of these cars yet....lol. 
We have major issues with the alt over here in salt land from corrosion build up and it seizing resulting in early death of said ALT. But we also have disgusting starters also for the same reasoning.  imho.   From what I hear very poor terminal connections which rot or corrode off resulting in new starters.   

 

So, does Serbia have the same salt issues as Canada or do they simply allow people to learn to drive in the snow and ice as we should and not destroy everyone's vehicles with bathing them in salt for 6 months of the year....lol.

 

Just a few questions is all....now back to the regularly scheduled programming......

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From what I read the alternator is the starter and that is why the belt needs to be so tight.

Edited by Nigel

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Absolutely idiotic system...IMHO.....did they leave the boss for the starter where it used to be? If so and workable I'd be figuring out how to retro fit a real starter or sell the damned car!  Sorry to say, it's just stupid they always keep making stuff so complicated that it does nothing more than create problems.  That's just my 2 cents worth and it's only worth 2 cents...lol

 

 

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It's not a bad idea per se, just dreadfully executed on the MHD.  You can't give them away over there, and dealers have been known to try and disguise that they are MHD's to get them to sell.  Earlier non MHD normally aspirated 451's are becoming quite sought after in clean condition as those in the know strive avoid the MHD and the 55 bhp diesel.

Edited by Chopper

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On ‎11‎/‎23‎/‎2019 at 4:25 PM, Willys said:

Absolutely idiotic system...IMHO

 

My Honda Goldwing has the same system.  It is 45 years old and there is 598,000 miles on it.  NO issues with the starter or charging system.  All original and untouched.

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Has anyone actually changed this piece of S ! to a Normal car, surely all it needs is an Alternator and a starter motor and some basic wiring , here in Darkest Spain a Smart is a Rare thing !

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On 11/23/2019 at 11:21 PM, Leadwing said:

 

My Honda Goldwing has the same system.  It is 44 years old and there is 598,000 miles on it.  NO issues with the starter or charging system.  All original and untouched.

 

because its a honda ..not a smart

 

honda tends to do things right the first time

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4 hours ago, cantabrian said:

Has anyone actually changed this piece of S ! to a Normal car, surely all it needs is an Alternator and a starter motor and some basic wiring , here in Darkest Spain a Smart is a Rare thing !

 

the MHD engine seems to have a ring gear...have you looked for a blockoff plate where a regular starter could be installed?

 

i dont think MHD was available in north america market so we dont know much about them

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5 hours ago, LooseLugNuts said:

 

because its a honda ..not a smart

 

honda tends to do things right the first time

 

Which is why my "big car" is a 32 year old Honda Civic and the Gold Wing Is still in my stable after 46 years of ownership.

 

 

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Thanks for the reply, sorry about such a long delay , still trying to find a blanking plate, would have thought that the engine would be the same across the range ?

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On 11/27/2020 at 11:50 PM, LooseLugNuts said:

 

the MHD engine seems to have a ring gear...have you looked for a blockoff plate where a regular starter could be installed?

 

i dont think MHD was available in north america market so we dont know much about them

]000494125970-5bda-4a9d-9.jpg

Yes The 451 MHD does have the starter ring gear. If you look underneath the engine at the back above the clutch actuator and to the left you will see a blanking plate held on with two bolts. This is where the standard smart starter motor is fitted. 

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Posted (edited) · Report post

The Smart fortwo MHD (mainly UK versions of the 451) starting system is unusual - it uses a system developed by Valeo called i-StARS but Smart call this system Micro Hybrid Drive where the engine can be stopped during certain vehicle conditions (to save fuel) and then instantly restarted to continue driving,  The Valeo i-StARS system combines the starting and the engine alternator functions into one unit.  This means that the starter is the alternator, the serpentine drive belt is made larger capacity than normal (to cope with starting the engine) and it is wider and has 6 grooves and the water pump pully has similar grooves.  For this reason, the MHD alternator serpentine belt is subject to very high stresses and failure rate is very high, usually with terminal engine overheat problems (water pump stops) as drivers carry on using the vehicle despite the alternator warning light being on.  Initial failure is indicated with frayed edges on the belt if you look carefully.

 

In essence, the MHD starting system needs 3 phase power to start the engine which is generated electronically by a small unit (called a StARS controller) mounted under the middle of the car near the petrol tank (looks like an oblong aluminium hedgehog), and connected to the alternator by a 3 phase special cable (which needs very good continuity less than 3.1milli Ohm per phase) other connections are also in place.  Starting the engine uses the StARS controller with its MOSFET transistors when the battery has enough power to supply (typically 120A or more) for starting electronically switching the 12V from the battery electronically.  The battery monitoring system has a important role and on MHD cars, the typically charge voltage is over 14V not 12V to cope with stop/start situations which is higher than normal cars.

 

In alternator mode, the controller collects current from the stator phases, and converts the alternate AC 14V signals with Metal Oxide Semiconductor Field Effect Transistors (MOSFET’s) via synchronous rectification.  The so called synchronous rectification also known as active rectification replaces the conventional power diode rectifier for a much higher efficiency.

 

The use of MOSFET’s to achieve the rectification function conventionally performed by diodes, improves efficiency, thermal performance, power density, and reliability.  Higher efficiencies can be achieved by synchronously switching the power transistors to emulate diodes,
taking advantage of the transistors’ low conduction losses.  Synchronous switching means getting a transistor to turn on and off according to the polarity of the AC waveform so it acts as a rectifier.  Choosing high performance MOSFET transistors reduces the forward voltage drop to a fraction of what any diode can achieve.  Hence, the synchronous rectifier will have a much lower loss than a diode, improving the alternator’s efficiency.  Synchronous rectification is one of the reasons for the outstanding 82% efficiency of the StARS starter alternator, which is a full 10% higher than the best conventional alternators on the market.

 

The same MOSFET bridge is used to control the machine in alternator and starter modes.  In alternator mode the transistor bridge receives
power from the stator phases, in starter mode it is the opposite situation.  In starter mode, the machine behaves as a three phase motor, it reacts to interactions between the stator and the rotor electromagnetic forces and rotates accordingly.

As in the alternator mode, in starter mode the alternator rotor coil is energized.  The power unit drives the stator phases according to a hall-effect magnetic position sensor that gives at any time the rotor relative position from the stator, knowing this relative position is crucial to the machine performance, notably for the torque output.  Stator and rotor electromagnetic forces interact creating a rotation.  The MOSFET bridges stimulate the stator phases generating a rotating field and thus torque to the rotor.  The rotor angular position and speed, as well
as the phase currents are monitored and processed to optimize the machine torque output.  Temperatures are monitored to take benefit from a maximum energy conversion.

 

The position sensor consists in three devices (H1, H2, H3), they are each 120° shifted and require a high positioning accuracy for the machine to deliver the appropriate torque output with minimized ripple.  The MOSFET half bridges are activated in multiple commutation sequences to create a 360° rotation.

 

●● Stator phases are excited two by two in a 360° sequence, triggering a rotating field
●● The rotor aligns to the stator magnetic field for each new sequence generating torque

●● The torque amplitude varies according to the position of the rotor, it is higher at each half bridges commutation and stator/rotor alignment
●● The machine output torque is maximized thanks to advanced control timings and communications overlapping on the MOSFET half bridges.


In StARS, the MOSFET bridge is capable of delivering a 600A starting current, generating enough torque to drive the engine immediately and at higher revs than a conventional starter.  The battery needs to be the special AGM type or similar.

 

Serpentine belt tension is also very important in MHD cars.  It is much higher than a standard car and adds additional loads to the alternator mounting points (which leads to premature failures or looseness) so needs careful adjustment and special tension pulley to control load on, load off (starting/generating).

 

Starter cranking power achieved using this i-StARS system in the MHD is1.2kW which is better than the 700A or more required by the traditional starter.

 

For many reasons, many UK version Smart fortwo MHD cars have had problems with the starting system, mainly associated with poor alternator mounting hardware (fix is available on eBay to increase mounting bolt sizes).  A simple system fix is to revert to using and adding a standard 12V starter from a CDI car (the 12V starter enable output is still available from the SAM panel on connector N11-6 pin 1).  I have done this myself (and fitted a starter to the aux plate above the clutch actuator but the result is that you need very a high capacity battery to deliver the 700A needed and you still need the i-StARS controller to provide battery charge voltage from the alternator during engine running.  The red 'battery not charging' indicator is provided by the engine management computer as well to the instrument cluster, so adding a standard alternator will not be useful.  Smart fortwo standard 12V starters have a few different versions, so some are clockwise and others anticlockwise so choose carefully.

 

The  i-StARS on the MHD controller can be interrogated by an OBD 2 diagnostic system like Launch, and certain faults are not obvious from the codes read.  When the system reports the the 3-phase line of the RSG is faulty, the code 100D is more associated with poor main battery performance.  Probably that the current is not able to supply to the alternator for starting, although the resistance figures are very low for the cable, so measuring this ohmic value accurately is tricky.

 

The end result is that advice is to not buy an MHD Smart fortwo as they are not reliable.  Stick with the standard cars!  In the UK, many dealers run a mile when you ask them about starting problems on the MHD, you have been warned, and for those who want to convert their cars to MHD - dream on!!!

 

One thing I forgot, laser alignment is best checked for the serpentine belt on the MHD Smarts, this is crucial for reliability of the system.  I use home-made laser tools for this for the crank, alternator and water pump.

 

 

 

 

 

 

 

 

Edited by pr3759
alignment
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On 23/11/2019 at 9:25 PM, Willys said:

Absolutely idiotic system...IMHO.....did they leave the boss for the starter where it used to be? If so and workable I'd be figuring out how to retro fit a real starter or sell the damned car!  Sorry to say, it's just stupid they always keep making stuff so complicated that it does nothing more than create problems.  That's just my 2 cents worth and it's only worth 2 cents...lol

 

 

Too right. If it's not broke, don't fix it. I'm a new owner and discovered the hard way about 'stop start' and Eco mode. The traffic in London UK is constant stop/start, tedious hearing the engine constantly restarting, never mind belt wear. So I just switch Eco off as part of initial startup. I can afford the miniscule amount of fuel it saves.

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