Abandon Starter Relay! (?)

[Laitch]

That spec sheet clipping you posted looks to me to be part number variants, depending on whether you want a relay spec'ed for intermittent use (4.8W) or continuous use (2.4W).  Those values get tacked onto the manufacturer's part number.  I don't think they represent power figures.

That clipping was part of the data sheet supplied via your link to the page for ordering the part, Robert. There doesn't seem to be any part offered other than that $12.34 part; those specs were published with it. Among the "dash numbers" there is one 12V for continuous and one 12V for intermittent but the only qualifier in the text is that if a 24V application is wanted, it should be specified when ordering. Is this part rated for both continuous and intermittent use?

To summarize my understanding and rephrase your previous observation: Is it fair to say that the advantage of this part is that if it gets only 10V instead of 12V it's probably not going to operate at all or if it does, it's not going to supply enough current to weld the contacts because the current is crossing four points rather than two. What is the outcome if it can't bridge the gap at all? Just search only for a charged battery instead for a charged battery and a new relay?

[bocutter Ed]

... the espresso maker

I switch to Turkish coffee on the road. No machine and uses less water. Oh, and very fast to brew.

[TrueAce]

Here is the old type starter relay along side the newer version, rated the same, but manufactured under license from Bosch. Note the dual contacts and heavy braided copper connecting wires.......bet this won't burn out or weld. Got it from Euromotoelectrics in Denver.

[arnonymous]

I was researching relays for a friend around another subject and came upon an interesting unit that could be used to replace the generally expensive and unreliable OEM starter relay.

Problem: When the battery has a low charge, attempting to start the bike could result in a damaged starter relay, with the consequence that the engine will continue to turn over until the battery is drained or it overheats and gets damaged.  The reason is because the low battery voltage combined with the high cranking current causes the relay’s contacts to weld together.

Solution:  I found a high current (120A/12V) contactor on Aliexpress that appears very promising as a replacement for the OEM starter relay.  What is the difference between a contactor and a relay?  The starter relay in the K-bike has a single pair of contacts through which all current flows when cranking the engine. 
...
My friend will be ordering some so if he can spare one, I’ll try it out in my K75 to see how it works.

Any news on this? Im looking forward to your results.
3rd time in a short period that i had a stuck relay, and im not gonna pay for a new crappy one.
What will you do with the 2 bits of electronics that are in the relay, i believe a resistor and cap, to prevent spikes on the ECU.


Last weekend i tried to replace the solenoid with a chinese 100Amp DC solid state relay i had. But i couldn't get it to run for some reason.
Actually i couldnt even detect a voltage on the ignition "activation wires" when i pressed the ignition, any ideas?

[rbm]

Any news on this? Im looking forward to your results. ...  What will you do with the 2 bits of electronics that are in the relay, i believe a resistor and cap, to prevent spikes on the ECU.

No news yet as I haven't talked to him in a while.  As for the resistor/cap, I'll not be substituting for them if the contactor doesn't have similar; just see how it goes.

Last weekend i tried to replace the solenoid with a chinese 100Amp DC solid state relay i had. But i couldn't get it to run for some reason.
Actually i couldnt even detect a voltage on the ignition "activation wires" when i pressed the ignition, any ideas?

Did you source a SSR designed for DC loads?  If you did manage to get it to work, it probably would have quickly self-destructed with the continuous pounding it receives from the inductive load of the starter motor.  SSRs don't handle large back-EMF well.  In this application, a mechanical relay beats a SSR.

BTW, did you connect the polarity of the input correctly.  SSRs use a LED in the control circuit and you need to observe and respect the polarity.

[Bill]

Solid state relays can be of 2 varieties ..... a power mosfet or triac.  A link or part number would help us figure out what the problem is   :dunno2:

[Martin]

Arnnonymous  fit a isolator switch in the earth lead, I have posted pictures and installation instructions in the Workshop under Re: Starter relay stuck November 22nd. It doesn't cure the relay problem, but it makes for a quick disconnect. it has other advantages as well, read the post.
Regards Martin.

[arnonymous]

Did you source a SSR designed for DC loads?  If you did manage to get it to work, it probably would have quickly self-destructed with the continuous pounding it receives from the inductive load of the starter motor.  SSRs don't handle large back-EMF well.  In this application, a mechanical relay beats a SSR.

BTW, did you connect the polarity of the input correctly.  SSRs use a LED in the control circuit and you need to observe and respect the polarity.

Yes i watched the polarities, but had to guess on the "switching" side. Well reading up more it seems like 100amps is not enough anyway. So iguess it died.

I will fit a quick kill switch but would like a good relay. And was hoping a ssr would work

[TimTyler]

My starter relay stuck again yesterday.

Today I installed the Cole Hersee solenoid that I bought earlier in this thread. It works!

Of course, the old starter relay is still in the chain but it's using a lot less voltage so hopefully it won't lock-up anymore. I was just thinking that I should install an on/off switch between the Bosch and Cole Hersee in case the Bosch sticks which might damage the solenoid. I wonder how much voltage the solenoid draws?

The large terminals on the Cole Hersee solenoid are wired directly to the battery and starter motor as expected. One of the small solenoid terminals is wired to GROUND (14 AWG) and the other to the Bosch relay terminal 87.

The large Bosch relay terminal 30 is wired (14 AWG) directly to the battery. I was wondering if I should add a fuse here?

The other large Bosch terminal 87 is wired to one of the Cole Hersee solenoid small terminals (as mentioned above).

[TrueAce]

Congratulations, Tim, that set-up should work for sure. Not sure why a fuse in the link to Bosch terminal 30 would be advantageous, seems that creates a weak link for blown fuses. The Bosch should handle the 12v input fine, its 75a rated. But I may be missing something......if a solenoid handles the starter load, why does the Bosch relay still need to be in the system? Why can't starter activation go directly to the solenoid?

[TimTyler]

Why can't starter activation go directly to the solenoid?

The Bosch has a diode that protects the ECU from voltage spikes, I think. (Discussed earlier in this thread)

I don't know enough about diodes to replicate that functionality without the Bosch.

Sure would be nice to get rid of the Bosch all together though. Space is tight in that relay box!

[TrueAce]

Nor do I know about said diodes & voltage spikes........I wonder how the generation of voltage spikes occurs, the magnitude, and whether the system is so sensitive as to loose starter relay/solenoid function. Sounds like its time for a tutorial by Brother RBM.

[TimTyler]

I remember... There was some question as to whether or not the voltage necessary to switch the Bosch would be enough to switch the larger solenoid.  The Bosch apparently only requires a little juice to do its job.

[TrueAce]

Now that makes sense............the low feed to activate the Bosch relay.......little in, large out.........might well be insufficient to activate the solenoid, hence a "step" relay. Would be interesting to look at actual values, cause theoretically, a relay should not be nesessary to activate a solenoid. Get RBM on the numbers!

[Bill]

Nor do I know about said diodes & voltage spikes........I wonder how the generation of voltage spikes occurs, the magnitude, and whether the system is so sensitive as to loose starter relay/solenoid function. Sounds like its time for a tutorial by Brother RBM.

The voltage spikes occur in the reverse polarity of the applied coil voltage. 

• 12 volts applied to the coil causing a magnetic field.
• Armature moves making the contact closure between 30 and 87
• Remove coil voltage, the magnetic field collapses, and induces a voltage in the coil
• Because the magnetic field is now moving in the opposite direction, the voltage polarity is reversed

[ii]The diode in parallel with the coil is oriented to conduct with the reversed polarity effectively shorting the induced voltage to ground[/li]
[/list]

As i have yet to venture hands on into the circuit rbm will have the best applied knowledge.

[rbm]

Nor do I know about said diodes & voltage spikes........I wonder how the generation of voltage spikes occurs, the magnitude, and whether the system is so sensitive as to loose starter relay/solenoid function. Sounds like its time for a tutorial by Brother RBM.

Bill is correct.  When a relay coil is de-energized, the sudden collapse of the magnetic field will induce a reverse potential (i.e. opposite polarity) voltage spike in the circuit proportional to the rate of collapse.  There is a lot of energy in this high voltage spike which must be dissipated.  The energy wants to dissipate across the transistor in the ECU that shut off the current to the relay (think of arcing that occurs in the switch when you shut off a light), thus destroying the transistor.  If a high speed diode is placed across the coil, when the voltage spike occurs the diode causes a short circuit across the relay coil.  The energy is captured inside the relay coils where it dissipates it as heat, thus protecting the transistor in the ECU.  This is called a snubber circuit.

Selecting the diode is straightforward.  Use a switching diode with about 400V - 600V reverse voltage and 1 Amp, like a common 1N4007.

[TrueAce]

Excellent explanation...........I knew you could take us to school. But how could the solenoid be employed without relying on the starter relay in the circuit?

[rbm]

The solenoid could work alone if the characteristics of the device doesn't exceed the capabilities of the ECU to drive it.  Afterall, a solenoid is just a large capacity relay in a different form-factor.  I'm talking about the operating voltage and current of the solenoid's coil.  The current draw of the solenoid shouldn't exceed 550mA and the pull-in voltage should be minimum 8V-9V.

[TimTyler]

Thanks, guys. I've put a call into Cole Hersee to get some specs.

So just one these diodes then?

[TrueAce]

Now, Tim.......just wire the solenoid direct and see if it blows the ECU, then we'll know. Where is your sense of adventure?

[Laitch]

Thanks, guys. I've put a call into Cole Hersee to get some specs.

Doesn't it seem that your intermittent duty solenoid may be drawing current in excess of Robert's observations according to one of the FAQs here, Tim?

[rbm]

Thanks, guys. I've put a call into Cole Hersee to get some specs.

So just one these diodes then?

Yes, Tim.  But that's exorbitantly expensive.  That should be the price of 25 of these diodes.  These are commonly available at any local electronics supply or online at Digikey or Mouser.

[TimTyler]

Doesn't it seem that your intermittent duty solenoid may be drawing current in excess of Robert's observations according to one of the FAQs here, Tim?

Sadly, it does :(

How much current does the control circuit in a solenoid draw?
Generally, the control circuit for a continuous duty solenoid rated at 12V DC draws about 0.70 of an ampere.
The control circuit for a 24V DC continuous duty solenoid draws about 0.34A.
An intermittent duty 12V DC solenoid draws about 2.73A, and the 24V DC about 0.83A.

I suppose I could replace the Bosch with a much more compact, lower amperage relay.

[TimTyler]

These are commonly available at any local electronics supply or online at Digikey or Mouser.

The last local electronic supply store within 40 miles of 98501 went out of business a few months ago!

[TimTyler]

Selecting the diode is straightforward.  Use a switching diode with about 400V - 600V reverse voltage and 1 Amp, like a common 1N4007.

Assuming I switch out the Bosch for a smaller, possibly more reliable relay, and knowing that the solenoid draws up to 3 amp, I assume the 1-amp 1N4007 will be under-rated?

Would I need a switching diode rated for 3 or more amps?