Abandon Starter Relay! (?)

[rbm]

That's a K1100 / Motronic thing.  It's not present on classic K's with Jetronic.

[TimTyler]

Installed the Starter Overhaul Kit from EuroMotoElectrics today. Found that my brushes were a little short and the armature contacts were very dirty. Cleaned the commutator contact area up with brake cleaner using a toothbrush & rag.

The brushes on the EuroMoto kit are configured differently than the OEM brushes in a way that makes them harder to install. Basically, they must be held in place when reassembling the starter. Took me forever. Would have been easier if I had three hands.

The terminal screw on the Denso brush set is also a little shorter than OEM. I chose to use my existing insulating plastic brush set pieces, so there's barely enough threads for the terminal tightening nut to hold the cable from the relay on.

When I was removing the old ball bearing assembly I chipped off a tiny piece of that ultra-hard plastic coating covering the armature wire wrap. Not sure what the plastic coating is for, but I assumed it's insulation. Filled the gap in with a glue gun, hoping  :dunno

Once reinstalled the starter get's the motor running quickly.

[TrueAce]

That is a lot of technical hassles for a remove & replace component, apparently related to a minor discrepancy in specs. Lesser folks would not have resolved as you did. I shudder to think about it..... Do our friends at EUro get feedback on this? They have been a good source to me, but I don't know if I would have figured out a problems like this. Good work Tim! No wonder you aren't fazed by starter relays like the rest of us!

[escodsm]

But my K100 project is a non-stock project that I am going to apply my Dale Earnhardt starter switch concept to next!

Excuse my ignorance, but what is a Dale Earnhardt (RIP) starter switch?

[TrueAce]

That refers to the starter button Dale Earnhardt Jr. Uses on his race car. I got frustrated with multiple burnt starter relays and figured out just running the starter with a race car starter button. It's the gold thingy in the picture.. no key no relay.

[escodsm]

I love that! What do you do for security...a U-Lock for the wheels?  This seems like a cool idea honestly.

[TrueAce]

Security?       line of sight plus Glock .40 cal

[Laitch]

 :clap:

[escodsm]

 :2thumbup:

[rbm]

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. 


As shown in the image above, a contactor has two pairs of contacts through which current flows, spreading the load across four contact pads, and being less likely to heat up and weld together.  Furthermore, the actuator arm consists of a bar with the contacts at both ends.  When the contactor is turned off, both contacts break, with a more positive cut in current flow.  Contactors are commonly used in high power switching applications.

The contactor I found has a very small package – just 42mm X 42mm X 42mm in size.  There are two ¼” spade terminals for connecting the coil leads and two M6 studs for connecting the starter battery and motor leads.  The pickup voltage is 7.8V and release voltage is 1.2V.  This low pickup voltage and broad hysteresis (difference between the voltages) means the contactor is not as susceptible to oscillation as is the OEM starter relay.  The main contacts are rated at 120A and the maximum power handling capacity is 1680 W (about 2.2 HP), more than enough to handle the current drawn which cranking the engine.  The price is also very attractive at around US$12 each; cheaper in larger quantities. 

http://www.aliexpress.com/store/product/200a-starter-relay-automotive-relay-contactor-relay-12v-24v/346626_1649592976.html?spm=2114.12010108.0.78.eRhDCI



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.

[TimTyler]

Interesting.

I wonder if that's the same as this or this or this on Amazon?

[rbm]

It might very well be the same, Tim.  I'm sceptical at the moment though.  The advertizing copy states that it is a contactor, however without having pictures of the components inside of the package and being from China, this is only marketing hype for the moment. And what about electrical ratings; are these peak values or continuous values?   I'd love to get my hands on one of these bad boys and dissect it.

[TimTyler]

If these alternative relay or solenoid options require more current from the ECU to connect the battery to the starter than the Bosch relay, will the ECU be damaged or will the relay/solenoid simply fail to connect the starter?

The Bosch/Tyco relay on EME's site is listed as " ...with resistor / diode to prevent voltage spikes potentially damaging the Engine Management System Control Unit (ECU)". Is that a real concern?

Like.... how dangerous is it to experiment?  :dunno  Inge?

[Laitch]

The pickup voltage is 7.8V and release voltage is 1.2V.  This low pickup voltage and broad hysteresis (difference between the voltages) means the contactor is not as susceptible to oscillation as is the OEM starter relay.

What's the relationship of the low pickup voltage of 7.8V to the intermittent work value on the spec sheet of the aliexpress item?

[Bill]

You can replicate the flyback diode or 'snubber' to another relay if not present. However it is critical to prevent ECU damage. 

[Bill]

You can replicate the flyback diode or 'snubber' to another relay if not present. However it is critical to prevent ECU damage.  Another concern would be how much current the ECU can source to the relay coil.

[Bill]

The pickup voltage is 7.8V and release voltage is 1.2V.  This low pickup voltage and broad hysteresis (difference between the voltages) means the contactor is not as susceptible to oscillation as is the OEM starter relay.

What's the relationship of the low pickup voltage of 7.8V to the intermittent work value on the spec sheet of the aliexpress item?

Initial current to pull in the contactor is the intermittent rating,  To maintain the contactor is the continous rating.   

[Laitch]

Initial current to pull in the contactor is the intermittent rating,  To maintain the contactor is the continous rating.   

How does the 7.8V fit in the equation, Bill?

[Bill]

They relay or contactor will 'pull in' or engage at 7.8 Volts.  Useful if the terminal voltage while cranking drops.... depending on the starter load some vehicles will drop to 9 volts when the starter engages, hence ECUs typically can work at 7 Volts.  Caterpillar for instance specs their ECU at 6.5 when starting a big diesel.  No point in cranking if the ECU and injectors are dead due to low voltage.  Remember that a DC Brushed motor at start is much like a short circuit.

[Laitch]

Thanks for the explanation, Bill.

[Bill]

Hope it helps .....  The original circuit has a reasonable tolerance for age and wear.  Redesigning it to make up for other components past their due date,  ie a tired battery or a fuel/ignition system that won't fire up readily.  The uncontrollable part is the operator that holds the starter engaged for a long time.  The starter motor is not designed for continuous duty.

[Bill]

I've only ridden mine 1/4 mile [bought it New Years Eve in Ontario].  A spare relay does seem like a good idea though ..... 

[Laitch]

It was a great quarter-mile though, wasn't it? :clap:

[Bill]

Had not swung a leg over in 25 years  but I was hooked all over again !

[rbm]

If these alternative relay or solenoid options require more current from the ECU to connect the battery to the starter than the Bosch relay, will the ECU be damaged or will the relay/solenoid simply fail to connect the starter?

The OEM starter relay sinks 546 mA into the ECU when operating and measures 19.1 Ohms across the coil.  The contactor I mentioned measures between 30 Ohms to 60 Ohms across the coil.  That's means this contactor will demand almost 1/3 less current compared to the OEM relay.  This contactor puts less load on the ECU drivers.

The Bosch/Tyco relay on EME's site is listed as " ...with resistor / diode to prevent voltage spikes potentially damaging the Engine Management System Control Unit (ECU)". Is that a real concern?

Like.... how dangerous is it to experiment?  :dunno  Inge?

As Bill mentioned, it's probably not a bad idea to put a snubber circuit across the relay coil to reduce EMF spikes that could take out the ECU.  Those spikes are not necessarily generated by the relay itself.  They might come about through the clutch switch.

What's the relationship of the low pickup voltage of 7.8V to the intermittent work value on the spec sheet of the aliexpress item?

As Bill also mentioned, it is the voltage at and above where the armature remains engaged. Tim linked earlier to a good document that describes Honda relays.  The following is taken from that document:
Operate (pickup) voltage is the voltage which closes the NO contacts when the relay is in the releasing state and coil voltage
is gradually increased.
Release (Dropout) voltage is the voltage which closes the NC contacts when the relay is in the operation state and the coil voltage is gradually reduced.

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.