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Hello.
I needed to replace my battery in my 2002 k1200LT. I put the positive or hot leads on first When I go to connect the negative leads on the new battery, the motor turns over without the key in the bike. It is almost like I am trying to "hotwire" the bike. The hold down bolt wanted to "weld" to the negative terminal. Any thoughts
 

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The starter relay has welded it's contacts together. I've read it is caused when you try to start the bike with a low battery. At some point BMW made an update kit to stop this from happening.

BMW sells what they call a "Retrofit kit, starter module", part #61357663945, which sells for $222.36, ouch! At some point BMW included the update on new bikes, but I don't remember what year this was done.
 
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azccj is correct. The kit includes a small wiring harness and a new type relay with embedded circuitry to prevent the starter from engaging below 11 volts and welding the relay contacts from high current draw. The relay is located in the electrics box under the tank. Two things to check. I thought 2002 was when they installed this at the factory but I may be wrong.

1. look at the diagnostic plug for the label in the picture indicating the new style relay is installed. If it was done already which seems unlikely with yours being welded, one of the steps is to place that label on the diagnostic plug to indicate the retrofit.

2. If no label, verify what type of relay you have before ordering one as a replacement. Once you get the tank off and the cover off the electrics box, look to see if it is a black starter relay ( expected) or the new blue one. You can see my blue one in the attached picture. the black one would be in the same location.

If it is black, you can order a replacement from beamer boneyard for less but I would recommend the upgrade to protect from this happening again if the battery should become low and you attempt to crank it like that. Yes it is more expensive but do you want to go through this again?

One thing you can try is to turn the key on and tap on the starter button while it is cranking and see if that will free up the relay temporarily. It still should be replaced once it has fused as it can do it again.
 

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Others have installed a Ford starter relay in place of the expensive BMW version with good results. There are a number of threads, I believe on this subject which have been posted over the years. The Ford relay is the one that I used on my old '66 Mustang. :bmw:
 

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With you needing to replace your battery, I suspect that the welded starter relay occurred at the final start attempt of your old battery. Speaks to the need of keeping in touch with your battery status and stop any attempts to start a bike with a low state of charge battery. Sorry for your hassles. This post is really for the next guy who reads this thread.
 

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I am not clear on this reasoning. Starter motor has a fixed resistance. KW of starter motor is based on Volts x Amps. Since the resistance does not change for normal starting, add a low voltage on battery and you should have a lower amp draw and lower KW reading on the motor . What am I missing ?
 

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Watts. To get the same power out of the starter (watts) say one HP, (745 watts) there is a formula "watts= amps x volts". If the volts go down you need the amps to go up. This is what causes the problem with low battery voltage.
 
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Watts. To get the same power out of the starter (watts) say one HP, (745 watts) there is a formula "watts= amps x volts". If the volts go down you need the amps to go up. This is what causes the problem with low battery voltage.
I agree with "get the same power out of the starter " but if the EMF is not present to push the Amps your out put on the motor will go down. Maybe the lower voltage causes a stall rotor current increase.
 

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I am not clear on this reasoning. Starter motor has a fixed resistance. KW of starter motor is based on Volts x Amps. Since the resistance does not change for normal starting, add a low voltage on battery and you should have a lower amp draw and lower KW reading on the motor . What am I missing ?
The resistance is virtually constant, but a motor is an inductive device and thus has a reactive component in addition to resistive. Look up power factor for a description of this. When the motor is stalled, there is no back EMF to limit the current and thus the motor current will be at its highest. Motors are designed for their normal operating current and will quickly overheat at the higher stalled (or even low rpm) current levels.

A low voltage won't provide enough current to spin up the starter motor to its normal full load rpm. Even with the slightly lower source voltage, the much lower effective motor resistance will allow much higher then normal current to flow which will overheat and destroy the starter motor or, in the case of the LT, the relay.
 

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Watts. To get the same power out of the starter (watts) say one HP, (745 watts) there is a formula "watts= amps x volts". If the volts go down you need the amps to go up. This is what causes the problem with low battery voltage.
Not exactly. Reactive devices like motors complicate this as their "effective" resistance is not constant. The absence of back emf at zero or low rpm is a dramatically larger effect than is dropping battery voltage from 12.6 to 11 volts.

Given the ridiculous location of the LT starter, I suspect BMW used the relay as the system fuse in order to protect the starter. Those who use the Ford relay make the starter the fuse. Prolonged starting with a weak battery will dramatically reduce the life of the starter as the brushes will be carrying much higher currents and the windings will run hotter shortening the life of the thin insulating coating.

I would spend the money for the BMW protective relay. The Ford relay could prove much more costly in the long run. The old penny wise and pound foolish scenario.
 

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Not exactly. Reactive devices like motors complicate this as their "effective" resistance is not constant. The absence of back emf at zero or low rpm is a dramatically larger effect than is dropping battery voltage from 12.6 to 11 volts.

Given the ridiculous location of the LT starter, I suspect BMW used the relay as the system fuse in order to protect the starter. Those who use the Ford relay make the starter the fuse. Prolonged starting with a weak battery will dramatically reduce the life of the starter as the brushes will be carrying much higher currents and the windings will run hotter shortening the life of the thin insulating coating.

I would spend the money for the BMW protective relay. The Ford relay could prove much more costly in the long run. The old penny wise and pound foolish scenario.
I bought the Ford relay and was intending to preemptively install it in place of the black relay but I had a space issue from other wiring installed around the battery box so I decided to just go ahead and get the retrofit kit and install it in the same space as the old one in the electrics box.
 

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The resistance is virtually constant, but a motor is an inductive device and thus has a reactive component in addition to resistive. Look up power factor for a description of this. When the motor is stalled, there is no back EMF to limit the current and thus the motor current will be at its highest. Motors are designed for their normal operating current and will quickly overheat at the higher stalled (or even low rpm) current levels.

What affect does Power Factor have on a DC circuit. None that I recall. Power Factor in a DC motor is always 0 . Is this not correct?
 

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The resistance is virtually constant, but a motor is an inductive device and thus has a reactive component in addition to resistive. Look up power factor for a description of this. When the motor is stalled, there is no back EMF to limit the current and thus the motor current will be at its highest. Motors are designed for their normal operating current and will quickly overheat at the higher stalled (or even low rpm) current levels.

What affect does Power Factor have on a DC circuit. None that I recall. Power Factor in a DC motor is always 0 . Is this not correct?
Yes and no. Power factor is primarily an AC concept, but the underlying issue is reactance, inductive primarily in the case of a motor. Most explanations of power factor explain this well, typically better than most motor explanations so I referenced that. DC motors create complex waveforms both inside the motor as commutation occurs as well as impressed on the power supply leads. Yes, you feed DC current nominally to the motor, but the motor draws current in a rapidly varying fashion so the waveform of the supply circuit is anything, but steady DC.

The net result is that you simply can't apply the DC version of Ohm's law to a "DC" motor. There are many time varying issues at play given that a motor is a field based device.

DC Motors -- motor (mis)behavior
 

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I put in a WPS lithium battery 490-2520 model. So far so good but only had it in for a week. Seems to start it effortlessly. My buddy put one of them tiny red lithium batteries (sorry forget brand) in his 2009 F650gs (800cc parallel twin) and it was pretty much DOA when we got it, bike wouldn't run with it even jump started, returned to motorcycle dealer got refund.

The WPS brand are all over ebay, I think I paid $185 but that was over a year ago (bike sat on trickle).
 

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Starter relay contacts are welded. Early models you can substitute a Ford relay. Look to the halls of wisdom for more info.
 
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