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Originally Posted by HRCNICK11
As long as the car is not started you will not hurt the bike. Period. For the record I got a 4.0 from NIT for electronics. If the car is not started it will not hurt the bike.
The only reason the running car will hurt the bike is the cars charging system does not hold a constant voltage and that voltage can be too high. The amperage has nothing to do with anything. Just like in a house if you plug a lamp into a 15 amp circuit it lights the same as a 20 amp circuit.
Best way I can explain it is the voltage is like the pressure in a water hose and the amps are the amount of water in the system before you run out. The pressure can cause problems having a larger volume at the supply with hurt nothing.
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You might have a 4.0 from NIT, But I have almost 35 years experience in the electronics industry, including 3 yr's doing IC failure analysis, a couple yr of Worse-case analysis of Military microwave circuits, 14 years as an application engineer for electronic design tools, as well as designing a Gate Array for NASA.
And while 12v's is 12v's, a 600-700 CCA auto battery connected to a dead (2-4v) MC battery that has an internal impedance of less than 0.05 ohm can cause huge current spikes. Currents this large can cause voltage spikes.
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12VDC IS 12VDC, but not all 12VDC systems are created or operate equally...
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Agreed
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The anecdotal stories / experiences about frying bike electrics I would guess come from the nature of the output of car/truck alternators. They're much higher amp output, and they also have a slightly sloppier tolerance for charging voltage. When the sense lead from the car/truck senses the voltage drop due to the now connected dead motorcycle battery, it goes into high output (voltage) charge mode. If you then 'rev' the car/truck, you should get a nice big 60-140A 'push' from the alternator at whatever the maximum output of the alternator.
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IMO I'm not so worried about the alternator output as being the cause, unless it's a bad alternator.
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And how many of these "it blew up my bike" stories left out the detail that they probably connected the negative terminals first (i.e. "drain"?) then connected the positive terminals (i.e. "supply"?)? I was taught that the order for jumper cable attachment is always:
1) Positive terminal of discharged battery
2) Positive terminal of the charged battery
3) Chassis Ground of the discharged battery
4) Negative terminal of the charged battery
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IMO this could be the source of most of the problem.
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How would jumping a bike from a car battery be any different to the electronics than jumping a car from another car/truck? The electronics inside the ECM/PCM are the same in either, are they not? I mean, a circuit is a circuit, a capacitor is a capacitor, a microprocessor is a microprocessor and so on. How would either of the two be any more fragile than the other?
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I vaguely remember issues with jumping cars when they first went to electronic controls, it's possible that since MC's are rarely jumped the various protection circuits were not added to to their electronic.
There are specific circuit features in IC's that for instance reduce the chances of a latch-up, each pin is unique, as are different microprocessors.