trenace
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posted August 22, 2005 01:17 AM
 Edited By: trenace on 22 Aug 2005 02:35
Is 16.9 volts (temporarily) risky to ECU?
Those quite familiar with this sort of electronics problem: would a voltage of 16.8 volts, when the manual-specified normal range for the ZX-12R is 14.2 to 15.2 volts, plausibly risk damaging the ECU and/or a Power Commander?
It would be convenient if I could apply what could be up to 16.9 volts to the wiring harness when starting the bike, and thereafter allow voltage to be according to what the stator and voltage regulator provide.
Thanks!
  
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eastbaydave
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posted August 22, 2005 05:46 AM
First realize all digital devices run on 5V. The voltage is stepped down somewhere; probably at the regulator/rectifier (guess.) There would surely be a V-drop during the "load" of starting the bike; & it's within 1.8V of stock....you'd think the regulator would hold voltage down IF you go thru it? However that would be defeating the purpose of getting extra juice to the starter. Perhaps if you ran that higher output battery directly to the starter? (in parallel=dual leads to starter & harness.)
My "guess" is you' d be ok momentarily; but I'd be very hesitant if it were my bike (risking the ECU.) The PC? Well we all know how tempermental those things are....I'd worry about it too; but you'd think the manufacturer would allow a couple volts leeway? I'm just guessing so this is just that...
FWIW, IMHO
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Enjoy the ride!
02' ZRX1200
00' ZX12R sold
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trenace
Needs a job
Posts: 3056
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posted August 22, 2005 08:28 AM
Edited By: trenace on 22 Aug 2005 09:47
The bike's voltage regulator (the one in the tail) regulates to 14.2 - 15.2 volts, but now that you mention it, stupid of me to not be thinking that through but my excuse will be it was late at night  certainly internally the computer is not running that.
I don't know whether the voltage regulator in the tail puts any of the lines to 5 volts, or whether this is done internally in the ECU and Power Commander but you must be right, something is reducing and regulating the voltage for these devices well below the "mains" voltage.
That seems to make me more comfortable with the slight overvoltage, as internally to these devices there should most likely then be no overvoltage at all, just "harder work" for their voltage regulation and only for a few seconds.
What the situation is, is that my original plan was having a rather powerful but very light battery (a high amperage LiPoly pack) for the starter, and it's working fine. It's at 16.8 or 16.9 volts when at full charge.
I was going to rely on the bike's charging system for electrical power when the engine is running, with only the most minimal little battery to "kick things off" (e.g. enable the starter relay, power the ECU and fuel injection, etc) while the motor cranks.
I figured the NiCd I chose would do fine. (The reason for NiCd instead of LiPoly is that NiCd can more safely be recharged by something like a vehicle's charging system.)
Problem is, apparently at idle the headlights run off the NiCd not off the stator, and that kills the NiCd. Just doesn't work. If I can run with no battery at all connected while the motor is running, only switched in manually for starting, that would be ideal. I would rather use the one battery required for the starter anyway than having a second battery, if having to use this switching system anyway.
The only advantage of instead using the NiCd in the switching scenario would be that it's one volt lower -- the disadvantages are far less capacity, an added failure mode, and extra weight. So if that being just under 16 volts instead of just under 17 isn't important anyway, then it seems I should not do it.
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