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Topic: Post Battery Change Engine Operation (Read 3 times) previous topic - next topic
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Re: Post Battery Change Engine Operation- Risky!
Reply #25 –
Yahoo Message Number: 88384
If one was to jumper the isolator it would be much better to jumper with a rather high value resistor. Say 120 ohms. I suspect the computer would still run fine because of it relatively low current draw but if one shorted something out there would be a current limiter in the circuit.
With a 120 ohm resistor used as the jumper the current would be limited by a short to something like 100 mA unless I misplaced a decimal point..
 Actually a 12 volt bulb with pigtails would make probably make the ideal jumper...

Garry

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Andy,
 A rubber glove would do, but it would probably be better to *wrap* the bare connector with it, rather than just putting the glove over it. The risk would still be there with thin rubber as used in many disposable gloves. The metal connector, even though insulated, bonking anything else of metal and grounded, could easily penetrate the rubber and cause violent arcing.
 There is another caution when doing this too. Normally one would remove the negative/ground wire from the battery first. This is done as it eliminates the risk of turning a wrench on the positive terminal first, and having that wrench also touch grounded metal!
 So, if jumpering the chassis batter at the isolator, one must be *very* cautious not to touch ground with any metal tool when removing the positive terminal - - even if the negative terminal is removed first, as the positive terminal will remain hot.

bumper Yonder Minden, NV
Re: Post Battery Change Engine Operation- Risky!
Reply #26 –
Yahoo Message Number: 88414
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If one was to jumper the isolator it would be much better to jumper
with a rather high value
 
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resistor. Say 120 ohms. I suspect the computer would still run fine
because of it relatively low
 
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current draw but if one shorted something out there would be a
current limiter in the circuit.
 
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With a 120 ohm resistor used as the jumper the current would be
limited by a short to

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something like 100 mA unless I misplaced a decimal point..
With this value, a draw of 20 mA would drop the voltage to 9.6V, for instance, and the phantom loads may draw more current than even that.
A light bulb might work out, as well as alerting of a short, but you'd have to find out experimentally which will have a sufficiently low resistance at the expected current draw. Of course, if you guess wrong, then you might as well have not bothered.

Steve
2004 FL
2013 Honda Fit
 
Re: Post Battery Change Engine Operation- Risky!
Reply #27 –
Yahoo Message Number: 88460
Steve
 Well 9.6 ought to be twice that required to run a computer...but a bulb is a better option here I think..
 And the beauty of a bulb is they have low resistance until there is enough current flow to warm up the filments. One used in the square ceiling RV lamps would be ideal. A 1141 bulb would be ideal limiting current to less that 1.5 amps with a short and dropping very little voltage while only powering the CPU.

Of course this whole exercise is more or less wasted effort as most everyone will run down the battery at one time or another and the cpu will go to default values and re-learn everything.

And it would be much better to guess wrong than to short things out with a short across the isolator, with the high current draw and possible damage.
 I think shorting out the isolator is a very bad idea and I am pretty much to take chances with things like this.  But I know how easy it is to short something out while working around batteries in these tight spaces..

Garry