Subject: unreliable DC 12v to regulated DC 12v
Date: 21 Dec 2002 06:35:15 -0600
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The plan is to regulate unreliable 12v input (from the car battery
directly, wired to the back of the car)
Currently, I am getting 0.9 volts drop over the distance.
With the engine running I have 13.6 at battery, and 12.5 at boot
with engine off, I have 12.6v at battery, 11.5v at boot
when cranking I have 11.8v at battery, 9.5v at boot
Now, this is to run a computer.
I have built a nice 60watt power supply, regulating all the voltages,
*IF* I have a clean 12v comming in (12v is note regulated, but direct)
so simply, I am trying to regulate 12v to 12v, which AFAIK can't be done
without stepping up the voltage, which then comes into a power wasting
system, which may be necessary, but I was wanting it to be as economic
having the 12v rail between 11.5 and 12.5 in my books will not hurt, but
much below 11.4 i feel is too low, and the computer will crash/lock
up/reboot, or be damaged by the spike to 12.5 when the engine starts.
I don't think running a 1,000,000 farad car audio cap would be any good,
because if I am at 11.5v already, its not going to be enough to hold the
voltage acceptable during the long time cranking.
If I had a battery switching tecnique, I'd want a SLA 12v in the boot
with it, bt will it safely handle the power the system is drawing?
So thats my dilemna... any ideas?
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