Subject: Re: unreliable DC 12v to regulated DC 12v
From: email@example.com (roma)
Date: Sun, 22 Dec 2002 10:21:29 GMT
NNTP-Posting-Date: Sun, 22 Dec 2002 03:21:29 MST
firstname.lastname@example.org (cvt) wrote in :
>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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an easy solution is to use a dc-dc converter with a 15 to 18 voltage output
rectify and regulate at the DC level required .