Newbie help. 12v regulator

[nugab]

Hello all, Nathan here. I'm new to this board.
I am really new to electronics, and have run into an embarrassingly simple problem.

I have a battery that can fluctuate from DC 12v to 17v providing up to 8 amps.
I have a load that needs 12v, up to 2.5 amps.

I realize how simple this must seem to the majority of you reading this. I have been working on this for some time, but knowing so little about the subject has made this problem a fiasco.

I have several 7812 Voltage Regulators from Radio Shack. The problem there is that they only allow up to 1 amp. I considered putting 3 of them in series, my thinking is that this would allow up to 3 amps, but keep the voltage at something close to 12. I don't know why I think this, but it makes sense

I also went out to a local store and bought a NTE970, but this component has proven too complicated for me to understand the finer points of setting the variable voltage to something I can use.

I would like a simple solution, if anyone knows what part I can use to provide 12vdc, with up to 2.5 amps. PLEASE let me know.


Thanks for your time.

-Nathan

 

[(*steve*)]

Several issues.

1) if you want more current capability, you'd place several regulators in parallel, not in series. However that's not a particularly good solution. You want to look for a higher current regulator, or use additional pass transistors to allow for extra current.

2) Regulators require some headroom. This is the difference between the input voltage to the regulator and the output voltage for the regulator. In the case of the regulators you mention, it is around 2V, meaning that when the battery falls below 14V you're not going to get a regulated 12V out of the regulator any more.

What is your load? It may be able to handle the higher input voltage (then again, it may not).

 

[davelectronic]

Regulators

Hi there and welcome, A battery fulcutuating to that extent wow thats a big diferencial, what Steve said is top advice, you can parallel regulators but there are some do's and dont's. RE UK reusable energy UK have some regulator parallel circuits, but a pass transitor, or a more powerfull regulator is other options. If that battery fluctuates that much on a full charge, ita got problems. Dave.

 

[poor mystic]

I think those fluctuations are pretty normal for a deep-storage lead acid battery.

 

[Resqueline]

17V is bad news for any 6 cell lead-acid battery, unless it's to be charged at 50 deg C below zero (or colder).