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12v DC Voltage Regulator


I am building a field power supply that incorporates a lead acid car battery. When fully charged the battery shows a voltage of more than 13 volts. It is a 35Ah battery.

I am using this battery to power 12 volt devices such as telescope tracking mount and a Surface Pro 4 computer/tablet that I use to drive the mount. I am not yet sure what amperage I may be needing but so far about 5 amp being available may be adequate.

The tracking mount voltage is specified as 11 to 16 volt DC and its hunger level is at 4Amps. The computer, on the other hand, does not provide a range of DC input. We are just going by the fact that its AC power supply claims it is producing 12 volts DC. Henceforth I want to make sure to regulate the power output to the computer to 12 volt DC.

I don’t imagine I need to limit how much amperage it would take in because that is really a function of the computer itself. But it does take something like 2.58 Amp.

Can you point me to a product you have that I can easily incorporate into my design?

When looking at the available regulators here I see small amps indicated and I am not sure if that is the amp needed to run the regulator or if it is the amp that can pass through the regulator and to its destination.

Thanks a lot.


Hello, Farzad.

We do not have any regulators that would be able to handle the current draw of your whole system, but It sounds like you could directly power your tracking mount from your battery. For powering the Surface you might be able to use our S18V20F12 regulator, but 2.5A is right at the limit of what it can do, so if your Surface draws that continually, I do not think the regulator would be powerful enough.


Hi Grant.

The surface may not draw that much power continuously. And I actually now realize that the surface may be operating from the internal battery and the chord is only for charging the battery.

Is there no way to design a voltage regulator that takes a voltage and reduces it to 12 volts without affecting thr amperage?

The only thing that I want to do is to be sure that the battery is supplying no more than 12 volts.

In response to your question, any voltage regulator is going to have a limit on how much current it can handle. I’m sure there are regulators that meet your current draw requirements, but we do not have any step-up/step-down regulators that can handle more than about 2.5 A. We do have step-down regulators that can handle significantly more current, but I don’t think that would be a good idea for your application since a step-down regulator’s output voltage would drop along with the battery voltage once it falls below 12 V, and your computer might be sensitive to an undervoltage condition like that.