How do you change the amp value of a battery

[Shane711]

I am trying to make a voltage regulator for my car.

My car puts out 14v and 500 amp battery.

I can not tell Multisim that I want a 500 amp battery.

How do I change the value?

This is important because I have to make sure I have at least 15amps output. No way to do this so far. Program is worthless.

[Tien_P]

The battery is an ideal part and the output current is based on Ohm's law V=IR.  Your load determines how current will be drawn.

If you need a constant current, there is a current source maybe you want to use that instead.

[Shane711]

I tried using the constant source. I still can not adjust the volatge and the amps. Whoever designed this program needs to fix it.

Every thing has volts and amps.

[johnsold]

Shane711,

It sounds like you have a fairly limited knowledge of electrical devices and basic circuit models. In forty years of electrical engineering I have not seen any device in which you can independently adjust the voltage and the current simultaneously.

A quick Internet search for "battery modelling" found several descriptions of circuit models for different types of batteries. This site shows these models:

The model used by Mathworks is an equation for which the document describes how to determine the values for the coefficients from the battery properties.

As you can see none of these is a simple constant voltage source which Tien P. said is used by Multisim. So you will need to take an appropriate model and adjust the parameters to match the characteristics of the battery you wish to model.

Lynn

[Shane711]

If I go to my car battery and measure the amps I am going to get a ready of the amps that battery puts out.

I recently had a multimeter that burnt up because when I connected it to the car it couldn't handle the amps.

In my understanding this should not have happened because there was not a heavy load but it did.

I have a basic understanding of electronics, I have been fiddling with it since I was 3 years old but never went to school.

I consider myself to know a lot but not everything.

All I want to do is make a simple voltage regulator having a constant voltage of 12 volts that does not reduce the amps below 15amps.

But can't find one made already and can't find anything on it at all.

Everything I see is not what I want. Pissing me off.

And as far as Multisim goes, If I want to use a 1,000 amp car battery I should be able to put it in there.

[Shane711]

After messing with the program I am very convinced. Multisim is a piece of crap.

It DOES NOT act like a real circuit.

I am done using it, worthless.

[johnsold]

Shane711,

Most multimeters can only handle ten amps or less, so it is not surprising that yours burned up.

How did you connect the multimeter while trying to measure the battery current? Cars have large, heavy wires connected to the battery because the large currents would destroy smaller wires. Your multimeter does not have connections or wires anywhere near as large as the battery cables. To measure the current you need to disconnect one of the cables and connect the meter in series with the cable. If you attempted to connect the multimeter in parallel with the battery as you would to measure voltage, you shorted the battery through the meter and probably had hundreds of amperes flowing, at least until a fuse blew or some wire burned out.

Your specification for the voltage regulator does not make any sense. A voltage regulator has an output voltage specification - yours is 12 V. It also has an input voltage range specification. You did not specify an input range. The output current is determined by the load via Ohm's Law. The specification includes a maximum current - Is that what you meant by 15 amps? Some regulator circuits also have a minimum output current specification, often a few mA. Optional specifications include tolerances on voltages, power dissipation, transient response characteristics, and so on. The design of the circuit depends on all of these specifications.  You will probably not find a single device which operates as a voltage regulator with 12 V output at up to 15 A.  A regualtor like that will probably contain one or more power transistors, some ICs, resistors, diodes, capacitors, and inductors.

Any simulator is only as good as the models used. From what Tien P. said in his earlier post, the battery in Multisim is an ideal voltage source. If so, it should easily produce currents of 1000 amperes. Just put a 12 milliohm resistor across the battery.  As I said yesterday, you will need to create a battery model circuit which has the characteristics you want in your battery.  What do you expect the output voltage to be at the battery terminals when drawing 1000 amps? What should it be with no current drawn? What should it be at 1, 10 , and 100 amps?

Lynn

[Shane711]

I am not sure exactly how many amps I will be drawing except that it will be at least 6amps but not more than 15 amps.

Most voltage regulators I find can not even supply 6amps so I wanted to make my own.

But I want it as small as possible and simple.

This will be running off a car. The battery voltage reads 13v and 14v when the car is running. I would like a constant voltage of 12v-12.5v

I am affraid my projuct is voltage sensitive and too many volts will cause it to burn up.

What I made cost about $700 and worth a lot more. I do not want to take the chance.

So I don't know everything but I think it is time I learned more.

Is there a schematic like what I am describing and maybe I can tinker with that to see if I can get it to work?

Do you know of any?

The only other thing I am thinking of is using 3   5A - 12V Voltage Regulators - LD1084V12

But then were talking about $18.00 just for those and I went over my target price.

So the best thing would be to buy one already made, but I CAN NOT find it anywhere.

So what can I do?