• 100% Satisfaction Guarantee

Edward, Consultant
Category: General
Satisfied Customers: 7966
Experience:  I am the #3 General expert on Just Answer.
3134513
Edward is online now

# how do i reduce dc current in a simple circuit

### Customer Question

How do I reduce the current from a 12 Volt car accessory socket down to 500mA in a simple circuit that could easily be constructed at home?
Submitted: 7 years ago.
Category: General
Expert:  Edward replied 7 years ago.

HiCustomer Thank you for asking your question on Just Answer. The other experts and I are working on your answer. By the way, it would help us to know:

-Could you explain your situation a little more?

-Could you tell me why you need to reduce the current to 500mA?

-What will you be using this circuit for?

Customer: replied 7 years ago.
Reply to Edward's Post: I want to make a suitable cable to charge a 12 Volt Ni-Cad battery from a 12 Volt DC car supply.

The original battery charger is 240Volts AC - 12Volts DC @ 500mA.

I want to be able to charge this Ni-Cad battery from the car accessory socket, which will be 12 Volts DC at presumably a much greater current than 500mA, by connecting an accessory plug which will then go to the Ni-Cad battery (to be charged).

The manufacturer of this 12 Volt DC Ni-Cad battery recommends that the charging current is not more than 500mA @ 12 Volts DC!

At the end of the day I want to make a cable suitable for charging the 12 Volt DC Ni-Cad battery from the 12 Volt DC supply in the car.

I want a simple electronic circuit, showing how to reduce the original current of the 12 Volt DC car supply down to 12 Volts DC @ 500mA, that I can easily solder up into a SAFE charging cable for this battery.

i.e. I want to reduce the 12 Volt DC current of the car battery down to 12 Volts DC @ 500mA!
Expert:  Edward replied 7 years ago.

The amps applied to the battery would depend on the state of charge of the battery, and the voltage being applied.

A simple circuit would be a rheostat and a amp meter to detect the charge rate. Adjust the rheostat to limit the charge rate.

For a more automatic solution, fIrst you would need a amp meter and volt meter up to determine the voltage needed to charge the fully discharged battery at 500mA. Once this voltage is established, you will know the max voltage that can be applied to the battery, to limit it's charge rate to 500mA.

Since the voltage from a automotive battery will vary, you would need to regulated the automotive power source to the established voltage, to keep it from charging more that the 500mA.

Check out http://ourworld.compuserve.com/homepages/Bill_Bowden/page12.htm for several simple voltage regulator circuits.

.

Ask-a-doc Web sites: If you've got a quick question, you can try to get an answer from sites that say they have various specialists on hand to give quick answers... Justanswer.com.
...leave nothing to chance.
Traffic on JustAnswer rose 14 percent...and had nearly 400,000 page views in 30 days...inquiries related to stress, high blood pressure, drinking and heart pain jumped 33 percent.
Tory Johnson, GMA Workplace Contributor, discusses work-from-home jobs, such as JustAnswer in which verified Experts answer people’s questions.
I will tell you that...the things you have to go through to be an Expert are quite rigorous.

### What Customers are Saying:

• Wonderful service, prompt, efficient, and accurate. Couldn't have asked for more. I cannot thank you enough for your help. Mary C. Freshfield, Liverpool, UK
< Last | Next >
• Wonderful service, prompt, efficient, and accurate. Couldn't have asked for more. I cannot thank you enough for your help. Mary C. Freshfield, Liverpool, UK
• This expert is wonderful. They truly know what they are talking about, and they actually care about you. They really helped put my nerves at ease. Thank you so much!!!! Alex Los Angeles, CA
• Thank you for all your help. It is nice to know that this service is here for people like myself, who need answers fast and are not sure who to consult. GP Hesperia, CA
• I couldn't be more satisfied! This is the site I will always come to when I need a second opinion. Justin Kernersville, NC
• Just let me say that this encounter has been entirely professional and most helpful. I liked that I could ask additional questions and get answered in a very short turn around. Esther Woodstock, NY
• Thank you so much for taking your time and knowledge to support my concerns. Not only did you answer my questions, you even took it a step further with replying with more pertinent information I needed to know. Robin Elkton, Maryland
• He answered my question promptly and gave me accurate, detailed information. If all of your experts are half as good, you have a great thing going here. Diane Dallas, TX

• ### Ron

#### Satisfied Customers:

21781
23 years with Ford specializing in drivability and electrical and AC. Ford certs and ASE Certs
< Last | Next >

### Ron

#### Satisfied Customers:

21781
23 years with Ford specializing in drivability and electrical and AC. Ford certs and ASE Certs

### Dr. Y.

#### Satisfied Customers:

18790
I am fellowship trained specializing in general urology and reconstructive urology.

### John

#### Satisfied Customers:

13453
Appliance repair business owner for over 43 years.

### Tina

#### Satisfied Customers:

8681
JD, BBA Over 25 years legal and business experience.

### dermdoc19

#### Satisfied Customers:

3954
30 years practice in general and cosmetic dermatology

### Dr. Pat

#### Satisfied Customers:

3464
25+ years working primarily or exclusively with birds

### Dr. Gary

#### Satisfied Customers:

3423
DVM, Emergency Veterinarian, BS (Physiology)

## Related General Questions

Chat Now With An Expert
Edward
246 Satisfied Customers
I am the #3 General expert on Just Answer.