Car battery charger circuit diagram and operation

Given below, is a very simple circuit that can be used for charging car batteries. In this circuit there is facility for monitoring the charging current and voltage.

The circuit is based on the IC MC78T12ABT from Freescale.The IC is nothing but a 7812 in TO-3 package with 3A capacity. The transformer T1 steps down the mains voltage and diodes D1&D2 does the job of rectification. Capacitor C1 does the filtering and C2 acts as a decoupling capacitor. The ground terminal of IC1 is lifted to 2.1V using the diodes D3, D4 and D5 . So the output from the IC1 will be a regulated 14.1V (12+2.1).The battery is charged via diode D6.The D6 blocks reverse flow of current from battery to charging circuit when the mains power is not available. Meter M1 shows the charging current and M2 shows the charging voltage.

Circuit diagram with Parts list.



  • The transformer T1 can be a 230V primary; 15-0-15V, 3A secondary step down transformer.
  • The meter M1 can be a 3A FSD ammeter.
  • Meter M2 can be a 20V FSD volt meter.
COMSUN Car Charger, Comsun Universal Dual Port USB Car Charger 24W 4.8A Smart Vehicle GPS Charger Travel Adapter Black
Wireless (COMSUN)
  • FEEL THE NEW SMALL: Dimension in 1.6x0.9x0.9 inch LWH, Comsun car charger is so tiny that in cars that have rubber dust boots over cigarette lighter ports you can...
  • DOUBLE PORTS DOUBLE POWER: With 24W/4.8A output, Comsun dual port USB car charger can charge two tablets or two smartphones with up to 2.4A simultaneously at their...
  • INVISIBLE SAFEGUARD: Build-in intelligent circuit design protects against short circuiting,over-heating, over-currents, over-charging. Comsun s MultiProtect safety...
  • MATERIAL THAT MATTERS: Over 10 manual working procedures, one-step injection molding, made of high flame retardation standard material and anti-oxidation refined...
  • LED INDICATOR: The ports glow red when power is supplied, which let you know that it s on. It s not so bright as to be distracting when driving in the dark, but...
TNP FM Transmitters Wireless Radio AUX Adapter - Mini Universal 3.5mm Plug Jack for Car iPhone 6 5 iPod iPad Android Smartphone Tablet PC Desktop Laptop MP3 MP4 Audio Players Stereo System
Network Media Player (TNP Products)
  • This wireless fm transmitter is the ultimate car companion; Compatible with Apple iPod Android Samsung Galaxy S6 S6 Edge Smartphones and Tablet PCs, MP3/MP4 audio...
  • Mini In-car FM transmitter, just pair it with car FM radio to play music in your device or make hands-free conversation through car speaker; Quality Longer Play...
  • The Mini FM Transmitter, utilizing the state of art technology and modern design, featuring a large digital display; Universal Mini FM Transmitter More stable FM...
  • Special Auto Power-Off: When no Music Input for One Minute, It Will Shut Down Automatically for the Energy Saving Purpose
  • Designed with a slim, tiny structure, it is an ideal portable accessory for use in cars, at home or outside
YCJUJU YCJUJU USB Charging Double Arc Cigarette Lighter, Tiger Shape for Table Placed (Black)
Sports (YCJUJU)
  • Tiger shape, symbol of anything good
  • Have a gift box
  • Windproof, Waterproof
  • Dual Arc, light sooner
  • Can Dismantling and assembly
EZYKOO DC 12V/24V Waterproof 4 Gang Circuit LED Rocker Switch Panel with Cigarette Power Outlet Socket and Dual USB Power Charger Adapter for Car Trcuk Trailer RV ATV Marine Boat
Automotive Parts and Accessories (Ecooltek)
  • PACKAGE INCLUDES: 4 Gang Rocker Switch + 1 x Cigarette Lighter Socket + 1 x Dual USB Port , Product Size: 130 x 120 x 90mm(5.12 x 4.72 x 3.54 inch).
  • HIGH QUALITY: Heavy duty ABS plastic face panel with short circuit / overheat protection for on-off rocker switch.
  • EASY INSTALLATION: Just put it into the switch hole, fix it with screws, and can be installed horizontally or vertically 12V or 24V DC, so simple and easy to install.
  • APPLICATION: Universal for all 12V-24V vehicles such as cars, bus, trailer, boats, marine, RV, ATV, etc.
SEXOX SEXOX Battery Charger Clamps, 500-Amp, Commercial Grade
Home Improvement (SEXOX)
  • The product is 500A Common Charge Clamps
  • 500 amp commercial grade battery charger clamps
  • Includes positive and negative clamps
  • Parrot Style zinc plated jaws for a great grip
  • Accepts up to #2-Gauge cable Heavy duty construction and easy grip handles

Related posts: