Battery charger circuit using SCR.
Description.
A simple battery charger based on SCR is shown here.Here the SCR rectifies the AC mains voltage to charge the battery.When the battery connected to the charger gets discharged the battery voltage gets dropped.This inhibits the forward biasing voltage from reaching the base of the transistor Q1 through R4 and D2.This switches off the transistor.When the transistor is turned OFF,the gate of SCR (H1) gets the triggering voltage via R1 & D3.This makes the SCR to conduct and it starts to rectify the AC input voltage.The rectified voltage is given to the battery through the resistor R6(5W).This starts charging of the battery.
When the battery is completely charged the base of Q1 gets the forward bias signal through the voltage divider circuit made of R3,R4,R5 and D2.This turns the transistor ON.When the Q1 is turned ON the trigger voltage at the gate of SCR is cut off and the SCR is turned OFF.In this condition a very small amount of charge reaches the battery via R2 and D4 for trickle charging.Since the charging voltage is only half wave rectified ,this type of charger is suitable only for slow charging.For fast charging full wave rectified charging voltage is needed.
Circuit diagram with Parts list.
Notes.
- Assemble the circuit on a good quality PCB or common board.
- The transformer T1 can be 230V primary, 18V /3A secondary step down transformer.
- The voltage of the battery at which the charging should stop can be set by the POT R4.
- The battery can be connected to the charger circuit by using crocodile clips.
I have available SCR’s two pcs., #NTE 5545 , can I use this SCR as substitute for 2N3668? of course I will replace the transformer of higher current, same voltage output.
What substitutes for BC 148 and SD 50?
Can I have a working circuit for DC motor Speed control using my available NTE 5545 SCR’s of readily available electronic parts in electronics store? Other part numbers are not available here in my country-Philippines.
Hi Nilesh Sharma If the thyrister is going to get shorted, first the fuse will blow immedeately due high current flow, if the fuse has not failed then the protective resistance R6 will be charred. So nothing will hapen to the battery.
Hi Edgardo you can use any NPN small signal transistor with Vceo 30 volts Ic max 300mA and Ptot 300mw and a hfe of aroung 150 at 50mA. SD 50 can be any 5volt 400mw zener diode, For the scr what you have got requires a gate trigger current of 30mA it will work as it is if not reduce R1 to 270 ohms
Respected All,
I am doing the automatic 120V Battery charger circuit. For that I need 140V reader circuit. If the Battery Max voltage reaches at 140V it should turn off the charging from the AC supply.
Kindly requesting please give solution as much as possible.
Hi Anil You can communicate me your exact requirement whether a relay should switch of thyristor to be turned off etc to me seethasub@hotmail.com i will send you a detailed circuit it will be mostly based on “High & Low voltage cut-off with delay& alarm” appeared on Circuits today. very useful circuit idea for so many applications.
Dear Admin/Seetharaman,
Thank you very much for the informations i got.
More power to you.
Nice circuit! To those who wants to put a diode to protect againt reverse battery polarity pls note you CANNOT put it between r6 and f1 or the charging will never stop and the battery will overcharge! putting it on the transformer secondary by pin #15 is ok but has no use! You cannot prevent current from flowing back into the resistor voltage divider network (r3 & r4 & r5) or the battery will start charging again, but you only loose very little power/current (about 12 mA)
Why do we need the R6 resistor? can it be removed?
Hi Kim you are right if the charger is off and only the battery is connected the wrong way. once you switch on the charger the fuse will blow due to battery voltage and charger voltage appearing across R6 Diode and resistance. I agree the diode is ultimately not going to serve any special purpose.
battery will not get over charged once the terminal voltage of the battery reaches the rated voltage of 13.6volt. the diode anode voltage will be more by 0.7 volt, you adjust the pot in such a way the terminal voltage at the battery including the diode is limitted to 13.6volt.
the other solution to protect battery reversal will be connect a 6Amp diode, anode to negative and cathode to R1 f1 Junction. If you reverse the battery the fuse will blow indicating the problem.
with the existing circuit if you reverse the battery and connect. battery voltage in series with charging voltage will appear across R6 and fuse, a very high current will flow, which will blow the fuse. Without R6 the entire voltage will appear across the thyrister the current will shoot up and it may blow the thyrister before the fuse.
i have a inverter , the charging method is not good,for current limitting capacitor is used ,so the fixed cuurent is going to the battery, so battery not fully charged,any circuit for current limiting instad of using capacitor,
the transformer voltage is 0v-160v -230v
i need charger like when the battery voltage increase the current will low,and the battery voltage low the current is high , current rating is 5A to 10A,any circuit for this.
Hi Vinu what is the battery voltage and AH rating. If it is lead acid battery the charging voltge should be regulated at 115% of the rated voltage of the battery. the current limit should be 25% to 30% of the rated capacity of the battery. These are the safe limits as recommended by the battery manufacturers.
Dear someone.I am looking for a 12v sealed lead acid battery charger circuit, the battery must operate leds ,and when the battery goes below 10volt, switches off automatically, it must now be charged again to its full capacity, and so on and so on.
Looking forward in hearing from anyone, thanks a lot. Regards.
Marinus
Hi Marinus I have made one ready with 12volt 7AH battery and 21 LEDs. send your email to seethasub@hotmail.com
Hi I like this circuit and want to build one. I need help understanding how to fully rectify the voltage. Any help for this hobbyist?
Hi Robert Connect the secondary of the transformer to a bridge rectifier and then feed it the SCR circuit
Hi is there some one tell me how can I assemble a lithium battery charge? so much thanks for your help.
best regards Me.
Hi Me
Please go through the following site for your requirement. Charging Lithium Ion Batteries are a bit complicated one. If you donot take proper care you may damage the battery permenetly.
http://www.powerstream.com/li.htm
This is the first time i am visiting this site. Its really very interesting where our doubts are answered. Great. I would like to have a circuit for making a home brew Inverter 1000 VA. Simple and effective. I am a HAM and know comething about electronics.
Looking farward to hearing from you
Kind regards,
VK
I need 12v lead acid battery charger with low bat and full indication and adjustable charging current
hi guys!….what is the voltage of the battery to be charged in this circuit?i hope for a reply guys….tanx in advance
why diodes are used in Scr battery charger..??anybody know..
Hi Lian This charger can be used for 12volts 7AH to 20AH batteries.
Hi Marron R2 D4 is for ripple charging for topping up. D1 D2 Q1 is for stopping the charging current the diodes are used for sharp switching and isolation. D3 is for protecting SCR gate cathode junction against reverse bias during Q1 conduction.
HI Seetharaman, IS there a possibility of adding a toggle switch for 6 and 12 volts charging and toggle switch for slow and fast charging in this circuit.
thanks a lot