# Help needed with a lead/acid battery charger circuit

Discussion in 'Homework Help' started by Claudia94, Mar 25, 2015.

1. ### Claudia94 Thread Starter New Member

Mar 25, 2015
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Hello, this is my first post here, my friend recommended this amazing forum to me, i took her advice and here i am. also sorry for my english

i am doing this small project, but i am stuck in the regulation part, i am seeking help here if some one can skip the work and help me with the circuit

so this charger has to charge two 12v 200AH lead acid batteries in parallel, also i want it the most simple as possible using thyristors, i am not really very qualified , i've been reading how these chargers work but didn't understand that much

here is what i tried to do, i have strong feeling this won't work , also later may need some help with the calculation

2. ### Dodgydave AAC Fanatic!

Jun 22, 2012
8,089
1,394
Sounds like a standard car battery charger, you would be better using a regulator like the LM317, or LM338 set to give out 13-15V using a power transistor booster,

have a look at the datasheet, page 15

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Apr 5, 2008
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Hello,

I made some changes to the charger and stated some voltages:

I do not know if the 14 volts will be enough to function as charger.

Bertus

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4. ### Claudia94 Thread Starter New Member

Mar 25, 2015
28
1
thank you for the fast replies , i can't use ready regulators, the problem is how can i get 20 Amps and two 12V exits , i will be using a 28v 500va transformer

edit: sorry i meant 13.8v at the exit so it can charge the battery

Apr 5, 2008
19,558
3,988
Hello,

The 1N4743 is a 13 Volts Zener:

The peak voltage at the input with a 14 Volts input will be about 14 X 1.414 - 0.7 = 19 Volts.

Wlth the 13 Volts zener, the output voltage will be 13 - 0.7 = 12.3 Volts.
This is likely to low to charge your battery.

The 10K resistor is likely a to high value to bias the zener.

Bertus

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6. ### Claudia94 Thread Starter New Member

Mar 25, 2015
28
1
these in in circuit were just random values, they don't mean anything, at first i have to make sure that the circuit is correct, then it will be time for calculating .
i am sorry it is confusing, the program i use may put it, i didn't pay attention

my circuit is just a voltage regulator, how can i add a current regulator so i get output of 20 A

7. ### Dodgydave AAC Fanatic!

Jun 22, 2012
8,089
1,394
You cant boost the current,
you're going to need a 15v transformer @ 20Amps, for 13.8v output if you use your design with a 2N3055 transistor and zener , the zener will have to be 14.5V ,which doesn't give good regulation,

most car battery chargers are just a transformer and bridge rectifier.

Last edited: Mar 25, 2015
8. ### Claudia94 Thread Starter New Member

Mar 25, 2015
28
1
i really don't know very much in electronics, and these things are completely new to me, i just read on the internet.

can anyone please spare few minutes of his time and design a circuit for me ? i hope i am not asking too much

also i found this: would it work ?

9. ### Dodgydave AAC Fanatic!

Jun 22, 2012
8,089
1,394
the simplest charger is as i said , a transformer, a bridge rectifier like this,
if your going to use regulators or zeners you need more voltage from your transformer

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10. ### Claudia94 Thread Starter New Member

Mar 25, 2015
28
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yes, i want to use zeners or any classic solution, , also i would like that the charger stops automatically ( a relay maybe ) when battery is full ,
can you suggest a circuit for me , i really need this for my mini project, this would have been much easier if i could use automatic regulators like you suggested in your first reply, but unfortunately i am not allowed

11. ### #12 Expert

Nov 30, 2010
18,076
9,684
Let me tell you what I am hearing.

Hi! I copied a basic rectifier circuit, but I didn't do any math. In fact, I didn't even pay attention to it. It doesn't have the thyristors I want to include and it can't use any 3 terminal regulators. I want this circuit to regulate current and voltage, both at the same time, because I did not understand that Ohms Law makes that impossible. Can somebody please show me how to do the impossible without using any devices that were invented after 1960?
Pretty please? It's for my homework assignment.

We really need you to get your needs defined.

12. ### Claudia94 Thread Starter New Member

Mar 25, 2015
28
1
Thank you very much just take a look how many tabs i have open in my browser . i am doing my best but it's beyond the limits of my brain

i know that you probably know it's for my home work, but i really couldn't say it directly
Dodgydave i really want to thank you for your time.
one last request is: would you please tell me how this circuit works in a few words ?
also here is why i couldn't do any of this, it's cause i study mechanics, but my college forces us to take these electronic classes..

and for your curiosity, these batteries are used to start diesel engines of big tank sized truck ,

Last edited: Mar 25, 2015
13. ### WBahn Moderator

Mar 31, 2012
24,237
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Why not? Because you are not allowed to get outside help on this homework assignment? Or because you thought that by not saying so you would be able to trick people into doing all of your work for you?

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14. ### WBahn Moderator

Mar 31, 2012
24,237
7,552
MOD NOTE: Moved from Projects to Homework Help.

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15. ### Claudia94 Thread Starter New Member

Mar 25, 2015
28
1
thank you very much Dodgydave . you really saved me, i won't forget it.

@WBahn this was really a college project, and to answer your question, first, my professor didn't want to offer help, he kept saying keep trying and bring me your work, i made 4 circuits and were all wrong, all he had to say is keep trying. i tried a french forum before i posted here, i told them it was for my project and i needed help, they told me if it's your project , then open your book and study.

i swear i never studied this, i went to college to study mechanics, and as a project , they gave me this electronic one , cause some truck engine needs it's battery to be charged. though i have electricity class, they just tought us basic things, what is a rectifier, diode, what they do etc ..
they should've given it to someone who actually studies electronics.

sorry if i write a lot.

Mar 25, 2015
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17. ### WBahn Moderator

Mar 31, 2012
24,237
7,552
Senior members are allowed to delete and/or edit their own posts. My guess is that he deleted his post because it probably violated the rules and intent of this forum for assisting with homework, which is that we try to guide you toward finding your own solution. If we just do the work for you, you learn nothing. In addition, if he can keep you from submitting HIS work as YOUR solution, he prevents you from committing academic dishonesty, which could get you expelled (and don't think that instructors don't monitor forums like this looking for stuff, they do).

18. ### #12 Expert

Nov 30, 2010
18,076
9,684
And can I ask why you posted 3 times in the last 100 minutes and still did not try to define what you actually need?
The lack of knowing what you need could easily be why you guessed 4 times and got no approval from your teacher.
Start at the beginning. What do you need?
Even if you don't tell me, you are simply stuck if you can not answer that question.

19. ### Claudia94 Thread Starter New Member

Mar 25, 2015
28
1
okay, i understand.
thanks everyone

20. ### Claudia94 Thread Starter New Member

Mar 25, 2015
28
1
@#12 what i need is a lead acid battery chager, that i can use to charge 2 batteries in parallel

battery specs : 12v 200AH
no new technology regulators are allowed,

preferably using thyristors . this is what i need plus little explanation how it works