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Make Circuit diagram for battery charge controller using schmitt trigger
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Siddhat:
I am planning to make a battery charge controller for my project.What I am planning to do is that I am going to make a 12-V lead-acid battery charger that cuts-off the power when the battery is fully charged and again starts charging when the charge in the battery goes below to a certain level(say 30%) using operational amplifier using schmitt trigger.But i could not make a proper circuit that works.Can someone help me out with the circuit diagram using schmitt trigger??
Doctorandus_P:
There is a lot of magic smoke inside battery chargers that you do not want to let escape.
- shor circuiting the battery,
- over / under charging...

And you will make mistakes during the design / build of your circuits. Everybody does.
A good Lead-acid battery charger is also a 2 step process:
1). Charge with limited / constant current untill the voltage reaches the maximum.
2). Charge with that voltage until the current drops below a threshold.

The second part is also important to fully charge the battery.

A schmitt trigger can be a part of a battery charger to start / stop the charge process
(Although I woud personally prefer a microcontroller, which also keeps track of (dis) charge currents etc).

Schmitt triggers can be made with even a simple single transistor, but it is easier to understand with an opamp. Start by making a few simple oscillator circuits with opamps. They almost always use a schmitt trigger of some kind. You can generally recognize this by any connection between the output and the non-inverting "+" input of the opamp.

The book "Opamps for everyone" slod006b is a free reference book from Texas Instruments and it is a very good refererence for everything related to opamps.
https://www.eevblog.com/forum/beginners/opamps-for-everyone-pdf/

Then later on in your design you will need some voltage references for the thresholds.
TL431 is a popular choise, but the LM317 (small TO92 ) is also a good candidate.
Chips like these are about a few bucks in a bag of 100 from Ali / Ebay.
digsys:
.. or just use something like the BQ24450. It handles ALL battery charge / conditioning, simple to use and able to go to 5A plus.
There are several all-in-one SLA / (other chemistry) charger ICs out there as well. I used to use micros, but this is so much easier.
Plus you can start to learn of all the chemistry etc from application notes.
rstofer:
That BQ24450 is a terrific device for valve regulated lead-acid batteries (SLA batteries).

There are thousands in stock at DigiKey at around $8 but the device is not recommended for new designs.  I imagine there is a replacement.

There is an evaluation board in stock (3) but it's pricey at $102.

Siddhat:
Check out this circuit that I made earlier which only cuts-off the power when the battery is fully charged. I used a L7812CV voltage regulator , 12V zener diode, a BC547 transistor, a relay and some resistors to make the circuit.
But I seem to have no idea how to use a Schmitt trigger.
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