12v Lead Acid Battery OVER and UNDER VOLTAGE protection

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biswajitdas49

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Hello everybody!
I want a circuit for 12v paralleled connected 4 lead acid battery over and under voltage cut-off. I found too many circuit using googling,but don't understand which is best and suitable circuit for my project,so I come to this best electronics forum.Please some give me a best solution for this.

Thanks!!!
 

Paste the links you saw on google so that I will help you make a choice. I am too busy to using my CAD software to draw the circuit, unless you want me to describe the circuit for you.
Also search for similar threads in this forum, I think we have treated cases like this before.
1. Are you charging the battery with constant voltage?
2. Will there be need for trickle charging.
 

Hi,

basically you need a comparator for overvoltage protection to stop charging of battery.
and a second comparator for undervoltage protection to stop discharge.

Klaus
 

If you are trying to put lead acid batteries in parallel then you need some form of current sharing resistors in series with each one. It only needs to be in the order of .1 ohms. Otherwise one battery will do much more work then the others and will wear out quickly, then another one will be the active one, until they are all worn out.
Frank
 


No, I don't need battery charger circuit, I just want low and over voltage indicator with hysteresis also if need any current limiting resistor for this ckt.

example link--
https://www.engineersgarage.com/contribution/voltage-level-display-12v-battery
 

The circuit you posted its link is for monitoring the battery level at anytime.
However it can only alert you through the buzzer but if you want it to disconnect the battery from overcharging and also cut off its output when it is low then you have to modify it. The circuit is working perfectly.
 

Yes "over voltage", rather indicates that this must be on the charging side and likewise "under voltage" must be on the discharge side.
So with these alarms , what do you intend to do with them? A fully automatic system would disconnect the battery if it is over voltage from the charger and if under voltage would disconnect the battery from its load.
Frank
 


I have some questions,that is-
1> Do I need any current limiting resistor because I connect four 12v battery in parallel.
2> I heard that if load is connected then after sometime battery will drain and its voltage becomes low and when disconnect the load again it will increase its voltage.that means I need hysteresis based circuit so please tell me how to solve this?
 



If you connect any voltages sources in parallel, the weakest will draw much power from the strongest. If they are matched in charge levels,and age which affects internal resistance, it will be ok, but unless you know for certain, then weakest one can drain the strongest without current limiting. A series wire can be calibrated in milliohms to measure current, with any constant current or ammeter.

We would need your full charging system design details,,to advise.
 

I just want low and over voltage indicator
Click to expand...

For this purpose, here is a clever 3-led battery monitor. (Someone posted it here at Edaboard, as I recall.)

Adjusted for a 12V system.



The scope traces display the action as battery voltage drops from 16V down to 9V. The different color led's light accordingly.

Green is lit between 11.5 and 13.5 V
Red, below that range
Yellow, above that range
 

1. Someone suggested that you should use current limiting resistors earlier, I support that.
2. Any circuit that involves op amps, for you to overcome hysteresis: locate the terminal (either the inverting or the non inverting input) in which the changing parameter is (not the fixed eg. reference) and connect a resistor between this pin and the output.


Normally, when a battery is in operation: it will continue to discharge and if adequate measure(s) are not taken, it will completely be drained.
 

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