Lm311

[ericgibbs]

the one that can charge a battery that came from a ups like maintenance free battery (is this the Sealed Lead Acid you mean?) and a battery of a car which need to refilled by distilled water...

hi
Look thru these links for both types of charger

How to charge sealed lead acid batteries. Custom battery chargers for OEMs in a hurry from PowerStream

Sealed Lead-Acid Battery Charger Circuit

12V Car Battery Charger | Circuit Diagram

**broken link removed**

 

[parker]

eric what type of battery that could be charged by the last circuit you have given?
what application it most suitable?

 

[ericgibbs]

eric what type of battery that could be charged by the last circuit you have given?
what application it most suitable?

The last link in my post is for wet acid car battery.

 

[parker]

The last link in my post is for wet acid car battery.

sorry eric i'm referring to the last circuit LM339 sample that you simulate.
what application should i use this?

 

[ericgibbs]

sorry eric i'm referring to the last circuit LM339 sample that you simulate.
what application should i use this?

hi P,
All that LM339 circuit is a battery state monitor which switches the charge to the battery ON and OFF depending on how you have set it.
For example it could be set to switch the charge ON when the battery voltage falls below say 11V and OFF when it reaches say 14V when charging.

Its NOT at battery charger...

A battery charger circuit would have to be configured to supply say a constant 14V output and connected where the 14V is shown.

 

[parker]

thanks eric,

please enlighten me again on circuit LM339, R4 68k and R8 18k is a voltage divider, and the current flowing through this (in my own understanding) is about .162mA
what is the basis of electing a total 86k resistance?
i try to calculate using ohm's law: (please correct me if i'm wrong!)
* 68k will have about 11.0697V
* 18k will have about 02.9302V
* R4 & R8 is 20.9% of 14VDC which is about 2.8V on their junction, then there is 15k R3 connected to this junction.
if the source of R3 is 2.8V with a current of .162mA, what is the current on junction R3 and -inps?
will the Voltage on junction R3 and -inps drop?

 

[ericgibbs]

thanks eric,

please enlighten me again on circuit LM339, R4 68k and R8 18k is a voltage divider, and the current flowing through this (in my own understanding) is about .162mA
what is the basis of electing a total 86k resistance?
The selection of resistors is to give the required voltage ratio from the voltage applied to the top of the divider and the junction of the two resistors. Usually high values are chosen so as not to draw too much current from the battery being monitored.
Obliviously the 68K and 18K add up to 86K, which when the top of the divider is at 14V a current of 0.162mA flow flow the two resistors, so the voltage across the lower 18k will be 2.93V.
An easier way is: - 14v * 18k/86k

i try to calculate using ohm's law: (please correct me if i'm wrong!)
* 68k will have about 11.0697V
* 18k will have about 02.9302V OK
* R4 & R8 is 20.9% of 14VDC which is about 2.8V on their junction, then there is 15k R3 connected to this junction.
if the source of R3 is 2.8V with a current of .162mA, what is the current on junction R3 and -inps?
Dont think in terms of current inputs to the LM339, think voltages.
This divided voltage of 2.93v is on one pin of the LM339 and the Vref voltage on the other LM339 input.
So when the divided voltage is greater than the Vref the charge relay is OFF and as the 14V battery voltage falls the divided voltage will fall to less than the Vref and the charge relay will be on.

will the Voltage on junction R3 and -inps drop?

hi,
You can see from my notes in blue how it operates...OK.?

 

[parker]

An easier way is: - 14v * 18k/86k

hi, i try this one and gives me a result of: 3.705 did i missed something?

if R4 and R8 can supply the necessary Volts and Amps then what would be the function of R3 on this Circuit?

 

[ericgibbs]

hi, i try this one and gives me a result of: 3.705 did i missed something?

if R4 and R8 can supply the necessary Volts and Amps then what would be the function of R3 on this Circuit?

hi,
You missed this from college.?? BODMAS..??
Read this link and try again.
Order of Operations - BODMAS

R3, I always have a current limit resistor on inputs, others don't.

 

[parker]

hi,
You missed this from college.?? BODMAS..?? Let's pretend that a fall asleep during my class Lol
Read this link and try again.
Order of Operations - BODMAS my brain got 2mm Rust

R3, I always have a current limit resistor on inputs, others don't.

How do i calculate that 2.93V/15k = 0.195mA is this right?

 

[ericgibbs]

How do i calculate that 2.93V/15k = 0.195mA is this right?

hi P,
I dont wish to sound picky, but I have explained this, do not think in terms of current at the inputs of the LM339.

For the example circuit I posted you can assume there is no current [ minute value] flowing in R3.

 

[parker]

thanks eric, i'll take your advice, i'll keep you posted...