Could you check this Li-ion charging circuit?

  • #1
emtae55
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TL;DR Summary
I made a Li-ion charging circuit with LTspice, and I wonder if it works well. Could you check this??
Can secondary cell can be described in circuit simulator?? With other symbols like capacitor. Also I wonder if there's a program that provide secondary cell(like Li-ion battery). Please help me
 
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Answers and Replies

  • #2
Baluncore
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It depends what you mean by “electric simulator”.
SPICE has a floating voltage source.
 
  • #3
berkeman
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Summary:: Can secondary cell can be described in electric simulator?? With other symbols like capacitor.

Can secondary cell can be described in electric simulator?? With other symbols like capacitor. Also I wonder if there's a program that provide secondary cell(like Li-ion battery). Please help me
What's a "secondary cell"? Do you mean a rechargeable battery? If so, just do a Google search on SPICE simulation rechargeable battery.
 
  • #4
anorlunda
Staff Emeritus
Insights Author
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We often use equivalent circuits to represent real life devices. For example, a transformer.

But we can't help you to find an equivalent circuit without much more specific information on the device and the application. Do you need to simulate one second? Hour? Year?
 
  • #5
emtae55
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We often use equivalent circuits to represent real life devices. For example, a transformer.

But we can't help you to find an equivalent circuit without much more specific information on the device and the application. Do you need to simulate one second? Hour? Year?

I want to know the time for charging it.
 
  • #6
Baluncore
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The capacity of a rechargeable chemical battery will be specified in amp*hours. If you know the charging current, then you can calculate the time needed to recharge an empty battery.
Hours = (amp*hours) / (charging current)

If you want to simulate the circuit of the charger and battery condition over time, then you should specify the simulator you will use.
LTspice is the most widely used circuit simulator available for free.
https://en.wikipedia.org/wiki/LTspice
 
  • #7
emtae55
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The capacity of a rechargeable chemical battery will be specified in amp*hours. If you know the charging current, then you can calculate the time needed to recharge an empty battery.
Hours = (amp*hours) / (charging current)

If you want to simulate the circuit of the charger and battery condition over time, then you should specify the simulator you will use.
LTspice is the most widely used circuit simulator available for free.
https://en.wikipedia.org/wiki/LTspice
I'd like to use LTspice, but I can't find the Li-ion battery component. Would you find me the component(or library)? Thanks.
 
  • #11
DaveE
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The thing about circuit simulators is that they do exactly what you set them up to do. They are absolutely not effective at telling you about the components in your circuit. That is the information that you must provide; you must characterize and model your battery. The circuit simulators can tell you how that will interact with other components that you have input into the model. If you program it incorrectly (i.e. unrealistic component models) it will happily simulate the wrong circuit and give the wrong answers; i.e. it will do exactly what you tell it to do.

Batteries of all sorts are typically modeled as capacitors, resistors, voltage sources, etc. If you are lucky you may be able to get access to a battery model that someone else created, but there is no guarantee that it will match the characteristics of your battery.

Circuit simulators are a poor substitute for understanding what you are building, particularly when it comes to individual components of that circuit.
 
  • #12
emtae55
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I made a Li-ion charging circuit with LTspice, and I wonder if it works well. Could you check this??
whole.png

potentiometer.png

battery.png
 
  • #13
Baluncore
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If you take the file.asc and rename it file.asc.txt you can then attach it to your next post, then we can run it to test it. You can do the same with a file.plt by appending .txt
 
  • #14
Baluncore
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There is no ground for the model. Without ground it will run very slowly due to current sources in the LT317 model.
I worry about current limit to the base of Q1.
Where is the model for the Li ion battery, what voltage is the battery?
 
  • #15
emtae55
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There is no ground for the model. Without ground it will run very slowly due to current sources in the LT317 model.
I worry about current limit to the base of Q1.
Where is the model for the Li ion battery, what voltage is the battery?
Well, because i can change the battery to 18650(standard), so you might not to be worry about that.
 
  • #16
Baluncore
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Well, because i can change the battery to 18650(standard), so you might not to be worry about that.
I made three points, worry about which?

What if the battery becomes short circuit? then regulator produces 1.2 volts and current is not limited, so the base of Q1 is destroyed.

What range of voltages can the battery be?
 
  • #17
emtae55
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I made three points, worry about which?

What if the battery becomes short circuit? then regulator produces 1.2 volts and current is not limited, so the base of Q1 is destroyed.

What range of voltages can the battery be?
Because it's a 18650, it might be about 3.7V.
Also, the max current of Q1 is 50 nano A.
 
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  • #18
Baluncore
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Also, the max current of Q1 is 50 nano A.
Where do you get that 50 nA value from? Which terminal, under what conditions.
The Q1 collector current during limiting is 1.2V / 470R = 2.55 mA. The base current is then about 25 uA.

But when the battery fails short, (or the terminals are accidentally shorted), the LM317 and battery current will be guaranteed to be more than 1.5A by the LM317 internal limiting, so there will be at least 1.5 volts across the 1R0 current sense resistor, in parallel with the forward biassed base-emitter PN junction of Q1. That is why LM317 data sheets usually recommend a series resistor of about 100R to the base of the Q1 current limiter. That will limit the Q1 base current to about 10 mA which should not destroy the junction.

The LM317 dropout voltage is about 2 volts, the Li cell being charging will be about 3.8V, the voltage drop across the current sense resistor will be about 0.7V, the 1N4001 drop is 0.9V which gives a total of 7.4V, so the charger will need more than the 6 volt supply you have specified.
 
  • #19
berkeman
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[Mentor Note -- Two threads on the same subject merged into one]
 
  • #21
Baluncore
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@emtae55
I see you have now taken your question to the LTspice group.
https://groups.io/g/LTspice/message/123869
That group works with LTspice operation and functionality rather than circuit design advice.

We are not mind readers.
If you want circuit advice you will need to answer the questions asked.
 

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