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li ion protection circuit

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student4ever

New Member
can i built the protection circuit myself? without using IC. if possible, can i model it first in simulation software? pls anyone that very kind to help me...
 

RadioRon

Well-Known Member
It doesn't make sense to restrict yourself to not using an IC. Here is a link with some explanation.

**broken link removed**
 

student4ever

New Member
"Each parallel string of cells in a lithium-ion pack needs independent voltage monitoring. In addition, each cell in series must be monitored for voltage." so how about the voltage monitoring circuit?
 

Boncuk

New Member
"Each parallel string of cells in a lithium-ion pack needs independent voltage monitoring. In addition, each cell in series must be monitored for voltage." so how about the voltage monitoring circuit?

The MCP73812 (TI) is an Li-Ion charger IC for one cell (max charge voltage 4.2V). It's programmable for individual charging currents and has no indication about the charge state of the connected battery.

This circuit is modified to indicate charging and termination of charging.

Board size is 0.76X0.85inches (all SMD, except for connectors)

Boncuk

P.S. The vias around the IC are thermal holes.
 

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bountyhunter

Well-Known Member
The MCP73812 (TI) is an Li-Ion charger IC for one cell (max charge voltage 4.2V). It's programmable for individual charging currents and has no indication about the charge state of the connected battery.

This circuit is modified to indicate charging and termination of charging.

Board size is 0.76X0.85inches (all SMD, except for connectors)

Boncuk

P.S. The vias around the IC are thermal holes.

But that's not what he asked for in the OP:

li ion protection circuit
A protection circuit is totally different than a charge control IC. The protect circuits monitor current and open a series FET to disconnect the battery in case of a short on the pack. It also has voltage monitoring to open the FET if the cell voltage gets too low or too high.
 

student4ever

New Member
so, actually , i've to use the available protection circuit for individu battery. and to design the control circuit for complete battery packs, is it?
 

bountyhunter

Well-Known Member
so, actually , i've to use the available protection circuit for individu battery. and to design the control circuit for complete battery packs, is it?
No, the protection IC goes inside the battery pack and monitors both cell voltages and the total pack current. Motorola makes the protection IC used by Sony in their battery packs and I think you could look at it and see the functions it does.

There may be some protection ICs designed for each cell, but that would be expnsive. The battery makers would want to buy only one IC for the pack, not one for every cell. The charge control circuitry is usually found in the charger, not the battery pack.
 
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