Battery management for Li-Ion

[keytapper]

I'm not that familiar with battery charger/discharger, but a friend of mine asked some idea, which I'm running short of.
So is there any of you with a basic concept, which I may get a starting point?

Basically I suppose to use a MOSFET to control the amount of the current that will flowing through. One PIC should use one comparator for sensing the programmed limits, so it will cut off the flow right to that limit. There could be necessary an amplifier for sensing the amount of the current passing through a low Ohmage resistor.

As the circuit will be opened then one more ADC channel will check how high/low the battery has gotten. Then this way should work at rather fast switching.

If the programming allows, there could be chances to use the device for different type of chemistry.

Am I on the right track?

[trastikata]

I think it would be much simpler and better using a dedicated chip - there are  plenty low-cost solutions on the market to choose from.

[Mapo]

I use the TP4056, you can find it on cards at very low cost, through the value of a resistor you decide the charging current

[rick.curl]

I agree with Trastikata- Use a dedicated chip.  That being said, many of them are in short supply.  I use the MCP73833.  Many of the major distributors carry them but they are mostly out of stock at the moment.

-Rick

[keytapper]

Well you all got me the inspiration off
In a certain manner it's pioneering to dare such with a PIC.

[top204]

A microcontroller is more than capable of managing the charging of a Li-Ion battery. However, they are very dangerous batteries, and one mistake with the controlling of the charging and the battery "will" overheat and catch fire!!!! Or if not charged enough, it will drop below its threshold voltage and never charge again, so the battery is dead and can never be recovered. If charging more than a single Li-Ion battery, things get more complex because it will need a battery balancer circuit, so that one battery does not get overcharged and catch fire.

Li-Ion batteries have a very steep voltage roll off, so only a tiny window of the voltage has to be monitored, unlike a standard Lead-Acid or Alkaline battery that rolls off over time. Li-Ion chargers have to use voltage and current monitoring, with a constant current circuit, and a timer built in so it never charges for too long, and the good chargers also have a simple temperature sensing thermistor to check the heat of the battery itself.

I agree with the others, use a dedicated charger chip that has a good reputation. Because if using a cheap Chinese knock-off, lives could be at danger and you will be responsible, which is not a good thing to happen to either party. :-)