Question about charging circuit

[Tjj226_Angel]

I am looking for confirmation before I do something potentially stupid.

I have a circuit I am working on where I need to charge 3 6000mah lithium iron phosphate batteries in series. I am not finding a cheap charge controller IC that can do 3 cells at 1.5 amps (0.3c for this particular cell).

I watched the video on lithium battery charging and I understand a normal charger will go from charging at constant current and switch to constant voltage at a given voltage (should be 3.6v for lithium phosphate). However, I do not actually want to hit 3.6V. I want to charge from 3.1v to roughly 3.5v to achieve a rough 20%-80% charge cycle.

I do not need the full charge depth since I will have two banks of batteries that will be swapped back and forth and I only want to maximize battery longevity.

My question is, can I simply use a current regulator to charge the batteries? I could use a comparator to turn the current regulator off once a certain voltage has been reached which means the only thing I am truly loosing is temperature protection. But since I am not in any danger of over or under charging the battery, does it even matter? If it does, are these dedicated temperature control ICs that I can use to integrate into the charge circuit?

If it helps any, this circuit will always be connected to power. This is not a portable device. This is just a way of trying to make a very low noise power supply that isn't connected to mains and will live inside of a shielded box.

[Andy Chee]

What cell balancing BMS will you be using?

[Tjj226_Angel]

No true bms.

Undervoltage will be handled by the circuit. And since this will be powering a filament, the chances of a sustained overcurrent situation is almost 0.

Battery balancing will be done passively through some comparators, mosfets, and resistors.

[Andy Chee]

Your circuit will also need to handle cell overvoltage, not just undervoltage.