I am involved in the development of a portable medical equipment with a 11,1V-6,6Ah Li-Ion battery pack (9 cells 18650 3,7 V 2200 mAh , 3 in parallel x 3 series). The equipment is a medium power unit (with this battery will have 4 hours of autonomy).
The equipment will operate in road and air ambulances, and on the field emergencies; it will be supplied/charged from a 18V DC-DC adapter (from the 12-24V battery car), and will be subjected to low and high temperatures (the worst condition could be in vehicles parked in the sun with the equipment connected).
Our battery manufacturer/supplier offers a pack with an integrated PCB with current and voltage protection (Vmax=4,2V, Vmin=2,8V, Imax discharge=3A, Imax charge=3,3A).
We don’t have experience with Li-Ion batteries.
At the beginning, I considered that BQ24610 could be a good selection, but after studying basic concepts from Texas, the tutorial ‘battery charging.mp4’, and reading many ‘verified answers’ from this E2E community, I think that we need an expertise advice.
I’d be grateful to receive help with regards to some fundamental doubts:
1. Which charging principle should be recommended for our application, switch mode or linear? (If switch mode should be the best, as EMC test in medical devices are really restrictive, I don’t know if high frequency operation in the battery charging system is appropriated, and in this case which is the recommended filtering procedure/components).
2. As this voltage (11,1V) and power (6,6A) is a very common Li-Ion battery solution (is the standard in laptops), maybe there is access to particular technical notes and schematics for charge management, Is it so?, Where?.
3. With the safety PCB integrated in the battery pack, should it be recommended to add a fuel gauge?, which?. Maybe the cells have its fuel gauges, I don’t know, Should it be important to know?.
4. The equipment must be able to be charged with the unit Off (or in CPU sleep mode), I think this rules out a ‘host controlled’ battery charger, Is it true?.
5. The battery pack can include a NTC or PTC that can be directly controlled form the internal PCB (battery with 2 wires) or controlled from outside (battery with 3 or 4 wires). which type should be recommendable?; there is a specific PTC or NTC recommended by TI?.
6. As ambient temperature is a problem in our device, it is able to add ambient temperature control to the charger? (as the charge can be started in Off/sleep mode, we cannot use the temperature control from the CPU).
