1 Cell LFP Battery Pack Protection

Question

I am starting a project that requires a single 3.2V LiFePO4 18650 cell to be in a housing with exposed contacts, suitable for easy swapping in and out of an unpowered device. The device will only be battery-powered, the battery packs will be charged elsewhere, so this is not a hot-swap scenario. The plan is to use spring contacts to connect the battery to the device.

My concerns/thoughts I'm hoping for feedback on are...

1. The proximity of the exposed contacts on the battery housing are prone to short-circuit. I am considering adding some additional form of short-circuit protection instead of relying 100% on the manufacturer's protection module in the cell. I'm thinking of adding at least a resettable fuse. Perhaps a protection IC of some kind like the LM66100, but I am not sure what is out there. Is this a good idea? If so, what are some good approaches for this?

2. How to protect the device against voltage spikes or other power anomalies resulting from insertion/removal involving spring contacts. I am considering an inrush-current limiter for this (image below), the cap C1 should take time to charge and smooth out any sudden changes. Perhaps there are ICs for this like the TPS22908? Or a simpler approach? (Please disregard the fuse and the "14V" in this example graphic from analog.com, the battery pack will be 3.2V as mentioned)

   
   _{Image source: Analog Devices - Advantages of IC-Based Hot-Swap Circuit Protection}

3. Since there is no thermistor on the cell itself, and the cell's PCM works with low-side cut-off, I found this reference design for how to safely incorporate a temperature sensor in the pack.

4. Other considerations not mentioned above?

Answer 1

The proximity of the exposed contacts on the battery housing are prone to short-circuit. I am considering adding some additional form of short-circuit protection

Whatever form that short circuit protection might take, it will be placed outside the cell holder. The current in a short circuit across the terminals of the cell holder will not flow through this short circuit protection device. Therefore, it will be unable to offer any protection.

The only ways to protect against a short circuit across the terminals of the cell holder are a) inside the cell; b) mechanical insulation around the cell holder.

How to protect the device against voltage spikes or other power anomalies resulting from insertion/removal involving spring contacts.

I disagree with your assumption. I see nothing that would generate voltage spikes upon insertion or removal of a cell from a cell holder. I believe this is a solution in search of a problem. (There will be pulses of current, not voltage, as the cell is inserted or removed. The load sets the magnitude of these pulses, not the cell holder.)