Reverse Current Protection for Li-SoCl2 Batteries

[rego21]

Hi,

Im currently designing a device that will be powered only by Li-SoCl2 batteries. These batteries does not accept reverse current and need to be protected for any possible reverse current. Initially I was thinking of using a Schottky diode, but it has a big voltage drop when the current starts to rise. So I decided to search for ideal diode ICs. However I have some questions:


1. The IC I choose needs to have a back to back MOSFET ? If i use a singe one does the internal body diode will conduct current from Vout back to Vin ? For this case Im looking at APD198 (https://www.analog.com/media/en/technical-documentation/data-sheets/adp198.pdf)

2. If the IC I pick has back to back MOSFET, do I need to pay attention to any leakage current that can possible flow to Vin ? For this I was looking at TPS25947. (https://www.ti.com/lit/ds/symlink/tps25947.pdf)

3. Or Im overthinking and I would only need reverse current protection if I have another source of power in my circuit ?

Overall there seems to be quite some products already available for this, but Im a little bit lost of what to pick for these kind of batteries since they are very dangerous. For context what I will be using is Saft LSH 20.

Thank you!

[Marco]

How exactly would this reverse current event occur? When the user forces one of the batteries in the wrong way?

[rego21]

Honestly, in this case it would be just to play safe since these batteries can just handle a few micro amps in and are very dangerous. But at the same time since its the only source o power probably I don`t need any protection for reverse current... For example I will be using a buck-boost converter, could it somehow create a significant reverse current (again just a few micro amps) that would go into the batteries ? Im a little bit lost on this topic, since I never used these batteries...

[MaTkEOxjC]

Maybe reconsider which requirements you actually have. Also in respect what the battery cells actually need.
Is there another power source in the circuit that can cause a reverse potential at the batteries? Maybe when they are inserted in the wrong orientation.
Functioning voltage range (you didn't specify that, can be very relevant)
Rev. pol. protection (what is the maximum permitted reverse current? I've seen some batteries with one specified.
Do you also need some overcurrent protection? (if you don't it makes component selection a bit easier)
Permitted IQ when everything is off.
Do you also need to protect the circuit from reverse inserted batteries?

1. The ADP198 is specified with reverse current blocking (maybe check out the detailed specification, like leakage...). The drawing in the datasheet might only be indicative, not representing the actual implementation.
2. Regarding TPS25947xx; you also want to check out the minimum voltage, 2.7V in this case.
3. Maybe you're overcomplicating it.
I'd go for a simple integrated solution and chose something with a nice datasheet. I assume this is just a hobbyist project and main focus is on getting it to work, so no point cost optimizing here to the last %.

Maybe also look at; LM66100, MAX40200, MAX40203


Edit:

Honestly, in this case it would be just to play safe since these batteries can just handle a few micro amps in and are very dangerous. But at the same time since its the only source o power probably I don`t need any protection for reverse current... For example I will be using a buck-boost converter, could it somehow create a significant reverse current (again just a few micro amps) that would go into the batteries ? Im a little bit lost on this topic, since I never used these batteries...

If the batteries are the only source I'd be more worried about them being inserted wrong and damaging the circuit.
Can't really see how a relevant reverse current could occur in your specified case.

[rego21]

Hi,

Thanks for the reply!
Regarding putting the batteries in the wrong position, this is currently not a concern since the connection from the batteries to the device will be done with a small cable that can only be inserted in one position. The device will work from 3.0 to 3.7 (it could probably go to 2.7 but at this point the batteries are completely drained). For the over current protections I will probably use a fuse. I have one question, if I have a super cap after the battery could it revers current into the battery in any scenario ?
Thanks again, maybe Im overcomplicating once again