What is the shelf life of a TB48 battery, I mean a brand new never opened battery?

Depends on DJI's "smart" circuitry

LiPo cells properly stored can last a few years. Personally, I'd use 6-12 months as a reasonable time for DJI's batteries to sit without major degradation.

Hi, good day mixchief. Thank you for raising this concern to us. We do have the calculation to this. If the battery has been charged for 20 times, its life decreases to 90%. (200-20) / 200=90%. Thus, if you have a battery that doesn't have any charge at all the life of the battery has a total of 100%. Should you have any other concerns please don't hesitate to reach us and we are more than happy to help you. Have a safe and happy flying always!

Thank you for your response Gamora, just to be totally sure, for argument sake, if the battery is still in it's original sealed packaging and it was originally purchased 2 years ago, it should still be 100%?

mixchief Posted at 4-16 09:33
Thank you for your response Gamora, just to be totally sure, for argument sake, if the battery is still in it's original sealed packaging and it was originally purchased 2 years ago, it should still be 100%?

I responded to your PM but decided to share these thoughts with everyone else in the forum. Again no disrespect to DJI, but in the effort to make batteries easy to handle for all users they caused other problems  IMO.
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I understand your frustration. What the problem is with DJI batteries is once they are put into storage, the battery management system (intelligent circuit) continues to drain the power. Older versions of the battery FW would not cut off the discharge cycle and cause the battery to drain to zero. With a brand new battery in the box depending on the FW will stay in storage for about 3 months or so. After that it could continue to  discharge. So even new batteries using the intelligent battery management circuit will need to be maintained. I had one brand new battery with a low cell. it sat in the box too long, but I fixed it. see my youtube video  ::::
Rich

One thing I have noticed is that when you press the power button and hold it for five seconds all the LED's light up - this shows an indication of it's remaining capacity. Every TB47 or 48 battery I have owned will show 3 full LED's and one flashing after the 20th recharge cycle - this denotes a capacity drop of 12.5% per 20 charge cycles. On that basis a battery should last for a minimum of 200 flights. With each flight lasting a minimum of 15 minutes this equates to 200 x 15 = 3000 minutes or 50 hours of flight time before the battery may be too depleted to be used efficiently. If you fly the battery say an average of twice a week, every week of the year it will last nearly 2 years. This will be heavily dependent on how you store and maintain the battery, how often you charge and discharge and what % you land on of course but gives a general indication on how long they may last.

When I purchased a brand new Inspire 1 V2.0 in July 2018 it appeared the drone was manufactured in late 2015 (long time on the shelf) - the TB47 was totally dead and needed to be replaced - which my DJI dealer did immediately. These batteries shouldn't be stored without use for 'years' - use it or lose it as they say. I do believe they put a chemical in the battery to help prevent over discharge during hybernation but they clearly can't sit around forever.

I have unopened batteries that are about 1 year old according to the box. Would it be preferable to open them up and start the cycling process? Mini 3 Pro though, but the lithium tech is the same?

I've had my opened batteries for some years. I've gotten charges of upwards of 200 and the capacity is just now dropping drastically. I've been flying an Inspire 1 for quite some years and really only recently had to start restocking my original battery supply. I fly a lot.