Hibernation and Deep Discharge

[hastern]

I was helping a friend update his classroom set to OS 3.9, and we discovered almost all his handhelds were in a "critically low" battery state. We checked his hibernation settings, and found that all of them were set to "Never" hibernate. I thought my classroom sets had come set to hibernate after four days, but wasn't sure, so I suggested we reset them to the factory default. Turns out that no hibernation is the factory default.

I may be getting my memories confused, but I seem to recall to tech support document from TI that advised against allowing lithium ion batteries (as CX units are equipped with) to go into deep discharge, because it would shorten the useful life of the battery.

How are we going to store handhelds, that don't hibernate, over the summer and NOT have them go into deep discharge? Is there a reason this setting defaults to a value which seems to be bad for battery longevity? Am I misunderstanding battery chemistry? What is the optimal hibernation setting (in a school district that has 3-day weekends about once a month)?

[Sean Bird]

The official word on storing and cleaning is found at
https://epsstore.ti.com/OA_HTML/csksxvm.jsp?nSetNumber=19191

It has a link to 'what about rechargeable' - https://epsstore.ti.com/OA_HTML/csksxvm.jsp?nSetNumber=33711

I was thinking it would say disconnect the lithium battery...
"

2.       Usage and Charging:

·         As lithium-ion batteries age, they lose capacity.  When properly maintained and under normal usage, batteries are expected to last at least 3 years.

·         Charge battery often and avoid waiting until full discharge.

·         Do not leave the handheld connected to charging devices for periods longer than 3 days.

·         Use only rechargeable lithium-ion batteries approved for the handheld.

·         Use the TI-Nspire handheld regularly and fully charge the handheld at least once per month.

•     Use only charging device(s) that you received with the handheld, or that you purchased from TI or a TI authorized dealer.

 

3.       Storage tips for TI-Nspire handhelds with lithium-ion batteries that will not be used for 3 or more months:

·         The best temperature for proper care and storage of lithium-ion batteries is between 0-25° C/32-~77°F. 

·         Do not allow the lithium-ion battery to be stored in a handheld for longer than 6 months without charging the handheld, or else deterioration to the lithium-ion cell may occur and reduce both battery life and capacity.

·         Prior to storing TI-Nspire handhelds the units should be fully charged.

·         It is ideal to store batteries disconnected or removed from the handheld before storage.  If handhelds are stored with the batteries engaged, they will discharge quicker and can become deeply discharged.

 

4.       Update Handheld Operating System as new updates become available:

·         Update the TI-Nspire handheld OS as new releases become available.  OS updates may contain new programs to optimize battery life. 

 

5.       For Instructions on how to replace a TI Rechargeable Battery in a TI-Nspire handheld please click here."

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Sean Bird
AP Calculus & Physics,
NHS Adviser & Rocket Team Supervisor
Math & Science Technology Coordinator
Covenant Christian High School
7525 West 21st Street
Indianapolis, IN 46214
Phone: 317/390.0202 x104 Fax: 317/390.6823
Website: http://covenantchristian.org/bird
work Email: sean...@covenantchristian.org
personal Email: covena...@gmail.com
Psalm 111:2 “Great are the works of the LORD, studied by all who delight in them.”

[hastern]

Most of that is in line with my prior understanding.

I didn't know the CX battery was a "user serviceable" item. I'm pretty sure that last year I was told I could NOT replace it myself.

Didn't know they shouldn't be in the charging bay for more than a few days (I often leave them in over vacations of a week and longer).

They don't address hibernation.

The recommendation is to remove the battery for long-term storage. Seems like a lot of work for multiple class sets of CX.

I'm curious what other people do. I give mine a full charge on the last days in June, and hope for the best come September.