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The TI-84 Plus CE is a graphing calculator released in Spring 2015 by Texas Instruments. It includes a 2.8 inch color screen, USB port, apps, storage, and a 1200 mAh battery.

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Why my charging light is always on? It kills the battery.

Last night after I unplugged my calculator, I found out the charging light was still on and it couldn't be turned off. The light is on all day today, and it really kills the battery, so by the end of today I have to recharge it . I tried to reset and remove the battery, but these methods didn't help. So I wonder what is wrong with my calc, should I get a new one or should i just get a new battery? Is there anyway i can do to save it? Help S.O.S. Thank you!

update: Thanks for all the help.

I changed to a new battery and updated my OS, but the charging light is still on and it really kills the battery life. Usually the ti-calculator can stand for at least 2 weeks, now I have to charge it every 12 hours. I would really like to know is there another way to fix it? Thanks!

Answered! View the answer I have this problem too

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@amy123

Hi, I think I can help you, but I need a bit of information. First, does the calculator still function perfectly other than the LED not turning off? What color is the LED? Can you transfer data between the calculator and your computer? (if you plug it into your laptop does your computer recognize something was plugged in?) If you install TI Connect CE, can you view your calculator's contents or does TI Connect CE throw an error? Did you try reinstalling the OS? TI-84 Plus CE Recovery Techniques.

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Thank you for your information. Other functions run perfectly except the led, and the color is green. I haven't tried to transfer my data between the calculator and the computer yet. My new battery is arriving today, and I will see how that will work.

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I changed to a new battery, but the charging light is still on.

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Ok, did you try connecting it to your computer yet? If not, try that and if it connects properly, then try reinstalling the OS. TI-84 Plus CE Recovery Techniques.

Please let me know how it turns out!

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Yes, I did, and everything else seemed normal, and I did reinstall the OS. But the light is still on.

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4 Answers

Chosen Solution

EDIT: If you’re someone who’s also having this issue, I would suggest looking at Nick’s answer where he suggests replacing the battery, it’s a much easier possible fix than what this answer is about to describe!

Wow I'm surprised, judging by your answers, this probably is a hardware issue!

(DrDnar and KermMartian helped me with this new answer, the original answer turned out to be not so accurate so I’ve updated this with my new knowledge)

Their best guess is that a surge of electricity fried your BMIC (one of the key components to charging your calculator). That would be the reason why your LED is stuck on.

Your LED however, is not the sole reason why your calculator is draining battery power since that LED barely draws any power at all. It sounds like BMIC is likely the culprit to where all that power is going.

Unfortunately, a BMIC repair is going to be very tricky and will require a donor calculator. You’ll need to be comfortable with soldering surface mount components. Before you go and try replacing it, I’d suggest contacting TI first to see if they can assist you at all or replace your calculator.

Here’s an image of the TI-84 Plus CE PCB. I’ve circled the location of the BMIC (it is in the same place on every hardware revision up to time of posting [Revision pre-A to N]).

Block Image

Let me know if you have any questions!

This is my old answer for posterity:

His best guess is that your power supply sent a surge of electricity that fried your driving transistor (basically it’s the thing that controls the LED). This could happen if you’re not using the original charger that came with the calculator. Unfortunately, to repair this, you’ll need some pretty hefty experience with fixing circuit boards and a good hot-air rework station which can cost upwards of $500. :( (If you have the experience and equipment to replace it, I can try to get some steps on how to do it.)

If you don’t want to go through the hassle of returning your calculator or fix it, you should be able to just sever the LED connections from the circuit board. You’ll still be able to charge the calculator, you just won’t know exactly when it’s fully charged.

Here’s a picture of the PCB. You should be able to de-solder the LED and just pop it right off. If you don’t have any experience with soldering, you could also try taking needle nosed pliers and twisting off the resistors located directly to the right of the LED (they’re marked R36G and R39G).

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As long as you're careful and use a desoldering wick, it shouldn't be hard to remove the LED. That said, it isn't for the faint of heart. You can also (carefully) break it enough to permanently disable it as well.

I'm surprised it wasn't the battery. It's usually a battery fault on these types of devices 9 times out of 10.

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I understand this is a year old but I am facing the same issue. I have experience with circuit boards and the equipment to do so. I'm having trouble locating the driving transistor. I can confirm this issue happened as a result of a surge of electricity through the USB charging port.

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Shahnawaz Haque (could you please add a way to @ you?) I'm seeing if I can get instructions now.

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Shahnawaz Haque I've updated my answer with new information!

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Hi,

I know that its been a while since this was posted but do you know if the normal TI 84 Plus has the BMIC chip?

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Most Helpful Answer

If the battery is more then ~3-4 years old, try replacing the battery. Modern lithium batteries don’t last as long because there are more onboard nannies on the BMS when compared to older ones that let you charge it with a dangerous fault. In most cases, a persistent charging light (or runtime issues) indicates a battery fault. This doesn’t always fix the problem, but it’s cheap to try and is easier then trying to repair the calculator’s PCB. If the issue persists, the board is bad and the battery is completely ruled out.

I don’t know if TI sells the battery directly or you need to use a 3rd party to get one, but the guide to replace it can be found here. If for some reason the battery is no longer available from the provided link, the part number that worked out for me is 3.7L1200SPA. I found what appears to be the OEM battery on Amazon. There is a possibility you will need this battery since TI appears to use 2 different types.

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@nick Hi, I was wondering where you got that information about the persistent charging light indicating a battery fault. Are you carrying that knowledge over from typical computer behavior or have you seen this happen before on a calculator? Thanks!

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@thelastmill It's a common theme I see with batteries in general. Doesn't matter if it's a phone, calculator or computer. We had the AA TI's in my school (TI-84/Plus?) so I've never seen how a rechargeable one fails. I bet it's the same as a computer or phone.

Unless there's something special about these calculators and their BMS and charging hardware that partially invalidates that (which I doubt because these rechargeable TI calculators aren't using different charging hardware then a phone or computer) I think it's a probable battery fault. When this happens, it's usually due to a battery that quit holding a charge.

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Ok cool! Thanks for replying, I've up-voted your answer.

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The only thing that's special about the TI calculators that I can find is they're mandatory by schools because of how TI got their hold on the education market. They don't do anything other calculators can do. The games are a feature that came to be because of how common they are.

They're way too expensive for what they are but the problem is they're mandatory and that's why they do it.

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A bit off-topic, but yeah I definitely agree with @nick . Every student-oriented calculator is overpriced in my opinion. However there are certainly calculators that have better value over others, such as the HP Prime G2. The HP cost less than the TI 84 Plus CE, even after overseas shipping costs and has a processor that's over 21 times as powerful! I wish the US would pass laws, like France did, that would make calculator competition field much more fair and competitive. But for now, we'll just have to either deal with the TI near-monopoly or find a way to convince the majority of students to abandon the US's familiarity with the TI 84 family and instead go for less-familiar calculators such as the Casio or HP brand. One thing I have to give TI credit for, they do make learning to use the TI 84 Plus CE very easy. That's one thing some other calculators out there aren't good at.

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The driving transistor for the charging LED is integrated directly into the BMIC, which is a nice feature. That's why you can't finding a driving transistor. (By contrast, the testing LED on so-equipped calculators does have a driving transistor. Two, in fact, as it's a two-color LED.)

However, you do not need to use a donor calculator; you can just buy the BMIC directly off a site like Digikey. The chip is a TI LM3658 and is marked L155B. A voltage surge could definitely damage the BMIC, so if you've got the skills, replacing it is definitely a worth a try.

Another possibility is that the USB port's boost converter is stuck on, causing the calculator to try to charge itself, which will actually waste a fair bit of power. The boost converter supplies +5 V to the USB port when the calculator is in host mode. If you never need to use something like a TI Rover or CBL, you might be able to identify and disable the offending circuit, either by cutting the output trace, or by cutting the input to the boost circuit. Do note, however, that doing so may also cause trouble with calculator-to-calculator linking; if you do experience trouble with linking, just swap cable ends, as you should only have trouble when a type A plug is inserted.

Additionally, TheLastMillennial, if the LED is on even when no cable is inserted, replacing the battery won't help. The BMIC will not drive the charging LED when no external power is supplied; in fact, it shuts down completely.

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Could be a shorted charge connector

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Is there any way I can fix it? Thanks

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have a look inside and see if something is stuck or a pin is bent

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Amy will be eternally grateful.
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