2 weeks or so ago my cat knocked a cup full of water over onto my calculator. I stupidly didn't take out the batteries and just let it air dry for a day and it seemed fine for a week, until the low battery icon popped up. This was weird because I had just replaced the batteries last month, but I figured they got water damaged so I replaced them with new ones from the store. Another week later the battery icon popped up again...so I took the calculator apart and saw that the coils had some rust as well as some of the parts on the circuit board above and to the left of where the batteries go. I cleaned everything with alcohol and put it back together, as well as switched to yet another set of new batteries and it worked fine...for a day. Today, the battery icon popped up again! Is this something that can be fixed or am I going to need to get a new calculator?
First, that is an unfortunate thing to happen to your calculator.
Second, (addressing the problem) I had a friend that dropped their calculator in a creek (on accident and it was a TI-83 Plus) and it has had a very similar problem. He, like you, has had to buy new batteries almost every month or so because his calculator keeps saying that the batteries are dead. I actually tested the batteries myself at one point (when the calculator said they were dead) and got a reading of about 1.08 Volts for each battery (they were triple A's). I wish I could say why this happens, but I honestly don't know. (maybe someone else knows more?) For now though, I would still use the same calculator and maybe just take out the batteries when you're not using it (that's what my friend did).
You could buy rechargeable batteries so that you wouldn't need to keep buying new ones. If the calculator still works, you shouldn't need to buy a new calculator Razz
The TI-89 declares batteries to be empty when the voltage drops to 4V. (combined voltage total)
If you have a multimeter (which you should - they're really useful), measure the current drawn by the device during various times (off, idle, running assembly program). The draw latter two will depend on what you're doing, but the off state should read about 90 microamps.
If it draws more than that (which I suspect it does - probably around 40-50 milliamps) there might be a short somewhere from the water. although, that's what the alcohol's for
If it really bothers you, you can modify your calc to use double A batteries. (There's a page on ticalc.org about that.)

Also, if you're not going to mod the calc, do not use rechargeable batteries. Unless, that is, you can find 1.5V AAA rechargeables. They are usually 1.2V, so they are declared empty faster.
Michael0x18 wrote:
Also, if you're not going to mod the calc, do not use rechargeable batteries. Unless, that is, you can find 1.5V AAA rechargeables. They are usually 1.2V, so they are declared empty faster.

I use rechargeable batteries all the time and have no issue with it. There isn't a problem with running out a little bit sooner since you're not wasting any more money, and if you buy 8 batteries and always have 4 charged at once, then you can just swap them back and forth.
I've never had issues with rechargeables, either. Alkaline batteries are only rated ā€œ1.5vā€ because they start at 1.5 before (relatively quickly) dropping steadily toward 1.2v or lower anyway. NiCd and NiMH, on the other hand, will retain that 1.2 to 1.3v more steadily for their entire discharge. One potential problem, though, is that they have a much sharper voltage drop-off when they do die. Don't expect the low-battery indicator to give you much time to recharge before the whole thing dies completely.
My rechargeables last about 2 days. My alkaline batteries last about four. (My calc sees heavy usage...)
I think that's likely more about capacity than voltage. It's possible alkalines might have a bit of a runtime advantage in low-drain applications like calculators, but it really depends on the type of rechargeable cells being used. NiCd/NiMH definitely perform much longer and more reliably in high-current applications than same-size alkalines, though, but I digress.

But IMO, the fact that rechargeables can be reused for years usually more than makes up for a slightly reduced single-charge runtime, especially if you're suffering an already low runtime to begin with.

Anyway, as it was suggested earlier, I guess one could try to do some probing inside and see if there's any obvious remaining corrosion or moisture that could be cleaned up which might reduce shorting. But best not get hopes up too high. If any components or boards were damaged by shorts at the moment it got wet with power connected, it's probably a write-off. Also, any remaining moisture and its contaminants left behind might cause continued corrosion damage over time, and the longer that sits, the less likely it will be viably repairable.
Register to Join the Conversation
Have your own thoughts to add to this or any other topic? Want to ask a question, offer a suggestion, share your own programs and projects, upload a file to the file archives, get help with calculator and computer programming, or simply chat with like-minded coders and tech and calculator enthusiasts via the site-wide AJAX SAX widget? Registration for a free Cemetech account only takes a minute.

» Go to Registration page
Page 1 of 1
» All times are UTC - 5 Hours
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum