How do Rechargeable batteries work? (specifically NiMH batteries)

I am watching my new portable TV right now (there’s a film with Sean Connery and Dustin Hoffman in it on) running on the rechargeables from my camera.

I started thinking - I will probably be recharging these batteries every single day (maybe several times a day) if I am to use this TV much (It is intended for watching in bed - TV helps me fall asleep). This is a huge increase in frequency from their previous charge rate - rougly one charge every 2 weeks.

(Wondering why I shared that. Maybe because I wanted this post to be more than just ‘how do they work’.)

Anyway, I then wondered - how [exactly, pedantically] do they work?

What is happening to them chemically/physically/electrically while they are being charged?
What is happening to them chemically/physically/electrically while they are being used?

Will they be able to handle being recharged every day? (the packaging says - good for 1000 charges. but it doesn’t say wheither they can cope with being recharged and used daily)

I could probably find all this out by googling (or altavistaing as I prefer it). But I thought a SDMB post would be better all round. As I will get human answers, rather than pre-compiled general purpose answers, and … heck GQ would be nothing if everyone went to google with their questions rather than the SDMB.

(There goes maintaining my 1111 post count - level with Wikkit)

Sorry, all I can give you is a link. It’s a better explanation than I can give, anyway.

As for recharging every night, that’s not a particularly demanding use. I’ve never heard fo that being a problem. Batteries can be damaged if drained completely, but a TV will probably shut down before that happens. Over-charging can also cause damage, but if you have a good quality charger it shouldn’t be a problem.

You do realize that an AC adapter will be cheaper in the long run, right?

I do, (DC actually).

I am just so disorganized that It will be a long time or never until I get one.

I tried a suitable (same voltage, same size connector) dc adaptor in the TV - nothing happened. So maybe I need to get the exact adaptor quoted in the documentation for the TV - which will make getting an adaptor harder- and therefore more unlikely.

My battery charger is as good as they get (quickest time, and stops charging when the batteries are charged)

And my mini TV is a brand new £80 casio thing. Is it likely to switch off before the the batteires are drained completely?

Aren’t you supposed to do that? The way I understand it, the more drained a battery is and the end of each use, the longer is will last in the long run, and each charge will last longer.

Well, sort of. It’s safe to completely discharge an individual cell. But if the cells are connected in series and you try to discharge this together, some cells will discharge sooner than others. Those will get reverse-charged by the remaining cells, and this reverse charging causes damage. So you can connect resistors to individual AA cells and discharge them independently, but you can’t put 4 cells in a flashlight and let it run down unattended.

The benefits of deep discharge is grossly exaggerated anyway. An occasional discharge can help rejuvinate a cell, but if you do it each time it will just shorten the life of the battery. It’s better to just top it off using a “smart” charger that monitors the voltage and shut off when the battery is fully charged. Good chargers also have a temperature sensor and timer to make sure you don’t over-charge.

Some companies do tell you to use up the battery before recharging. That’s because those products come with el-cheapo chargers that use a timer for shutoff. Since the charger cannot detect full charge, the only way to prevent over-charging is to start with a discharged battery. My old bicycle lamp (a high-end NiteRider which cost over $100) was like that, and I hated it - a typical example of using the owner’s manual to fix design flaws. (Though I understand this is no longer the case with NiteRider)