Signs of a bad NP-200 battery?

What is the lifespan of the Minolta NP-200 batteries? I've had a couple going on 3 years now, and I'm just hoping I need new batteries and that it's not a camera issue. On my DiMage Xt, both batteries appear to not be holding a charge. The charger indicates they're fully charged, but once in the camera and on for a few minutes I get a low battery warning and the camera turns itself off.

So... do I just need a need a new battery? And if so, are the non-OEM batteries okay to use?
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Ron
Torrance, CA
Galleries: http://www.pbase.com/rambler358

You can try to give them a "refresh cycle" to get the lazynes out of them,if there is any.

All rechargeble batteries can get "lazy" although the problem is mostly associated with Nicad's.

Because most electronics shut off before the battery is completly emty the remaining charge becomes over time larger and larger and eats away the capacity.

A refresh cycle means you manualy fully discharge the battery and recharge it for 2 or 3 times.
To fully discharge it you can use a 12 volt lightbulb.

You have to fiddle a bit with sticky tape to get two wires connected to the battery but it can be worth it, i recently rescued two sets of AA from the bin by giving them this treatment.

I didn't think Lithium-Ion batteries had this problem. Maybe my best bet is just to order a couple of NP-200s (they're cheap enough) and try them out?
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Ron
Torrance, CA
Galleries: http://www.pbase.com/rambler358

forgot: non KOMI batteries can be of the same quality but there is a lot off rubish, especialy on ebay.Dont buy them on ebay.
Go to your local elektronics shop and buy a respectable brand.

Varta is a very respectable brand with good quality replacement batteries: http://www.en.varta-consumer.com/content.php?path=/1127920379.html&&domain=www.en.varta-consumer.com

The standard Minolta NP-200 is a 3.7v 750mAh battery. I checked out the Varta site you mentioned and their NP-200 replacement is a 3.6v and 650mAh battery. I've used SterlingTek before, so I might give them a shot.

I was just mainly curious if the problems were indeed due to the batteries being old? I bought the DiMage Xt camera back around Aug 2003, and the standard NP-200 has lasted until now - I'm thinking (hoping) that after 3 years, the problem should likely be fixed with a new battery.
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Ron
Torrance, CA
Galleries: http://www.pbase.com/rambler358

This is typical for aging li-ions as well as poorly made ebay ones. I bought a spare off of ebay and after 1 year it exhibited this behavior. I can tell you why it happens:

Each battery has 2 li-ion cells. each cell is individually monitored by the battery circuit, but they are both charged in series.

The monitoring circuit shuts the battery down when it senses either of the cells has dropped to a preset discharge level, and likewise turns of charging when either cell reaches a preset charge voltage.

Over time, one cell becomes the 'weak link' and discharges faster, not allowing the other to fully discharge before the circuit is tripped. Then, during charging, the other cell reaches its charged state before this cell is charged, prematurely stopping charging.

This cycle continues until you're left with one cell discharged and the other almost always charged. It can be fixed by opening the pack and manually charging the dead cell or manually discharging the full cell, then charging them bot together.

Unfortunately, this is the common failure mode of most grouped li-ion packs - the designers should monitor AND charge the cells individually, but don't. Too bad for us consumers.

Thanks for that very informative explanation. And it makes me feel better that the problem is most assuredly with the batteries.

I'll be ordering a couple replacements online as they're inexpensive enough, and that I'm not comfortable with trying to recharge individual cells and the like.

Thanks again.
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Ron
Torrance, CA
Galleries: http://www.pbase.com/rambler358

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AussieToo

drlava: This could be helpful advice for me in my current problem (see my thread under Battery Mystery). Is it necessary to open the battery pack to discharge both cells or can I just connect a lamp to the two terminals?

Yep you have to open the pack. Not too hard if you're an electronics surgeon - use a dremel to cut around the seam and listen for when you cut the plastic case down to hair thin - about 2mm through. Too far and you cut into sensitive circuit board (on the top) and batteries (on the sides). Then use a flat blade screwdriver to pop the case open.