I use rechargeable batteries for my wireless system, but after a gig the battery still will remains with some juice.

I'd like to find an easy way to fully discharge the battery before going to charge it up again, to prolong it's life...

Is there some easy way to do that? With me when touring I only have the wireless system that could be used to "waste"/discharge the battery but the wireless system must stay packed with all other guitar sttuf, in order to have it ready to the next gig.

Thanks
Kleber AG

way to open a can of worms! There's so much discussion about this that's it's hard to see the forest for the trees.

My personal opinion is that NiCd batterys don't suffer from memory effect, provided you slow charge them properly and take them off charge as soon as they are ready. See this article, and many others can be found via google.

Note carefully the first sentence of section 2.

Also, NiCd are best charged JUST before you use them as they begin to loose charge as soon as they are disconnected from the charger. You should only need to "deep discharge" them once in a while.

Are these batterys NiCd?

QuoteAre these batterys NiCd?

Yep, they are.

Quoteprovided you slow charge them properly and take them off charge as soon as they are ready

When is ready (charged)
And 15hours at 10mA is it slow charge?

QuoteAlso, NiCd are best charged JUST before you use them as they begin to loose charge as soon as they are disconnected from the charger

Yes I've noticed I must charge them just before using'em...
Nice article, thanks!

But, can I build some "waste power" circuit to deep discharge them someday??
Kleber AG

QuoteAnd 15hours at 10mA is it slow charge?

yup.

Your best bet is to invest in a decent battery charger/discharger. I have here a Christie CASP2000 that is fully programmable and will do any battery at any voltage at any charge rate... just about.

A good unit will detect a fully charged battery using delta peak cutoff techniques (or perhaps even more sophisticated)

It will also provide you with a good way of discharging the battery.

The Christie unit I have here will do a "recondition" cycle. discharge then charge, three times over. This is sometimes useful for reviving dead NiCds, but you have to be lucky.

Buying a decent charger/discharger is worth it, building one would prove difficult and expensive.

Do they have Ni-MH versions of the 9V? The AA ones are terrific.

yup, they sure do! about $10 a peice!

Kinda low on the Ah rating though

QuoteYour best bet is to invest in a decent battery charger/discharger

Ouchhh... I've just spent around 25 bucks on a charger I tought "hey looks like a good one, I must have it" but now that I see your description the one I just bought is pretty poor, just simple generic charger, and yes I had never ever seen one like the one you described... :roll:
Thanks anyway!

......................................Kleber AG

NiMh
 The Metal Hydride ones are the ones I like to use, I had some NiCd's but they didn't work as good or last as long, I've been using one of those Hi Cap ones for over a year, all the time.
 I used a motor from a VCR, hook that up and it discharges it in less than about 10 min. and you can tell when it's done, I do it while I'm building or tweaking.
 You could experiment with resistor values across the terminals, light bulbs etc. Measure the current draw and do the math, or watch the meter volts change, and figure the time out.  You have to watch the max draw, I don't think you're supposed to get near a direct short, I know they get very hot and expand when a coin hits the terminals....lol...[what's that burning sensation in my pocket?  ...dohh]
 I like the NiMh, but got to someday try carbon battery mojo on the FF and TB.

idealy you want to discharge it at the same rate as the circuit it's used in would discharge it. Also, you want to keep it above the lower threshold for cell voltage, otherwise you are doing more harm than good.

This is why I recommended a decent charger. You can set the minimum cell voltage and discharge will stop once it's reached that level.

My traditional way of discharging a 9v NiCad is to install it in a cheap transistor radio, turn the radio on, and stick the radio between two pillows or somewhere where I won't have to listen to it.  Most such radios will contune to draw current from the battery until it's down to about 2v or less, which provides lots of headroom for recharging.  Works like a charm for me.

QuoteAlso, you want to keep it above the lower threshold for cell voltage, otherwise you are doing more harm than good.

I agree with this, especially with series-connected multi-cell batteries.  If you have a weak cell it's possible for that cell to go to zero volts before the others. When dischanging that cell starts to reverse polarize which can stuff it.

You need lithium batteries. Sony makes these though there pricey$$$ No memory effect there.

QuoteNo memory effect there

there IS no memory in NiCd either... it's just that they're often poorly maintained.

Lithium batterys might have good capacity, but they age quickly and basically drop off the twig unannounced one day leaving you high and dry, without even so much as a half working battery.