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Electronics => Electronics => Topic started by: vin.lwh on March 15, 2009, 11:00:12 AM

Title: Will the energizer rechargeable batteries overcharge?
Post by: vin.lwh on March 15, 2009, 11:00:12 AM

Just bought the AA NimH 2500mAh rechargeable batteries. I recharge them fully.
If I use them for only 10 minutes and then recharge them for another 8 hours, will they be overcharged?

Title: Re: Will the energizer rechargeable batteries overcharge?
Post by: want2learn on March 15, 2009, 01:01:33 PM

Your charger should prevent them from being overcharged, unless it's just a timer based charger, then i'd imagine that you'll damage the batteries. Someone with more knowledge than me is bound to post soon enough

Title: Re: Will the energizer rechargeable batteries overcharge?
Post by: Soeren on March 15, 2009, 01:06:15 PM

Hi,

That depends entirely of your chargers End-of-charge termination method.
What charger do you have?
A weblink and/or a datasheet on the charger will help in deciding that.

Title: Re: Will the energizer rechargeable batteries overcharge?
Post by: SmAsH on March 15, 2009, 01:12:20 PM

why do you not just drain them? hook the up to a joule theif or something, i have heard that not fully discharging can damage battery packs but you could also take them out every 5-10 mins and test them?

Title: Re: Will the energizer rechargeable batteries overcharge?
Post by: Soeren on March 15, 2009, 01:31:57 PM

Hi,

Quote from: SmAsH on March 15, 2009, 01:12:20 PM

why do you not just drain them? hook the up to a joule theif or something, i have heard that not fully discharging can damage battery packs but you could also take them out every 5-10 mins and test them?

Draining the battery after 10 minutes of use is quite wastefull (and a bit insane), since you'll use a most of the available total capacity (over the entire lifetime) on discharging. A bit like filling your gas tank, driving a short trip and then emptying the rest of the gas on the ground.

If the battery needs draining (eg. to balance the cells) on a rare occasion, discharge each cell separately and just connect a power resistor of 1 Ohm/2W over each cell for at least 8 hours (a full 24h if possible).

Title: Re: Will the energizer rechargeable batteries overcharge?
Post by: SmAsH on March 15, 2009, 01:36:12 PM

wait i forgot to ask the simple question, why? why would you want to recharge them after only 10mins use?

Title: Re: Will the energizer rechargeable batteries overcharge?
Post by: vin.lwh on March 16, 2009, 06:17:37 AM

I don't have time to drain them, because I have to present my project to my supervisor in the next 2 days.
I think I've already used them for approximately half an hour, to date.
I want the batteries to be fully charged, because I want to be certain that the batteries will have enough charge during my whole presentation.

To charge them completely full, I have to charge them for 8.5 hours.
Btw, I'm using 8 of them (batteries). And the charger only have 4 'ports'. So all in all, to complete charging all 8 of them it'll take me 8.5 hours times 2. That'll be 17 hours.

This is the charger I'm using.
http://www.energizer.com/SiteCollectionDocuments/pdf/rechargeable/CHCC.pdf (http://www.energizer.com/SiteCollectionDocuments/pdf/rechargeable/CHCC.pdf)

So with this charger, will it overcharge the batteries when I charge them for another 8.5 hours if I only used them for half an hour after fully charged?

Thanks soo much, guys, for your time. Appreciate it!  :)

Title: Re: Will the energizer rechargeable batteries overcharge?
Post by: vin.lwh on March 16, 2009, 06:19:55 AM

Btw, its says that it is designed with trickle charge. What does "trickle" mean?

Title: Re: Will the energizer rechargeable batteries overcharge?
Post by: SmAsH on March 16, 2009, 02:30:25 PM

a tricle charge is putting very low current into the battery at a time. ie. 50ma over 10-15hrs

Title: Re: Will the energizer rechargeable batteries overcharge?
Post by: superchiku on March 16, 2009, 02:33:07 PM

wat was the total cost of the batteries and the charger

Title: Re: Will the energizer rechargeable batteries overcharge?
Post by: ArcMan on March 16, 2009, 02:34:58 PM

You don't have to worry about "overcharging" your NiMH batteries using that charger.  NiMH batteries don't have "memory" like some older design NiCd batteries.  It's no problem to discharge them a little and then recharge them.  Go crazy.  They'll recharge about 1,000 times in their life.

Title: Re: Will the energizer rechargeable batteries overcharge?
Post by: vin.lwh on March 17, 2009, 06:25:04 AM

Awesome!!
Thanks! I'll recharge them right away.

Title: Re: Will the energizer rechargeable batteries overcharge?
Post by: Soeren on March 17, 2009, 04:10:45 PM

Hi,

Unfortunately, I never got to pressing the "post" button yesterday and when I did now, it all disappeared  :(

Here's the short version:
Your charger should not be used for that purpose. It will have a too high voltage for it. For a single time, they should survive without significant loss however. The only kind of chargers you should try recharging semi-discharged cells with, is quick charging smart-chargers with dU/dT charge termination (and slow, tapered-charge chargers with a rigid voltage control).

Memory Effect has never been a problem in consumer grade nickel based battery cells and charge/discharge methods.
What you will be dealing with if you do it regularly is voltage depression and to some degree venting of the cells.
1000 recharges is a myth based on cells 100% controllable and correct environment and charge/discharge characteristics.

The only battery technology that can be safely topped up is Lithium.