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Author Topic: why charge a new item far longer after 100% is achieved ?  (Read 2736 times)

Offline neilep

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Dearest chargeologists,

As a sheepie i of course just luff to charge things up and to satiate my never ending desire to charge stuff i have to keep buying new stuff all the time .

Anyway, why does the instructions  say that when i charge something up for the first time that i have to charge it up for a protracted period of time ?...even though I may reach 100% charge I could  still have quite a few hours of charging joy to do...why's that then ?...Why charge a thing up for far longer the first time even though 100% charge is reached very early ?

I just do not know !

hugs and shmishes!


mwah mwah mwah


Neil
Positive and Negative..they're the main two eh ?
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« Last Edit: 16/02/2012 19:48:06 by neilep »


 

Offline CliffordK

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Re: why charge a new item far longer after 100% is achieved ?
« Reply #1 on: 16/02/2012 19:58:21 »
I assume they want the device fully charged before you call technical support to complain the device isn't working.

If one has an unregulated charger, it is quite possible that the battery gets 99% of the charge in the first hour or so, and slowly gets the rest of the charge over the next few hours.  Not that I think the initial charge is that much different from using the device out in the field, throwing the battery on the charger for 10 minutes to get a partial charge, then going back to using the device.

I would assume a regulated charger would be different, especially with batteries such as lithium batteries that are highly susceptible to overcharging.

Assuming the charger has a charge indicator light...  one should simply need to wait until the charge indicator light turns green (which could be overnight, but may in fact be in an hour or so when using a one-hour charger).
 

Offline neilep

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Re: why charge a new item far longer after 100% is achieved ?
« Reply #2 on: 17/02/2012 00:55:32 »
I assume they want the device fully charged before you call technical support to complain the device isn't working.

If one has an unregulated charger, it is quite possible that the battery gets 99% of the charge in the first hour or so, and slowly gets the rest of the charge over the next few hours.  Not that I think the initial charge is that much different from using the device out in the field, throwing the battery on the charger for 10 minutes to get a partial charge, then going back to using the device.

I would assume a regulated charger would be different, especially with batteries such as lithium batteries that are highly susceptible to overcharging.

Assuming the charger has a charge indicator light...  one should simply need to wait until the charge indicator light turns green (which could be overnight, but may in fact be in an hour or so when using a one-hour charger).

Thanks Clifford for your kind response. Comments read and understood !   Such gravitas in your expertise !



 

Offline RD

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Re: why charge a new item far longer after 100% is achieved ?
« Reply #3 on: 17/02/2012 01:23:22 »
with a lithium-ion battery the prolonged first charge is to cause a permanent chemical change in the battery ...

Quote
The vast majority of commercial lithium-ion cells have graphite as the negative active material, as depicted in Figure 1.
Figure 1 also shows a layer on the surface of the negative denoted ‘SEI’ for Solid-Electrolyte Interface. This is actually the
significant enabling feature of lithium-ion technology, since the graphite electrode potential is so low (so negative) that the
intercalated lithium ions would be expected to react immediately with the solvent of the electrolyte. What happens, however, is that on the first charge a permanent passivation layer, the SEI, is formed, which then protects the lithium ions in the negative. The SEI is permeable to lithium ions but not to the electrolyte and its stability is an important requirement for long operating life.
http://www.battcon.com/PapersFinal2008/McDowallPaper2008PROOF_9.pdf
« Last Edit: 17/02/2012 01:25:04 by RD »
 

Offline CliffordK

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Re: why charge a new item far longer after 100% is achieved ?
« Reply #4 on: 17/02/2012 11:46:29 »
Thanks RD. 
Excellent article.

However, the question remains that with charge controllers that have overcharge protection (required for Lithium, and many other battery types), then once the overcharge protection kicks in, there would be no reason to charge it further. 

So, if your charge controller has a red/green charge indicator LED...  the device should be ready to use once it kicks over from red to green, no matter whether it is the first cycle or not.

The only reason to not to use it immediately would be if there was an additional requirement such as cooling down.

If there is no charge status indicator, then perhaps one can go by time.  But, if one has a 1 hour charger, then I would still question the need to leave it on for 8 hours.
 

Offline SeanB

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Re: why charge a new item far longer after 100% is achieved ?
« Reply #5 on: 17/02/2012 19:42:00 »
Normally with LiIon cells they come with a slight charge, and the prolonged charge is there to ensure that the cell will get to the defined full charge voltage, as the cell initially will go from say flat ( low voltage cutout level) to say 50% in say 15 minutes, but then will take 30 minutes to get to 75%, and after an hour will be at say 80%. The long charge allows the controller to calibrate itself  so that is is able to give a more accurate charge level for that particular cell, so it needs to have the cell accept charge until it is at the right level, even if the last portion happens slowly.

With NiCd and NiMH cells they should be charged either at the correct C10 rate, or if a fast charger is used then only for the recommended time. Charging at the C10 rate is tolerable for 24 hours, but normally the cells should only be charged for 14 hours. Long periods of charging will kill the cells in short order ( they will literally go short circuit or boil off all the electrolyte) so should be avoided. A fast charger needs proper charge termination, and most do not really do so, charging the cells until they heat up rapidly from overcharging and stopping there ( either from a voltage drop as the cell heats up or from a thermal sensor in the pack) hopefully before the cells vent.
 

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Re: why charge a new item far longer after 100% is achieved ?
« Reply #5 on: 17/02/2012 19:42:00 »

 

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