half-drained batteries???

[Loa]

Hello,

Since I use a lot of AA batteries for my flashlights, I bought a bunch of Eneloops and a nice Maha MH-C800S charger. It has a quick charge, soft charge and a cycle. Everything was covered. I love both the batteries and the charger.

Thing is, there is no discharge -> charge mode on it. The cycle is C -> D -> C.

Question is simple: what do I do with a battery that has only been partially (let's say about 50%) discharged after use? I know that the memory effect is small, but still...

Thanks a lot,

Loa

 

[Marduke]

The "memory effect" is a myth, and doesn't really exist. Just charge partially used cells up like normal. There is no need to discharge them.

 

[SilverFox]

Hello Loa,

Welcome to CPF.

Unfortunately, it seems that Marduke hasn't run enough tests with NiMh and NiCd batteries to observe the memory effect. It actually does exist.

However, he has come to a very sound conclusion.

Charge them up and go.

Sanyo discusses the memory effect and parts of it are a myth, but the fact remains that if you only partially discharge a cell several times in a row, and if you discharge that cell down to about the same level of discharge each time, your cell will show voltage depression during a discharge. This is often referred to as the memory effect, but in fact is simply voltage depression. With equipment that is voltage sensitive, this results in short run times.

By running the cell through a complete discharge and charge cycle, most of this voltage depression is removed and the cell is brought back to normal performance.

This effect is most noticeable with NiCd chemistry, but also can be demonstrated with NiMh chemistry. I believe it takes about 10 partial discharge cycles to initiate it, and you have to pay close attention to the charge cycle as overcharging tends to eliminate the problem.

Since it is somewhat difficult to reproduce, people tend to dismiss it, but I run into it frequently with battery packs. I often have people give me poorly performing battery packs to see if I can revive them, and often the problem is voltage depression. A few charge/discharge cycles brings the pack back to decent performance, and I am rewarded with a beer or two for my "magical" resurection of the battery pack.

There is far fewer incidents of this with single cells, but I do see it occasionally when people are using chargers that charge cells in pairs.

Here is the link to Sanyo's comments on this in regard to NiMh cells, and here is where they go into a little more detail of the memory effect with NiCd cells.

Tom

 

[Marduke]

Hello Loa,

Welcome to CPF.

Unfortunately, it seems that Marduke hasn't run enough tests with NiMh and NiCd batteries to observe the memory effect. It actually does exist.

However, he has come to a very sound conclusion.

Charge them up and go.

I was separating the mythical "memory effect" from "voltage depression"

 

[Burgess]

to Loa --


Welcome to CandlePowerForums !


:welcome:




Enjoy yer' Sanyo Eneloops.


They are fine batteries.


:twothumbs

_

 

[TakeTheActive]

...Since I use a lot of AA batteries for my flashlights, I bought a bunch of Eneloops and a nice Maha MH-C800S charger. It has a quick charge, soft charge and a cycle. Everything was covered. I love both the batteries and the charger.

Thing is, there is no discharge -> charge mode on it. The cycle is C -> D -> C.

Question is simple: what do I do with a battery that has only been partially (let's say about 50%) discharged after use? I know that the memory effect is small, but still...

A little knowledge is a dangerous thing: Information from Answers.com ​

IMO, many Newbies get overly obsessed with 'Rules' when they should be more concerned with 'Why'. You bought good batteries and a good charger. All you need to learn now is "proper maintenance". And for that you should remember the phrase "Use it or Lose it". Sometime within every 30-90 days you want to 'exercise' *ALL* of the chemicals in your cells. You can use a device (i.e. flashlight, MP3 player, etc...) and get some use out of the energy or you can use a 'Smart' Charger and heat your house a bit.

My thoughts:

1. LABEL your cells.
2. ROTATE THEM between your high current / deep discharge and low current / shallow discharge devices.
3. CHARGE them as needed.
4. EVERY ~30-90 days, replace a CHARGE cycle with a C ->D ->C cycle, preferrably after use in a high current / deep charge device.
5. DON'T WORRY about 'Up to 1000 Recharges' because unless you're cycling them much more than once-per-week, they're going to die of 'old age' (~10 years) anyway.

I thought that I knew a LOT about rechargeable cells, after using them for ~20+ years. But, then I spent several hours per week reading the CPF Archives. CLICK on my Sig Line LINK for a list of my favorite posts. :thumbsup:

 

[Loa]

Thanks for the added info, I'll read up on the other side of your link!

Loa

(don't know how this is going to appear on forum because my earlier reply still hasn't been "authorized...)