Bad idea to top off LSD NiMH Eneloops?

TyJo

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I tried a few searches but I am not good with batteries or their associated terminology. I have a Maha Powerex charger and Eneloop AA and AAA batteries. I prefer to have a light with a "topped off" battery when I leave the house. I know Eneloops are low self discharge and are regarded as the best. Are there any problems with charging them to "top-them-off" to full capacity after a small discharge (lets say 90% remaining capacity)?
Thanks.
 

VidPro

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what he said ^
when you have one of them chargers that needs to torture the battery more :) then it is not so good to keep topping them off.
if the charger is cool on them , then it is , , , nuff said.
 

Rod911

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What should the top-off rate be? For a regular charge, it's 0.5C for me on my Maha, so would something less strenuous at say, 0.2C or 0.3C be better as a top-off rate?
 

march.brown

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I top up all my LSD NiMh batteries every few months ... I did them on 25 March 2011 and before that it was 25 November 2010 ... I top them up more or less when I remember about them , whether they need it or not ... I replace the batteries in my EDC torches every few months from my stock of AA and AAA Eneloops , charge the used cells and put them back into stock.

I have been doing this with NiMh cells for many years as I did with previous rechargeable cells ... I don't now have any non-LSD cells and sometimes it can be many months between top-up charges.

I can't see the point in having batteries in stock that are not fully charged ... LSD cells are the best thing since sliced bread (as the saying goes) and no longer do I have to top up every few weeks or even just before use.

My cells all seem to last for ages though I do now have one that takes a lot longer to charge than the others ... When it eventually fails, it will be recycled and eventually in a couple of years I will get another pack of AA Eneloops if necessary.

I don't have a huge stock of cells ... 13 AA's (soon to be 12 probably) 8 are Eneloops and 5 are Hybrios and 16 AAA's 2 Eneloops , 6 Hybrios and 8 GP Recykos ... My torches use Eneloops and the other household items use the other makes which I have found to be very reliable.

As the batteries gradually die , they will be replaced with Eneloops ... No particular reason , but at least they will all be the same colour.
.
 

Russel

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What should the top-off rate be? For a regular charge, it's 0.5C for me on my Maha, so would something less strenuous at say, 0.2C or 0.3C be better as a top-off rate?

If you want to top your Eneloops off, use the same charge rate (0.5C) that you normally use, for the same reasons that you use it to charge them when they are completely depleted.
 

TakeTheActive

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I tried a few searches but I am not good with batteries or their associated terminology...
If you're a Newbie here, interested in learning more, CLICK on my Sig Line LINK - I've assembled a list of my favorite 'Questions & Answers' from when I was a Newbie. ;)

...I prefer to have a light with a "topped off" battery when I leave the house... ...Are there any problems with charging them to "top-them-off" to full capacity after a small discharge (lets say 90% remaining capacity)?
Just out of curiosity:
  1. What is your (flashlight?) application that you're so worried about 'topping off' your cells?
    .
  2. Have you ever NOT 'topped off' your cells and subsequently ran out of power (in an emergency situtation)?
    .
  3. Is there any reason why you cannot carry SPARE cells?
    .
  4. WHICH Maha Powerex charger do you have?
    .
  5. Does it terminate properly?
    - Is Your Charger Terminating Properly?
Possibly you're creating unnecessary work for yourself.

Personally, I like to run my cells down to ~0.9VDC as often as possible to 'exercise' *ALL* of their chemicals (both keeping them healthy and getting my money's worth). Maybe if I were taking our 4 AA digital camera to a special event I might 'top off' the cells currently installed. But, I would also carry along (probably) two sets of LSD SPARES (not necessarily 'topped off', but at least charged within the last 3 months).

LSD cells, especially Sanyo Eneloops, have made such a DIFFERENCE in the way I treat / regard my rechargeable cells since they're just so good...
 

TyJo

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My main EDC is going to be a HDS Rotary once I get it back, it uses RCR123s which I know how to take care of and will top off (to around 4.1v or 4.15v, not all the way to 4.2v). I don't see the point of having a light with me if it isn't at almost full capacity, lets say at least above 80%. I don't use my lights for my job or for any life or death situation, but I prefer to have a light in case I need it. This is only a hobby for me and I knew it was OK to top of Li-ions but wasn't sure about LSD NiMH. I have the Powerex MH-C9000 and I will try the terminate properly test on a rainy day, but I am pretty sure it is doing its job. The reason for the OP was to see if there are any negative consequences to topping off these cells after a partial discharge, such as 75% remaining capacity. AAs aren't in my main EDC, but I use them in lights I have around the house and the lights in my car and other electronics.
 

WDG

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You've got the right cells and the right charger. Unless there's some peculiar issue with your MH-C9000, it should have no trouble terminating, at least with Eneloops. Topping after some use, the way you describe, should be fine. I prefer to simply keep charged cells on hand, so all I have to do is swap & charge. I normally only change my EDC cell once a week, which works out to about 75% capacity remaining, in my usage. I also carry a couple spares, just in case.

BTW, I normally just use the default 1000mAh charge rate on AA Eneloops, in this charger.
 

bbb74

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Cells that are cycled to the same point continuously can develop what some people call the memory effect. I think it is more accurately described as voltage droop - when you try to discharge the cell below the point where it normally gets a recharge, the voltage will be lower than it otherwise would be. Different cells will perform differently, eneloop claim they don't have any memory effect (I'm not sure if I believe this or not though - would be curious if anybody has tried it). Cycling the battery a couple of times removes the effect of the voltage droop.

I suspect that you don't even need to discharge to the same point each time to create this effect, its just the material that has not been discharged and has been frequently charged over the top off will start to change in structure causing the droop - but this is just what I suspect.

Curious if anybody could test if eneloops do suffer from this. Test would be to cycle an eneloop 20 times, and stop the discharge at the same point each time, preferably on a small way (say 20%) into the discharge where the effect is increased. And then do a charge & discharge and watch the voltages through the entire discharge curve.
 

s0lar

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LSD Cells can be stored fully charged. Before using you can top them off so they're full just before use.
Depending on what your equipment needs it can be a good idea to top off.
In low power electronics it's quite useless. Topping off and storing them again is also useless.
Normal high capacity NiMH cells are best stored empty to 1/4th charged. You can store LSD cells fully charged witout any problem.
It can be a good idea to store LSD cells fully charged and then top off for a few hours in an overnight charger before actual use.
If you have the charger that is. Fully charging at 1A in your MAHA C-9000 only charges to 90-95% without the extra 2h of topping off at 100mA.
 
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