NiMH Batteries

Hi all, I am wanting to buy some rechargable batteries for my Led Lenser P14 but I don't really know much about the new batteries you get these days.

Im wonderin do either the LSD or normal NiMH batteries have much of a memory? As in do I have to run them flat before I charge them? Or can I just run them for about an hour and charge them again without causing harm to them?

What I want is a battery that will give the brightest beam for about 2 or 3 hours, but I don't mind if I have to charge them a lot as I use my torch a lot, but I don't want anything thats going to have a short life because I don't fully discharge them.
Wether or not that exists I have no idea, lol.

I think I also read somewhere about Sanyo Eneloop batteries having the same current output as the battery discharges, did I read this correctly?

Any info about what batteries to get would be a great help.

Thanks Sam

If you are going to use it a lot, get 2700 mah Sanyo's. Eneloops is great if you want to use the light only once a month or so.

Eneloop are always good batteries, they can keep the charge if you do not use them, but they also take heavy use very well.

The Sanyo's aren't going to make your light run any brighter. It might run a little longer.

Eneloops are pretty much the gold standard. I'd stick with them. I have some Powerex 2700's that I use fresh off the charger when I want longer life, but that's limited to a few items.

It's my understanding the "memory effect" is more of a myth. I think the effect is more from damage caused by overcharging: chargers with timers have no idea the cell isn't empty, some budget "intelligent" chargers have a difficult time seeing the termination point, and dumb chargers (the ones found in supermarkets) just get left on while the batteries cook. My Maha C9000 has no trouble figuring out if I accidentally try to charge a full cell, but it still stuffs at least 100mah in there (not counting the topping-off charge if I had left it in for two more hours.)

Still, the general advice I saw and follow is to fully discharge (down to 0.9-1v) NiCd cells once per month and once per three months for NiMH. I don't think it's too critical, but it can't hurt.

For your purposes, standard NiMH is probably the way to go if you're using them every week. The capacity is a bit higher, and realistically they keep a good charge at least one month. I prefer the LSD cells in case I don't use them for some time, and I think they're more tolerant to abuse.

My post in this thread covers my take on it: http://www.candlepowerforums.com/vb...lenght-do-LSD-batteries-loose-their-advantage

Wrend said:

It depends on the specifics. Some of the LSD cells offer other advantages, such as having a somewhat higher operational voltage, having less internal resistance, and having a higher cycle life potential (Eneloops), while some non-LSD cells seem to quickly develop high internal resistance, and higher self discharge after a hand full of cycles (2500mAh Energizer Rechargeables).

It also depends on the specific application these cells are being used in, and its operational requirements.

But just as a generalized response, yes, there are some circumstances where some high capacity non-LSD cells perform better than the LSD ones.

For me personally, I prefer the LSD ones. I've standardized mostly all of my AAAs and AAs to Eneloops. It's easy enough to leave them charged and switch them out whenever I need them. I don't find 25% more usable capacity from non-LSD cells to be much of an advantage when compared to the other advantages Eneloops offer.

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I don't think battery memory is a myth at all. I just bought 12 Sanyo 2500mAH cells cheap off ebay and told they were "Store Returns".
All were drained to .9v except for two that were .02v and even tho i cant say what abuse these cells were given, I can say they never saw a good charger in their lifetime. I have a BC-9009 and most cells were back too 2300-2450mAH with 2-3 refresh cycles.
They all suffered from memory issues and would only hold 800-1250mAh on the first charge.

So my advice would be to only buy non LSD batteries if you have a charger that can discharge and cycle the cell.
If you just have a basic charger id go with LSD cells like the Eneloop, They say they have no memory but i havent tested them to prove it. But id tend to believe it.

Its also true the Eneloop can deliver high amounts of amps and do it above 1v, So it can take some heavy power loads without dying immediately.
The Eneloop test is about half way down the page, It took 10amps like a champ.
http://www.candlepowerforums.com/vb/showthread.php?79302-NiMh-Battery-Shoot-Out

Its just not gonna run as long compared to a 2700mAH cell.
The closest LSD cell with higher capacity 2400mAh AA IMEDION Powerex Maha, I have some also but haven't tested them yet.

So in the end it comes down to if you have a charger that can cycle a cell and discharge it, If not get a LSD cell.
But with the amperage output ability of the Eneloop you may be better off with them, Just buy extra cells for more capacity.

........

I gave away my 20+ standard NiMh and went for Eneloop, Recyko and Imedion. LSD batteries are able to hold charges much much longer than standard NiMh. You don't want to run into a situation where you charged some normal NiMh, left it in your flashlight or devices for 2 or 3 months. Then one day you decided to use it and realized there are no more juice in them!
Standard NiMh are notorious for losing charge fast.

1. As far as I know, the P14 is not rated for NiMH. The unregulated LED Lensers rely on the internal resistance of the primary cells. Use NiMH at your own risk...

2. You not only don't need to run NiMH flat before recharge, you even have to avoid it, since they will lose capacity when subjected to discharge below 0.9V.

Just a few comments having had considerable experience with hi cap NiMh (2500-2700mAh), "traditional" NiMh (non-LSD), and eneloop LSD cells.

I don't have any experience with the Lenser P14, but if you really need the extra capacity that hi cap NiMh cells provide, they will do the job better than the other choices if used soon after the cells are charged...... for a while. Depending on the level of current cells experience during discharge in any device, hi cap NiMh cells will either fall below the performance level of LSD, or traditional 2000mAh cells after just a few cycles, or quite a few cycles.

Hi cap NiMh cells are fragile in construction compared to other NiMh cells, due to necessary compromises in construction necessary to obtain the high capacity that these cells exhibit. In other words, they just don't last as long. At very low discharge rates, this is not so much of a problem. At higher discharge rates however, the higher the discharge current level, the fewer cycles these cells will deliver, before a noticeable drop in capacity occurs and rapid self discharge begins to set in.

For medium discharge rate devices (eg. ~1A for an AA cell), traditional NiMh cells will often deliver more cycles than Hi Cap cells. For higher rates of discharge (eg. 1-4A, for an AA cell) LSD cells hold up better. In 4A+ applications, I've had Sanyo 2500 and 2700 AA cells crap out after 10 cycles, whereas 1900mAh traditional NiMh cells have lasted 25 cycles. I've never used LSD cells in these particular applications, as I prefer to use high discharge rate cells, such as Elite 1700's, but others here on the Forums have had good success using eneloops.

As for the so called "memory effect", there has been much discussion as to whether NiMh cells suffer form this as NiCd cells do. My personal opinion is they do, but to a much lesser extent. Also, the actual cause of this apparent phenomenon may not actually be the same, however the resulting effect is the same (voltage depression), and the recommended treatment is also the same, ie. slow discharge the cell to 0.8-0.9 Volt followed by a 16hr 0.1C "forming charge" and repeat if needed.

While it is important to keep in mind that habitually discharging any NiMh cell to ~0.9 Volt every cycle is not good for the cell (unlike NiCd's), doing so every 3 months or so isn't going to hurt anything, and has been shown to actually benefit traditional NiMh cells. LSD cells do not appear to benefit from scheduled discharging as much. In fact, it may not be necessary at all. IMO however, discharging LSD cells and then charging at a 0.1C rate for 16hrs, once or twice a year, helps keep the chemical mix within the cell more evenly distributed, just as with traditional NiMh cells. At the very least, this type of LSD maintenance isn't going to hurt anything.

I'll add that obviously, LSD cells retain their charge better than any other type of NiMh cells, when not in use, as I haven't mentioned that. As a result, for me anyway, LSD cells are gradually replacing all of my other NiMh cells, with the exception of the Elites. LSD cell's low self discharge, better ability to hold voltage under high current loads, and general "sturdiness" IMO, outweigh any advantage that in particular, hi cap NiMh cells may have. For some though, hi cap NiMh cells still have their place, but again, usually require much more frequent replacement, in most applications.

Dave

I gotta admit Dave, Your full of answers and knowledge. I think i need to track some of your previous posts and read them as each one ive read lately has taught me alot. Im catching on tho, And have alot of mistakes to learn the hard way also.
This is why i have a few packs of Powerex 2700 and Sanyo 2500's just mainly to test my needs and how they fit into my scheme of flashlight use.
But more than half of my NiMH cells are LSD Eneloops, Duraloops and Imedions.

I need to go back and review the test results of NiMH cells with high amp draw, But i know for a fact the Eneloops couldn't be beat. Holding 10A above 1v for even a few minutes is amazing imo, Which they did. But i need to revisit how the high cap cells i own did in the tests.
Im gonna start a chart just for my own purposes and test each and every cell i own for self discharge and the rates they do it.

You didn't mention it, But i think that someone who uses Eneloop cells exclusively could get away with a $10 sony charger that comes with certain bundles.
But if you buy non LSD cells you better have a Maha or La Crosse charger if you want your cells to work well for a long time.

Out of the 12 Sanyo 2500 "store returns" i bought of ebay i was able to revive 6 just with two .5c cycles.
The other six are gonna take at least two more cycles at .2c to get them above 2200mAH again.
This is why i believe in "cell memory" as if it wasn't happening i wouldn't be able to revive these cells like this.
These things looked like brand new cells also, So what ever hot them hit hard and fast.

I eventually seeing myself going to all LSD cells also, Just so much easier to store and take care of.
Since they aren't able to have the higher capacity ill just have to buy a few more. But not really needed considering all my Li-ion cells i have and their ability to work in the same lights.

This is why i believe in "cell memory" as if it wasn't happening i wouldn't be able to revive these cells like this.

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To touch on what Dave and Mad-Bassist said, it's also my understanding that what is often referred to as "memory effect" is now really just a catch-all for anything that causes cells to not performing to their potential. With NiCds this (apparently) was mostly because of leaving the cells trickle charging for days on end without fully discharging them while in use before charging them up again. This would cause significant build up of large crystals, which would then cause their voltage to sag more when used in higher drain rate applications, making it appear as though the cells were running low. The analogy I often use to describe this is to compare it to wood in a fire. One big log takes longer to burn down than several smaller twigs of the same mass.

I'm not sure if the same holds true for NiMHs, but I assume they can also develop these larger crystals.

Another cause might be uneven distribution of electrolyte within a cell, which could also make the cell less electrochemically active. Pbs can suffer from a form of this if the electrolyte gets low.

Cycling NiCd and NiMH cells a few times can help "reactivate" them, seemingly by properly redistributing their electrochemical components.

I have read that eneloops supply a constant voltage as the battery drains, does this mean my torch stay the same brightness as the battery drains?

More constant than alkaline cells. It's really more of an S-shaped discharge curve. Coupled with their low internal resistance and higher effective capacity, they should stay brighter longer than alkaline cells as they discharge, though the alkaline cells might start out brighter because of their higher initial voltage.

As far as I know, the main reason Eneloops should perform better than some other NiMHs (in this regard) is because of their relatively low internal resistance.

Here's a link to a test graph I did in one of my transmitters that shows the S-shaped voltage discharge curve: http://static.rcgroups.net/forums/attachments/2/7/0/8/7/5/a3143676-72-Eneloop%20T6EX%20Test%20Graph.jpg?d=1269599458

I've had a variety of NiMH cells and I intend to stick with Eneloops. Reason is I've never had AFAIK a single Eneloop cell that has shown the slightest variation from my others in terms of the voltages of the cells before, during and after a usage cycle, and I have 24 AAAs and 28 AAs, some of them going back 3 years. This is more than impressive.

I use the eneloops and works out well

Except Eneloops i highly recommend Maha's Imedion.
Very happy with both brands after long time using them.

garbman said:

Except Eneloops i highly recommend Maha's Imedion.
Very happy with both brands after long time using them.

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+1 on the Imedions. After sitting for one year the imedion will still have the remaining capacity of a freshly charged eneloop.:thumbsup:
Keith