How do I know when my Eneloops are getting low?

[shane45_1911]

OK, sounds sort of like a noob question at first , but...

If I am running pair of AA 'loops in my Fenix LD20 (for example), and I don't want to run the risk of reverse polarizing a battery - how do I know when the batteries are getting low - without getting too compulsive like keeping a log of useage time.

Since the LD20 does not have a "low battery warning", and has several different output levels - it is not as easy as simply noticing a drop in lumens.

If I was constantly using the light at one constant output setting, I would be able to notice a decrease in brightness - but I am not.

Is it as simple as assuming the light will no longer go into turbo mode, for example, if the batteries are too low? I assume it still would with constant regulation, however?

 

[mcnair55]

I cannot comment on your light but on my EZAA,when I am on low and it will not switch to high I know it is time to feed the batteries.With my AAA EDC lights I just use them and if I feel my Itp has been worked a lot over the week I charge them up on a Saturday morning,if I feel not done that much work I charge them once a month.

I look forward to answers from the experienced members.

Also be warned the mods may move this to the battery section.

 

[march.brown]

Just top them up anyway ... The Eneloops won't mind.

You can get a cheap battery tester for a couple of dollars on Ebay ... It puts a load on the battery and gives a colour-coded reading of good , low and replace/recharge on the small moving coil meter ... Mine works fine , though I just recharge my Eneloops when I think they need it anyway.

You can always run the batteries down a bit at home , then recharge them if you wish ... I don't do this though as it is fairly easy to guestimate when the Eneloops need a top-up ... Don't worry , just carry spare Eneloops with you or in the car just in case.
.

 

[Ohmic]

OK, sounds sort of like a noob question at first , but...

If I am running pair of AA 'loops in my Fenix LD20 (for example), and I don't want to run the risk of reverse polarizing a battery - how do I know when the batteries are getting low - without getting too compulsive like keeping a log of useage time.

Since the LD20 does not have a "low battery warning", and has several different output levels - it is not as easy as simply noticing a drop in lumens.

If I was constantly using the light at one constant output setting, I would be able to notice a decrease in brightness - but I am not.

Is it as simple as assuming the light will no longer go into turbo mode, for example, if the batteries are too low? I assume it still would with constant regulation, however?

No offense but I think you're already getting a bit compulsive.

I own a bunch of Fenix lights, Including an LD20, and all are powered with eneloops. I too am concerned about reverse polarity, but as long as both batteries have the same charge state as each other when inserted, I don't see the problem.

If you're not noticing a drop in light output then in my opinion the batteries are not flat.

It's pretty obvious when the batteries are depleted. The torch dims down to the same sort of light output as the lowest mode.

However if you want to be ultra careful about it, change the batteries on the first sign of drop in lumen output.

I was a bit like you at first, but seriously, the eneloops are pretty robust batteries, and like I said earlier, as long as the batteries go in with the same charge level, they'll generally discharge at the same rate and likelyhood of reverse polarity is pretty darn low.

If you haven't already done so, get a decent charger like the MAHA C9000 and use its built in display to observe battery capacity, I have around 60 AA eneloops and have found them to be remarkably well matched (according to my C9000), so long as they're from the same packet:thumbsup:

 

[Battery Guy]

If I am running pair of AA 'loops in my Fenix LD20 (for example), and I don't want to run the risk of reverse polarizing a battery - how do I know when the batteries are getting low - without getting too compulsive like keeping a log of useage time.

The voltage an internal resistance of a NiMH changes very little with state of charge. Only at the very top and bottom of charge is there a significant difference, so between 10% and 90% you are pretty much flying blind.

Think of it kind of like driving a car with a broken gas gauge and odometer. The only time you know the tank is full is when you top it off, and the only time you know it is empty is when you run out of gas. So maybe you let it run out of gas one time just to get a feel for how long you can drive on a full tank, but most of the time you are probably going to be pretty diligent about keeping it topped off.

So my advice: keep your Eneloops topped off and don't worry about it.

Cheers,
BG

 

[shane45_1911]

No offense but I think you're already getting a bit compulsive.

Honey, is that you???

(If I had a dime for everytime my wife has said that...)

Thanks for the comments guys - and yes, I have a couple C9000s that see regular use.

 

[45/70]

I do as others have mentioned. When running any of my NiMH cells in series applications, I try to run cells that are fairly well matched in known/tested capacity. This reduces the risk of reverse charging occurring. In addition, I familiarize myself with either the estimated runtime I will get from the "pack", or based on actual runtime until the cells became depleted, and then attempt to always charge the cells up well before they become discharged.

Running both standard NiMH cells and LSD's, I have had good success with this method. Standard NiMH cells I figure last about 5 years (or longer) before they wear to a level where they need to be replaced. So far, my eneloops look to be able to extend this lifetime considerably. I think the most important consideration, is to try to recharge more often when using cells in series, rather than trying to eek out every last bit of capacity each use. This will help to avoid reverse charging and thus prolong cell life.

Dave

 

[noisebeam]

Look at the relative light output charts in this review. Note where the eneloops take a corner in output, a sudden and easily noticeable drop in output. Stop using them right there.

As I use my L2D as a bike headlight I run them to that point and often a bit further before I have a chance to stop and change batteries and have not ruined any eneloops yet.

 

[tandem]

Since the LD20 does not have a "low battery warning", and has several different output levels - it is not as easy as simply noticing a drop in lumens.

As you know your light won't fire up into Turbo or High when the cells have depleted past a certain level. I honestly don't know if that level is too low, or not.

I can tell you that I use both the LD20 and LD10 on max output more often than any other output level and in a single session regularly run the light on freshly charged cells all the way to the point where output significantly dims... that's my normal way of using them.

I've not noted an appreciable drop in capacity over the the last few months of regular use but I've only been running the two cell LD20 hard over the last several weeks of darker cycling here in the wet Pacific North West. The internal impedance check voltage shows all the cells I'm using for this purpose (a group of 8 from two packs bought early in the summer) are all still vibrant. Ask me next year how they are!

If your use is intermittent and you happen to notice once in a blue moon that the light doesn't go to high or turbo output because you've not recharged recently, it seems unlikely that you'd be driving one of the cells into reverse polarity, assuming you have roughly balanced cells in use together. Without longer experience and hard data I'm just guessing but it seems as if the LDxx lights shut things down early enough.

To be honest, if if my usage did kill a couple batteries every winter, I'd consider that plenty cheap. They only cost me $1.75 per cell, so I'm getting more or less free power after using them through just a few cycles.

Worst case and you do sabotage a cell or two? At least the things won't blow up on you like li-ions can (and I have these too... just am a lot more careful / less cavalier in using them).

 

[shane45_1911]

Thanks for all the comments guys.