Rechargeable vs. Alkaline Batteries | Hacker News Reader

Rechargeable vs. Alkaline Batteries

nytimes.com

64 pointsbookofjoe90 comments

  Electronics that constantly draw low amounts of power — such as
  some wall clocks, headlamps, or bike lights — work better with
  disposable alkaline batteries. Alkalines release power consistently
  right up until they die, whereas a rechargeable battery’s voltage
  gets gradually lower and lower over time, slowing down the device or
  cutting off power prematurely.

This is very wrong, and makes me doubt the article's correctness. Every NiMH discharge curve I've ever seen is much flatter than a typical alkaline curve.

NiMH batteries drop down to around 1.25V pretty quick when discharging, but they stay around 1.25-1.15V for almost the entire discharge cycle. Alkaline batteries are almost dead by the time they get down to 1.2V.

So the reason why NiMHs drop out early on some devices isn't because they're out of charge, or because alkaline batteries have a flatter discharge curve (they don't). It's because some devices stop working at around a 1.2V cell voltage, regardless of how much charge is left in the battery.

1.2V cut-off is ridiculously high even for alkalines. Looking at the charts from e.g. Energizer datasheets[1], it seems like going form 1.2V cut-off to something more reasonable like 0.8V gives you whopping extra 50% service life. Alkalines are definitely not "almost dead" at 1.2V.

[1] http://data.energizer.com/pdfs/en91.pdf

that's a pretty interesting datasheet! If you assume a constant-power load like a low-dropout boost regulator, it looks like it depends a lot on the current draw.

On that graph, you're right that the 200mA draw goes quite a bit farther after 1.2V. The 100mA draw is around 65-75% done at 1.2V. Presumably that exends to lower-power draws too.

Thanks for linking that, it was neat. TIL

> that's a pretty interesting datasheet! If you assume a constant-power load like a low-dropout boost regulator, it looks like it depends a lot on the current draw.

One of my unrealized project ideas was to create a battery life estimation calculator, something you could feed in battery configuration, some power supply details (efficiency, cutoff), and consumption figures and get an estimate of battery life. The log-log charts are not all that easy to read and have only limited number of curves available.

https://www.google.com/search?q=battery+life+calculator&oq=b...

All of the first-page results do just dumb nominal capacity divided by current calculation, which is pretty useless. This Microchip one seems bit more clever, but it is limited to Microchip microcontrollers only and is a separate installable application, so that is no good either: https://www.microchip.com/SWLibraryWeb/product.aspx?product=...

I thought that NiMH will lose about 1% per day, thus making them a poor choice for standby devices.

True for older style NiMH, but the newer 'pre-charged' types like Eneloop have very low self-discharge

No, after 5 years eneloop AA batteries still retain ~70% of their charge. I have been using them in remotes, bathroom scales, flashlights, and the like for over a decade and they usually last a couple years before I need to recharge them. The only place I have Alkalines any more is my emergency box, and those tend to self-corrode almost as quickly the NiMH self-discharge.

I think the name brands (Energizer, Duracell) have similar performance these days as well.

From personal experience I couldn't get my wall clock (cheap Ikea one) to run on an eneloop, even after I think I charged it, without the second hand going all weird and failing. Works just fine on a disposable, what am I doing wrong? This article may be incorrect but the conclusion matches my experience.

Rechargeable NiMH cells have a voltage of 1.2v, and stay pretty much at that voltage until they're flat. Alkaline (and other disposable) cells start at 1.5v (actually a little higher), and gradually diminish in voltage over they're life. If the appliance requires more that 1.2v, then a NiMH cell will simply work.

In any case, clocks tend to draw a very small amount of power over a longer time, which doesn't tend to suit NiMH cells due to a higher rate of self discharge (eneloops and other similar 'ready to use' rechargeables are much better though)

Partially true, but you're measuring the cells wrong. Alkaline batteries typically start around 1.5v and are advertised to be around 1.5v. A fully charged NiMH cell will be advertised at 1.2v but at peak charge will actually be around 1.4-1.5v.

Even without discharging the NiMH cell at all the peak will wear off within a few hours.

Furthermore, NiMH charges can go stale, trapping electrons inside the cells forever. These trapped electrons occupy cell capacity that can no longer be filled with viable electrons. Thus, a 2,000mah cell that has been left with 1,000mah worth of stale charge will likely only ever charge to 1,000mah for the rest of its life.

If you measure the curve from the delta peak of a NiMH battery the curve is way more extreme than any alkaline.

They should probably have said instead: When NiMH discharges completely in such device, it's prone to failure.

It is also possible that the article mistook the cell discharge curve with their self discharge. Self discharge happens due to imperfect chemistry regardless of what is connected to the battery: you charge a cell at 100% then put it in a drawer, and after some time it falls below any usable current by itself. Usually it takes months but I had very poor cells self discharging in less than two weeks, although they could indeed deliver the advertised current in shorter times.

As you pointed out, NiMH cells have a much flatter curve than alkaline ones, but they also self discharge quicker than alkalines, so for example in very low power devices such as remote controls or clocks where one would expect long times between recharges, they aren't the best option because their self discharge time is much shorter than their use time.

In my kitchen I have an exception: an old electromechanical wall clock in which I swapped the alkaline cell with a NiMH one, but both use and self discharge are dealt with by a small solar panel connected in parallel with the cell, which in this case works as a voltage stabilizer too. So far about 4 years passed without changing or recharging anything, and it gets direct sunlight for a very short time every day.

For any 2xAA or 2xAAA device without a center tap, you can use a 3.2 volt LiFePO₄ cell with a "0 volt" spacer.

I use LiFePO₄ to run my rear bike light and a wireless thermometer, both 2xAAA devices. The total capacity is reduced because half the space is wasted, but that's not a big deal if you're only recharging a few times a year.

I haven't tried this with remote controls, since the batteries last basically forever in those.

Another option is to use 3.7 volt lithium ion with an LDO regulator, but I haven't tried that yet.

Fun hack! Do you have a line on cheap LiFPO4 or is it just to get a longer run time between swaps?

I prefer not to use disposable batteries for environmental reasons. But with NiMH, a light designed for 3V will be dim, and an LCD will have low contrast. In that sense, the effective run time is zero, so NiMH is a non-starter.

I found some AAA-size LiFePO₄ cells, spacers, and a charger on AliExpress a few years ago.

LDOs introduce their own inefficiency into the process so it's usually not worth the trouble.

Slightly related, and maybe you could provide more knowledge here: common knowledge for safety critical devices, such as avalanche beacons, is to only use disposable alkaline batteries. The reasoning I've heard is that due to the flat power curve of non-alkaline batteries, if you put a nearly-dead one in the beacon and check the battery level, it will read as fuller than it really is, and you run the risk of having it die on you during a normal usage period (maybe 12 hours). With an alkaline battery, when it's close to done, it will more accurately register as such on the device.

Alkaline batteries start off at 1.5-1.6 volts and the voltage follows the charge reasonably linearly down to about 1.0 volts. So that's correct, alkaline batteries at 1.5V per cell are 'good' full stop. Where a rechargeable at 1.2V might or might not be. Who really knows if it charged all the way[1][2].

[1] Gallant is careful to put his nmh batteries in the the charger each night. Goofus got high and forgot. In the morning Goofus swapped his dead ones for the ones in Gallants charger.

[2] Power went out between 11pm and 6am while everyone was asleep.

I have one of the few avalanche beacons that have separate modes for alkaline and NiMH batteries. (Specifically, the Barryvox Pulse.)

My understanding is that "alkaline mode" measures the voltage to determine charge level, as one would expect. The "NiMH mode" instead uses a timer-based approach to estimate charge level due to the different discharge curve.

That seems like sound reasoning to me. I've spent many many hours staring at manufacturer provided curves, and countless days running my own and would absolutely use that as a rule.

All of it is wrong, and it's frustrating that things like this get promulgated with an authoritative voice. It seems to happen especially often about battery technology, for some reason, or else I only notice it more because I know a little bit about battery technology.

My other not-favorite thing, tangentially, is how marketing for anything that stores electrical energy has gravitated to "mAH" as the sole unit. I know it's because the uninformed consumer will compare based on the bare number, but every time I see "15000 milliamp hours" I cringe. Off to drive 7 megamicromiles to work.

https://en.m.wikipedia.org/wiki/Gell-Mann_amnesia_effect

I don't think this sentence from the article is correct: "Alkalines release power consistently right up until they die, whereas a rechargeable battery’s voltage gets gradually lower and lower over time, slowing down the device or cutting off power prematurely."

If you look at the discharge curve for an alkaline battery (for example, http://madscientisthut.com/wordpress/wp-content/uploads/2013...), it seems more linear than for a NiMH cell (http://4.bp.blogspot.com/_7azY596Jbs8/TVHgoP3gUkI/AAAAAAAAG4...). In other words, it's the NiMH cell that gives consistent voltage until it dies, whereas the alkaline battery will gradually lose voltage. (It's not totally clear, some other graphs of alkaline discharge curves do show more of a "knuckle", with a flat initial section and then a steep drop-off).

Electronics that constantly draw low amounts of power — such as some wall clocks, headlamps, or bike lights — work better with disposable alkaline batteries

I use low discharge NiMH rechargables in all of my battery bike lights and they work great, they'll last for about 3 months of my usage (I run the taillights night or day), but I charge them all at the end of the month (I have 2 sets, so one set's on the bike and one set is charged and ready to swap out). I'm on the same set of Eneloops I bought 6 years ago. Every year or so I have my charger run a discharge test and they are still within about 90% of rated capacity.

I'd have thrown away 24 sets of disposable batteries in that timeframe (since I keep an extra set of batteries charged, so it's a ratio of 1:12). I paid ~2.50 each for the eneloops when I bought them, so cost wise it's been a good investment, works out to around 20 cents each so far (ignoring the cost of electricity)

It's getting harder to find non-rechargable bike lights, my main headlight uses a non-replacable LiIon battery.

It's a shame that so many products default to built in, non-replaceable LiIons now. For many products, it's nicer to have a replaceable rechargeable so you can pop in charged battery and go instead of having to plan for state of charge of yet another device.

I suspect building them is in an environmental benefit in a lot of cases, a lot of people just buy huge packs of alkaline disposables and can't be bothered with rechargeables unless they're built in. I'd be interested to see the statistics but I wouldn't be surprised if 80% of people use disposable batteries given the opportunity.

Probably true, but if the LiIon batterypacks/modules were required to be replaceable, that would keep that benefit while reducing the waste of lights that are thrown away after the LiIon battery degrades.

Though I'm not sure how much of a factor that is - I don't know how often lights are discarded because the battery life because too short versus lights are discarded because someone wanted a newer/smaller/brighter light.

I just don't get why replaceable standard-sized lithium ion batteries have pretty much completely failed to take off other than those 18650 flashlights and vape pens.

The proprietary replaceable batteries are an improvement over non-replaceable but in anything other than cameras the replacements seem to get discontinued by the manufacturer by the time you actually need one.

E-cigs and Teslas, that is.

Aren’t Teslas running on 21700?

Only the Model 3. Model S and X are still using something close to 18650 (although I haven't followed Tesla's batteries for the last 8 to 9 months).

I’m building a solution: integrated bike lights on my bike (various strips, etc.), with a 3S 18650 battery holder that’s supposed to let me run nearly unlimited amperage (but with protection).

I’ll probably just recharge over USB, but I could swap the cells if on a longer trip.

The plan might include a motorcycle horn.

It will be nice to have hard-mounted lights and 1 central battery that I can stow-and-go at any time, rather the attaching and detaching everything to avoid theft.

Li-ion cells provides 3.6V, which makes them incompatible with traditional alkaline or NiMH. I don't think we've invented a standard for Li-ion batteries yet.

One concern about lithium cells is safety. Shorting alkaline cells won't do much, and even nimhs are relatively benign, but lithiums can start fires or explode when mishandled. Shipping lithum cells is for that reason bit of a hurdle too.

I think that's why the raw cells aren't used as the level of swappable unit very often. If the battery is at all removable, they're often integrated into packs which have some level of built-in protection.

The problem with bare 18650 cells is in their chemistry. A bad charger + good cell = nasty fire and a good charger + bad cell = the same. Considering the fact that every major online retailer including Amazon has trouble policing fake cells, the liability risks are fairly extreme. If there was a way to completely block all non-UL rated products as well as those with fake UL stickers, I'd say your idea has merit. Unfortunately, the near frictionless world of online markets allows for too much counterfeit risk to enter the picture for such an idea to be workable.

My bike lights are very bright, so I get maybe 10 hours out of them from the AA one i had before it broke. We have a lot of Eneloop batteries so it was great to be able to just swap out the power without waiting for a recharge.

My current light is also lithium and gets about 10 hours because of the brightness level, but it's a little smaller. I do miss being able to find ones that use replaceable batteries, though.

It's still super easy to find bike lights that use replaceable 18650 cells.

The giant blinding headlight ones that are great for off-roading at night, yes.

But most other use cases, no.

If you get a $3 18650 flashlight off ebay with the single XM-L led, they're fairly low brightness (I'd guess 250 lumen) and can be mounted as a bike headlight with a $2 adapter.

How are they using their bike lights and head lamps? Wall clocks, sure, use a constant draw. Bike lights and head lamps use a decent amount of power only when you have them switched on, which is intermittent.

I was expecting an informative discussion on the impact of producing/disposing/recycling Rechargeable vs Alkaline? Instead I just got, rechargeable = better.

My gut tells me rechargeable is better, but only if they are properly disposed/recycled 100% of the time. We don't need more heavy metals in our air/water from rechargeables being incinerated.

Any recommendations for chargers that don't require paired batteries? Some of my recent devices need batteries in 3's and 1's.

I've had good luck with the Nitecore intelligent chargers. Most of those allow for independent charging including different chemistry between slots.

I've recharged alkaline batteries and reused them quite a bit before they turned to muck.

> We don't need more heavy metals in our air/water.

Batteries in landfills are pretty inert. None of the heavy metal reactants in a NiMH or lithium cell[1] are ever in a liquid or dissolved state (the charge carriers are hydroxide and lithium ions respectively). One of the reasons they're so pervasive is precisely that these chemistries are safe and relatively non-toxic.

Really, if you're worried about discrete cell batteries and the environment, the solution is to minimize your use of them, not to worry about recyclable vs. not.

[1] Lead acid batteries are an exception, because the sulfuric acid does indeed dissolve some lead. But these really aren't the subject of the article, and in fact they're already being quite effectively recycled in practice.

Yes, I'd imagine so in properly capped and lined landfills. But those are on their way out as our landfills are filling up up[1] faster than new ones built. More and more towns are moving to incineration.

[1] https://www.globalcitizen.org/en/content/us-landfills-are-fi...

There are a lot of chargers with separate charging circuits for every slot.

I've had good luck with an Opus brand charger. The one I have allows selecting charging rates (200-1400 mA), and it has an LCD that tells you voltage, rate, status, etc. It also supports some discharge/refresh/test cycle stuff, although I don't know if the practicality of that is real. (If a battery isn't performing right, I feel like it's usually a lost cause.)

The Panasonic BQ-CC55 charger will charge from 1 to 4 cells, AA or AAA, in any combination. I've got 2 and they've worked great.

For about $10 more, also see La Crosse Technology's BC700. It can do some neat things like measure the capacity that was charged or run a "refresh" cycle that repeatedly drains and charges a battery (up to 20 times) until the measured capacity stops increasing.

Like the BQ-CC55, it has four independent channels that can charge either AA or AAA in any mix. You can even run different modes on each channel, like charging 1 and 2 while refreshing 3 and 4.

Ha! You beat me on making that recommendation. I have used a BC700 for about two years now, and am very satisfied with it.

I particularly appreciate how each of the four battery slots is separate. Not only does that mean each battery can be doing something different (charging, refreshing, etc.), it also means you can remove and insert different batteries at different times. This is great when some batteries are more (or less) discharged than others.

Also, worth noting that the BC700 supports NiCd and NiMH, in addition to AA and AAA.

I've had the BC700 (or possibly one of the identical builds under a different brand name) for years, but switched to the BQ-CC55.

The latter is "put in and forget". The former means fiddling with really bad buttons (because you can! Not really because you have to. But if I can manually set and micro-optimize the charging current, by God I will).

I worry much less about charging nowadays.

I can't say I've used the custom charging current options, but the refresh mode has rescued some batteries that (very unscientifically) did not seem to be holding much charge.

IIRC the default behavior is to charge at 200 mA and discharge at 100 mA.

These are great but toward the end of the charge cycle they make a lot of high-pitched sounds.

> Any recommendations for chargers that don't require paired batteries?

I've had a Powerex MC-C9000 [1] that I have used for at least a decade with no problems, mostly with Eneloops. It does not require pairing.

[1] https://www.amazon.com/Powerex-MH-C9000-WizardOne-Charger-An...

Photographers will tell you that using rechargeable batteries are the way to go when it comes to using flash/speedlights. They charge up much quicker than Alkaline and they either work or do not. Alkaline charges you flash at a slower rate and will give you weaker inconsistent power when they are dying (rechargeable give you all they can or just die out).

Disappointing. No mention of rechargable lithium batteries than are extremely popular for use in flashlights, among other things. No mention of the non-draining NiMH (eneloop) in comparison to traditional NiMH batteries. Just a reminder to use alkaline in smoke detectors, and even there it failed to distinguish between alkaline types (some last far longer than others).

I think the article makes the assumption that modern NiMHs are all of the Eneloop type. I think that's fair -- it seems like almost all the NiMHs I see for sale these days are the same type. The longer Wirecutter test article it references does go into a bit more about the history of the Eneloops and all the batteries it tested are the same type (which it calls "Low Self-Discharge NiMH").

Also, despite the title, I think the article is really "rechargeable" vs. "single-use". It doesn't explicitly say that the 10-year smoke alarm batteries are alkaline. The ones I've seen are actually lithium.

Probably not much of a coincidence, but I was researching smart chargers about twelve hours ago and ended up going for Panasonic's flagship (bc55). (As depressing as always, one bloke with a credit card can out-do any other organisation's economies of scale when importing anything into Australia.)

I've re-embraced eneloops partly for cost (already covered by OP) but also because they perform better (last longer, fail less frequently) in cold weather. This bites me each winter with a bunch of residential grade irrigation computers that use 2 x AAA. Confidence / reliability also factors in - when those things die I might not notice for a couple of weeks, until some plants start to look unwell, but aggressively replacing all the alkalines every six months (they usually last 9-12 months) worries me more from the rampant waste perspective than cost.

Supposedly IKEA LADDA batteries are rebranded Eneloops. It's not official, but the capacity and and discharge curves are the same:

https://petapixel.com/2018/02/16/eneloop-pro-20-batteries-ik...

Bought the IKEA charger because it was so slick and compact. Very happy with both charger and batteries, can recommend. Crazy low price as well, but to me that wasn't a factor.

Charger review here: https://lygte-info.dk/review/Review%20Charger%20Ikea%20Ladda...

That's interesting. My first thought was it's probably another of those things that IKEA sells everywhere except Australia - but happily the LADDAs are available here.

Though with one small caveat - the white LADDAs evidently come out of the same Japan factory that makes almost all the other good eneloops, but the brown LADDAs are known to come out of PRC, and don't exhibit the same quality.

Alkaline batteries are NOT good at low temperature.

The most reliable power I have found are the single-use lithium batteries, especially when the temperature drops.

I should also mention - use rechargeable batteries for devices you care about.

If they come with batteries, usually alkaline batteries, there's a good chance they will discharge, then start leaking and either damage or destroy the device they came in.

Meanwhile, rechargable batteries have much better sealing and rarely leak even if fully discharged.

Small(ish) price to pay to preserve an expensive device.

I wish more products would adapt 18650 batteries. My flashlight can pump out over 2000 lumens or still very bright for a really long time. 18650 has very high density, can be charged and discharged rapidly depending on the cell, and has safety fuses. I've thrown away a bunch of rechargable AA batteries and not a single 18650.

With lumens like that you would want 28650 otherwise it wouldn't last for too long.

Is there an easy way to get rid of rechargeables once they're dead? I have a bunch of them sitting in a drawer, because it's a pain to go to the city recycle facility. I highly doubt most people go to the effort. This is the big drawback to alkaline batteries for me, since those can be thrown away in the trash.

A number of big-box stores will let you properly dispose of them at the door - Best Buy and Target are two examples that come to mind.

Staples accepts all manner of used electronics for recycling, I just brought a sack of dead scanners, LCD panels, and about four years worth of dead AA's and coin batteries.

I don’t know that “can be thrown away” means “should”. IIRC, “disposable” batteries still contain mercury and other nasty shite. We take our alkalines to the community recycle day thing.

Most alkaline batteries manufactured today don't contain any mercury. Maybe since like 1996.

http://www.rayovac.com/products/batteries/educate/faqs.aspx

https://www.duracell.com/en-us/help/faq/do-your-batteries-co...

https://www.energizer.com/batteries/energizer-max-alkaline-b...

I use the bins right by the entrance of Lowe's and Home Depot stores. They also have bins for compact florescent bulbs.

I wish they had a bin for tube fluorescents - I want to change out my shop and garage lights for LED tubes, but I don't know where to get rid of my old tubes (short of waiting for a hazardous waste drive day - I always miss those).

Try Ikea if there is one in your area. My local ones all have bins for tubes and CFLs.

Note that I am in Vancouver BC which also has numerous recycling depots.

The public library near us accepts them. No idea how common this is, but it is worth it to check yours.

Those "dead" rechargeable batteries may have more life in them. Don't throw them away yet!

If your charger won't charge the battery anymore (showing the battery as "null"), there's a way to make it charge again.[1]

The technique is basically to use a paperclip to connect the positive terminals of a working and "dead" battery while they're both in the charger, only (unlike in the video) I do this with the charger unplugged from the wall socket. This only needs to be done for a few seconds for the "dead" battery to come back to life.

I used to discard many rechargeable batteries that I thought were dead before I discovered this trick. Since I started doing this, I've been able to keep using my old rechargeable batteries continuously, except that after a while they seem to hold less and less charge, so eventually I do get rid of them, but I no longer do so simply because my charger tells me they're "null".

[1] - https://www.youtube.com/watch?v=rFapDUSOgnY

Whatever you do, do NOT do this with lithium ion batteries. At low voltages, chemical side-reactions start to occur which result in dendrite formation which can pierce the membrane, shorting the battery: the result is fire. LiIon batteries generally have protection that permanently blow a fuse if the voltage goes below a minimum safe voltage, but raw 18650 cells often do not. The video above refers to NiMH cells. Afaik, this is safe to do for NiMH.

In Germany everyone who sells batteries has to take them back as well. I thought that was the case everywhere...? Also throwing alkalines into the trash doesn't sound right.

When it comes to recycling/sorting, it’s safe to say Germany is at the top, and everyone else is some mild to severe level lower.

Everywhere in the EU should do something similar, as part of the WEEE directive.

Sweden has pretty good recycling too, most things can be sorted within walking distance in bigger towns (guess 500+ people). Many garbage rooms have spaces for batteries and fluorescent lights.

Note that in EU alkaline batteries should not be thrown in mixed waste, so that is moot point around here.

What about Lithium AA[A] batteries?

I'd use them for critical applications (flashlight during camping/desert travel)

Better to just switch to lithium-first gear in that kind of situation.

Why buck 3.7V to 1.5V only to buck/boost it again?

I asked about it in another thread higher up https://news.ycombinator.com/item?id=20502338

In my trainings I've specifically been told not to use Lithium ion batteries in critical applications, like headlamps and beacons.

> Smoke alarms that are not hard-wired into your home’s electrical system get power in one of two ways: a built-in battery designed to last up to 10 years, or a disposable 9-volt battery that you should replace once a year.

No, they definitely make smoke alarms that take two AA.

Or Nest Protects at six lithium non rechargable cells. But specced to last five or ten years.

New York state banned the sale of smoke alarms with removable batteries earlier this year.

> Starting Monday, all new or replacement smoke detectors sold in the state must either be powered by a non-removable battery good for at least 10 years or be made to be hard-wired to buildings.

https://www.nbcnewyork.com/news/local/Law-Bans-Smoke-Detecto...

> built-in battery designed to last up to 10 years

Good luck with that. I have yet to see any of those make it past 10 weeks, let alone 10 months. And when they false alarm, you have to destroy the device to turn it off.

Great article, encourages me to go buy another battery recharger.

We have an XBox in the house, and 3 enthusiastic users. Lots of batteries....

Reply on news.ycombinator.com