Lithium 1.5v rechargeable batteries... why not?

[Paul_in_Maryland]

For now, the PowerGenix nickel-zinc AA cell comes closest to your 1.5V ideal rechargeable: 1.6 to 1.8V under load, outstanding safety, great cold-weather performance, and cheap. The main drawbacks are: fickleness (failing at an unusually high rate when overdischarged), a self-discharge rate that's higher than most of us would like; lowish amp-hour capacity (better than 14500, but worse than NiMH); and they require their own charger. Oh, and they're no longer made; when they're gone, they're gone.

 

[wadesrc]

I have been waiting for a battery like this too!!!

http://www.aliexpress.com/item/8-pc...13802224.html&cv=11032041&af=cj_3836173&vd=30

 

[ALW248]

For now, the PowerGenix nickel-zinc AA cell comes closest to your 1.5V ideal rechargeable: 1.6 to 1.8V under load, outstanding safety, great cold-weather performance, and cheap. The main drawbacks are: fickleness (failing at an unusually high rate when overdischarged), a self-discharge rate that's higher than most of us would like; lowish amp-hour capacity (better than 14500, but worse than NiMH); and they require their own charger. Oh, and they're no longer made; when they're gone, they're gone.

Other brands still offer NiZn.

 

[Frog_Botherer]

wadesrc:

I've seen those batteries too, and while the idea is exciting I'm not going to go out and buy those particular ones. I don't exactly trust a manufacturer who prints "mWh" on their batteries when they mean "mAh". If they can't keep that straight, what other corners are they cutting? That said, if someone braver than me wanted to buy these and run some tests on them that would be wonderful.

A AA-sized LiPo rechargeable with a step-down circuit to 1.5V would be a really neat thing though, and those batteries seem to imply that it's on the horizon. If the idea is a feasible one then hopefully we'll see better manufacturers coming out with batteries like that in the near future. If they can keep the energy density higher than LSD NiMH while fitting in the step-down and protection circuit, and if they can manage to keep the current capacity reasonably high, they could be a real step forward. It's probably a matter of technology rather than physics – packing a step-down-and-protection circuit in there that is robust, efficient, small, and has high current-carrying capacity is no trivial thing but with the right electronics it sounds doable.

They'll probably always be a bit more expensive and lower energy-density than normal 3.6V LiPos because that step-down circuit is going to take up space and increase the price, but there's just so much gear out there designed for 1.5V AAs, and AAs are so easy to come by (you can always find a crappy Alkaline at the corner store in a pinch) that I would love it if something like this became common and high-quality. Another advantage I could see is that the step-down circuit would work as a built-in voltage regulator, so that you would have a nice 1.5V output right up until the end (followed of course by a very sharp cutoff, but that's why we carry spares for critical applications, right?).

1.5V rechargeable AA lithium batteries may well be the next step forward in the evolution of rechargeables. If you ask me we're probably not quite there yet (unless somebody knows of a source of high-quality ones that's already out there) but maybe we will be soon.

 

[ginbot86]

wadesrc:

I've seen those batteries too, and while the idea is exciting I'm not going to go out and buy those particular ones. I don't exactly trust a manufacturer who prints "mWh" on their batteries when they mean "mAh". If they can't keep that straight, what other corners are they cutting? That said, if someone braver than me wanted to buy these and run some tests on them that would be wonderful.

A AA-sized LiPo rechargeable with a step-down circuit to 1.5V would be a really neat thing though, and those batteries seem to imply that it's on the horizon. If the idea is a feasible one then hopefully we'll see better manufacturers coming out with batteries like that in the near future. If they can keep the energy density higher than LSD NiMH while fitting in the step-down and protection circuit, and if they can manage to keep the current capacity reasonably high, they could be a real step forward. It's probably a matter of technology rather than physics – packing a step-down-and-protection circuit in there that is robust, efficient, small, and has high current-carrying capacity is no trivial thing but with the right electronics it sounds doable.

They'll probably always be a bit more expensive and lower energy-density than normal 3.6V LiPos because that step-down circuit is going to take up space and increase the price, but there's just so much gear out there designed for 1.5V AAs, and AAs are so easy to come by (you can always find a crappy Alkaline at the corner store in a pinch) that I would love it if something like this became common and high-quality. Another advantage I could see is that the step-down circuit would work as a built-in voltage regulator, so that you would have a nice 1.5V output right up until the end (followed of course by a very sharp cutoff, but that's why we carry spares for critical applications, right?).

1.5V rechargeable AA lithium batteries may well be the next step forward in the evolution of rechargeables. If you ask me we're probably not quite there yet (unless somebody knows of a source of high-quality ones that's already out there) but maybe we will be soon.

I think the mWh versus mAh rating is just to make the numbers look bigger. mWh = mAh * 3.7 volts, in the case of a Li-ion cell. I've been waiting on a 4-pack of the AA sized batteries since early October, and they haven't arrived yet. As for the regulator, I doubt that it'd be able to hold a steady 1.5 volts over a large current range. We'll just have to find out when/if I receive them.

I saw a chart outlining the discharge current and voltage and the plot is rather interesting. (Image re-hosted from my personal blog)

EDIT: Note how there is no real current data as for each load line. Without any data to correlate current and voltage, this graph isn't exactly helpful...

My whole blog post talking about this cell is available here: http://ripitapart.wordpress.com/201...hium-polymer-aa-battery-what-sorcery-is-this/

 

[StorminMatt]

I saw a chart outlining the discharge current and voltage and the plot is rather interesting. (Image re-hosted from my personal blog)

At what kind of discharge current was this made? Without any indication of discharge current, this is pretty much meaningless.

 

[ginbot86]

At what kind of discharge current was this made? Without any indication of discharge current, this is pretty much meaningless.

That's what I'm saying. The lack of actual current information means that the sales page image has pretty much no useful data.

My blog post talks about the graph in a bit more depth. That said, the forum and blog posts were done in the early hours of the morning, so my apologies if the postings are a little rough around the edges.

 

[HKJ]

At what kind of discharge current was this made? Without any indication of discharge current, this is pretty much meaningless.

Because the NiMH and alkaline has about the same capacity, it has to be at a fairly low current, maybe 100mA.

 

[glire]

A TPS54719 could draw some current and still be efficient at light loads.
But it would be strange to put 2-3-4 AA in series that, each, downs to 1.5V from 3.7V...
Or only one down to 1.5V then pushed to ~3.2V to drive a LED.

IMHO the question is not "why not rechargeable 1.5V AA" but "why is still AA alive at 1.5V" ?
HMDI replaced old fashion video connections thanks to industry agreements. I wish the same for cells, a standard prismatic cell of about 50x20x8mm embedding 5Wh of energy at least would be nice.

 

[Frog_Botherer]

Well I think it's just because 1.5V AAs are so damn ubiquitous and so much pre-existing gear runs on them, and devices that run off of other battery types are not backwards-compatible. With HDMI it was only a matter of replacing one or two pieces of equipment, and for a long time televisions and the like were backwards-compatible and would work with either the old connectors or the new (and some still do).

If 1.5V AAs disappeared a lot of people (including a lot of hardcore battery nerds, even) would suddenly have a lot of non-functioning gear that would need to be replaced, which would be annoying to say the least. And 1.5V AAs are perfectly fine for many applications (my wireless mouse will run for about a month on a pair of them, for instance) so that would mean that people would have to replace a lot of equipment that was otherwise perfectly good, just because the batteries to power it had become unavailable.

That said, better batteries (and gear that runs from them) are becoming gradually more common. 3.6V 18650s and the like have already mostly replaced AAs (or maybe it would be more appropriate to say that they've replaced C and D cells, which were what we used to use when we needed more capacity) in high performance applications like powerful flashlights and electronic cigarettes. And various custom-form-factor LiPo batteries are ubiquitous in stuff like cameras and phones where space and power are at a real premium.

1.5V AAs are probably here to stay for the foreseeable future, though. Perhaps something like a 14500 or a standardized prismatic will eventually replace them, but it will be a slow phase-out and AAs will stick around for a long time so that people can continue to run low-performance gear that works perfectly satisfactorily on 1.5V AAs. In the meantime, it will only be a good thing if manufacturers can continue to push the capacity and performance envelope for that battery type -- a lot of that technology (not all of it, but a lot) will carry over to other types of batteries, improving things across the board.

 

[Gauss163]

How batteries are designed - a glimpse into the mind of an expert

Is there any chance to develop a 1.5v rech. at a reasonable price or is the chemistry a limiting factor?

A look at future battery chemistries is a nice glimpse into the design decisions involved in constructing a rechargeable battery. It explains briefly how anode/cathode elements are chosen from the periodic table to meet various design constraints (including voltage). The author Yevgen Barsukov is a leading expert in battery technology at Texas Instruments (who did much of the work on TI's widely-used Impedance Tracking battery fuel gauge). The article is part of TI's Fully Charged blog, which contain many interesting, informative entries.

 

[ginbot86]

Re: How batteries are designed - a glimpse into the mind of an expert

I just bought a 4-pack of these Kentli AAs, along with a charger for it. A teardown and performance (voltage-vs-current, capacity, etc.) analysis will be done once I receive them.

Let's see if it actually arrives this time...

 

[ginbot86]

Re: How batteries are designed - a glimpse into the mind of an expert

After much anticipation, my 4-pack of Kentli AAs and its charger have arrived today! When I get to doing a teardown and analysis on them, I'll make a separate thread for it.

 

[Richwouldnt]

Re: How batteries are designed - a glimpse into the mind of an expert

ginbot86; Glad to hear it. Looking forward to some good analysis and performance numbers. The posted link batteries seem mighty expensive at about $12 per cell. I agree with the earlier post about using watt hours for bigger numbers as the nickel zinc battery makers did exactly the same thing. All a numbers game and DO NOT read the fine print!

The reason for the continued existence of alkaline batteries is that they ARE CHEAP and work fine in most low current demand devices. They are lousy at higher current draws and have a propensity for leaking but for the average consumer the price per battery seems to be the main consideration. After all what is the justification for the continued production and sale of Carbon Zinc batteries with their minimal performance other than they are even cheaper than alkaline batteries to produce so can be sold for less. I have a batch of Panasonic AA Platinum Power batteries coming from Amazon and they claim reduced risk of leakage construction and a 10 year shelf life when properly stored. Pretty good if true at 50 cents per battery including shipping and I have seen alkaline AA batteries going for 25 cents each from some sources. Panasonic is, I believe, now the largest battery manufacturer on the planet.

 

[ginbot86]

Re: How batteries are designed - a glimpse into the mind of an expert

Yep; I can understand why many other manufacturers don't go with this route of putting a regulator in a Li-ion battery and turning it into a 1.5 volt battery. Paying $10+ for a single cell is pretty steep (and the AAAs are even more expensive).

I can understand why Kentli wants to characterize their cells using mWh rather than mAh (at least from an engineering standpoint). The use of mAh (constant-current modeling) for capacity isn't as accurate when dealing with batteries with a different nominal voltage. The use of mWh (constant-power modeling) allows the batteries' energy to be more accurately represented. Additionally, the use of a switch-mode buck converter in the battery means that the Li-ion cell inside will essentially see a constant-power load, even if the device is drawing a constant current from the 1.5-volt side.

But of course, bigger numbers look better.

 

[cenz]

Re: How batteries are designed - a glimpse into the mind of an expert

I heard this type battery before, but not in flashaholic field, is portable audio field, specially used for AMP/PCM recorder.. here is the link which is a chinese thread that the reviewer use "ear to feel" to test this Kentli with 2 typical Ni-MH brand, he said the bass is more powerful (solid / tight bass?) with Kentli, so the sound is different/enhanced because of high/constant current from the 1.5v li-ion tech.?

He also intro that is type of li-polymer constant-voltage 1.5v

 

[Sivy]

Re: How batteries are designed - a glimpse into the mind of an expert

Can these Kentli batteries be charged in a regular Li-ion charger?

 

[HKJ]

Re: How batteries are designed - a glimpse into the mind of an expert

Can these Kentli batteries be charged in a regular Li-ion charger?

There is a problem with the connection, the plus pole need a special shape:

 

[ginbot86]

Re: How batteries are designed - a glimpse into the mind of an expert

Finally got a teardown finished on this little battery, performance data coming soon!

http://ripitapart.wordpress.com/2014/12/06/teardown-of-kentli-ph5-1-5-v-li-ion-aa-battery/

 

[StandardBattery]

Re: How batteries are designed - a glimpse into the mind of an expert

Finally got a teardown finished on this little battery, performance data coming soon!

http://ripitapart.wordpress.com/2014/12/06/teardown-of-kentli-ph5-1-5-v-li-ion-aa-battery/

Excellent. Thanks!