Kentli LiIon AA batterys with 1.5V regulated output

[Julian Holtz]

Hi guys!

Anyone heard of these:

KENTLI AA 1.5Volt lithium polymer rechargeable battery

They must have squeezed in a little switching DC/DC converter to get the 1.5V.

Capacity of the LiIon cell must be around 700-800mAh, judging from the strange "mWh" rating they use.

I guess that the switching converter is activated if the positive contact is depressed. Otherwise, it would be on all the time, and drain the battery with rather high quiescent currents.

This means in return, that the battery must be inserted shortly before use, and is rather useless in long-term applications like TV remotes.

 

[TEEJ]

I think it also means that in use, an Eneloop would have more run time?

 

[uk_caver]

A freshly-charged standard Eneloop would seem to be a little over 2000mWh, so these cells would seem to have more energy capacity if the figures are accurate.

That said, with a mAh capacity of ~1870, that's a shade lower than a standard Eneloop.

A lot would depend on the application.
Put into a 3-cell LED light with a linear regulator, these cells would give pretty much the same runtime while causing more heat to be generated.

Used in a light with a buck and/or boost driver, the higher claimed capacity should give longer runtimes, though not massively greater than an Eneloop Pro, and for much higher cost and more inconvenience re: chargers.

Also, with a completely flat output, that would essentially render any kind of battery monitoring impossible, rather than just difficult.

Maybe someone will get hold of some and see how the claimed capacity works in reality, though at that price...

 

[Julian Holtz]

I also doubt their claim of 2800mWh.

At 1.5V output, this would translate to a capacity output of 1866mAh.

For the LiIon cell at 3.8V, this would mean 736mAh.

700-800mAh is the norm for normal LiIon cells of the 14500 (AA) size. Now take into account the space needed for the DC/DC converter and its efficacy, which will be 70% at best.

So let's take 600mAh x 3.8V x 0.7 = 1600mWh
1600mWh / 1.5V = 1070mAh


These are the limits of technology if they don't have Harry Potter in the design department.

 

[stp]

For the LiIon cell at 3.8V, this would mean 736mAh.

700-800mAh is the norm for normal LiIon cells of the 14500 (AA) size. Now take into account the space needed for the DC/DC converter and its efficacy, which will be 70% at best.

On one of the pictures from link in your first post if you look closely you can read: 760mAh (3.7V)
It's on the wrapper of the battery on the side, white letters on black background.

 

[moozooh]

These would actually be great for any voltage-demanding appliance that doesn't have a boost driver and can't handle PowerGenix's voltage range, i.e. a portable laser or something else like that. I really don't appreciate the fact that I absolutely have to use lithium primaries for my laser in order to make it burn as well as expected beyond the first ten minutes of battery life.

 

[ginbot86]

I bought a 4-pack of the Kentli AA batteries. When they arrive I'll get some 'internal' pictures and some battery capacity and internal resistance measurements. :3

 

[stp]

I bought a 4-pack of the Kentli AA batteries. When they arrive I'll get some 'internal' pictures and some battery capacity and internal resistance measurements. :3

I'm interested mostly in capacity and patiently waiting for your report

 

[arnstein]

This is interesting. I have an old Sony camera flash that only gives about 12 flashes on a set of 4 NiMH cells. Performance using lithium primary cells is much better.

Perhaps the higher voltage of the Kentli cells would work well in my flash.

Can you charge the Kentli cells in an ordinary Xtar charger, or is a specialized charger required?

 

[StorminMatt]

Another thing to keep in mind is that the power output of these cells is going to be limited by the electronics. In other words, these cells may have problems delivering sufficient current to high drain applications. Also, reliability of the electronics could be a concern. I would imagine that, in the name of keeping costs low, quality might not be the best.

 

[ginbot86]

(...) Can you charge the Kentli cells in an ordinary Xtar charger, or is a specialized charger required?

You can't charge this with a standard charger. There is a secondary contact (a ring around the 1.5 volt battery 'nipple') but you can probably get an electrical contact using a small spring (the original charger for these batteries does this).

Another thing to keep in mind is that the power output of these cells is going to be limited by the electronics. (...)

That's why I decided to buy these batteries. I was also interested in the power output of the battery's built-in regulator.

 

[chillinn]

Its been quite some time... did your Kentli cells arrive? What are your impressions? What is the actual capacity? The voltage consistency must be its selling point... no moon mode.

Even though they're $10 each, 2 month ship, I'm surprised to find there is not more technical information on them on CPF (educated speculation is nice, but it doesn't compare to the shared experiences of the accuracy-blessed members).

 

[ginbot86]

The first set I ordered never arrived and I eventually got a refund from the seller. I bought a new set (with the OEM charger) on eBay and it arrived a few months ago, but the testing and teardown's been on the "Pending" list for a while now. x3

One reason I haven't gotten to it is because I need to remake my battery fuel gauge setup to work with a 1.5-volt source; it should be done soon and I hope to get a teardown and capacity test in a few weeks' time.

 

[chillinn]

Sorry for my impatience. I just learned of their existence yesterday, yet I swear since learning of the existence of 4.2v Li-ion earlier this year, instantly I wondered if these existed. In considering the fantasy, prior to yesterday, I thought they'd be fantastically popular because of the energy density which I fantasized was the same as a 4.2v cell. Though I'm pre-emptively disappointed with the capacity, I am surprised by the makers claim and interested in its output curve. I am not turned off too much by the price, but the more I think about it, the crazier it sounds. That being said, I still want them.

Way off subject, but I also discovered NiOX yesterday as well... and now count... at least 13 different AA/AAA battery chemistry/voltage combinations commercially available including primaries and secondaries, and if LSD is really distinct from non-LSD NiMH, its really 14. "At least," only because I'm not a deep researcher, and as I said my adventure started months ago not years, but to be specific, prior to 2014, all I thought there was available was duty, alkaline, L-energizers, and NiCd. I believe we are in the midst of the golden age for batteries. There are quite a few massive, busting at the seams CPF belly-rubbing love-mine-and-whats-available flashlight these days threads, I think they come up periodically, but we need a dedicated AA and a different AAA battery thread like that (as well as for the other popular standards). I know there's many tester result threads, and query threads, but that's not what I mean. I'm starting to see that batteries, in a way, are not unlike coins or stamps on the one hand, and bottles and bottle caps on the other. If I can figure out what I'm trying to say, I'll start one myself.

 

[ginbot86]

No worries! I slacked off the past month by not having put out any blog posts and my blog's view count was down, consequently.

I've just peeled off the label of one of these and it's laser-welded at the top. I'll have to find a (fairly) non-destructive way of getting into this battery, maybe a carefully used pipe cutter...

EDIT: Got it open, the laser-welded seam came apart with only 2 turns of my pipe cutter. Inside is a cylindrical (!) Li-ion polymer cell, curiously labeled with 2.66 Wh of energy (compared to the outer label which stats 2.8 Wh...

 

[ginbot86]

Just finished my teardown and subsequent blog post!

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

 

[StandardBattery]

Seems like one could make a little cap for these batteries which would allow them to be charged in some standard chargers, such as those that have adjustable connectors in their battery bays. This would make these cells more appealing.

 

[chillinn]

Just finished my teardown and subsequent blog post!

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

I'm not sure how many are reading this thread, but something tells me I wasn't the only one breathing a sigh of relief after your last post. Then... wow, nice blog. Nicely done. Thanks... thank you!

 

[ginbot86]

Seems like one could make a little cap for these batteries which would allow them to be charged in some standard chargers, such as those that have adjustable connectors in their battery bays. This would make these cells more appealing.

So far, I was able to charge these batteries in my Intellicharger i4 using a small ring that I made out of some solar cell "bus wire" which is essentially just some thick copper ribbon. A spring can be used to do the same thing (heck, the official charger I have uses a spring to connect to the battery's 3.7-volt terminal).



I hope to have performance data within a week or so. I'm wrapping up a bunch of test data I collected on a fairly cheap Duracell-branded power bank, with a custom-made board for measurements. I'll adapt that board so I can simultaneously measure the battery and 1.5-volt outputs' voltage, current, and mAh delivered. Gotta love Texas Instruments' line of battery fuel gauges for this sort of work. :twothumbs

 

[StandardBattery]

So far, I was able to charge these batteries in my Intellicharger i4 using a small ring that I made out of some solar cell "bus wire" which is essentially just some thick copper ribbon. A spring can be used to do the same thing (heck, the official charger I have uses a spring to connect to the battery's 3.7-volt terminal).



I hope to have performance data within a week or so. I'm wrapping up a bunch of test data I collected on a fairly cheap Duracell-branded power bank, with a custom-made board for measurements. I'll adapt that board so I can simultaneously measure the battery and 1.5-volt outputs' voltage, current, and mAh delivered. Gotta love Texas Instruments' line of battery fuel gauges for this sort of work. :twothumbs

:thumbsup: Good going. I'm waiting for your data before picking up a pack.