{"id":483,"date":"2014-10-24T16:02:50","date_gmt":"2014-10-24T22:02:50","guid":{"rendered":"https:\/\/txsound.com\/blog\/?p=483"},"modified":"2016-05-21T09:38:58","modified_gmt":"2016-05-21T15:38:58","slug":"saga-kentli-lithium-ion-1-5-volt-aa-evers","status":"publish","type":"post","link":"https:\/\/txsound.com\/blog\/saga-kentli-lithium-ion-1-5-volt-aa-evers\/","title":{"rendered":"A saga of Kentli Lithium-Ion 1.5 volt AA rechargeable cells."},"content":{"rendered":"

Many folks are\u00a0very excited<\/strong> to see the first rechargeable Li-Ion AA battery, made by Kentli.\u00a0<\/strong><\/p>\n

\"KENTLI-8pcs-1-5V-2800mWh-font-b-AA-b-font-rechargeable-Li-font-b-polymer-b\"<\/a>

Kentli AA Lithium-ion rechargeable cells and charger.<\/p><\/div>\n

 <\/p>\n

\u00a0Here’s a cut-away view of their exciting new AA cell:<\/p>\n

\"so_8\"<\/a>

The guts of a Kentli Cell.<\/p><\/div>\n

The Kentli AA Lithium-Ion cell\u00a0was perceived as an exciting development, because all Lithium Ion cells are normally 3.7 volts. So even if the cell could fit into the AA form<\/strong>, the voltage was too high for\u00a01.5 volt applications. \u00a0What Kentli did was cram a 3.7 volt Lipo cell into an AA enclosure, and also stick a 3.7volt-to-1.5volt regulator\u00a0<\/strong>inside there as well. \u00a0The charging groove <\/strong>(see diagram) allowed the cell to be charged directly by the charger at 3.7 volts, bypassing the “motherboard” (regulator).<\/p>\n

Why would we want a Li-on AA cell, anyway? \u00a0The perceived advantages:<\/strong><\/p>\n

1. Ni-mH cells, the current rechargeable of choice, provide only 1.2 volts per cell. \u00a0That missing 3\/10ths of a volt can really add up when using multiple cells in series (battery)! The lower voltage also increases current draw<\/strong>, shortening the power-up time of the cell.<\/p>\n

2. Lithium Ion cells maintain almost\u00a0their rated<\/strong>\u00a0voltage<\/strong> right up till they\u00a0die\u00a0<\/strong> Other cells,\u00a0the voltage slowly drops as\u00a0the cell discharges. \u00a0Many digital devices will\u00a0shut-off\u00a0<\/strong>when the supply voltage falls to a certain level, leaving much potentially live-giving energy in the cell.<\/p>\n

3. For their weight, Lithium-Ion cells currently provide the most deliverable power than any other type of cell. They charge fast, are very\u00a0reliable, and last for many charge cycles. They are also tolerant to recharging at various states of discharge.<\/p>\n

More Advantages:<\/strong><\/p>\n

4. Rechargeable batteries create less land-fill waste.<\/p>\n

5. Rechargeable batteries create income,\u00a0<\/strong>as you can bill the client for these batteries like disposables. \u00a0So, they can routinely add about $20 or more to your daily rental income, without buying disposable batteries. \u00a0Over a year, that can add up (conservatively) to about US$3000. (<\/strong>that’s\u00a0<\/strong>if you work only about 14 days a month as a professional location sound mixer)<\/p>\n

So how well do Kentli Li-ion AA cells work?<\/strong><\/p>\n

As Chinese Industry is\u00a0prone to do, Kentli did some slight-of-hand marketing\u00a0with these products. They listed the capacity in milli-watt-hours<\/strong>, so\u00a0they could print that big 2800 mWh\u00a0<\/strong>on the side of the cell. \u00a0For people who don’t pay attention, this rating gives the mistaken impression that they are more powerful than 2700 mAh\u00a0<\/strong>(milli-amp-hour) Ni-MH rechargeables. 2700<\/strong> is a common value when looking for a high quality Ni-MH rechargeable. \u00a0At 1.5 volts, 2800 mWh translates to about 1867 mAh, \u00a0so the Kentli cell technically has less power. But Kentli claims their cell lasts as long as\u00a0the\u00a0Ni-MH, because the regulator allows the 1.5 volts<\/strong> to be maintained till the cell is completely exhausted.<\/p>\n

The street price for these Kentli AA cells is about US$11<\/strong> per cell, and the charger about US$20<\/strong>. More expensive than Ni-MH rechargeable. They are shipped directly from China through a few distributors, including sellers on ebay.<\/p>\n

 <\/p>\n

\"lectrosonics<\/a>

A Lectronics SMV transmitter. 1\/3rd of the package is for the cell.<\/p><\/div>\n

We bought 12 AA cells and 2 chargers to give these units a workout in our Lectrosonics SMV transmitters<\/strong>. \u00a0The SMV uses only one AA cell. \u00a0A disposable\u00a0Energizer Lithium AA<\/strong> will power it for 5 hours (the longest). The best NiMH\u00a0rechargeable will power it for about 3.5 hours.<\/p>\n

And the result? A fresh Kentli AA, right out of the box ,will power the SMV for 3.5 hours.<\/strong>\u00a0Same as a high quality, 2700 mAh Ni-MH rechargeable.<\/p>\n

But here’s the rub<\/strong>, in a few easy steps.<\/p>\n

1. In my application, Kentli AA’s take their internal cell from a full charge<\/strong> to near-exhaustion<\/strong> in every cycle. Over the long term, I think Li-Po rechargeables prefer a lighter charge-discharge\u00a0cycle. so with this workout,\u00a0these Kentli cells\u00a0won’t last for very many cycles. A Lectro SMQV would treat the cells more gently, distributing the current draw between two cells, and possibly resulting in better performance.<\/p>\n

2. Kentli AA’s use\u00a0a 3.7v Li-Po cell and convert it to 1.5 volts. There is inherent inefficiency<\/strong> in this conversion process. \u00a0The Lectro SMV<\/strong> then takes the 1.5 volts and inverts it up<\/strong> to 5\u00a0volts, and 3.3 volts, to serve the various internal functions. Every time you convert a voltage,\u00a0you lose some efficiency and power, in the form of heat. \u00a0<\/strong>The Kentli is already stretching the capacity to the max of its tiny 3.7 volt, 760 mAh cell, every time it is charged and used. With the SMV, there are multiple conversions, and those power losses\u00a0add up.<\/p>\n

3. These days, \u00a0the “power down” mode of many devices\u00a0is not a true<\/strong> power-down. Even after its turned-off, the SMV draws a tiny “quiescent current.” This is simply power\u00a0to enable the SMV to power back up with a momentary button-push<\/strong>. The Kentli sees this quiescent current, and therefore keeps its motherboard alive, affecting a continuous drain on its cell. So leave a freshly charged\u00a0Kentli in the SMV overnight, and it will be dead in the morning<\/strong>.<\/p>\n

4. Maintaining AA rechargeables for location sound use is a pain in the ass<\/strong>. They get lost<\/strong> easily. I lost one in the snow<\/strong> on the very first shoot! They are difficult to keep separate between used and unused<\/strong>. They require chargers to be travelled and plugged-in. They require\u00a0extra time to sort and charge and check<\/strong> at call and wrap.\u00a0\u00a0They create a level of uncertainty<\/strong> in the production process. Will this be the shot when the battery dies for good?<\/p>\n

5. And obviously<\/strong>, in the SMV, a rechargeable will run for only 3 hours, and a AA li-ion disposable will burn for 5 hours<\/strong>. \u00a0In most cases, 5 hours is enough time to get us to lunch, <\/strong>when the battery can be replaced.\u00a0 <\/strong>The SMV is designed to accept a cell that swings from 1.9 volts to .9 volts, and before it dies, will suck\u00a0every last ounce of power from the cell!<\/p>\n

6. Don’t talk to me about the Lectro SMQV, the double AA version. I know they will run twice as long. I don’t care. I like the smally-small SMV for so many reasons. I use it as a drop-weight\u00a0<\/strong>when running the lav cable down shirts and blouses and pant-legs. The SMQV is almost as large as a UM400A, Lectros classic 9-volt transmitter, of which I already have a shit-ton<\/strong>. \u00a0The SMV is great for use on children<\/strong>, with their tiny pockets and elastic waistbands. It also has the lowest profile<\/strong> in a pocket or bra-strap.<\/p>\n

Oh, and the Kentli Chargers tend to die.\u00a0<\/strong><\/p>\n

\"kentli<\/a>

The Kentli Charger with its ring-groove contacts. They contact directly with the Li-Po battery and charge at 4.2 volts.<\/p><\/div>\n

\"kentli,<\/a>

The innards of the Kentli AA charger<\/p><\/div>\n

\"P1010256\"<\/a>

A 5 volt phone charger inserted into the 5 volt rails of the Kentli charger. Fixed!<\/p><\/div>\n

Of the two Kentli chargers I originally ordered, one died a couple of months in. The dealer asked for photographic proof that the charger was dead. They sent a replacement from China, which never arrived, and then sent me another. \u00a0Eventually I received both chargers, so now I had four<\/strong>. Then the other 2\u00a0chargers\u00a0immediately died<\/strong>. \u00a0Taking this opportunity to either throw away the dead chargers, or take them apart,<\/strong> what do you think I did? The charger consists of a very flimsy switching power supply converting your\u00a0AC house current<\/strong> to 5 volts DC. The voltage is then applied to a smart charging circuit for the AA cells. The flimsy switch-mode supply was the obvious culprit, so it was replaced with an outboard 5 volt phone charger, of much more robust design. So now we\u00a0have 4 chargers.<\/p>\n

 <\/p>\n

Then, the Kentli\u00a0AA’s\u00a0start to show signs of age.<\/strong><\/p>\n

This is about the time that the Kentli AA cells stopped delivering<\/strong> 3 hours of power to the SMV’s. \u00a0This is not the cell\u00a0you want in a transmitter that goes out on a competition shoot<\/strong>, where you don’t have access to the talent once the action begins. I would guess I got about 100 charges<\/strong> on my Kentli’s before they began to show signs of expiration. The chargers show a full charge even on the cells that have stopped performing. In a less-demanding environment, (like an LED flashlight or an ipod dock) they may give better service.<\/p>\n

And Alas! one Kentli drops to the floor and pops open<\/strong> like a Zippo Lighter<\/strong>! (Also the shrink wrap on the cell will begin to tear and peel with daily use. )<\/p>\n

\"kentli<\/a>

Pops open like a Chap-Stick!<\/p><\/div>\n

\"kentli<\/a>

The Kentli regulator board.<\/p><\/div>\n

UPDATE<\/strong>\u00a0: Curious about the quiescent current draw of the Kentli Cell, on its own, we hooked up a micro-amp meter between the regulator board and the Li-Po cell. The result:<\/p>\n

\"kentli<\/a>

Kentli AA cells discharge on thier own, with a constant current draw of 29 microamps from the internal “motherboard.”<\/p><\/div>\n

You guessed it. The Kentli motherboard is drawing 29 microamps from the cell\u00a0at all times<\/strong>. \u00a0By comparison, Lectro transmitters, when powered down, draw about 5 microamps<\/strong> from the cell. \u00a0This is in conflict<\/strong> with the advertising claim<\/strong> made on the Kentli promotional material:<\/p>\n

\"discharge<\/a>

Advertising claim from Kentli’s promotional materials<\/p><\/div>\n

\u00a0\"P1010251\"<\/a>And whats this?<\/strong> A 3.7 volt, 2.66 wH li-po cell! That’s 2660mWh, or 718 mAh<\/strong>! Not 760 mAh, as the label claims!<\/p>\n

So there’s no doubt the Kentli folks are really pushing the envelope<\/strong> with this initial attempt at a 1.5V Lithium-Ion rechargeable. A little more conservative design paramaters are required for location sound use. But for flashlights and home use, I’m sure theres no telling! And no telling of what’s to become of my little AA canisters for a location sound mixer on the road!<\/p>\n","protected":false},"excerpt":{"rendered":"

Many folks are\u00a0very excited to see the first rechargeable Li-Ion AA battery, made by Kentli.\u00a0   \u00a0Here’s a cut-away view of their exciting new AA cell: The Kentli AA Lithium-Ion cell\u00a0was perceived as an exciting development, because all Lithium Ion cells are normally 3.7 volts. So even if the cell could fit into the AA […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[6,7],"tags":[89,88,92,87,90,55,91,82,19],"_links":{"self":[{"href":"https:\/\/txsound.com\/blog\/wp-json\/wp\/v2\/posts\/483"}],"collection":[{"href":"https:\/\/txsound.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/txsound.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/txsound.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/txsound.com\/blog\/wp-json\/wp\/v2\/comments?post=483"}],"version-history":[{"count":55,"href":"https:\/\/txsound.com\/blog\/wp-json\/wp\/v2\/posts\/483\/revisions"}],"predecessor-version":[{"id":799,"href":"https:\/\/txsound.com\/blog\/wp-json\/wp\/v2\/posts\/483\/revisions\/799"}],"wp:attachment":[{"href":"https:\/\/txsound.com\/blog\/wp-json\/wp\/v2\/media?parent=483"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/txsound.com\/blog\/wp-json\/wp\/v2\/categories?post=483"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/txsound.com\/blog\/wp-json\/wp\/v2\/tags?post=483"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}