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Author Topic: Anyone know this battery?  (Read 4412 times)

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Offline capnhook

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Re: Anyone know this battery?
« Reply #15 on: April 01, 2012, 01:38:59 PM »
I have one battery that is ready for re-cellin'....I'll see you at Shakori, byronsos!
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kirk97132

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Re: Anyone know this battery?
« Reply #16 on: April 01, 2012, 03:32:48 PM »
Well, it certainly meets the specs on the page, but it is only 13300 mAh at 3.6V, not 9V.  At 9V, it is 5400 mAh.  Price seems a little high for that capacity.

I'm not sure this is exactly right either.  Based on what I know about the 18650 battery cells, which is what these DVD batteries are made from, the highest mAh rating out there is 5000 mAh @ 3.6 volts.   I am not exactly sure where the battery manufacturer is getting their ratings and that is where the confusion comes in.  The DVD battery is 3.6 x 2 = 7.2volts and then they step up the voltage to 9 volts.  When you step up the voltage you "step down" the mAh capacity.  SO,  the highest capacity cells would give you 15,000 mAh rating which would be about right for a 9 volt DVD battery rated at 13,300.  We don't know the exact formula to adjust for the voltage conversion done internally in the battery.  The real kicker is that 48Wh rating does not match anything.   And if that number is correct then the battery really works out to about a 4200mAh battery.   Which is on the low side of DVD batteries.  OR depending on how they arrived at that number it works out to about 10,000 mAh @ 9 volts.  Most that we use are 5400 and 6000 mAh rated.  Those batteries use the 2000 and 2400 mAh cells. This is just more confusion since there is no "standard" way to list battery capacities so a manufacturer can work the gray area's to make a battery look like it is bigger than it's real world application reveals.  The only way to be sure would be to see if the batteries in the that new DVD battery actually had a rating one them.  BUT even IF you open it there is no guarantee that the battery will have it printed on it.   

stevetoney

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Re: Anyone know this battery?
« Reply #17 on: April 01, 2012, 05:32:47 PM »
The only way to be sure would be to see if the batteries in the that new DVD battery actually had a rating one them.  BUT even IF you open it there is no guarantee that the battery will have it printed on it.

Bryonsos you could cycle your new battery a couple of times (you aren't supposed to need to do this with Li-ions, but I still do) and then using a recorder or something that you know the current load of see how long it takes to drain the battery and then do some math.  Should get you a reasonable estimate of the actual battery capacity. 

If you don't know the current draw from anything, you could 'calibrate' the current draw of one of your 9V devices by checking run times off a fresh set of batteries.  The specs of commercial batteries are published on the web.  Course, that would only work if your device was capable of also being powered external from the DVD battery and you have a cable for that.

Offline Todd R

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Re: Anyone know this battery?
« Reply #18 on: April 03, 2012, 11:14:59 AM »
Well, it certainly meets the specs on the page, but it is only 13300 mAh at 3.6V, not 9V.  At 9V, it is 5400 mAh.  Price seems a little high for that capacity.

I'm not sure this is exactly right either.  Based on what I know about the 18650 battery cells, which is what these DVD batteries are made from, the highest mAh rating out there is 5000 mAh @ 3.6 volts.   I am not exactly sure where the battery manufacturer is getting their ratings and that is where the confusion comes in.  The DVD battery is 3.6 x 2 = 7.2volts and then they step up the voltage to 9 volts.  When you step up the voltage you "step down" the mAh capacity.  SO,  the highest capacity cells would give you 15,000 mAh rating which would be about right for a 9 volt DVD battery rated at 13,300.  We don't know the exact formula to adjust for the voltage conversion done internally in the battery.  The real kicker is that 48Wh rating does not match anything.   And if that number is correct then the battery really works out to about a 4200mAh battery.   Which is on the low side of DVD batteries.  OR depending on how they arrived at that number it works out to about 10,000 mAh @ 9 volts.  Most that we use are 5400 and 6000 mAh rated.  Those batteries use the 2000 and 2400 mAh cells. This is just more confusion since there is no "standard" way to list battery capacities so a manufacturer can work the gray area's to make a battery look like it is bigger than it's real world application reveals.  The only way to be sure would be to see if the batteries in the that new DVD battery actually had a rating one them.  BUT even IF you open it there is no guarantee that the battery will have it printed on it.

I think Kirk is on the right trail, though I'm not following everything.

Overall, I'd say the 48Wh is an accurate description, and this is basically the same DVD-type battery in widespread use at ts.com -- namely, 9v and 5400mAh.

48Wh could be a slightly rounded figure, say it is actually 48.4Wh, or 48400mAh:  at 9v, that is a capacity of 48400/9 = 5378mAh, or again rounding, 5400mAh -- same as the typical DVD battery.

As for the 13,300mAh spec'd rating:  48,000mWh/13,300mAh = 3.6V, which is the voltage of a typical, single Li-ion cell.  Pretty sketchy marketing, but the battery probably has 13,300mAh of capacity internally, except that that is at 3.6v, not 9v, and needs to be stepped up.

As Kirk notes, step up the voltage, and you need to step down the mAh capacity at that voltage.  Worse, a DC-DC step up circuit will not be 100% efficient, so if you step a 3.6v battery to 9v, you'd need to multiply the 3.6v mAh capacity by 3.6/9 to get the new 9v mAh capacity, and then multiply that again by say 90% (total ballpark here) to account for the inefficiency of the DC-DC converter.  If there really are 13,300 mAh of 3.6v cells inside, that would be 13,300*3.6/9*0.90 = ~4800mAh, or only about 43Wh total capacity.

Hopefully, they are putting in something like six 3.6 V, 2500mAh capacity Li-ion cells, which would yield 6*2500 = 15000 mAh capacity at 3.6v, or at 9V:  15000*3.6/9*0.90 = 5400 mAh capacity at 9v, or ~48Wh capacity as labeled.

Bottom line, this is most likely just a 9v, 5400mAh very typical DVD battery, with some pretty sketchy marketing.
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kirk97132

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Re: Anyone know this battery?
« Reply #19 on: April 03, 2012, 11:39:53 AM »
Todd, I made the mistake of multiply the rating by the voltage not dividing it, which lead me to the conclusion that the Wh rating was wacky.  Nice catch.  So bottom line is we arrive at the same conclusion that is very unlikely these are a 10,000mAh total capacity with a 48Wh rating.   SO far I have opened up four different DVD batteries 3 - 9volt version and 1 - 7.2volt version.  All different manufacturing labels and all have run either 2000 or 2400 mAh 18650 cells in them.  It is a shame that they can con you with shady marketing tricks.  It reminds me of amplifiers that would list their output at something like 200 watts and then in fine print say it was 100 watts per channel.   I have not seen any DVD battery sold that exceeded the 8,000 mAh total capacity.  I've seen other style "laptop" batteries that get up in the 12,000 plus ranges but not the typical "wallyworld" style that is prevalent among us tapers. 

website for Wh to mAh conversion and related battery voltage differences:
http://www.camerahacker.com/Definitions/Battery_Capacity_Conversion.shtml
« Last Edit: April 03, 2012, 11:44:30 AM by kirkd »

Offline bryonsos

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Re: Anyone know this battery?
« Reply #20 on: April 03, 2012, 01:58:40 PM »
In retrospect, I should've looked more closely at the specs, but it's a good battery so I'm not upset. Like I said, reputable dealer (shadowy advertising maybe) rather than the outright eBay scammers. This is one I found there on a quick search, so the price I paid isn't too far off:

http://www.ebay.com/itm/ULTRALAST-UL-DVDL-UNIVERSAL-9V-PORTABLE-DVD-BATTERY-NEW-/360035400988?pt=LH_DefaultDomain_0&hash=item53d3c83d1c#ht_3049wt_1398

In the course of looking for other DVD batteries to compare, I found this interesting battery. Seems too good to be true. Kirk et al., does their math make sense? For $25, it's probably worth a try, although the mechanical on/off switch could be a problem.

http://www.ebay.com/itm/dual-outputs-5V-9V-12V-USB-Super-Capacity-Recharge-Li-ion-Battery-/150767785265?pt=US_Batteries&hash=item231a75d531
« Last Edit: April 03, 2012, 02:01:10 PM by bryonsos »
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kirk97132

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Re: Anyone know this battery?
« Reply #21 on: April 03, 2012, 02:50:13 PM »
I actually have one of those.  My opinion is rather ..eh...on them.  Drawbacks, no meters at all.  Has an on off switch that can easily get turn off, I made a guard for mine.  Takes a long time to charge.  And there has been discussion about the battery causing noise, it is very low and down in the mic self noise range but it is there.  I got it for the USB output and at 5V it's ok, I found it has a hard time supplying my USBPre 2 with enough current for my mics that draw 10mA.  Granted they are very high draw mics.  I can't say I'd give it a great endorsement.  The lack of a meter is a huge downside. 

The other problem you will have in determining the total capacity is you don't know how the batteries are connected.  IE: how many are parallel and how many are in series.  Then the rating does not tell you at what voltage it will supply 500mA.  I could find any specs or websites for the cells they listed as being used.

Offline bryonsos

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Re: Anyone know this battery?
« Reply #22 on: April 03, 2012, 02:53:28 PM »
I actually have one of those.  My opinion is rather ..eh...on them.  Drawbacks, no meters at all.  Has an on off switch that can easily get turn off, I made a guard for mine.  Takes a long time to charge.  And there has been discussion about the battery causing noise, it is very low and down in the mic self noise range but it is there.  I got it for the USB output and at 5V it's ok, I found it has a hard time supplying my USBPre 2 with enough current for my mics that draw 10mA.  Granted they are very high draw mics.  I can't say I'd give it a great endorsement.  The lack of a meter is a huge downside. 

The other problem you will have in determining the total capacity is you don't know how the batteries are connected.  IE: how many are parallel and how many are in series.  Then the rating does not tell you at what voltage it will supply 500mA.  I could find any specs or websites for the cells they listed as being used.

Thanks! Glad I waited to hear responses. The lack of a meter is a deal breaker for me, when I get a few  :suds: in me, I need things to be as idiot proof as possible.
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