EEVblog #1200 - BUSTED! - Energizer & Duracell NiMH

[Barny]

Are you getting ripped off with Energizer and Duracell D cell NiMH rechargeable batteries? Why is a D cell NiMh the same capacity or lower than the smaller C or even AA cell? Teardown time!

[Barny]

Ca. 1995 I got D Cells from Hofer (Austrian version of Aldi).
They where Sony branded (I think).

They had standard AA cells stuck in place.

By the way, Dave got really lucky.
Clive took NiMh apart and they ot really exiting.

https://www.youtube.com/watch?v=tBg4ximDrsk=related#t=16m10

[helius]

He said he fully discharged them before disassembly; I think he is quite aware of the danger if you skip that step.

[digsys]

Well, I'm sold :-)
Not sure if this holds for all brands etc but this is similar to finding out what is inside a 9V battery, and why such poor capacity !

[drussell]

He said he fully discharged them before disassembly; I think he is quite aware of the danger if you skip that step.

Big Clive discharged those AAs before disassembly also!!

That's part of the reason why he was so surprised when the flames erupted...  Big Clive isn't often at a loss for words, but he was absolutely flustered at about 18m into the video. 

Just because a cell is in a discharged state doesn't mean there isn't still the potential for chemical reactions and energy release from the materials composing said cell!

What's inside Eneloop and LIDL NiMh cells (fire, apparently)
...
I thought that discharging the cells completely would avoid little unexpected combustion incidents.... I was wrong.

https://youtu.be/tBg4ximDrsk?t=980

I was rather disappointed that Dave didn't even need an Explosion Containment Pie Dish...   

No flames even?  I suppose we should all unsubscribe!   

Edit:  I did get a good chuckle when at 12m Dave said "I won't pretend to know the exact chemistry inside..." because it was very reminiscent of Big Clive's "Ok...  Right... Yeah... Not, not sure the science of this, but this is all going on fire quite rapidly.  So, that's quite an exciting chemical.  Oh, this isn't necessarily quite good.  Where is my Explosion Containment Pie Dish?"

 

But then there were no flames....

Of course, I suppose to fit the 2500 mAh into the AA size case instead of C, they have to do things a tad bit more "energetically"?

[G7PSK]

I took a Duracell apart some years ago and it had an AA cell inside so at least they have increased the capacity over the last seventeen years or so since then.

[BravoV]

Eneloop uses smaller 3xAA for D, or 4xAAA for C size.

[Moshly]

The D cell in these 80's rat shack batteries was a C cell with a tall nipple & lager plate spot welded to the bottom.

[jonovid]

Well, I'm sold :-)
Not sure if this holds for all brands etc but this is similar to finding out what is inside a 9V battery, and why such poor capacity !

I have seen 9V battery half full of button cells
but back in the day a 9V battery had a Full deck of cards dipped in wax.

also
I remember a time when I was only 5yro
I remember a time when "D"  Dry cell batteries had a graphite rod cathode inside t

from the 1960s and 1970s  radio and telephone use

http://archive.siliconchip.com.au/cms/gallery/article.html?slideshow=0&a=110151&i=12

[DDunfield]

This is actually very common. I've seen many D (and even C) NIMH cells which are constructed from smaller physical cells.

It stems from the fact that "back in the day", The commonly used carbon/zinc batteries had a relatively high internal resistance, and you needed physical size of elements to get higher currents. As a result many applications where D cells were spec'd were more for current capability and less for longevity.

Alkaline cells improved on this, but not enough to change the practices. Along comes NICAD and NIMH and now you can get a lot of current from a much smaller cell.

Add to that the fact that you need a smart (& beefy) charger to charge a 10,000mah cell in a reasonable time, and for many consumer applications the "reduced" D cells almost-kinda make sense. They are (maybe) lower cost, can be recharged with a simpler, cheaper charger (the kind a typical non-EEVBLOG consumer is likely to buy), and operate higher draw devices as well as and often better than non-rechargeable cells.  Sure they may not last as long, but they are rechargeable and the consumer will smile about how much money he's saving every time he recharges them.

While I don't fully agree with it, I don't think the reduced cells are a blatant scam... they are fitting new technology into an old form factor in a way that for some applications is reasonable.
They could be more up-front about it, but like most products "Caveat emptor" - you really need to know what you are buying.

A better (at least more up-front) alternative is that you can buy adapters to convert smaller NIMH batteries into larger form factors for cases where doing so makes sense.

Dave

[HKJ]

Well, I'm sold :-)
Not sure if this holds for all brands etc but this is similar to finding out what is inside a 9V battery, and why such poor capacity !

I have seen 9V battery half full of button cells

That is not common for primary cells. I took a lot of them apart here:

https://lygte-info.dk/info/BatteryDisassembly9VAlkaline%20UK.html

And did not find a single button cell

[madires]

The pricing is also interesting. GP ReCyko+ ready-to-use NiMH cells for example, a double pack of D cells with 2200mAh is EUR 10.70, double pack of 2000mAh AA cells EUR 5.40 and the double pack 2600mAh AAs just EUR 8.20. You pay a premium for the "larger" cell despite having a low Ah rating. Varta seems to be reasonable, double pack ready-to-use D cells with 3000mAh for EUR 8.99 and the double pack of AAs with 2600mA is EUR 7.25.

[HKJ]

I have done some performance test on C & D cells, both NiMH and Alkaline: https://lygte-info.dk/review/batteries2012/CommonCDcomparator.php

Comparing them to AA can be done here: https://lygte-info.dk/review/batteries2012/CommonAAcomparator.php

The low capacity D cells are better than AA cells at high current.

[madires]

That makes perfectly sense when you consider that the nearly C sized inner cell with 2.x Ah has more surface area than a AA with the same Ah rating.

[SilverSolder]

Perhaps there is a safety issue here as well?  -  A product with 12 "real" D cells inside it could release quite a lot of energy if something went wrong?

For those that know what they are doing, there are thankfully "real" batteries available...

[free_electron]

Old news. That has been the case since they first introduced NimH batteries. A true D cell is at least 5000mAh.

D-cells are on their way out. apart from flashlights very little stuff uses that, and with the advent of powerful LED lights the flashlight marked has moved to LiIon rechargeable. You can find many adapters to convert C to D or 3 or 4 AA or AAA to D.

[johnlsenchak]

That  Duracell  battery  with  it's  electrolytic capacitor  rolled  design is much different   then the ones in the late  seventies  that I took  apart as  a kid. Back then it was  a full  battery compartment   of  black wet powder   with a big carbon rod  in the center as the positive  anode.


This video   real shows how consumer  battery technology changed in the last  forty  years.

[james_s]

Almost all D cell rechargeable batteries have a sub-C or in modern types even a AA inside, this has been standard since the beginning. You can buy true D cell NiMH batteries but they are much more expensive and quite hard to come by. At least these list the true capacity on them.

[thm_w]

The pricing is also interesting. GP ReCyko+ ready-to-use NiMH cells for example, a double pack of D cells with 2200mAh is EUR 10.70, double pack of 2000mAh AA cells EUR 5.40 and the double pack 2600mAh AAs just EUR 8.20. You pay a premium for the "larger" cell despite having a low Ah rating. Varta seems to be reasonable, double pack ready-to-use D cells with 3000mAh for EUR 8.99 and the double pack of AAs with 2600mA is EUR 7.25.

Its fair to charge some premium as the cell is larger in size and probably not sold in such a high quantity. 2x seems quite a bit though.

Tenergy D 8000mAh - $5.87
Energizer D 2500mAh - $4.00
Energizer AA 2300mAh - $3.00
Alkaline D 12-18kAh - $1.00

So, Energizer is overpriced, if they actually made a full D cell they would probably charge $10 for it, which may be too much for consumers to stomach.

[james_s]

The Tenergy cells I've had were garbage and did not meet quoted capacity, it's possible this has changed though.

I'm thankful for modern chargers that measure capacity, it is making it a lot harder for companies to screw people by lying about the capacity.

[tsman]

That  Duracell  battery  with  it's  electrolytic capacitor  rolled  design is much different   then the ones in the late  seventies  that I took  apart as  a kid. Back then it was  a full  battery compartment   of  black wet powder   with a big carbon rod  in the center as the positive  anode.

You're thinking of primary cells like zinc carbon or alkaline. Rechargeable batteries have the roll construction instead for low internal resistance.

[thm_w]

The Tenergy cells I've had were garbage and did not meet quoted capacity, it's possible this has changed though.

Yeah their normal cells are crap, I should have specified its the Tenergy Centura low self discharge, which are a bit better.

[digsys]

... That is not common for primary cells. I took a lot of them apart here: https://lygte-info.dk/info/BatteryDisassembly9VAlkaline%20UK.html

Very handy / informative sites, including links. Great work

[retiredcaps]

When I needed several D cells to run for several hours, I got the AA to D adapters and used eneloops.  Worked great for the time I needed them.

[james_s]

I do that too, although it can't match the capacity of a true D cell which is handy in some applications.