Energizer 15 minute NiMH charger

This is the place for any magazine-related discussions that don't fit in any of the column discussion boards below.
User avatar
MrAl
Posts: 3862
Joined: Fri Jan 11, 2002 1:01 am
Location: NewJersey
Contact:

Energizer 15 minute NiMH charger

Post by MrAl » Tue Sep 05, 2006 5:00 am

Hello there,

Anyone try this charger?

I got one yesterday and checked it out and it looks like
the charger unit doesnt put out enough current in order to
charge 2200mAh cells in 15 minutes. It looks like it should
take 20 minutes but the charger stops charging at the high
rate after 15 minutes anyway.
LEDs vs Bulbs, LEDs are winning.

User avatar
Sambuchi
Posts: 366
Joined: Tue Jan 18, 2005 1:01 am
Location: Orlando FL
Contact:

Re: Energizer 15 minute NiMH charger

Post by Sambuchi » Tue Sep 05, 2006 5:36 am

MrAl wrote:
Anyone try this charger?

Who makes it! What model?

User avatar
MrAl
Posts: 3862
Joined: Fri Jan 11, 2002 1:01 am
Location: NewJersey
Contact:

Post by MrAl » Tue Sep 05, 2006 7:00 am

Hi,

As the subject 'suggests', it's made by "Energizer", and its
probably the only 15 minute charger made, but here is the
model number...

CH15MN

.
LEDs vs Bulbs, LEDs are winning.

User avatar
Sambuchi
Posts: 366
Joined: Tue Jan 18, 2005 1:01 am
Location: Orlando FL
Contact:

Post by Sambuchi » Tue Sep 05, 2006 1:07 pm

opps!

I saw NiMH charger and jumped to the post.

I have the same charger .. Energizer 15 minute charger uses an algorithm for charging. It dumps around 7.5 amps into the cells.

What do you see your charge current being...

I've also heard that these chargers only charge up to 96%

User avatar
MrAl
Posts: 3862
Joined: Fri Jan 11, 2002 1:01 am
Location: NewJersey
Contact:

Post by MrAl » Tue Sep 05, 2006 2:58 pm

Hi there,

Well it's easy to calculate what current will charge a given cell up
to in some length of time.

For example, for a 2.2Ah cell assuming 10% charge loss during charge
and charging to 100 percent capacity

2.4 amps will charge it in 60 minutes
4.8 amps will charge it in 30 minutes
9.6 amps will charge it in 15 minutes

In other words when you double the charge current you halve the
time it takes to charge.

Note above however that it takes 9.6 amps to charge in 15 minutes,
not the 7.5 amps the charger actually puts out to the cell.
LEDs vs Bulbs, LEDs are winning.

User avatar
haklesup
Posts: 2978
Joined: Thu Aug 01, 2002 1:01 am
Location: San Jose CA
Contact:

Post by haklesup » Tue Sep 05, 2006 3:52 pm

But you rarely discharge a battery to 0%. Their rating might reflect the more common occurance or recharging after recent use rather than a long dead battery in the bottom of a drawer. Also their bost might only apply to their own batteries which are well characterized to them. Another brand might charge slightly differently.

You wouldn't want to charge much faster or closer to 100% anyway. At that rate, the resulting heat would ultimately shorten the battery life and increase the risk of catastrophic failure of the cell (leaking or rupture). Fire is unlikely unless the charger were defective and did not shut down current when a short was detected. These are better called smart chargers since a simple rectifier/regulator wouldn't provide enough protection to risk such a fast charge rate.


BYW, dispite the product name, the datasheet does spec a charge time of 20 minutes
http://data.energizer.com/PDFs/ch15mn.p ... 2CH15MN%22 Dang marketing guys.

Note also the requirement for a cool room (less than 77F) and a suggestion that an extra 10 minutes of charging obtains full performance (trickle charge to 100%). Good hints that the technical capabilities are what you expected but covered up by a marketing idiot.

bigkim100
Posts: 94
Joined: Fri Jul 26, 2002 1:01 am
Location: Canada
Contact:

Post by bigkim100 » Tue Sep 05, 2006 5:02 pm

For those that dont know this charger, it has a integrated fan that really blows like crazy onto the internal circuit board. There must be a feedback to the fan, as it continually speeds up and slows down during the charging cycle. It sounds like a tiny little jet airplane in the kitchen while charging.

I have tried MANY different AA sized battery chargers from MANY different manufacturers...and this is the ONLY unit that works with my el-cheapo battery-pig camera. All the other chargable batteries...and even super expensive batteries designed specifically for digital cameras, last for only 10-15 pictures (some show a low battery warning immediatly after being charged) while this unit gives me about 50 pictures without breaking a sweat. These batteries also seem to last the longest after charging when the camera is not in use. Often I take my camera out of the closet after several months and the batteries are good.
The charger stops by itself...not giving me a chance to try to overcharge them.
It was in use this am. when the kids were off to school for their first day. I paniced...slapped the charger into the wall, and it stopped after about 10 minutes. I then took 30 pictures and about 10 minutes of MPEG video/audio, and the batteries still show up as 38% good.
My only complaint is that the batteries come out of the charger sizzlin' hot....but it hasnt seemed to effect them at all. :evil:
Kim..The man with the cute little girls name...and Frankensteins face and body.

User avatar
haklesup
Posts: 2978
Joined: Thu Aug 01, 2002 1:01 am
Location: San Jose CA
Contact:

Post by haklesup » Tue Sep 05, 2006 5:09 pm

If the Internal series Resistance of the battery were only 300m ohms, that would be 2-3W coming off the battery itself. Certainly enough to get hot in 15 minutes

http://www.batteryuniversity.com/partone-22.htm
See Figure 5 this webpage for Battery resistance.

User avatar
MrAl
Posts: 3862
Joined: Fri Jan 11, 2002 1:01 am
Location: NewJersey
Contact:

Post by MrAl » Wed Sep 06, 2006 12:08 am

haklesup:
Actually i always use my cells to close to zero percent charge because
i use them in a flashlight and i know to charge when the light dims
considerably, and the voltage at that point measures just under 1 volt.
Thanks for the link to that 'manual' for this product. It confirms
that they use 7.5 amps charge current.
I also considered that the cells that came with my unit were actually
rated less then stamped on their sides (which i've found many cells to
be anyway) and that would make them appear to charge faster because
they require less charge, but when i put the cells that are 'done'
(more on this later) into a slower charger, the cells seem to take
another 500mAh of charge. This seems to confirm my suspicion that
it doesnt charge to full charge. I could easily repeat this test
after i take my cells out of my flashlight too.
More about the cells being 'done':
Since the manual does state that you should leave the cells in for
another 10 minutes to get the maximum benefit from the charger i
did do that before placing into the slow charger to see if they
would take any more charge. The problem here is again the manual
says one thing but simple calculation says another: that is, the
manual says "leave in another 10 minutes" and it also says
"secondary charge current for AA cells is 100ma". Well guess what?
A cell charged at 100ma for only 10 mins means it gets a total
additional charge of 17mAh, which is not nearly the calculated amount
actually needed which is about 400 to 500mAh. To be sure you would
have to leave it in the charger for another 5 hours!

To recap the math, to charge a 2.2Ah cell from 0% charge to 100% charge
using a constant current of 7.5 amps requires 19.36 minutes assuming a
10 percent charge efficiency loss. In other words:
t=2.2*1.1/7.5 (t is time in hours).
Since the charger turns off in 15 minutes, the actual charge put into
the cell(s) is 15/19.36 times 100% which gives us 77.5 percent charge.
Thus, for 2.2 Ah cells the fast charger charges them to almost 80 percent
capacity and to get the other 20 percent leave in for 5 hours after the
green light comes on.
This isnt too bad i guess, because you are getting 80 percent charge
in 15 minutes.
Interestingly, if the cells really have a lower capacity then they
are marked (say 2050mAh minimum like they are also marked) then
they would charge to full capacity in 18.04 minutes, meaning they
would charge to 83.1 percent of full in 15 minutes.
Also interesting, if the cells are rated at 1800mAh they would charge
to full in 15.84 minutes. BTW, 1800mAh cells were tried in the
charger too and they shut off after only 10 minutes. They probably
are not 'really' rated at 1800 though, only the publish rating says
that. They did get pretty darn hot though, unlike the Energizer cells
that came with the unit (four 2200mAh cells).

Thanks again for link as not all that info was included in the
little tiny 'manual' that came with the unit. I am now able to
determine how long to leave the cells in for if i want to make
sure the cells are truely fully charged.


bigkim:
The fan in my unit blows up through slots in the housing to cool the
cells as they are being charged. The 'manual' says they use temperature
sensing too, and so the fan shuts off when the cells cool down after
the charge cycle has completed. This is a very nice feature if you ask
me. I noticed that after the charge is down most cells cool down very
quickly, which is good for the cells.


haklesup(2):
The cells that came with the unit get warm but not hot, while the lower
rated 1800mAh cells i have get surely hot (!) as you can barely touch them!
The Duracell brand NiMH cells get warm too but not hot, but they stay
a little warm after the main charge has completed.
LEDs vs Bulbs, LEDs are winning.

User avatar
haklesup
Posts: 2978
Joined: Thu Aug 01, 2002 1:01 am
Location: San Jose CA
Contact:

Post by haklesup » Wed Sep 06, 2006 11:51 am

You can answer a lot of your questions by inserting an ammeter between the power pack and the charging base. With the exception of the fan and the standby current of the charger, this should give you a good indication of the rate of charge at any time. Inserting the ammeter in series with one cell might also work but the meter resistance might throw things off.

The brand name battery manufacturers probably do a better job minimizing the internal resistance hence the lesser heating. Rapid charging sometimes is a balance between supplying the most current and not cooking the cells while you do so.

User avatar
MrAl
Posts: 3862
Joined: Fri Jan 11, 2002 1:01 am
Location: NewJersey
Contact:

Post by MrAl » Thu Sep 07, 2006 12:26 am

Hi again,

haklesup:
When i use an ammeter for a cell the charger rejects it as 'bad'.
I havent used an ammeter between wall wart and charger base
because that doesnt show the current, as there is a down converter
built into the base unit which takes the 16v, 4 amp input and
converts it to 7.5 amps.
LEDs vs Bulbs, LEDs are winning.

w8vnz
Posts: 2
Joined: Fri Sep 08, 2006 8:43 am
Contact:

Charger

Post by w8vnz » Fri Sep 08, 2006 8:49 am

I have used this same charger for over a year now with no problems till I tried to run it from a small inverter plugged into my truck. The charger started the charge cycle but shortly after starting started blinking red led indicating a problem with the charge/batterys. From that point on, I am unable to charge the larger capacity cells 2200ma although it will charge cells of half that capacity fine. Sometimes though it will even balk at the smaller cells but not all of the time.

Evidently the charger did not like the output of the inverter and took out a component inside.

It was a good charger till that occurance.

User avatar
MrAl
Posts: 3862
Joined: Fri Jan 11, 2002 1:01 am
Location: NewJersey
Contact:

Post by MrAl » Fri Sep 08, 2006 9:49 am

Hi there w8vnz,

Oh wow, i am very sorry to hear that. I had paid 30 bucks for mine
and wouldnt want that to happen either.
But i must mention one thing...
If the charger and/or cells were sitting outside for any lenght of
time (even overnight) or heck even a little old now, you may wish
to clean the terminals very very good. I had problems with two of
my RS cells (rated 1800 each) and couldnt get the charger to
accept them until i scraped the oxidation off the plus and minus
terminals of both cells ( i did the other 2 after that also).
After cleaning well, they worked just as well as the other cells.
This kind of oxidation could build up on the cells or on the
charger contacts so you may wish to try cleaning both.
This could work.

As a side note, i picked up a set of Energizer 2500mAh rated cells
and they too stopped before the expected time period. I unplugged
the charger and plugged it back in and they took another minute and
a half ha ha. Cells got pretty darn hot though.
LEDs vs Bulbs, LEDs are winning.

w8vnz
Posts: 2
Joined: Fri Sep 08, 2006 8:43 am
Contact:

re: Oxidation

Post by w8vnz » Fri Sep 08, 2006 10:02 am

Thanks for the tip, although the odds of each of the cells having bad contact surfaces all at the same time is miniscule, seeing as they have never been outside. I did try charging the cells singly and in pair along with inserting them with other smaller capacity cells and no go. I tend to think that a current sensing component in the charger went south when I tried to use the charger on the inverter.

Thanks

User avatar
MrAl
Posts: 3862
Joined: Fri Jan 11, 2002 1:01 am
Location: NewJersey
Contact:

Post by MrAl » Sat Sep 09, 2006 4:16 am

Hi again,

Oh ok, well sorry about that.

I have an update on the charger however...

After measuring the current and voltage going into the charger from the
wall wart i have determined that there is almost 64 watts of power
getting in there. After estimating the efficiency to be around 80 percent,
that puts approximately 9.9 amps through each cell rather than
the 7.5 amps number stamped on the package. This is enough to
charge the cells in 15 minutes (almost exactly so too).
The 7.5 amp figure must be for when you only have 12v input
(like if you plug it into the car cig lighter or something) and that
would cause the charger to take longer, because doing the same
calculation with only 12v input yields a 7.5 amp current through
the cells.
All this means the charge times i am seeing are all ok and normal,
and if i instead connect to a 12v battery i will see about 25 percent
longer charge time, which is also ok.

The only funny thing left is that the wall wart is stamped 4 amps output
while in real life it is putting out 5 amps ha ha. As long as it continues
to work ok im not worried though.
LEDs vs Bulbs, LEDs are winning.

Post Reply

Who is online

Users browsing this forum: No registered users and 11 guests