# battery charger speed question

X

#### Xah Lee

Jan 1, 1970
0
i have two battery chargers. One takes 13 hours to charge, while the

i'm curious, is there any draw-back with the faster charger? Is the
faster one due to technological advance, or is there some trade off
here?

Both are branded RadioShak. The slower one is model Cat. No. 23-418A,
bought around 2000. The faster one is called FAST CHARGER Ca. No.:
23-043, bought around 2003. They charge AA sized rechearble Ni-MH
batteries.

Xah
[email protected]
âˆ‘ http://xahlee.org/

H

#### Hactar

Jan 1, 1970
0
i have two battery chargers. One takes 13 hours to charge, while the

i'm curious, is there any draw-back with the faster charger?

"More heat generated in the battery" and "a bigger transformer is
required" are the obvious drawbacks. I don't know how it affects total
Is the faster one due to technological advance, or is there some trade
off here?

I would guess "more expensive" and maybe "a better understanding of NiMH
chemistry" are (some of) the differences.

W

#### w2aew

Jan 1, 1970
0
The faster charger simply charges with a higher current than the slower
charger. There are potential problems with charging at higher
currents. When charging at a low rate, there is little danger of
overheating the batteries, or causing damaging internal pressure
increases. When you charge with a higher current, these dangers can
exist. The trick is to know when to terminate the charging cycle.
NiMH batteries exhibit a subtle "flattening" or slight negative delta-V
of the cell voltage when they reach full charge (much more subtle than
the negative delta-V of NiCDs). Decent chargers will look for this
"signature" to terminate the charging cycle. If you don't do this, you
run the risk of overcharging, which can damage the cells (high
temperature, pressure, etc.). The importance of proper charge
termination increases dramatically as you increase the charging current
(decrease the charging time). The slow 12+ hour chargers are
essentially trickle type chargers that cause little or no cell damage
with overcharging, so no charge termination is usually necessary.

G

#### Greg Goss

Jan 1, 1970
0
"More heat generated in the battery" and "a bigger transformer is
required" are the obvious drawbacks. I don't know how it affects total

I would guess "more expensive" and maybe "a better understanding of NiMH
chemistry" are (some of) the differences.

I know that when I was buying a NiMH battery for my cell phone, they
to control charging rates. Because the charging rate was controlled
by the battery, the $12 car charger was affordable. I don't know how that works for generic NiMH batteries like AA or such. Is the chip still "in the battery"? If not, then "better understanding" of the chemistry and the charging profile, and perhaps a more expensive chip to allow handling more power as it passes through the control chip. P #### Peter Bennett Jan 1, 1970 0 I know that when I was buying a NiMH battery for my cell phone, they made a big issue that you had to buy a battery with the chip included to control charging rates. Because the charging rate was controlled by the battery, the$12 car charger was affordable.

I expect that your cell phone battery is Lithium Ion, not Nickel Metal
Hydride.

Lithium Ion batteries are very fussy about how they are treated, and
will apparently explode if mistreated, so they are not available as
individual cells on the consumer market. Even companies that will
rebuild battery packs of other technologies often won't touch LiI.
I don't know how that works for generic NiMH batteries like AA or
such. Is the chip still "in the battery"? If not, then "better
understanding" of the chemistry and the charging profile, and perhaps
a more expensive chip to allow handling more power as it passes
through the control chip.

No - NiMH batteries don't need a chip in the battery - the AA
"batteries" are really single cells. (A battery _should_ refer to two
or more cells connected together (usually in series.))

R

#### Rich Grise

Jan 1, 1970
0
i have two battery chargers. One takes 13 hours to charge, while the

i'm curious, is there any draw-back with the faster charger? Is the
faster one due to technological advance, or is there some trade off
here?

Both are branded RadioShak. The slower one is model Cat. No. 23-418A,
bought around 2000. The faster one is called FAST CHARGER Ca. No.:
23-043, bought around 2003. They charge AA sized rechearble Ni-MH
batteries.

I don't understand the question. The "FAST CHARGER" charges the
batteries faster. What seems to be the problem? ;-)

Actually, it's probably just a matter of the available charge
current, or it could be that sometime between 2000 and 2003 somebody
implemented a faster charging profile algorithm.

Hope This Helps!
Rich

K

#### Kitchen Man

Jan 1, 1970
0
No - NiMH batteries don't need a chip in the battery - the AA
"batteries" are really single cells. (A battery _should_ refer to two
or more cells connected together (usually in series.))

Well now, that's a little known piece of information that is nice to
know! Thanks for the info.

Replies
4
Views
361
Replies
6
Views
341
Replies
4
Views
375
Replies
14
Views
889
Replies
2
Views
408