Makita Charger

[Bob]

Does anyone know how to change a Makita 9.6 volt battery charger made for
NICAD's . I want to be able to charge 9.6 volt NiMH in it and it refuses to
work.
The NiMH battery has the same physical dimensions as the NICAD

 

[Dale Farmer]

Does anyone know how to change a Makita 9.6 volt battery charger made for
NICAD's . I want to be able to charge 9.6 volt NiMH in it and it refuses to
work.
The NiMH battery has the same physical dimensions as the NICAD

Go buy a new charger. It has the smarts to figure out
what kind of battery you have and properly charge it.
Charging it on an nicad charger will probably damage the
Nimh battery beyond repair.

--Dale

 

[larry moe 'n curly]

How does a charger tell a regular NiCad from a regular NiMH until it
charges it for some time and sees the voltage depress (or just flatten
out) or the temperature go up?

 

[Haggis]

Does anyone know how to change (I'm guessing this is a 'typo' - should
read "charge"?) a Makita 9.6 volt battery charger made for NICAD's . I
want to be able to charge 9.6 volt NiMH in it and it refuses to work.

The NiMH battery has the same physical dimensions as the NICAD >

By "refuses to work" what do you mean? Does it not charge at all, or is the
charge rate too high/low?
Try: http://www.powerstream.com/Ni-Coin-ceLL.htm for a good rundown on the
type of charger you need. Probably a p/n PST-5830-8 will work?
There's also a lot of information on the same site about charge/discharge
rates etc. (usual disclaimer - I have no interest in the company).
A "trickle" charger can be easily built from a junked walwart with a
dropping resistor to limit the charging current to what you need. Not too
sophisticated, but will do the job if you watch the amount of time you leave
it plugged in (i.e. don't leave it on charge for weeks at a time
Hope this helps. If not, drop me a line (delete the obvious) - I've made
several inexpensive (read "cheap") chargers for small NiMH batteries to
replace original NiCad packs.
Haggis.

 

[Dave Plowman (News)]

A "trickle" charger can be easily built from a junked walwart with a
dropping resistor to limit the charging current to what you need. Not
too sophisticated, but will do the job if you watch the amount of time
you leave it plugged in (i.e. don't leave it on charge for weeks at a
time Hope this helps.

You can build a constant current charger with one transistor and a few
extra components if you have a suitable DC wall wart. Really not much more
expensive than the resistor and much better.

 

[no]

Does anyone know how to change a Makita 9.6 volt battery charger made for
Be glad it somehow refused to charge. Never attempt to charge a NiMH
battery with a NiCd charger! People have burned down their houses this
way.

How does a charger tell a regular NiCad from a regular NiMH until it
charges it for some time and sees the voltage depress (or just flatten
out) or the temperature go up?

I can't see how it would. Thats the difference between a NiCd and an NiMH
charger. A NiCd charger may not detect when a NiMH battery is full and
continue rapid charging. The excess charge will turn into heat,
destroying the battery and possibly anything surrounding it.

 

[Dorian McIntire]

A "smart enough" charger could distinguish between a Ni-Cad and a NiMH
battery by looking at the voltage and charging current profile over time in
a test session, and "knowing" how many cells were in the battery. Most
chargers however are set up to charge based on a specific cell chemistry and
"looking" at the rate of change of voltage over time to decide if a cell is
charged.

Fast chargers must take many more factors into consideration, temperature
being one, in order to charge a cell or battery quickly without distroying
it.

Dorian

 

[larry moe 'n curly]

A "smart enough" charger could distinguish between a Ni-Cad and a NiMH
battery by looking at the voltage and charging current profile over time in
a test session, and "knowing" how many cells were in the battery. Most
chargers however are set up to charge based on a specific cell chemistry and
"looking" at the rate of change of voltage over time to decide if a cell is
charged.

Fast chargers must take many more factors into consideration, temperature
being one, in order to charge a cell or battery quickly without distroying it.

What puzzles me is how that Makita charger knows right away when NiMHs
are connected to it. I've read of only one other case like that, for a
Norelco shaver where the user replaced the 500 mAH cells with something
like 1000 mAH cells, but they were charge only up to 500 mAH. I.e.,
the charger didn't run twice as long with the higher-capacity cells.

 

[Dave Plowman (News)]

A "smart enough" charger could distinguish between a Ni-Cad and a NiMH
battery by looking at the voltage and charging current profile over time
in a test session, and "knowing" how many cells were in the battery.
Most chargers however are set up to charge based on a specific cell
chemistry and "looking" at the rate of change of voltage over time to
decide if a cell is charged.

I've got a charger which knows how many cells and what type without any
operator input.

 

[Bob Monsen]

I've got a charger which knows how many cells and what type without any
operator input.

It can tell the difference between NiCD and NiMH? I wonder how it does
that? The charging profiles are nearly identical.

--
Regards,
Bob Monsen

"A man who dares to waste one hour of time has not discovered the
value of life"
-- Charles Darwin

 

[Dave Plowman (News)]

It can tell the difference between NiCD and NiMH? I wonder how it does
that? The charging profiles are nearly identical.

http://www.mascot.no/uk/

 

[larry moe 'n curly]

It can tell the difference between NiCD and NiMH? I wonder how it does
that? The charging profiles are nearly identical.

In addition to www.linear.com, www.maxim-ic.com has lots of info about
battery charging, including graphs showing charge state verses
temperature and voltage for NiCads and NiMHs, and some of their chips
can handle both types, I think by measuring the rate of temperature
rise. They also give out free samples.

 

[Bill Jeffrey]

I'm certainly no expert, but I've noticed that many battery packs have
several contact pads. Several meaning as many as 5. Some of these
"extra" contacts may carry info about battery internal temp. But others
could be simple one/zero info to tell the charger about battery type or
charge profile.

Just a thought.

Bill Jeffrey
~~~~~~~~~~~~~~~~~~~~~~`

 

[H. Dziardziel]

Does anyone know how to change a Makita 9.6 volt battery charger made for
NICAD's . I want to be able to charge 9.6 volt NiMH in it and it refuses to
work.
The NiMH battery has the same physical dimensions as the NICAD

High capacity (of same physical size) and old cells have high
internal resistance..