I have had the batteries on charge in the MFJ-259Z for over a day now. The
jumper inside the unit is on for charging. The batteries were at 12.6V when
put on charge and are still 12.6V. The PSU is working fine. Because I can
run the unit off the PSU that came with it.

Any ideas on what can be wrong with it now?

It certainly sounds to me as if the charging circuit is not working,
or is not working effectively.

12.6 volts is 1.26 volts per cell, which is what I'd expect to see in
the no-load or light-load case of a NiMH with a fractional charge
(maybe half-charged?). The cell voltage will rise, as charging
continues, to as high as 1.4 volts or more (depending on charging
current).

It could be that the charging circuit simply isn't working at all.

It's also possible that the charging circuit is only delivering (by
error or design) just enough of a trickle charge to prevent an
exernally-charged NiMH battery from self-discharging. If the
battery is only receiving 10-20 mA, this would be the case - the
battery will essentially *never* recharge itself completely under
these conditions.

There's a real tradeoff with NiMH cells. Any simple charger which is
capable of recharging them in a reasonable amount of time (say, a day
or less) should *not* be left hooked up to them indefinitely - it'll
overcharge them and significantly shorten their life. Conversely, a
simple charger which *can* be left hooked up for days at a time, will
not recharge a dead battery rapidly enough to be useful.

Charger circuits *can* switch between two charging modes (fast and
maintenance) but it requires quite a bit more complexity.

So... what to do now. My suggestions:

[1] First, measure the voltage across each individual cell in the
battery. If they're all around 1.25 or so, then the cells are
probably OK, and the problem is in the charging.

If you find that most of the cells have a higher voltage, and one
is very low, then that one cell is junk and should be recycled and
replaced.

[2] Get a digital multimeter with small alligator-clip leads. Set it
on its "DC current" scale, remove the charging jumper in the MFJ,
and connect the two leads of the multimeter to the two pins that
had been jumpered together (stick a bit of paper between them to
prevent the multimeter leads from shorting). Plug the MFJ into
its wallwart (with the power switch turned off) and read the
current on your DMM. This will tell you how much current is
flowing into the battery through the charging circuit (assuming
that it's a simple linear charger and not a pulse-charger).

If the current consistently reads zero, then the charger is not
working at all.

If it's charging at a rate of below 50 mA, then it's just a
maintenance trickle-charger... sufficient to keep charged
batteries alive in standby mode, but insufficient to recharge them
in any reasonable amount of time. You'll need to do the major
charging using an external charger.

If it's charging at 100-200 mA, then it'll take a day or more to
fully recharge.

If it's charging at over 200 mA, then it'll recharge effectively
in under a day, but should *not* be left hooked up indefinitely...
it'll overcharge the batteries and shorten their service life.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Hi Dave



I checked the voltages in all the cells and they were all even voltages.
The batteries should be ok.



I checked the current on the two pins like you said and there was no
reading.

I checked the voltage on the two pins. No voltage on the outside pin and 5
volts on the middle pin.

I checked the voltage coming from the charger and its 18 volts.

I checked the voltage from the + side to the - side of the battery pack with
the charger on and got the 12.6 volts.

I checked the voltage from the + side to the - side of the battery pack with
the charger off and unplugged and got 12.6 volts.

I checked the voltage from the battery pack with the charger on and using
the case as the ground. It was 17.9 volts.



The charger says output voltage 12VDC 300mA 3.6VA.



Hope you can point me in the right direction. Do you know what sort of
voltages I should expect when it's charging properly?



Many thanks



Barrett






"Dave Platt" wrote in message
...
I have had the batteries on charge in the MFJ-259Z for over a day now.
The
jumper inside the unit is on for charging. The batteries were at 12.6V
when
put on charge and are still 12.6V. The PSU is working fine. Because I can
run the unit off the PSU that came with it.

Any ideas on what can be wrong with it now?

It certainly sounds to me as if the charging circuit is not working,
or is not working effectively.

12.6 volts is 1.26 volts per cell, which is what I'd expect to see in
the no-load or light-load case of a NiMH with a fractional charge
(maybe half-charged?). The cell voltage will rise, as charging
continues, to as high as 1.4 volts or more (depending on charging
current).

It could be that the charging circuit simply isn't working at all.

It's also possible that the charging circuit is only delivering (by
error or design) just enough of a trickle charge to prevent an
exernally-charged NiMH battery from self-discharging. If the
battery is only receiving 10-20 mA, this would be the case - the
battery will essentially *never* recharge itself completely under
these conditions.

There's a real tradeoff with NiMH cells. Any simple charger which is
capable of recharging them in a reasonable amount of time (say, a day
or less) should *not* be left hooked up to them indefinitely - it'll
overcharge them and significantly shorten their life. Conversely, a
simple charger which *can* be left hooked up for days at a time, will
not recharge a dead battery rapidly enough to be useful.

Charger circuits *can* switch between two charging modes (fast and
maintenance) but it requires quite a bit more complexity.

So... what to do now. My suggestions:

[1] First, measure the voltage across each individual cell in the
battery. If they're all around 1.25 or so, then the cells are
probably OK, and the problem is in the charging.

If you find that most of the cells have a higher voltage, and one
is very low, then that one cell is junk and should be recycled and
replaced.

[2] Get a digital multimeter with small alligator-clip leads. Set it
on its "DC current" scale, remove the charging jumper in the MFJ,
and connect the two leads of the multimeter to the two pins that
had been jumpered together (stick a bit of paper between them to
prevent the multimeter leads from shorting). Plug the MFJ into
its wallwart (with the power switch turned off) and read the
current on your DMM. This will tell you how much current is
flowing into the battery through the charging circuit (assuming
that it's a simple linear charger and not a pulse-charger).

If the current consistently reads zero, then the charger is not
working at all.

If it's charging at a rate of below 50 mA, then it's just a
maintenance trickle-charger... sufficient to keep charged
batteries alive in standby mode, but insufficient to recharge them
in any reasonable amount of time. You'll need to do the major
charging using an external charger.

If it's charging at 100-200 mA, then it'll take a day or more to
fully recharge.

If it's charging at over 200 mA, then it'll recharge effectively
in under a day, but should *not* be left hooked up indefinitely...
it'll overcharge the batteries and shorten their service life.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

If you are really having this much trouble troubleshooting the unit and it
is still under warranty - for a couple of bucks in postage you should send
it back to MFJ for the warranty repairs... If you continue to try and get
into the unit you may end up VOIDing the warranty and then it will cost you
a BUNCH of bucks to get it repaired!

"Barrett" wrote in message
...
Hi Dave



I checked the voltages in all the cells and they were all even voltages.
The batteries should be ok.



I checked the current on the two pins like you said and there was no
reading.

I checked the voltage on the two pins. No voltage on the outside pin and 5
volts on the middle pin.

I checked the voltage coming from the charger and its 18 volts.

I checked the voltage from the + side to the - side of the battery pack
with the charger on and got the 12.6 volts.

I checked the voltage from the + side to the - side of the battery pack
with the charger off and unplugged and got 12.6 volts.

I checked the voltage from the battery pack with the charger on and using
the case as the ground. It was 17.9 volts.



The charger says output voltage 12VDC 300mA 3.6VA.



Hope you can point me in the right direction. Do you know what sort of
voltages I should expect when it's charging properly?



Many thanks



Barrett






"Dave Platt" wrote in message
...
I have had the batteries on charge in the MFJ-259Z for over a day now.
The
jumper inside the unit is on for charging. The batteries were at 12.6V
when
put on charge and are still 12.6V. The PSU is working fine. Because I can
run the unit off the PSU that came with it.

Any ideas on what can be wrong with it now?

It certainly sounds to me as if the charging circuit is not working,
or is not working effectively.

12.6 volts is 1.26 volts per cell, which is what I'd expect to see in
the no-load or light-load case of a NiMH with a fractional charge
(maybe half-charged?). The cell voltage will rise, as charging
continues, to as high as 1.4 volts or more (depending on charging
current).

It could be that the charging circuit simply isn't working at all.

It's also possible that the charging circuit is only delivering (by
error or design) just enough of a trickle charge to prevent an
exernally-charged NiMH battery from self-discharging. If the
battery is only receiving 10-20 mA, this would be the case - the
battery will essentially *never* recharge itself completely under
these conditions.

There's a real tradeoff with NiMH cells. Any simple charger which is
capable of recharging them in a reasonable amount of time (say, a day
or less) should *not* be left hooked up to them indefinitely - it'll
overcharge them and significantly shorten their life. Conversely, a
simple charger which *can* be left hooked up for days at a time, will
not recharge a dead battery rapidly enough to be useful.

Charger circuits *can* switch between two charging modes (fast and
maintenance) but it requires quite a bit more complexity.

So... what to do now. My suggestions:

[1] First, measure the voltage across each individual cell in the
battery. If they're all around 1.25 or so, then the cells are
probably OK, and the problem is in the charging.

If you find that most of the cells have a higher voltage, and one
is very low, then that one cell is junk and should be recycled and
replaced.

[2] Get a digital multimeter with small alligator-clip leads. Set it
on its "DC current" scale, remove the charging jumper in the MFJ,
and connect the two leads of the multimeter to the two pins that
had been jumpered together (stick a bit of paper between them to
prevent the multimeter leads from shorting). Plug the MFJ into
its wallwart (with the power switch turned off) and read the
current on your DMM. This will tell you how much current is
flowing into the battery through the charging circuit (assuming
that it's a simple linear charger and not a pulse-charger).

If the current consistently reads zero, then the charger is not
working at all.

If it's charging at a rate of below 50 mA, then it's just a
maintenance trickle-charger... sufficient to keep charged
batteries alive in standby mode, but insufficient to recharge them
in any reasonable amount of time. You'll need to do the major
charging using an external charger.

If it's charging at 100-200 mA, then it'll take a day or more to
fully recharge.

If it's charging at over 200 mA, then it'll recharge effectively
in under a day, but should *not* be left hooked up indefinitely...
it'll overcharge the batteries and shorten their service life.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

I have only taken the back off at this point and was hoping it would be some
thing simple to fix, rather than send it back.

Is there an MFJ in the UK?


"Howard W3CQH" wrote in message
. ..
If you are really having this much trouble troubleshooting the unit and it
is still under warranty - for a couple of bucks in postage you should send
it back to MFJ for the warranty repairs... If you continue to try and get
into the unit you may end up VOIDing the warranty and then it will cost
you a BUNCH of bucks to get it repaired!

"Barrett" wrote in message
...
Hi Dave



I checked the voltages in all the cells and they were all even voltages.
The batteries should be ok.



I checked the current on the two pins like you said and there was no
reading.

I checked the voltage on the two pins. No voltage on the outside pin and
5 volts on the middle pin.

I checked the voltage coming from the charger and its 18 volts.

I checked the voltage from the + side to the - side of the battery pack
with the charger on and got the 12.6 volts.

I checked the voltage from the + side to the - side of the battery pack
with the charger off and unplugged and got 12.6 volts.

I checked the voltage from the battery pack with the charger on and using
the case as the ground. It was 17.9 volts.



The charger says output voltage 12VDC 300mA 3.6VA.



Hope you can point me in the right direction. Do you know what sort of
voltages I should expect when it's charging properly?



Many thanks



Barrett






"Dave Platt" wrote in message
...
I have had the batteries on charge in the MFJ-259Z for over a day now.
The
jumper inside the unit is on for charging. The batteries were at 12.6V
when
put on charge and are still 12.6V. The PSU is working fine. Because I
can
run the unit off the PSU that came with it.

Any ideas on what can be wrong with it now?

It certainly sounds to me as if the charging circuit is not working,
or is not working effectively.

12.6 volts is 1.26 volts per cell, which is what I'd expect to see in
the no-load or light-load case of a NiMH with a fractional charge
(maybe half-charged?). The cell voltage will rise, as charging
continues, to as high as 1.4 volts or more (depending on charging
current).

It could be that the charging circuit simply isn't working at all.

It's also possible that the charging circuit is only delivering (by
error or design) just enough of a trickle charge to prevent an
exernally-charged NiMH battery from self-discharging. If the
battery is only receiving 10-20 mA, this would be the case - the
battery will essentially *never* recharge itself completely under
these conditions.

There's a real tradeoff with NiMH cells. Any simple charger which is
capable of recharging them in a reasonable amount of time (say, a day
or less) should *not* be left hooked up to them indefinitely - it'll
overcharge them and significantly shorten their life. Conversely, a
simple charger which *can* be left hooked up for days at a time, will
not recharge a dead battery rapidly enough to be useful.

Charger circuits *can* switch between two charging modes (fast and
maintenance) but it requires quite a bit more complexity.

So... what to do now. My suggestions:

[1] First, measure the voltage across each individual cell in the
battery. If they're all around 1.25 or so, then the cells are
probably OK, and the problem is in the charging.

If you find that most of the cells have a higher voltage, and one
is very low, then that one cell is junk and should be recycled and
replaced.

[2] Get a digital multimeter with small alligator-clip leads. Set it
on its "DC current" scale, remove the charging jumper in the MFJ,
and connect the two leads of the multimeter to the two pins that
had been jumpered together (stick a bit of paper between them to
prevent the multimeter leads from shorting). Plug the MFJ into
its wallwart (with the power switch turned off) and read the
current on your DMM. This will tell you how much current is
flowing into the battery through the charging circuit (assuming
that it's a simple linear charger and not a pulse-charger).

If the current consistently reads zero, then the charger is not
working at all.

If it's charging at a rate of below 50 mA, then it's just a
maintenance trickle-charger... sufficient to keep charged
batteries alive in standby mode, but insufficient to recharge them
in any reasonable amount of time. You'll need to do the major
charging using an external charger.

If it's charging at 100-200 mA, then it'll take a day or more to
fully recharge.

If it's charging at over 200 mA, then it'll recharge effectively
in under a day, but should *not* be left hooked up indefinitely...
it'll overcharge the batteries and shorten their service life.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Barrett wrote:
I have only taken the back off at this point and was hoping it would be some
thing simple to fix, rather than send it back.

Is there an MFJ in the UK?
==================================
No ,you probably have to return it to the UK importer Waters & Stanton.

I have used the MFJ259 (bought in the USA) for many years with an
external small Sealed Lead Acid battery .
I find it a very useful piece of equipment to test antenna matching
units and resistors/capacitors used for RF purposes . Also stubs and
coax cable.

It is also used whenever a UK Foundation Licence trainee in my area
needs to do an antenna assessment eg plotting the SWR curve of a wire
dipole with the exercise to be repeated with a slightly shorter dipole
,showing a shift of the SWR graph towards a higher frequency.
All this is done with a dipole for 28 MHz.


Frank GM0CSZ / KN6WH

I have two questions. On the power socket on the MFJ-259, there are 3
terminals on this socket.
1. Is the centre pin that is + volts.
2.. Is the negative side pin that connects to the GND track on the board.
3,. Is another negative pin that connects to the chassis.

Are the two negative pins in the power socket connected in anyway inside the
socket itself?

They are not connected on the board.

If I bridge a wire from one negative pin to the other on the socket the
batteries start to charge. I don't want to do this if its bypassing the
problem.

I'm beginning to suspect a bad power socket. What do you think?

MFJ just e-mailed back and said.
got to be a short somewhere in the battery compartment then. or there is a
faulty smt diode or resistor. if you have a way of testing the components,
check around the charging jumper circuit.

Many thanks

Barrett


"Highland Ham" wrote in message
...
Barrett wrote:
I have only taken the back off at this point and was hoping it would be
some thing simple to fix, rather than send it back.

Is there an MFJ in the UK?
==================================
No ,you probably have to return it to the UK importer Waters & Stanton.

I have used the MFJ259 (bought in the USA) for many years with an external
small Sealed Lead Acid battery .
I find it a very useful piece of equipment to test antenna matching units
and resistors/capacitors used for RF purposes . Also stubs and coax cable.

It is also used whenever a UK Foundation Licence trainee in my area needs
to do an antenna assessment eg plotting the SWR curve of a wire dipole
with the exercise to be repeated with a slightly shorter dipole ,showing a
shift of the SWR graph towards a higher frequency.
All this is done with a dipole for 28 MHz.


Frank GM0CSZ / KN6WH

Of course the board is multi layered that's why the pins look as if there
not connected. I've checked for dry solder joints and they all look ok to me
so I think its some thing a bit more serious than that, so back it goes.


"Barrett" wrote in message
...
I have two questions. On the power socket on the MFJ-259, there are 3
terminals on this socket.
1. Is the centre pin that is + volts.
2.. Is the negative side pin that connects to the GND track on the board.
3,. Is another negative pin that connects to the chassis.

Are the two negative pins in the power socket connected in anyway inside
the socket itself?

They are not connected on the board.

If I bridge a wire from one negative pin to the other on the socket the
batteries start to charge. I don't want to do this if its bypassing the
problem.

I'm beginning to suspect a bad power socket. What do you think?

MFJ just e-mailed back and said.
got to be a short somewhere in the battery compartment then. or there is
a faulty smt diode or resistor. if you have a way of testing the
components, check around the charging jumper circuit.

Many thanks

Barrett


"Highland Ham" wrote in message
...
Barrett wrote:
I have only taken the back off at this point and was hoping it would be
some thing simple to fix, rather than send it back.

Is there an MFJ in the UK?
==================================
No ,you probably have to return it to the UK importer Waters & Stanton.

I have used the MFJ259 (bought in the USA) for many years with an
external small Sealed Lead Acid battery .
I find it a very useful piece of equipment to test antenna matching units
and resistors/capacitors used for RF purposes . Also stubs and coax
cable.

It is also used whenever a UK Foundation Licence trainee in my area needs
to do an antenna assessment eg plotting the SWR curve of a wire dipole
with the exercise to be repeated with a slightly shorter dipole ,showing
a shift of the SWR graph towards a higher frequency.
All this is done with a dipole for 28 MHz.


Frank GM0CSZ / KN6WH

"Barrett" wrote in message
...
Hi Dave



I checked the voltages in all the cells and they were all even voltages.
The batteries should be ok.



I checked the current on the two pins like you said and there was no
reading.

I checked the voltage on the two pins. No voltage on the outside pin and 5
volts on the middle pin.

I checked the voltage coming from the charger and its 18 volts.

I checked the voltage from the + side to the - side of the battery pack
with the charger on and got the 12.6 volts.

I checked the voltage from the + side to the - side of the battery pack
with the charger off and unplugged and got 12.6 volts.

I checked the voltage from the battery pack with the charger on and using
the case as the ground. It was 17.9 volts.



The charger says output voltage 12VDC 300mA 3.6VA.



Hope you can point me in the right direction. Do you know what sort of
voltages I should expect when it's charging properly?



Many thanks



Barrett






"Dave Platt" wrote in message
...
I have had the batteries on charge in the MFJ-259Z for over a day now.
The
jumper inside the unit is on for charging. The batteries were at 12.6V
when
put on charge and are still 12.6V. The PSU is working fine. Because I can
run the unit off the PSU that came with it.

Any ideas on what can be wrong with it now?

It certainly sounds to me as if the charging circuit is not working,
or is not working effectively.

12.6 volts is 1.26 volts per cell, which is what I'd expect to see in
the no-load or light-load case of a NiMH with a fractional charge
(maybe half-charged?). The cell voltage will rise, as charging
continues, to as high as 1.4 volts or more (depending on charging
current).

It could be that the charging circuit simply isn't working at all.

It's also possible that the charging circuit is only delivering (by
error or design) just enough of a trickle charge to prevent an
exernally-charged NiMH battery from self-discharging. If the
battery is only receiving 10-20 mA, this would be the case - the
battery will essentially *never* recharge itself completely under
these conditions.

There's a real tradeoff with NiMH cells. Any simple charger which is
capable of recharging them in a reasonable amount of time (say, a day
or less) should *not* be left hooked up to them indefinitely - it'll
overcharge them and significantly shorten their life. Conversely, a
simple charger which *can* be left hooked up for days at a time, will
not recharge a dead battery rapidly enough to be useful.

Charger circuits *can* switch between two charging modes (fast and
maintenance) but it requires quite a bit more complexity.

So... what to do now. My suggestions:

[1] First, measure the voltage across each individual cell in the
battery. If they're all around 1.25 or so, then the cells are
probably OK, and the problem is in the charging.

If you find that most of the cells have a higher voltage, and one
is very low, then that one cell is junk and should be recycled and
replaced.

[2] Get a digital multimeter with small alligator-clip leads. Set it
on its "DC current" scale, remove the charging jumper in the MFJ,
and connect the two leads of the multimeter to the two pins that
had been jumpered together (stick a bit of paper between them to
prevent the multimeter leads from shorting). Plug the MFJ into
its wallwart (with the power switch turned off) and read the
current on your DMM. This will tell you how much current is
flowing into the battery through the charging circuit (assuming
that it's a simple linear charger and not a pulse-charger).

If the current consistently reads zero, then the charger is not
working at all.

If it's charging at a rate of below 50 mA, then it's just a
maintenance trickle-charger... sufficient to keep charged
batteries alive in standby mode, but insufficient to recharge them
in any reasonable amount of time. You'll need to do the major
charging using an external charger.

If it's charging at 100-200 mA, then it'll take a day or more to
fully recharge.

If it's charging at over 200 mA, then it'll recharge effectively
in under a day, but should *not* be left hooked up indefinitely...
it'll overcharge the batteries and shorten their service life.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!


you should check out these sites:

http://www.w8ji.com/mfj-259b_calibration.htm

http://www.mfjenterprises.com/man/pd...9d4b5163ded 5

http://www.mfjenterprises.com/MFJ-25... 9d4b5163ded5

http://qrp.kd4ab.org/2002/020129/0029.html

This is unbelievable. I was sent another new unit, my second MFJ-259Z from
WSPLC and its another bad unit. The batteries won't charge. It does have
39mA on the jumper switch this time. But still will not charge the
batteries. I will phone them again tomorrow after the unit has been on
charge for over 24 hours.

Andy


"Howard W3CQH" wrote in message
. ..

"Barrett" wrote in message
...
Hi Dave



I checked the voltages in all the cells and they were all even voltages.
The batteries should be ok.



I checked the current on the two pins like you said and there was no
reading.

I checked the voltage on the two pins. No voltage on the outside pin and
5 volts on the middle pin.

I checked the voltage coming from the charger and its 18 volts.

I checked the voltage from the + side to the - side of the battery pack
with the charger on and got the 12.6 volts.

I checked the voltage from the + side to the - side of the battery pack
with the charger off and unplugged and got 12.6 volts.

I checked the voltage from the battery pack with the charger on and using
the case as the ground. It was 17.9 volts.



The charger says output voltage 12VDC 300mA 3.6VA.



Hope you can point me in the right direction. Do you know what sort of
voltages I should expect when it's charging properly?



Many thanks



Barrett






"Dave Platt" wrote in message
...
I have had the batteries on charge in the MFJ-259Z for over a day now.
The
jumper inside the unit is on for charging. The batteries were at 12.6V
when
put on charge and are still 12.6V. The PSU is working fine. Because I
can
run the unit off the PSU that came with it.

Any ideas on what can be wrong with it now?

It certainly sounds to me as if the charging circuit is not working,
or is not working effectively.

12.6 volts is 1.26 volts per cell, which is what I'd expect to see in
the no-load or light-load case of a NiMH with a fractional charge
(maybe half-charged?). The cell voltage will rise, as charging
continues, to as high as 1.4 volts or more (depending on charging
current).

It could be that the charging circuit simply isn't working at all.

It's also possible that the charging circuit is only delivering (by
error or design) just enough of a trickle charge to prevent an
exernally-charged NiMH battery from self-discharging. If the
battery is only receiving 10-20 mA, this would be the case - the
battery will essentially *never* recharge itself completely under
these conditions.

There's a real tradeoff with NiMH cells. Any simple charger which is
capable of recharging them in a reasonable amount of time (say, a day
or less) should *not* be left hooked up to them indefinitely - it'll
overcharge them and significantly shorten their life. Conversely, a
simple charger which *can* be left hooked up for days at a time, will
not recharge a dead battery rapidly enough to be useful.

Charger circuits *can* switch between two charging modes (fast and
maintenance) but it requires quite a bit more complexity.

So... what to do now. My suggestions:

[1] First, measure the voltage across each individual cell in the
battery. If they're all around 1.25 or so, then the cells are
probably OK, and the problem is in the charging.

If you find that most of the cells have a higher voltage, and one
is very low, then that one cell is junk and should be recycled and
replaced.

[2] Get a digital multimeter with small alligator-clip leads. Set it
on its "DC current" scale, remove the charging jumper in the MFJ,
and connect the two leads of the multimeter to the two pins that
had been jumpered together (stick a bit of paper between them to
prevent the multimeter leads from shorting). Plug the MFJ into
its wallwart (with the power switch turned off) and read the
current on your DMM. This will tell you how much current is
flowing into the battery through the charging circuit (assuming
that it's a simple linear charger and not a pulse-charger).

If the current consistently reads zero, then the charger is not
working at all.

If it's charging at a rate of below 50 mA, then it's just a
maintenance trickle-charger... sufficient to keep charged
batteries alive in standby mode, but insufficient to recharge them
in any reasonable amount of time. You'll need to do the major
charging using an external charger.

If it's charging at 100-200 mA, then it'll take a day or more to
fully recharge.

If it's charging at over 200 mA, then it'll recharge effectively
in under a day, but should *not* be left hooked up indefinitely...
it'll overcharge the batteries and shorten their service life.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!


you should check out these sites:

http://www.w8ji.com/mfj-259b_calibration.htm

http://www.mfjenterprises.com/man/pd...9d4b5163ded 5

http://www.mfjenterprises.com/MFJ-25... 9d4b5163ded5

http://qrp.kd4ab.org/2002/020129/0029.html

In article ,
Barrett wrote:

This is unbelievable.

Alas, MFJ equipment's reputation for sterling quality control would
cause some to disagree with you.

I was sent another new unit, my second MFJ-259Z from
WSPLC and its another bad unit. The batteries won't charge. It does have
39mA on the jumper switch this time. But still will not charge the
batteries. I will phone them again tomorrow after the unit has been on
charge for over 24 hours.

39 mA is probably *not* enough to effectively charge 2000 mAh NiMH
cells. It only a C/50 rate.

NiMH cells have a low "charge acceptance" efficiency at such low
current rates... relatively little of the energy going into them
actually goes into the electrochemistry. The manufacturer's
literature I've read, recommends against using this sort of "trickle
charge" with NiMH cells... it just doesn't work very well. It might
be adequate to maintain fully-charged NiMH cells against
self-discharge, but it's apparently less than idea even for that.

40 mA of charge current might make sense if you loaded the analyzer up
with typical 1000 mAh NiCd cells - it'd be a C/25 rate, and since
this battery chemistry responds reasonably well to low charge rates
you'd probably find the batteries topped up in 36 hours or so.

As it is, you might need to wait a week or more for the NiMH batteries
to charge up, *if* they do so at all.

Seems to me you have three workable alternatives:

- Return this charger and insist that they provide you one with a
more sophisticated/effective NiMH charging circuit. Seems unlikely
to me that they have one at this time - it would require
significantly fancier circuitry.

- Figure out how the charging circuit works, and modify it yourself
to provide a significantly higher charging current. NiMH cells
seem to react well to a C/10 charge rate - around 14-16 hours from
a fully-discharged state seems to bring them up to full power and
break them in properly. This change might require no more than
replacing a single resistor in the charging circuit, depending on
how MFJ designed it.

- Use NiCd cells rather than NiMH (which is what I do with my MFJ
259/269 analyzers). 36 hours of charging should bring 'em up to
the Plimsoll line.

- Use a real NiMH AA charger to break in and charge your NiMH cells
outside the analyzer, then install them and plug it into the brick
for a few hours a day to keep the batteries from self-discharging.
Remove the batteries and recharge externally whenever they've been
run down significantly.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!