In article ,
Barrett wrote:

Can some one give me an idea on how long these 2600mA should last in the
MFJ-259 when left on without turning off?

One manufacturer's data writeup (for the Twicell batteries) says "The
amount of electricity which a [NiMH] battery loses through
self-discharge at 40 degrees C in one day following full charge is
approximately 5% of the rated capacity."

If it lost this same percentage of its total charge every day, the
battery would be completely self-discharged in about three weeks.

If it lost 5% of its current charge level per day, it'd be down to 50%
charge in a couple of weeks, maybe to 25% at the end of a month.

Even if the self-discharge rate is as low as 2% per day, you'd find
them with little charge remaining after a couple of months.

The high-capacity, fast-self-discharging NiMH cells seem to be a
reasonable choice for certain application - those in which you expect
to drain 'em within a few days of use, and will need to recharge them
regularly in any case. Photo-flash applications, or listen-and-talk
applications in a portable radio, or that sort of thing.

They're a poor choice for occasional-use or standby applications.

If you're using your MFJ-259 for several hours per week, standard 2600
NiMH cells may be a good choice. If you use the analyzer only
occasionally, I think you'll be happier with either NiCd, or
low-self-discharge 2000/2100 NiMH.

--
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're using your MFJ-259 for several hours per week, standard 2600
NiMH cells may be a good choice. If you use the analyzer only
occasionally, I think you'll be happier with either NiCd, or
low-self-discharge 2000/2100 NiMH.
================================================== ===
NiCad and NiMH batteries (usually having a capacity exceeding 400mAh)
which need to perform at all times I normally charge constantly with 10
mA when not in use. This trickle charge level keeps them in good condition.
I have a Wahl ISOTIP 2.4 V soldering iron which in this way is always
available. When in use I switch the charging current to 300 mA

Frank GM0CSZ / KN6WH

Finally got the batteries charged, discharged and charged again. I have
managed to fully charge them now.

How long should they last for with the MFJ-259 left on continuously being
used?

Is it normal to only get 10 - 15 minutes worth of on time before getting the
low battery warning on the MFJ?

Also the MFJ-259 is new. What is the best ways to check it to make sure its
working properly?

Thanks


"Highland Ham" wrote in message
news
If you're using your MFJ-259 for several hours per week, standard 2600
NiMH cells may be a good choice. If you use the analyzer only
occasionally, I think you'll be happier with either NiCd, or
low-self-discharge 2000/2100 NiMH.
================================================== ===
NiCad and NiMH batteries (usually having a capacity exceeding 400mAh)
which need to perform at all times I normally charge constantly with 10
mA when not in use. This trickle charge level keeps them in good
condition.
I have a Wahl ISOTIP 2.4 V soldering iron which in this way is always
available. When in use I switch the charging current to 300 mA

Frank GM0CSZ / KN6WH

In article ,
Barrett wrote:

Finally got the batteries charged, discharged and charged again. I have
managed to fully charge them now.

How long should they last for with the MFJ-259 left on continuously being
used?

The MFJ 269 manual says that it draws a maximum of 150 mA on HF and
VHF, and max 250 mA on UHF. Given the similarity of the instruments
I'd guess that the 259's current drain is similar to that of the 269
on HF/VHF.

This would suggest a useful run-time of around 12 hours for
fully-charged 2000 mAh cells, and perhaps 16 hours for the
larger-capacity 2500 mAh types. You'll get more time if the MFJ goes
into power-saving mode.

Is it normal to only get 10 - 15 minutes worth of on time before getting the
low battery warning on the MFJ?

If you're getting a flashing low-battery warning after only 10-15
minutes of use with freshly-charged cells - no, that's not good. It
would suggest to me that either one (or more) of the cells in the
battery stack is defective (or not fully charged) or that the MFJ's
low-battery detector is misadjusted.

Don't mistake the flashing low-battery warning, with the "display goes
mostly blank" sleep mode. The latter would be expected after some
minutes of non-use, while the former should not appear for hours.

NiCd and NiMH cells have a rather flat discharge characteristic - the
voltage remains almost the same across a broad part of the discharge
curve (from 90% charged to 10% charged). By the time that the voltage
starts to drop off, there's very little charge left in the cell, and
you have little warning.

Well-designed devices which were designed to run on NiCd batteries
will often have a low-voltage shutoff circuit, which deliberately
turns off the device once the voltage hits the "almost drained" knee
point of the curve (nominally 1.0 volts per cell or so). This is done
to avoid "over-discharging" some cells in the battery (continuing to
pull current through them after they're completely exhausted, but
while other cells in the battery still have some charge left).
Overdischarging can permanently damage a NiCd or NiMH cell.

I suggest that you try this: fully charge the cells. Put 'em in the
MFJ. Turn it on. Let it run until the low-battery warning appears.
Then, with the MFJ still turned on, use a digital voltmeter to
carefully measure the voltage appearing across each of the cells in
the battery, and across the full battery stack.

Under these conditions (fresh charge, little discharging, and a low
current drain) the stack ought to be reading at least 12 volts, and
probably more than that.

If you find a "freshly-charged" cell that is not reading at least 1.2
volts under these conditions, it's probably bad.

Also the MFJ-259 is new. What is the best ways to check it to make sure its
working properly?

Test a variety of known-value loads (e.g. 25, 50, and 100-ohm
resistors) and confirm that the MFJ's readings are not unreasonably
wrong.

Cut a length of coax of a known type, short the far end, perform the
"velocity of propagation" tests shown in the manual. Typically a coax
with a solid polyethylene dielectric will have a VOP of around 0.66,
while a foamed-poly dielectric cable will calculate out at around 0.8
or so.

--
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:
Is it normal to only get 10 - 15 minutes worth of on time before getting the
low battery warning on the MFJ?

That's exactly why I went to a gelcell for my
MFJ-259B. It will last all day.
--
73, Cecil http://www.w5dxp.com

"Barrett" wrote in message
...
Finally got the batteries charged, discharged and charged again. I have
managed to fully charge them now.

How long should they last for with the MFJ-259 left on continuously being
used?

Is it normal to only get 10 - 15 minutes worth of on time before getting
the low battery warning on the MFJ?

Also the MFJ-259 is new. What is the best ways to check it to make sure
its working properly?

Thanks

For what it'sworth, I looked at an MFJ-269 manual, and it claims to trickle
charge at 10 - 20 ma. At that rate it will take a long time to charge a 2600
maH battery. They say minimum Vbat is 11V, but mine gets flakey below 12.
You might want to measure the under load battery voltage when it fails and
when you think it is fully charged.

Tam/WB2TT

Tam wrote:
For what it'sworth, I looked at an MFJ-269 manual, and it claims to
trickle charge at 10 - 20 ma. At that rate it will take a long time to
charge a 2600 maH battery. They say minimum Vbat is 11V, but mine gets
flakey below 12. You might want to measure the under load battery
voltage when it fails and when you think it is fully charged.

Tam/WB2TT

I don't think a 2600 mAh cell will ever become anywhere near fully
charged at that charge rate. That's barely enough to maintain an
existing charge.

Roy Lewallen, W7EL

After charging and discharging over the past few days they are finally
keeping there charge. I have had the MFJ-259Z switched on with the power
save turned off for the past 10 hours and still have 12.6V left in the
batteries. A big difference from the 10-15 minutes I was getting from them
when I purchased it. All I have to do now is to learn and then test the unit
to make sure it is working ok. As I am new to using a Analyzer.

Many thanks all for your help.

73 Barrett


"Roy Lewallen" wrote in message
news:-qidnTDq7ap4GWTanZ2dnUVZ_jKdnZ2d@easystreetonline.. .
Tam wrote:
For what it'sworth, I looked at an MFJ-269 manual, and it claims to
trickle charge at 10 - 20 ma. At that rate it will take a long time to
charge a 2600 maH battery. They say minimum Vbat is 11V, but mine gets
flakey below 12. You might want to measure the under load battery voltage
when it fails and when you think it is fully charged.

Tam/WB2TT

I don't think a 2600 mAh cell will ever become anywhere near fully charged
at that charge rate. That's barely enough to maintain an existing charge.

Roy Lewallen, W7EL