Reply
 
LinkBack Thread Tools Search this Thread Display Modes
  #21   Report Post  
Old April 4th 08, 07:35 PM posted to rec.radio.amateur.antenna
external usenet poster
 
First recorded activity by RadioBanter: Jul 2006
Posts: 464
Default MFJ-259Z

In article , hasan wrote:

I've had the same set of NIMH 2100 maH Energizer cells in my 259B for
over 3 years. I have had them on the internal charger 24x7, except when
in use. I have had no trouble with the batteries overcharging with the
internal charger in the 259B. (obviously, or I would have cooked them a
long time ago).


Good to know, thanks! Possibly the trickle charge is of a low enough
rate that the cells do not overcharge much and overheat. Heat is the
enemy of service life.

According to the battery-manufacturer literature I've read, NiMH cells
tend to have poor "charge acceptance" when trickle-charged at very low
rates. If you try to charge them at a rate of, say, .01C (20 mA, for
a 2000 mAh cell), almost none of this energy actually recharges the
cell - essentially all of it turns into heat.

One manufacturer's writeup I've read says that if it's necessary to
trickle-charge the cells to combat self-discharge, it's best done
through a periodic pulse-charging technique. Pulses of current in the
range of .05C through 1C, lasting for .1 to 60 seconds, are suggested,
with the time between pulses set so that the average rate of charge
delivered is around .02C per day. This is enough to combat
self-discharge, without overcharging.

One thing I've learned about NIMH batteries...they don't sit well. They
do wonderfully if kept trickle charged, but if let to sit, they will
self-discharge in less than two weeks. (at least for digital camera
purposes)I've observed this on three different "sets" of NIMH AA
batteries. All act the same way. Two weeks of sitting and they will only
operate the camera a very short time. Left in the charger and put
directly into service I can shoot well over 75 pictures in a row with no
difficulty.


High self-discharge rates are indeed an issue with the older NiMH
formulas (which account for most of the higher-capacity cells on the
market).

There seems to be a very real tradeoff between capacity and
self-discharge rate... it's a result of the different metal-hydride
alloy formulas used.

The new-generation "ultra-low self discharge" batteries are quite a
bit better in this regard. The Sanyo Eneloops and similar types are
billed as losing no more than around 10% of their total charge after a
month of storage, and still retaining as much as 60% after a year.
The price you pay for the longer holding time, is a reduced maximum
capacity (typically 2000-2100 mAh for an AA, as opposed to 2500-2700
for the ultra-high-capacity type).

Many reports indicate that new NiMH cells, and older ones which have
been sitting around unused for some time will exhibit reduced
capacity, until they've been fully charged and discharged once or
twice.

--
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!
  #22   Report Post  
Old April 4th 08, 08:23 PM posted to rec.radio.amateur.antenna
external usenet poster
 
First recorded activity by RadioBanter: Oct 2007
Posts: 69
Default MFJ-259Z

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

Thanks


"Highland Ham" wrote in message
...
Barrett wrote:
The jumper is on in the unit and all the batteries are in there correct
position. The link for the MFJ-259Z on the W&S site is
http://www.wsplc.com/cgi-bin/ss00000...=14&ACTION.y=3

They won't even charge in my Smart charger. They just shut down the
charging as if there no good, but they are supposed to be brand new. Just
borrowed some 1800mA and these are charging fine in the MFJ-259, so it
looks like the problem is with the batteries. I have never experienced
this with these type of batteries before only NiCad's.

=======================================
Suggest you allow a say 100 mA current to flow through the individual
(new)batteries , monitoring the voltage across the battery.
As soon as the voltage is 1.2 V you can further charge in your automatic
charger.
When fully charged , discharge either in your automatic charger or
manually (with a 12 to 15 Ohms resistor) ,down to
1Volt and recharge. The (new) batteries should then work well.

New NiMH batteries often need a few manually imposed charging
/discharging cycles before working properly.

Good Luck

Frank GM0CSZ / KN6WH



  #23   Report Post  
Old April 4th 08, 08:52 PM posted to rec.radio.amateur.antenna
external usenet poster
 
First recorded activity by RadioBanter: Jun 2006
Posts: 1,374
Default MFJ-259Z

hasan wrote:

One thing I've learned about NIMH batteries...they don't sit well. They
do wonderfully if kept trickle charged, but if let to sit, they will
self-discharge in less than two weeks. (at least for digital camera
purposes)I've observed this on three different "sets" of NIMH AA
batteries. All act the same way. Two weeks of sitting and they will only
operate the camera a very short time. Left in the charger and put
directly into service I can shoot well over 75 pictures in a row with no
difficulty.


This was true until a short while ago, but no longer is. A new chemistry
is now being used for some NiMH cells which greatly reduces the
self-discharge rate. Some of the more popular brands are Sanyo's
Eneloop, Rayovac's Hybrid, and Sony's Cycle Energy, but there's a
growing number of others. A bit of web searching will bring a great deal
more information about this. "Low self discharge NiMH" is a good search
string to start with.

So far, the LSD cells have a bit lower capacity than the very highest
capacity conventional cells, with 2000 mAh typical for AA and 800 mAh
for AAA. But they have almost as much capacity after sitting for an
extended time. And the Eneloops, in particular, typically have a
slightly higher voltage under discharge, and hold up very well under
high discharge rates. They're very good cells -- I use them almost
exclusively now.

Roy Lewallen, W7EL
  #24   Report Post  
Old April 4th 08, 09:23 PM posted to rec.radio.amateur.antenna
external usenet poster
 
First recorded activity by RadioBanter: Jul 2006
Posts: 464
Default MFJ-259Z

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!
  #25   Report Post  
Old April 5th 08, 12:18 PM posted to rec.radio.amateur.antenna
external usenet poster
 
First recorded activity by RadioBanter: Jul 2006
Posts: 250
Default MFJ-259Z

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


  #26   Report Post  
Old April 6th 08, 08:28 PM posted to rec.radio.amateur.antenna
external usenet poster
 
First recorded activity by RadioBanter: Oct 2007
Posts: 69
Default MFJ-259Z

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



  #27   Report Post  
Old April 6th 08, 08:49 PM posted to rec.radio.amateur.antenna
external usenet poster
 
First recorded activity by RadioBanter: Jul 2006
Posts: 757
Default MFJ-259Z

On Apr 2, 11:54 am, (Dave Platt) wrote:


Another possibilty is that the 2600 mAh cells are actually OK, but
were delivered to you in a completely-run-down state.


That could well be the case. I just got a new cell phone
that had batteries that had no charge whatsoever.
At first the phone would not recognize them and start
charging. I'd check the voltage and zero.
I tried manually charging a small bit with a couple
of wires from a power source to see if I could kick start
em.
I'm not sure if that did the trick, but the phone finally
noticed the batteries and started charging.
There was nothing wrong with them, as when fully
charged, they last as long or longer than any of
my others.
  #28   Report Post  
Old April 6th 08, 09:21 PM posted to rec.radio.amateur.antenna
external usenet poster
 
First recorded activity by RadioBanter: Jul 2006
Posts: 464
Default MFJ-259Z

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!
  #29   Report Post  
Old April 6th 08, 10:40 PM posted to rec.radio.amateur.antenna
external usenet poster
 
First recorded activity by RadioBanter: Mar 2007
Posts: 3,521
Default MFJ-259Z

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
  #30   Report Post  
Old April 7th 08, 03:09 AM posted to rec.radio.amateur.antenna
Tam Tam is offline
external usenet poster
 
First recorded activity by RadioBanter: Jan 2008
Posts: 42
Default MFJ-259Z


"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

Reply
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT +1. The time now is 12:07 PM.

Powered by vBulletin® Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 RadioBanter.
The comments are property of their posters.
 

About Us

"It's about Radio"

 

Copyright © 2017