Home |
Search |
Today's Posts |
|
#1
|
|||
|
|||
MFJ-259Z
I 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. What brand and type are the batteries that don't work? It's possible that you simply received a bunch of batteries that are completely defective (open) or are counterfeit dummies. Seems a bit implausible. Another possibilty is that the 2600 mAh cells are actually OK, but were delivered to you in a completely-run-down state. That seems plausible... the manufacturer may not have precharged them, or they may have self-discharged in storage after manufacture. The older type of NiMH cells do have a relatively high self-discharge rate, and can go flat after as little as three or four months of storage. If the batteries read 0 volts, then it's possible that a smart-charger might fail to detect their presence and start charging... I believe that some of the newer NiMH-aware charge-control ICs depend on the detection of _some_ voltage from the cell to detect the cell and start the charge. Try sticking a few of the cells into an old-style "dumb and slow" NiCd battery charger for a few hours. These are usually fixed-current chargers (100 mA or so) with no battery-detect or charge-cutoff circuits, so they're not a good choice for general use with NiMH cells. They _will_ feed some charge into the cells if the cells aren't entirely open, and should bring the cells up to 1.0 volts or better fairly quickly. After 2-3 hours, take the cells out of the dumb charger, check the open-circuit voltage, and put them in your smart-charger, and see if they are accepted and begin charging. If so, they may be OK. If not, they're probably defective or bogus and you may want to return them to the seller for a refund. Since an MFJ analyzer is the sort of device that tends to sit around unused for weeks at a time, I think that high-capacity high-self- discharge NiMH cells (e.g. most 2500 or above) are a poor choice. Unless you recharge for an hour or so once a week, you'll probably find them weak or dead when you want use the analyzer. High-capacity NiCd cells are the traditional choice for this sort of application (and are what I use in my own MFJ). Another possibility is the newer low-self-discharge NiMH cells, such as the Imedions, Eneloops, Hybrios, and Hybrids. These are typically 2000-2100 mAh, and will hold the majority of their charge for a year or more. If your MFJ has been modified to charge NiMH properly (e.g. with a good temperature or zero-delta-V cutoff circuit) they might be a good choice. -- 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! |
#2
|
|||
|
|||
MFJ-259Z
Dave Platt wrote:
High-capacity NiCd cells are the traditional choice for this sort of application I have been most happy with a small gelcell velcroed to my MJF-259B. -- 73, Cecil http://www.w5dxp.com |
#3
|
|||
|
|||
MFJ-259Z
Cecil Moore writes:
Dave Platt wrote: High-capacity NiCd cells are the traditional choice for this sort of application I have been most happy with a small gelcell velcroed to my MJF-259B. I've had mine for four years, and am still on my first set of disposable batteries. Just have to make sure it doesn't turn on accidentally under transport - I wrap some tape over one of the batteries. LA4RT Jon |
#4
|
|||
|
|||
MFJ-259Z
Dave, the batteries are called Supreme Power 2600mA standard charge 14-16 HRS x 260mA, quick charge 4-6 HRS x 550mA. REG USA Made in China.
I am waiting for a friend to bring by his old NiCad charger and I will give it ago. I will let you know how I got on. For future reference would you have an idea on how long I should charge the batteries for using the MFJ? I don't know who or how the charger circuit has been modified. I could ask W&S what sort of circuit has been used. "Dave Platt" wrote in message ... I 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. What brand and type are the batteries that don't work? It's possible that you simply received a bunch of batteries that are completely defective (open) or are counterfeit dummies. Seems a bit implausible. Another possibilty is that the 2600 mAh cells are actually OK, but were delivered to you in a completely-run-down state. That seems plausible... the manufacturer may not have precharged them, or they may have self-discharged in storage after manufacture. The older type of NiMH cells do have a relatively high self-discharge rate, and can go flat after as little as three or four months of storage. If the batteries read 0 volts, then it's possible that a smart-charger might fail to detect their presence and start charging... I believe that some of the newer NiMH-aware charge-control ICs depend on the detection of _some_ voltage from the cell to detect the cell and start the charge. Try sticking a few of the cells into an old-style "dumb and slow" NiCd battery charger for a few hours. These are usually fixed-current chargers (100 mA or so) with no battery-detect or charge-cutoff circuits, so they're not a good choice for general use with NiMH cells. They _will_ feed some charge into the cells if the cells aren't entirely open, and should bring the cells up to 1.0 volts or better fairly quickly. After 2-3 hours, take the cells out of the dumb charger, check the open-circuit voltage, and put them in your smart-charger, and see if they are accepted and begin charging. If so, they may be OK. If not, they're probably defective or bogus and you may want to return them to the seller for a refund. Since an MFJ analyzer is the sort of device that tends to sit around unused for weeks at a time, I think that high-capacity high-self- discharge NiMH cells (e.g. most 2500 or above) are a poor choice. Unless you recharge for an hour or so once a week, you'll probably find them weak or dead when you want use the analyzer. High-capacity NiCd cells are the traditional choice for this sort of application (and are what I use in my own MFJ). Another possibility is the newer low-self-discharge NiMH cells, such as the Imedions, Eneloops, Hybrios, and Hybrids. These are typically 2000-2100 mAh, and will hold the majority of their charge for a year or more. If your MFJ has been modified to charge NiMH properly (e.g. with a good temperature or zero-delta-V cutoff circuit) they might be a good choice. -- 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! |
#5
|
|||
|
|||
MFJ-259Z
Dave, the batteries are called Supreme Power 2600mA standard charge
14-16 HRS x 260mA, quick charge 4-6 HRS x 550mA. REG USA Made in China. Hmmm. I see various web sites offering that brand, but I don't see much in the way of comments about their quality (good or bad). I am waiting for a friend to bring by his old NiCad charger and I will give it ago. I will let you know how I got on. Please do - I'm curious. For future reference would you have an idea on how long I should charge the batteries for using the MFJ? Depends on the charger. In general, a fully-discharged NiMH cell will need to be "fed" somewhere around 150% of its rated capacity in order to reach full charge - some of the energy fed into it is dissipated as heat and doesn't go into rebuilding the electrochemistry. The "standard charge" recommendations you quoted are feeding the battery at a rate of .1C (10% of its capacity per hour) for 14-16 hours, so that's just about right. If you're using a different charger, you'd need to determine the amount of current being fed to each cell, divide that into the cell's rated capacity (to get the time required for 100% capacity delivery), and then add around 40-50%. These calculations apply *only* to cells which are fully discharged! If a cell is partially charged when you start to recharge it, it'll reach full charge sooner than these calculations indicate... and at that point the cell starts to heat up pretty rapidly. Most of the NiMH technology sheets I've read, seem to recommend charging these batteries at a relatively fast rate (no less than .2C, with .5C and 1C being common) and using a temperature sensor as the primary means of figuring out when to turn off the charge. Zero-delta-V is often used as a secondary method, with a timer being the final fallback. I don't know who or how the charger circuit has been modified. I could ask W&S what sort of circuit has been used. That would be a good idea! The 259/269 have a simple slow/trickle-charge circuit built in... it's OK for NiCd cells but isn't ideal for NiMH. It would be very interesting to know how this was modified for NiMH in the 259Z model. -- 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! |
#6
|
|||
|
|||
MFJ-259Z
On Apr 2, 6:08*pm, (Dave Platt) wrote:
Dave, the batteries are called Supreme Power 2600mA standard charge 14-16 HRS x 260mA, quick charge 4-6 HRS x 550mA. REG USA Made in China. Hmmm. *I see various web sites offering that brand, but I don't see much in the way of comments about their quality (good or bad). I am waiting for a friend to bring by his old NiCad charger and I will give it ago. I will let you know how I got on. Please do - I'm curious. For future reference would you have an idea on how long I should charge the batteries for using the MFJ? Depends on the charger. *In general, a fully-discharged NiMH cell will need to be "fed" somewhere around 150% of its rated capacity in order to reach full charge - some of the energy fed into it is dissipated as heat and doesn't go into rebuilding the electrochemistry. *The "standard charge" recommendations you quoted are feeding the battery at a rate of .1C (10% of its capacity per hour) for 14-16 hours, so that's just about right. If you're using a different charger, you'd need to determine the amount of current being fed to each cell, divide that into the cell's rated capacity (to get the time required for 100% capacity delivery), and then add around 40-50%. These calculations apply *only* to cells which are fully discharged! If a cell is partially charged when you start to recharge it, it'll reach full charge sooner than these calculations indicate... and at that point the cell starts to heat up pretty rapidly. Most of the NiMH technology sheets I've read, seem to recommend charging these batteries at a relatively fast rate (no less than .2C, with .5C and 1C being common) and using a temperature sensor as the primary means of figuring out when to turn off the charge. Zero-delta-V is often used as a secondary method, with a timer being the final fallback. I don't know who or how the charger circuit has been modified. I could ask W&S what sort of circuit has been used. That would be a good idea! The 259/269 have a simple slow/trickle-charge circuit built in... it's OK for NiCd cells but isn't ideal for NiMH. *It would be very interesting to know how this was modified for NiMH in the 259Z model. -- 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 may want to use the NiCd charger on them for a few minutes and then move them to the NiMH charger. Jimmie |
#7
|
|||
|
|||
MFJ-259Z
A NiMH or NiCd cell reading of zero volts usually indicates an internal
short, caused by metallic dendrite growth. If this is the problem with the cells, they won't respond to any ordinary attempt to charge them. It's sometimes possible to "zap" a shorted cell (by discharging a very large capacitor into the cell) to burn out the shorts, but you end up with a cell that has higher than normal self-discharge and a tendency to grow shorts again. So if they don't respond to normal charging, I recommend tossing them and getting some new cells. If the device has a charger designed for NiMH cells, that is, one that charges at a fairly high rate and properly detects the end of charge, then I highly recommend one of the newer low-self discharge cells such as the Sanyo Eneloop. If it doesn't have a proper NiMH charger and just pumps in a constant current charge without end of charge detection, you should use NiCd cells because they can tolerate that charge regimen much better than NiMH cells can. I've had very good luck with Sanyo and Panasonic NiCd cells. Don't be suckered by inflated capacity claims which the minor brands liberally use. Even with the better brands, the highest capacity cells have historically had more problems with overly fast self discharge and premature cell failure. Roy Lewallen, W7EL |
#8
|
|||
|
|||
MFJ-259Z
Barrett wrote:
Dave, the batteries are called Supreme Power 2600mA standard charge 14-16 HRS x 260mA, quick charge 4-6 HRS x 550mA. REG USA Made in China. I am waiting for a friend to bring by his old NiCad charger and I will give it ago. I will let you know how I got on. For future reference would you have an idea on how long I should charge the batteries for using the MFJ? I don't know who or how the charger circuit has been modified. I could ask W&S what sort of circuit has been used. "Dave Platt" wrote in message ... I 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. What brand and type are the batteries that don't work? It's possible that you simply received a bunch of batteries that are completely defective (open) or are counterfeit dummies. Seems a bit implausible. Another possibilty is that the 2600 mAh cells are actually OK, but were delivered to you in a completely-run-down state. That seems plausible... the manufacturer may not have precharged them, or they may have self-discharged in storage after manufacture. The older type of NiMH cells do have a relatively high self-discharge rate, and can go flat after as little as three or four months of storage. If the batteries read 0 volts, then it's possible that a smart-charger might fail to detect their presence and start charging... I believe that some of the newer NiMH-aware charge-control ICs depend on the detection of _some_ voltage from the cell to detect the cell and start the charge. Try sticking a few of the cells into an old-style "dumb and slow" NiCd battery charger for a few hours. These are usually fixed-current chargers (100 mA or so) with no battery-detect or charge-cutoff circuits, so they're not a good choice for general use with NiMH cells. They _will_ feed some charge into the cells if the cells aren't entirely open, and should bring the cells up to 1.0 volts or better fairly quickly. After 2-3 hours, take the cells out of the dumb charger, check the open-circuit voltage, and put them in your smart-charger, and see if they are accepted and begin charging. If so, they may be OK. If not, they're probably defective or bogus and you may want to return them to the seller for a refund. Since an MFJ analyzer is the sort of device that tends to sit around unused for weeks at a time, I think that high-capacity high-self- discharge NiMH cells (e.g. most 2500 or above) are a poor choice. Unless you recharge for an hour or so once a week, you'll probably find them weak or dead when you want use the analyzer. High-capacity NiCd cells are the traditional choice for this sort of application (and are what I use in my own MFJ). Another possibility is the newer low-self-discharge NiMH cells, such as the Imedions, Eneloops, Hybrios, and Hybrids. These are typically 2000-2100 mAh, and will hold the majority of their charge for a year or more. If your MFJ has been modified to charge NiMH properly (e.g. with a good temperature or zero-delta-V cutoff circuit) they might be a good choice. -- 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'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). 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. |
#9
|
|||
|
|||
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! |
#10
|
|||
|
|||
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 |