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#21
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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 |
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