KX3 and charging batteries (when, and why do they get hot?)
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KX3 and charging batteries (when, and why do they get hot?)
 
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So I got a new, factory-assembled KX3 yesterday, with charger installed.
I bought eight Rayovac Platinum NiMH 2000mA cells ready to go, inserted them, and ran the radio on batteries for just a few minutes, when I got the LO BATT message. So I started charging them, with timer on 12 hrs. After about two hours, they had gotten over 40° and charging halted until they had cooled down again. The next morning, charging was in its last 7 minutes, so it must have halted more often over the course. Is this normal? Or is my ingoing voltage too high, coming from a wall wart rated at 13-15.8V @ 960mA? Are the batteries (or one/some of them) defective? I bought them in two packs of four each. Were the batteries still way too full when I started charging? I didnt check voltage at the LOW BATT warning. When should such batteries get charged, at what voltage level? Other than that, I cannot say much because I am still working on an antenna. But the CW code practice setting works really nice :-). It even goes up to 700 Hz (not 600 as per manual). Thank you for your expert advice. 73, Arno ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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>>...must have halted more often over the course.
>>Is this normal? Yes, with some concern. The short answer is I suspect you have a bad cell. The KXBC3 will attempt to keep the temperature at or below 40deg C, and sill suspend charging as required to allow cool down. It is a bit troubling that you didn't get more out of the first discharge cycle. It could be that they just sat on the shelf for a long time, but it could also be caused by a one or more defective cells. A defective cell may generate heat when charging, causing the KXBC3 to suspend charging. That can also happen with all good cells, but usually when ambient temperatures are high or during simultaneous transmission and charging. I recommend that you measure the cells' voltage individually. I know, it is a pain to split the case, but you may not have to take them out to check them. I haven't tried that. Just be very careful with the probe if you don't. When measured individually with a volt meter, they should all be within 0.1 volt or so of each other, and all of them should be above about 1v. Any cells below 0.9v should certainly be considered faulty. If NiMH cells are run much below 1.0v, they will most likely be damaged. Any cells that have damage to their plastic case should be discarded as well. A couple of weeks ago, I charged up a box of 14 used Energizer NiMH cells (2500maH) of unknown origin which had been given to me. I just checked them today, and 10 measured slightly higher than 1.3v each (excellent), one measured 1.28v (fairly good), and 3 measured less than .9v (BAD). Given this, 10 are good, 1 is a bit questionable but will probably level out with the others when charged a few times, and the 3 low voltages ones will be sent to the battery recycle bin. >>Were the batteries still way too full when I started charging? No. The KXBC3 charges with a constant current of approximately 200ma. At that current, you will not overcharge 2000aH (or larger) NiMH cells, and no damage will occur as long as the temperature is kept below 40deg C. So even if they were completely full, you could charge them with the KXBC3 for the full 16 hours without significant damage. That doesn't mean you should keep them on charge all the time. That would certainly shorten their life. I think the KXBC3 documentation mentions something about that. >>When should such batteries get charged, at what voltage level? Don't let them go below 1v per cell...about 8 volts total on the KX3 display...8.5V would be safer. Elecraft recommends setting the BAT MIN menu to 8.5 V (KX3 Owner's Manual Pg. 36) to give you some warning that you need to think about recharging. This is about 1.06V per cell. The KX3 will shut down at 8 V which is about 1V per cell, very near the absolute minimum for NiMH chemistry. There isn't much energy left below 1.06v per cell, so running them below that level really doesn't give you much extra operating time. Some folks set the BAT MIN to 9V to give them more warning and plenty of time to finish their QSO and shut the station down. By the way, the NiMH cells do not need to be fully discharged before starting the charge cycle. They do not have the strong "memory" that the older NiCad chemistry has. They can be "touched up" as you feel they need it. My Eneloope and Panisonic NiMH cells are very consistent, especially after several charges. The voltage of NiMH cells tend to self level (equal voltage of all cells within the battery of 8) when charged with the KXBC3. I don't have any personal experience with the Rayovac cells, but I think I recall that some folks had some problems with brand new ones right out of the box. I suggest you check the voltages of the cells individually, and get rid of the ones that measure below 1v and replace them with new cells of the same brand/capacity. Once you get a good set of cells, you will gain more confidence in them and in the KXBC3, and you will be able to tell where you are in their charge/discharge cycle by the KX3 displayed battery voltage. Hope this helps. Mark KE6BB ________________________________ From: Arno Dienhart <[hidden email]> To: [hidden email] Sent: Thursday, June 6, 2013 4:12 PM Subject: [Elecraft] KX3 and charging batteries (when, and why do they get hot?) So I got a new, factory-assembled KX3 yesterday, with charger installed. I bought eight Rayovac Platinum NiMH 2000mA cells “ready to go”, inserted them, and ran the radio on batteries for just a few minutes, when I got the LO BATT message. So I started charging them, with timer on 12 hrs. After about two hours, they had gotten over 40° and charging halted until they had cooled down again. The next morning, charging was in its last 7 minutes, so it must have halted more often over the course. Is this normal? Or is my ingoing voltage too high, coming from a wall wart rated at 13-15.8V @ 960mA? Are the batteries (or one/some of them) defective? I bought them in two packs of four each. Were the batteries still way too full when I started charging? I didn’t check voltage at the LOW BATT warning. When should such batteries get charged, at what voltage level? Other than that, I cannot say much because I am still working on an antenna. But the CW code practice setting works really nice :-). It even goes up to 700 Hz (not 600 as per manual). Thank you for your expert advice. 73, Arno ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: KX3 and charging batteries (when, and why do they get hot?)
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In reply to this post by Arno Dienhart
Mark,
Thank you for this excellent response. This is exactly what I need: solid advice with rationale behind it. I checked a few things. All eight cells are now at 1.4V. When I turn the TRX on, the integrated meter shows 10.5 V now. I think this morning, when I checked after the full charge, it showed 11.6V. Not sure if that is a good sign after only having it on for a bit, tinkering. The BAT MIN was at the default setting of 10.0 V. I changed it to 8.5. Kent briefly contributed his opinion that a wall wart would not be good for charging the KX3 but did not give his reasons (I will not operate it off that adapter). What is your opinion, particularly regarding the wall charger's specs of 13 - 15.8V (@960mA). Is this peak voltage potentially too high? Other than that, I fail to construe even one reason why this adapter would not be fit to feed the 200mA charger or cause my heating issue. Thanks a bunch! 73, Arno Kg7bjm ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: KX3 and charging batteries (when, and why do they get hot?)
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In reply to this post by Arno Dienhart
Mark,
Having thought about this some more, I believe your point below is hitting the nail. My BAT MIN was still at the factory default of 10V, which obviously meant still lots of capacity. So the batteries were still quite full and thus got warm soon and repeatedly. Phew! I am not worried anymore. Thank you again! 73, Arno kg7bjm >> >>When should such batteries get charged, at what voltage level? >>Don't let them go below 1v per cell...about 8 volts total on the KX3 display...8.5V would be safer. Elecraft recommends setting the BAT MIN menu to 8.5 V (KX3 Owner's Manual Pg. 36) to give you some warning that you need to think about recharging. This is about 1.06V per cell. The KX3 will shut down at 8 V which is about 1V per cell, very near the absolute minimum for NiMH chemistry. There isn't much energy left below 1.06v per cell, so running them below that level really doesn't give you much extra operating time. Some folks set the BAT MIN to 9V to give them more warning and plenty of time to finish their QSO and shut the station down. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Arno Dienhart
Arno,
>>All eight cells are now at 1.4V. When I turn the TRX on, the integrated meter shows 10.5 V now. I think this morning, when I checked after the full charge, it showed 11.6V Excellent. All appears to be normal and is almost exactly what I typically see on mine. Immediately after charging, the voltage is highest. It usually settles pretty quickly down to about 10.5 or so volts, even if I don't actually use the batteries much. You can see this in the discharge curve shown in the Eneloop data sheet: www.eneloop.info/fileadmin/EDITORS/ENELOOP/DATA_SHEETS/Datasheet_-_HR-3UTG.pdf (Sorry, I have not been able to find a datasheet on Rayovac rechargeable NiMH cells). The voltage over the majority of the discharge curve is between 1.3 and 1.2 volts per cell, or 10.4V and 9.6V for the 8 cell battery. Once you get down below that 9.6V, you can see that the voltage drops off rapidly down to the 1v per cell level, or 8 volts for the battery. That is roughly how you will see the voltage drop when operating. By the way, a little study of the charge/discharge curves will help you understand what you are seeing on the KX3 voltage display during charge/discharge cycles. >>Kent briefly contributed his opinion that a wall wart would not be good for >>charging the KX3 but did not give his reasons The output voltage of wall warts varies pretty wildly with load. It is hard to really know if your particular wall wart would work well or not. I don't really like to see voltages on the display higher than 15V (14V some places in the KX3 Owner's Manual), because that is the maximum Elecraft recommends; however, the radio does have excellent protection circuits so that may not be a problem. There have been lots of cases of "greater than 15V" supplies applied to the KX3's, and I haven't heard of a failure yet. The KX3 simply shuts down at about 16V. Maybe others on the list have more experience with this. In a later post you mentioned: >>So the batteries were still quite >>full and thus got warm soon and repeatedly. I agree. There are a lot of things going on during charging that generate heat, but in general, as the battery approaches full charge, less and less of the total power applied to the battery is used for the chemical change, and a larger percentage simply gets converted to heat by the internal resistance of the battery. Try to charge a fully charged battery of cells, and the KX3 will get warm since there is no more chemical conversion going on, and all of the power delivered by the KXBC3 is converted to heat by the internal resistance of the cells. In this case, the KXBC3 will cycle off occasionally keeping the temperature below 40deg C. That is completely acceptable to 2000maH (or larger) cells since the current remains at about 200ma, and the temperature remains below 40 deg C, well within the manufacturers specs. Bedtime. Mark KE6BB ________________________________ From: Arno Dienhart <[hidden email]> To: [hidden email] Sent: Thursday, June 6, 2013 8:08 PM Subject: Re: [Elecraft] KX3 and charging batteries (when, and why do they get hot?) Mark, Thank you for this excellent response. This is exactly what I need: solid advice with rationale behind it. I checked a few things. All eight cells are now at 1.4V. When I turn the TRX on, the integrated meter shows 10.5 V now. I think this morning, when I checked after the full charge, it showed 11.6V. Not sure if that is a good sign after only having it on for a bit, tinkering. The BAT MIN was at the default setting of 10.0 V. I changed it to 8.5. Kent briefly contributed his opinion that a wall wart would not be good for charging the KX3 but did not give his reasons (I will not operate it off that adapter). What is your opinion, particularly regarding the wall charger's specs of 13 - 15.8V (@960mA). Is this peak voltage potentially too high? Other than that, I fail to construe even one reason why this adapter would not be fit to feed the 200mA charger or cause my heating issue. Thanks a bunch! 73, Arno Kg7bjm ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: KX3 and charging batteries (when, and why do they get hot?)
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In reply to this post by KE6BB
I know it's an added expense but I use an external charger/reconditioner with all of my NiMH batteries. Always with new batteries the first time before use then again after about 6 rechargers. If you buy one make sure it's a charger/reconditioner it’s the last one that counts for long lasting batteries.
I keep the batteries in sets (plastic cases) of 8 for my KX3 with date of last charge in external and total number of charges in radio. Gives me a little idea of life per brand and amount of discharge rate while idle, this is important to me. This tells me what battery to put in what item I'm using it in being the KX3 or whatever. I have a Grundig G3 radio for emergency's and after 5 months one set of my NiMH batteries had only lost about 20% of their charge, should remain there for close to a year shelf life. -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of Mark Petiford Sent: Thursday, June 06, 2013 8:26 PM To: [hidden email] Subject: Re: [Elecraft] KX3 and charging batteries (when, and why do they get hot?) >>...must have halted more often over the course. >>Is this normal? Yes, with some concern. The short answer is I suspect you have a bad cell. The KXBC3 will attempt to keep the temperature at or below 40deg C, and sill suspend charging as required to allow cool down. It is a bit troubling that you didn't get more out of the first discharge cycle. It could be that they just sat on the shelf for a long time, but it could also be caused by a one or more defective cells. A defective cell may generate heat when charging, causing the KXBC3 to suspend charging. That can also happen with all good cells, but usually when ambient temperatures are high or during simultaneous transmission and charging. I recommend that you measure the cells' voltage individually. I know, it is a pain to split the case, but you may not have to take them out to check them. I haven't tried that. Just be very careful with the probe if you don't. When measured individually with a volt meter, they should all be within 0.1 volt or so of each other, and all of them should be above about 1v. Any cells below 0.9v should certainly be considered faulty. If NiMH cells are run much below 1.0v, they will most likely be damaged. Any cells that have damage to their plastic case should be discarded as well. A couple of weeks ago, I charged up a box of 14 used Energizer NiMH cells (2500maH) of unknown origin which had been given to me. I just checked them today, and 10 measured slightly higher than 1.3v each (excellent), one measured 1.28v (fairly good), and 3 measured less than .9v (BAD). Given this, 10 are good, 1 is a bit questionable but will probably level out with the others when charged a few times, and the 3 low voltages ones will be sent to the battery recycle bin. >>Were the batteries still way too full when I started charging? No. The KXBC3 charges with a constant current of approximately 200ma. At that current, you will not overcharge 2000aH (or larger) NiMH cells, and no damage will occur as long as the temperature is kept below 40deg C. So even if they were completely full, you could charge them with the KXBC3 for the full 16 hours without significant damage. That doesn't mean you should keep them on charge all the time. That would certainly shorten their life. I think the KXBC3 documentation mentions something about that. >>When should such batteries get charged, at what voltage level? Don't let them go below 1v per cell...about 8 volts total on the KX3 display...8.5V would be safer. Elecraft recommends setting the BAT MIN menu to 8.5 V (KX3 Owner's Manual Pg. 36) to give you some warning that you need to think about recharging. This is about 1.06V per cell. The KX3 will shut down at 8 V which is about 1V per cell, very near the absolute minimum for NiMH chemistry. There isn't much energy left below 1.06v per cell, so running them below that level really doesn't give you much extra operating time. Some folks set the BAT MIN to 9V to give them more warning and plenty of time to finish their QSO and shut the station down. By the way, the NiMH cells do not need to be fully discharged before starting the charge cycle. They do not have the strong "memory" that the older NiCad chemistry has. They can be "touched up" as you feel they need it. My Eneloope and Panisonic NiMH cells are very consistent, especially after several charges. The voltage of NiMH cells tend to self level (equal voltage of all cells within the battery of 8) when charged with the KXBC3. I don't have any personal experience with the Rayovac cells, but I think I recall that some folks had some problems with brand new ones right out of the box. I suggest you check the voltages of the cells individually, and get rid of the ones that measure below 1v and replace them with new cells of the same brand/capacity. Once you get a good set of cells, you will gain more confidence in them and in the KXBC3, and you will be able to tell where you are in their charge/discharge cycle by the KX3 displayed battery voltage. Hope this helps. Mark KE6BB ________________________________ From: Arno Dienhart <[hidden email]> To: [hidden email] Sent: Thursday, June 6, 2013 4:12 PM Subject: [Elecraft] KX3 and charging batteries (when, and why do they get hot?) So I got a new, factory-assembled KX3 yesterday, with charger installed. I bought eight Rayovac Platinum NiMH 2000mA cells “ready to go”, inserted them, and ran the radio on batteries for just a few minutes, when I got the LO BATT message. So I started charging them, with timer on 12 hrs. After about two hours, they had gotten over 40° and charging halted until they had cooled down again. The next morning, charging was in its last 7 minutes, so it must have halted more often over the course. Is this normal? Or is my ingoing voltage too high, coming from a wall wart rated at 13-15.8V @ 960mA? Are the batteries (or one/some of them) defective? I bought them in two packs of four each. Were the batteries still way too full when I started charging? I didn’t check voltage at the LOW BATT warning. When should such batteries get charged, at what voltage level? Other than that, I cannot say much because I am still working on an antenna. But the CW code practice setting works really nice :-). It even goes up to 700 Hz (not 600 as per manual). Thank you for your expert advice. 73, Arno ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ----- No virus found in this message. Checked by AVG - www.avg.com Version: 2013.0.2904 / Virus Database: 3184/6388 - Release Date: 06/05/13 ----- No virus found in this message. Checked by AVG - www.avg.com Version: 2013.0.2904 / Virus Database: 3184/6388 - Release Date: 06/05/13 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: KX3 and charging batteries (when, and why do they get hot?)
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In reply to this post by KE6BB
As the batteries discharge and reach the knee where voltage begins to
drop off quickly, imbalances in capacity between the cells can lead to wider voltage differences between the individual cells. If discharge isn't stopped in time, it's also possible for the weakest cell to be subjected to a reverse charge. For example, 7 cells at 1.2V per cell is 8.4V. If there's an 8th cell in series, running the pack down to 8V would mean that the weak cell has -0.4V across it. This is a bit simplified and extreme, but the real goal is to not let an individual cell get below 0.9V, which is the typical manufacturer's spec for maximum discharge. Starting with 8 new, good quality batteries is the easiest way to get what should be a pretty well matched set, and picking a conservative voltage to stop at will help get maximum life from the batteries. As Mark points out, there really isn't much left near the end anyway. 73, Rich AC7MA One thing to be mindful of when setting the low battery warning, but particularly when On 06/06/2013 06:26 PM, Mark Petiford wrote: >>> When should such batteries get charged, at what voltage level? > Don't let them go below 1v per cell...about 8 volts total on the KX3 display...8.5V would be safer. Elecraft recommends setting the BAT MIN menu to 8.5 V (KX3 Owner's Manual Pg. 36) to give you some warning that you need to think about recharging. This is about 1.06V per cell. The KX3 will shut down at 8 V which is about 1V per cell, very near the absolute minimum for NiMH chemistry. There isn't much energy left below 1.06v per cell, so running them below that level really doesn't give you much extra operating time. Some folks set the BAT MIN to 9V to give them more warning and plenty of time to finish their QSO and shut the station down. > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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