KX3 internal battery problems
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KX3 (ser. no. 08146) works OK on external power, but recently I am experiencing problem using it on internal rechargeable cells.
The AA cells are relatively new Varta Professional No. 5706, 2700 mAh NiMH. They have been charged with a techno-line BC-1000. Measured capacity via an automatic discharge/recharge cycle is according to spec. I have attached a 50 Ohm dummy-load to the KX3. When turned on, it indicates BT 9,7V. BAT MIN is set to 8,2V. When I press ATU TUNE, it turn itself off immediately. With TUN PWR set to 0,1W it works OK when pressing TUNE, but BT drops to 7,6V. If TUN PWR is set to 1W, it switches off when TUNE is pressed. Strange that the voltage drops so much, even if the charger indicated normal cell capacity when automatically discharging them. Any ideas? Per-Tore / LA7NO
73,
Per-Tore / LA7NO |
Re: KX3 internal battery problems
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I can offer a little info :
New charged cells in my KX-3 show about 10.4V when I turn the unit on (after it's been laying around for weeks). A new fully charged pack shows about 0.7 ohm internal resistance (by the voltage drop and current when transmitting). Ie that's over the 8 cells. Don't fully discharge NiMH batteries. Cycling them as you'd do with the old nickel cadmium cells rapidly raises the internal impedance of the NiMH batteries. You'll find them useless long before they get anywhere near the published number of cycles because of that rise in internal impedance. Just top them up after use and that's it. I've gone through a couple of battery changes in the KX-3. That internal impedance is going to be way more important to you than the capacity of the pack. On a typical SOTA outing I'd be lucky to use more than about 20% of the capacity (I use the LSD kind at about 2.5Ahr). The packs still have close to their full capacity long after the internal impedance rules them out for use in the KX-3. Last pack probably only got cycled about 10 times before the impedance was too high to get the 5W out. I concluded from good old google the cause was deep discharge. After just 10 cycles I considered them relatively "new" but they'd not hold up under transmit load (guestimate of around 1.5 ohms for the pack). They worked fine for lower current use and still operated the KX-3 in receive for the same duration (ie capacity had not diminished). The "new" pack in the unit will never get cycled just topped up. 73's Peter VK4JD -----Original Message----- From: Elecraft [mailto:[hidden email]] On Behalf Of LA7NO Sent: Friday, 6 May 2016 8:07 PM To: [hidden email] Subject: [Elecraft] KX3 internal battery problems KX3 (ser. no. 08146) works OK on external power, but recently I am experiencing problem using it on internal rechargeable cells. The AA cells are relatively new Varta Professional No. 5706, 2700 mAh NiMH. They have been charged with a techno-line BC-1000. Measured capacity via an automatic discharge/recharge cycle is according to spec. I have attached a 50 Ohm dummy-load to the KX3. When turned on, it indicates BT 9,7V. BAT MIN is set to 8,2V. When I press ATU TUNE, it turn itself off immediately. With TUN PWR set to 0,1W it works OK when pressing TUNE, but BT drops to 7,6V. If TUN PWR is set to 1W, it switches off when TUNE is pressed. Strange that the voltage drops so much, even if the charger indicated normal cell capacity when automatically discharging them. Any ideas? Per-Tore / LA7NO -- View this message in context: http://elecraft.365791.n2.nabble.com/KX3-internal-battery-problems-tp7617201 .html Sent from the Elecraft mailing list archive at Nabble.com. ______________________________________________________________ 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 Message delivered to [hidden email] ______________________________________________________________ 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 Message delivered to [hidden email] |
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In reply to this post by LA7NO
I think you will find that one of the cells used in this series
arrangement will have a high internal resistance. You also mentioned a brand that I have seen the worst performance from (my personal experience). I have been using one of the Blue ESR meters (80 bucks) for about 4 years to look at batteries that don't perform well, high resistance in a cell has always been the issue.. Before all the engineers jump on and say there is a difference between resistance and impedance and I don't understand, and this is not the correct way to read internal resistance. I can say that I also understand how to load a battery and at the same time and take a resistance reading of the cell. But who has the time.. I have no intent of testing in a laboratory, when the shop is sufficient. First off make sure you don't use any of the really expensive ESR meters that measure the voltage first and if they see any the go into a capacitor discharge cycle.. that would not be good. I simply hook the battery across the meter and read the resistance.. While this is not a exact laboratory measurement you can tell a lot from the reading.. look at each cell in the string, if one is higher just get rid if it you will see an improvement of string capacity. As an example not long ago I had a battery pack that could last about 5 minutes after it was charged.. reading the whole pack's resistance it showed about 9 ohms of resistance on a 14 volt pack. opening the pack I found two of the cells bad.. one measured 2.5 ohms the other was 3.1, that is 4.5 ohms just from two of the batteries.. the rest were around .85 ohms.. I have also tested thousand of SLA batteries this way, and can tell you instantly if the battery will deliver the rated capacity.. from experience if a cell is more than .8 or .9 I don't use it.. Regards.. Fred I had to post this message two time to get it to the list.. I can honestly say this is the first time since using the internet that my post was rejected for have a digital signature, so will have to remember to turn it off.. The message's content type was not explicitly allowed On 5/6/16 6:06 AM, LA7NO wrote: > KX3 (ser. no. 08146) works OK on external power, but recently I am > experiencing problem using it on internal rechargeable cells. > > The AA cells are relatively new Varta Professional No. 5706, 2700 mAh NiMH. > They have been charged with a techno-line BC-1000. Measured capacity via an > automatic discharge/recharge cycle is according to spec. > > I have attached a 50 Ohm dummy-load to the KX3. When turned on, it indicates > BT 9,7V. BAT MIN is set to 8,2V. > When I press ATU TUNE, it turn itself off immediately. > With TUN PWR set to 0,1W it works OK when pressing TUNE, but BT drops to > 7,6V. > If TUN PWR is set to 1W, it switches off when TUNE is pressed. > > Strange that the voltage drops so much, even if the charger indicated normal > cell capacity when automatically discharging them. > > Any ideas? > > Per-Tore / LA7NO > > > > > -- > View this message in context: http://elecraft.365791.n2.nabble.com/KX3-internal-battery-problems-tp7617201.html > Sent from the Elecraft mailing list archive at Nabble.com. > ______________________________________________________________ > 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 > Message delivered to [hidden email] -- Fred Moore Ham: WD8KNI Cell 321-217-8699 email: [hidden email] ______________________________________________________________ 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 Message delivered to [hidden email] |
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In reply to this post by LA7NO
Also using LSD (Eneloop standard) cells and non-transmit voltage reads 10.4V even after several months of no use.
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Re: KX3 internal battery problems
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In reply to this post by LA7NO
Another thing to check is corrosion resistance at the battery
contacts. I find this problem frequently with flash LED head-mounted lights. When I have a problem like this, I like to measure the cell voltages under load. You may be able to run the KX3 into a dummy load at the 0,1W tune setting and measure each cell. If one cell shows significantly lower voltage, it is the problem. Running this test again several days after the battery was last charged will show cells which have high internal self-discharge. 73 Bill AE6JV On 5/6/16 at 3:06 AM, [hidden email] (LA7NO) wrote: >KX3 (ser. no. 08146) works OK on external power, but recently I am >experiencing problem using it on internal rechargeable cells. > >The AA cells are relatively new Varta Professional No. 5706, 2700 mAh NiMH. >They have been charged with a techno-line BC-1000. Measured capacity via an >automatic discharge/recharge cycle is according to spec. > >I have attached a 50 Ohm dummy-load to the KX3. When turned on, it indicates >BT 9,7V. BAT MIN is set to 8,2V. >When I press ATU TUNE, it turn itself off immediately. >With TUN PWR set to 0,1W it works OK when pressing TUNE, but BT drops to >7,6V. >If TUN PWR is set to 1W, it switches off when TUNE is pressed. > >Strange that the voltage drops so much, even if the charger indicated normal >cell capacity when automatically discharging them. ----------------------------------------------------------------------- Bill Frantz | Since the IBM Selectric, keyboards have gotten 408-356-8506 | steadily worse. Now we have touchscreen keyboards. www.pwpconsult.com | Can we make something even worse? ______________________________________________________________ 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 Message delivered to [hidden email] |
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In reply to this post by Fred Moore
Hi list,
and thanks for useful information. I usually do not deeply discharge the cells. This was only for checking the actual capacity at the cells before testing. I just measured the voltage of the 8 cells, once with the KX3 off, once with receiving with high volume. These are the results: Cell KX3 off KX3 on ------------------- 1 1,36 1,17 2 1,36 1,16 3 1,36 1,26 4 1,36 1,13 5 1,34 1,12 6 1,34 1,22 7 1,34 1,19 8 1,34 1,13 This does not look good. I have now ordered new Panasonic Eneloop PRO AA Mignon Akku LR06 2450mAh. Looking forward to testing those. Per-Tore / LA7NO
73,
Per-Tore / LA7NO |
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Per-Tore,
With increasing cycle count, individual cells are showing differences. If you don't charge them individually, these differences are getting bigger, as reflected by the numbers you posted. You mentioned that you verified cell capacity using your charger. At what discharge current? Most probably not at the 1.5A which the KX3 draws when transmitting. While powering my KX3 with 8 internal Eneloop cells and varying output power, I found a total internal resistance of 1.15 Ohms. A single Eneloop cell showed 34mOhm (I have an instrument measuring Ri by applying short discharge current pulses). In total, only 25% of the total Ri comes from the 8 cells. Battery holder and wiring are responsible for 75%. 73, Markus HB9BRJ |
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Hi Markus, thanks for interesting info.I am using a TechnoLine BC-1000 charger. It handles the 4 cells individually. Max. charging current is 1.500 mA, discharge current max 500 mA - all selectable,. Seems to work quite well. On 9 May 2016 at 11:07, hb9brj [via Elecraft] <[hidden email]> wrote: Per-Tore,
73,
Per-Tore / LA7NO |
Re: KX3 internal battery problems
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In reply to this post by LA7NO
Re: With increasing cycle count, individual cells are showing differences.
Cycle count agravates the differences, but the most common CAUSE is a failure to FULLY CHARGE the series set of cells, so some of the cells never reach their FULLY CHARGED voltage. Damage occurs during use as the cells are discharged. The cells that were not fully charged reach the damaging voltage of <1.0V per cell first, possibly before the KX3 low voltage warning is set. Below that voltage, they will be damaged and will never again have the capacity of the good cells. Re: If you don't charge them individually, these differences are getting bigger, as reflected by the numbers you posted. Individual cell charging is one way to prevent damage, but the KXBC3 can manage this problem as well, saving the cost and trouble of an external charger. When charged with a properly designed constant current charger such as the KXBC3, NiMH cells in a series configuration are self leveling. Cells with a higher charge will reach their fully charged CHARGING voltage of about 1.5v per cell (varies somewhat with temperature, charge rate, etc.) and then level off. The lower voltage cells will then continue to rise to a similar FULLY CHARGED voltage if they are healthy. Eventually they will all be at the CHARGING voltage. With the KXBC3's 200mA rate, 12 hours will usually do it for 2000mAH cells, and 16 hours for 2500mAH cells. I do not mean to knock external chargers or battery managers. I am simply saying that YOU, along with the KXBC3, can learn to manage rechargable NiMH cells. This hobby is about learning, isn't it? BTW, I just checked my 3.5 yr. old Eneloop 2000 LSD cells, and they are all within .04V resting. I never disharge the set below 8.8V. Mark, ars: KE6BB ______________________________________________________________ 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 Message delivered to [hidden email] |
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