+++++++++++++++++++++ See Also Battery Charging +++++++++++++++++++++++++++++++++++++++++++++ Date: Sun, 11 Mar 2001 19:17:17 -0500 From: "Bob Lewis \(AA4PB\)" Subject: Re: [Elecraft] Charging the internal battery of the K2 Yes, keeping the K2 connected to a 14.2 volt power supply at all times will keep the internal battery properly charged. You must have the rear pannel battery switch in the ON position. Turning this switch off will completely disconnect the battery and it will not receive any charge via the power input connection. The K2 has a reverse polarity protection diode (D10) which has a 0.4 volt drop. This causes the K2 circuitry and its charging circuit to operate at 13.8 volts. At 13.8 volts an SLA battery such as the one used in the K2 will self-regulate the charge. There is no danger of overcharging. With a regulated 14.2 volt power supply you can operate the K2 and the battery will still maintain a proper charge. This assumes that the power supply can handle the K2 current plus the charging current without the voltage dropping - your Astron VS-35M certainly qualifies. ++++++++++++++++++++++++++++++++++++++++++++++++++ Date: Sun, 11 Mar 2001 20:37:12 -0500 From: "Don Wilhelm" Subject: Re: [Elecraft] Charging the internal battery of the K2 Bob and folks, In general, a power supply voltage of 14.2 or 14.3 volts will keep the battery on float charge with no danger of overcharging. There is however some variation in the voltage drop of the reverse polarity protection diode, and the best applied voltage will be a wee bit different from one K2 to the next. If you want to adjust your power supply 'right on the money' - measure directly at the battery terminals (with the battery fully charged and at room temperature) then set your power supply to give 13.8 volts to the battery (this is the float voltage for SLA batteries at normal room temperature). Once you have done that, record the input voltage to the K2. That way in the future, you can adjust to the proper voltage without opening the K2. The K2 is speced for up to 15 volts input, so no danger to the K2 if you stay under that - adjust to the best input for battery health. With the switch on the OFF position, the battery is completely out of the circuit, so you can apply any voltage to the K2 under that condition - good when you are not sure of the supply voltage. 73, Don Wilhelm -Chapel Hill, NC W3FPR home page: http://www.w3fpr.webprovider.com QRP-L # 485 K2 SN 0020 mailto: w3fpr at arrl.net - ----- Original Message ----- From: "Bob Wilderman" > > Is there any danger of overcharging the battery, discharging the battery or > damaging the K2 using the above procedure? This is assuming that the battery > slide switch on the rear panel of the radio is turned to the "off position" > while the K2 is using the external P/S. ++++++++++++++++++++++++++++++++++++++++++++++++++++ Date: Sun, 11 Mar 2001 19:29:40 -0700 From: "James E. Fuller" Subject: Re: [Elecraft] Charging the internal battery of the K2 At 06:37 PM 3/11/01, Don Wilhelm wrote: >If you want to adjust your power supply 'right on the money' - measure >directly at the battery terminals (with the battery fully charged and at >room temperature) then set your power supply to give 13.8 volts to the >battery (this is the float voltage for SLA batteries at normal room >temperature). Once you have done that, record the input voltage to the K2. >That way in the future, you can adjust to the proper voltage without opening >the K2. I just tapped K2 "display" button so that it showed the voltage/current, and adjusted the supply so that the K2 display said "13.8". (Actually, it mostly says "13.7", but sometimes it says "13.8"). - -- Jim Fuller N5XH --------Continue Date: Sun, 11 Mar 2001 20:47:44 -0700 From: "James E. Fuller" Subject: [Elecraft] Re: Charging the internal battery of the K2 At 08:35 PM 3/11/01, Jay Rutherford wrote: >Hi Jim, > >I read your reply to this question from Bob. > >It sounds like you didn't know that the voltage display on the K2 >reads 0.3 or 0.4 volts low (due to the diode), so you're putting net >14.1 or 14.2 volts on your battery as a float charge, instead of the >13.8. You might want to check this out.... as I'm going to do this >minute here! > >73, Jay You are exactly right. I had not thought about that. So, now I put the meter across the battery and adjusted the supply for about 13.8 (13.78 with no load) and the K2 internal voltage display says "13.5" with receive current about 240 (Perf, Nite, Dot). With the receive current load, the meter reading across the battery drops to 13.65 or so. Thanks for the correction. I hope my battery isn't too mad at me for overstimulating it. - -- Jim Fuller N5XH ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Date: Mon, 12 Mar 2001 08:39:42 -0500 From: "Bob Lewis \(AA4PB\)" Subject: Re: [Elecraft] Charging the internal battery of the K2 Actually, I don't think the float charging voltage is that critical. The Power Sonic Technical Handbook specifies a float charging voltage range of 2.25 to 2.30 volts per cell at 77 deg F ambient temperature. For a six cell battery that is 13.5 to 13.8 volts. The Handbook also states "as a rule of thumb, temperatue compensation is desirable in the charging circuit when operating outside the range of 41 deg F to 95 deg F pevailing ambient". This is an indication that we need not be overly concerned about one or two tenths of a volt or the differences in voltage drop between one schottky diode and another (which also probably varies with temperature) for the temperatures we will normally be operating at. To get an overall point of reference, the chart in the Handbook shows a total range of 13.5 volts at 122 deg F and 14.04 volts at 4 deg F. +++++++++++++++++++++++++++++++++++++++++++++++++++++ Date: Mon, 12 Mar 2001 07:35:38 -0700 From: "James E. Fuller" Subject: Re: [Elecraft] Re: Charging the internal battery of the K2 At 06:50 AM 3/12/01, Bob Lewis \(AA4PB\) wrote: >No, you don't want to measure the voltage across the battery. There is >a series resistor in the charging circuit so the battery voltage may >not be correct depending on its state of charge. Actually, that is exactly where I want to measure the charging voltage, with the battery charged, the K2 turned Off, and the supply delivering its voltage into no load other than the trickle to keep the battery topped off. Having the battery charged is important. I went through three stages on this: 1. Set the supply at about 14.2 volts. This worked fine, and would have been just fine for the long term, as it turned out. 2. After using it for a couple of days and checking the voltage display on the K2 regularly, and having had it connected long enough to be moderately certain that the battery was really fully charged, I set the supply voltage to provide 13.8 volts on the K2 display, thinking that that measurement was at the ideal place in the circuit. That actually gave me about 14.02 volts at the battery terminals, which, as others have pointed out, probably is non-fatal, but it is over the battery's rated voltage. 3. I put the meter across the fully charged battery with the K2 turned Off and adjusted the supply to 13.8 (13.78-13.79) which is as close as I can get to the spec with the number of digits my little meter has. I think that this is the ideal way to adjust the charging supply, although it needs to be done with the battery fully charged and no load (K2 Off). >Being that precise is probably not necessary for the temperatures most >of us operate in - see my previous post. Aha. I didn't realize that you were the "someone" who said that. Exactly. 9.718281828 digits of precision isn't really necessary here. But I am glad that for the correction that led me to readjust the voltage at the battery terminals to spec. - -- Jim Fuller N5XH ++++++++++++++++++++++++++++++++++++++++++++++++ Date: Mon, 12 Mar 2001 20:26:32 -0500 From: "Francis Belliveau" Subject: Re: [Elecraft] Re: Charging the internal battery of the K2 After reading all the discussion over this I must clarify something that James and Bob are both aiming at from different directions without explicitly saying it. You do not want to allow the battery voltage to be driven above 13.8 volts for a long time. James is looking to ensure this by measuring the voltage directly across the battery. To be successful he must set his supply, allow time for the battery to reach equilibrium at that amount of drive voltage and measure again. Bob is assuming that the amount of current drawn by a fully charged battery will be so small that the voltage drop across the series resistor will be negligible. Remember that 0.1 volts will not be a big deal unless you get into temperature monitoring and all sorts of complicated stuff in order to extend your battery life by what, 5%? If you believe James then I would suggest that you check and readjust every 12 to 24 hours until you get a stable reading for 24 hours. That will ensure that you are taking the reading at full charge equilibrium. Otherwise you can follow Bob's advice and be sure that you will not overcharge. You pick for yourself. The only problem with the advice that James gives is that you must be sure that you have a fully charged battery when you make the adjustment. I'm not an electrical engineer, just another amateur that has studied recharging technology (SLA and NiCd) for a number of years before making my choices. I cannot give you web sites because my studies ended before the web became so easily accessed. The best references can be gotten from the battery manufacturers but they can get a bit technical. Good Luck to all, Fran K2 s/n 314 Without internal battery option. I use an external one. ++++++++++++++++++++++++++++++++++++++++++++++++++ 12 Mar 2001 19:01:39 -0700 From: "James E. Fuller" Subject: Re: [Elecraft] Re: Charging the internal battery of the K2 At 06:26 PM 3/12/01, Francis Belliveau wrote: >James is looking to ensure this by measuring the voltage directly across the >battery. To be successful he must set his supply, allow time for the >battery to reach equilibrium at that amount of drive voltage and measure >again. Well, that's what I did, but not by design. It just turned out that way. I knew that the battery was fully charged, having been using it on and off for several days. >Bob is assuming that the amount of current drawn by a fully charged battery >will be so small that the voltage drop across the series resistor will be >negligible. His method is better and safer for insuring that the battery does not get driven above 13.8. The voltage ahead of the drop across the resistor will always be higher than the voltage that appears across the battery itself. >Remember that 0.1 volts will not be a big deal unless you get into >temperature monitoring and all sorts of complicated stuff in order to extend >your battery life by what, 5%? That's what we all tend to forget sometimes in trying to analyze and set things to the nearest microwhatever. Sometimes it doesn't really matter that much. >If you believe James then I would suggest that you check and readjust every >12 to 24 hours until you get a stable reading for 24 hours. That will >ensure that you are taking the reading at full charge equilibrium. Actually, I just measured the current flowing into the battery. A meter was already hooked up to see if the internal current display was reasonably accurate (it was, and it always read a little high). After a few hours (about 6 hours) charging, the battery was drawing a little under 3 milliamps (2.72 on the meter), so I judged that it was more or less fully charged. That amounts to about 17 millivolts difference between before the resistor and after it. >Otherwise you can follow Bob's advice and be sure that you will not >overcharge. You pick for yourself. The only problem with the advice that >James gives is that you must be sure that you have a fully charged battery >when you make the adjustment. True, and important. But actually, I wasn't trying to give advice. I was describing what I did, and that it worked. >Good Luck to all, >Fran >K2 s/n 314 >Without internal battery option. I use an external one. One of the things that I really like about the K2, one of the things that made it my choice for the first ham gear that I have owned since 1975, was the idea of having everything needed, except for an antenna and input device(s), in the same box. No separate antenna tuner needed, no external speaker required, no external battery pack necessary,-- it all is in the box. It makes packing easy. And it all works, well. Love it. - -- Jim Fuller N5XH ++++++++++++++++++++++++++++++++++++++++++++++++++ Date: Wed, 13 Sep 2000 20:45:34 -0400 From: "Francis Belliveau" Subject: [Elecraft] Battery Testing I saw the posting by Dean and decided to send this to the group. I have a copy of the Gates Application Manual for Sealed Rechargeable Batteries. This was published in 1989 by Gates Energy products and was the standard reference text for a long time. This covers both Ni-Cad and Lead Acid technologies. The appendix contains a flow chart to use to determine if a battery is useful or not. I am willing to send a scanned copy of this in TIF format to anybody who requests one. I have found it very useful over the years. The bottom line says that if the Open Circuit Voltage is <1.81 Volts/Cell (10.86 for 12 volt battery), throw it away. There are further charging, resting and discharging tests that are also shown for the purposes of determining battery usability. I have recharged batteries that start out below the above threshold but find that they do not hold a charge very well and seldom take more that 2 rechargings before failing altogether. 73, Fran - --- Submissions: elecraft at qth.net Please note: The list server automatically rejects HTML encoded emails. List Archive page: http://www.qth.net/archive/elecraft/elecraft.html Elecraft Web Page: http://www.elecraft.com ------------------------------ Date: Wed, 13 Sep 2000 21:12:02 -0400 (EDT) From: "baltimoremd at baltimoremd.com" Subject: Re: [Elecraft] Battery Testing On Wed, 13 Sep 2000, Francis Belliveau wrote: > battery is useful or not. I am willing to send a scanned copy of this in > TIF format to anybody who requests one. Love to have one, and I'll put it on the web page http://www.min.net/~thom/qrp/ 73 thom +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ From: Charles R Greene Subject: Re: [Elecraft] Battery Testing On Wed, 13 Sep 2000 20:45:34 -0400 "Francis Belliveau" writes: Francis, Yes, I would like a copy. As the experience with the K2 battery increases, it is apparent that there are a number of instances where the battery is showing reduced capacity. The only common thread is that the battery is being charged in the float mode at a voltage around 14 volts. I really don't believe those batteries are near failure, but they need a restoration, and right now, I'm not sure what the best way to do it is. 73, Chas, W1CG > I saw the posting by Dean and decided to send this to the group. I > have a > copy of the Gates Application Manual for Sealed Rechargeable > Batteries. > This was published in 1989 by Gates Energy products and was the > standard > reference text for a long time. This covers both Ni-Cad and Lead > Acid > technologies. The appendix contains a flow chart to use to > determine if a > battery is useful or not. I am willing to send a scanned copy of > this in > TIF format to anybody who requests one. I have found it very useful > over > the years. The bottom line says that if the Open Circuit Voltage is > <1.81 > Volts/Cell (10.86 for 12 volt battery), throw it away. There are > further > charging, resting and discharging tests that are also shown for the > purposes > of determining battery usability. I have recharged batteries that > start out > below the above threshold but find that they do not hold a charge > very well > and seldom take more that 2 rechargings before failing altogether. > > 73, > Fran +++++++++++++++++++++++++++++++++++++++++++++++++