Announcement

Collapse
No announcement yet.

dead nicad battery rejuvenation?

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • dead nicad battery rejuvenation?

    I have a lot of bad rechargeable battery packs and there is a guy on eBay that claims that he has a way to bring them back to life without replacing cells. Has anyone tried this? Did it work? How is it done? thanks--Mike.

  • #2
    Check these out. I haven't tried any of these myself

    http://www.youtube.com/watch?v=1e8hHLyXAyQ

    http://www.youtube.com/watch?v=PzIlVLOH9XI

    there is a lot of stuff out there if you do a search on "rejuvenating nicad batteries" or similar

    bollie7

    Comment


    • #3
      Mikem,

      There are 3 basic failures in NiCd battery packs. The first is shorted cells. If this is the problem you can sometimes clear the short with a high current pulse. This can be risky as the battery can explode and hurt you. The second failure is simply the battery chemistry is kaput, done, dead ..... A typical NiCd battery is rated for between 400 and 700 charge/discharge cycles before the chemistry is finished. In this case there is really nothing that can be done to "fix" the problem. The third failure is "memory effect". This is where the battery looses capacity due to short discharge cycles. If a NiCd battery is discharged say 25% then recharged and this pattern continues, very soon the battery will only last for that 25% time. If this is the problem the battery can often be rejuvenated quite easily. Without special equipment the procedure is to fully discharge the battery to between .8 and 1 volt per cell (each NiCd cell is 1.25 volts fully charged so do the math to figure out how many cells are in your battery). Next full charge the battery, slow charge is best but the rapid charge is OK. Now repeat the discharge / charge cycle 3 to 5 times. Your battery will now be in better shape than when you started. A NiCd with memory has been damaged and will never be as good as would be with proper care, but you can get a lot more use out of one this way.

      Just a note about measuring battery voltage... After charging a NiCd battery you can measure the voltage and determine if there are any shorted cells. Put a small load on the battery (I often use an automotive test light for the load) and measure the DC voltage. If there are any shorted cells the battery will almost always read low by a multiple of 1.25 volts. You MUST use a load on the battery or the reading will be misleading as a fully charged battery will read high without a load. I have seen 7.5 volt batteries read 9.5+ when fresh out of the charger without a load. Put a load on them and they will drop right down to 7.5-7.7 like expected.

      The above info is only applicable to NiCd batteries as other chemistries have different characteristics.
      Robin

      Happily working on my second million Gave up on the first

      Comment


      • #4
        Mike. I did most everything to rejuvenate the batteries to my two Dewalt 12 volt drills. Including rebuilding the batteries. A new battery is $50.00. A new 18 volt Riobie(?) drill driver with two batteries and a saw is $89.00 an Home depot. In this instance I think I'm going to throw money at the problem.

        Comment


        • #5
          I think there is a thread here on rejuvenating batteries using a welder. the battery is hooked with reverse polarity and give a short jolt of power.

          I have looked and can't seem to find it, maybe someone else remembers the thread.

          Comment


          • #6
            I did the welder thing with my Dad's 14,4V Bosch Pro drill battery.
            I used a inverter welder kicking out 58V and set to the lowest current to charge the battery by just touching it with the welder in the correct polarity.
            I gave it 5 short pulses and popped the Battery in the charger and she works.
            Before it just gave a error on the charger and refused to charge.
            What can I say My Dad is one of those guys that leaves the Batt in the charger till he remembers to take it out .... Could be in a hour could be next week.

            Kobus
            If you are using violence and it does not work, You are not using enough or it is upside down.
            You can always just EDM it...

            Comment


            • #7
              Mike..
              Have a look at this site.
              http://www.hangtimes.com/redsbatteryclinic.html

              Top notch nicad stuff....

              bert

              Comment


              • #8
                Nicads do not have 'memory' effect that you would ever see outside a satalite that has EXACTLY precise charge/discharge cycles. Nicad chemistry has changed since the story of memory first started, and its now reduced to such a level you'd never experiance it.

                Secondly, I would never use a welder on a nicad.. I have however, successfuly used about 10,000uf capacitors charged to 20v or so, shorted into a single cell, about 10~50 times, with a DMM across the capacitors, with a current limited power supply (about 100mA is all you need really) charging the capacitors

                With thick, short wires, you connect one end of the cap to the cell, and tap the other on its terminal repeatly, then hold it there for a few seconds and watch the DMM, if the DMM rises above 1V, the cell is unshorted. If not, repeat untill unshorted, Generaly once it rised above 1V I would let it charge via the current limited charger for about 20 seconds, and it would hold its charge for long enough for me to do the other cells and get the pack into the charger.

                If your battery pack isent outputing its rated voltage after a very quick charge, its most likey a cell is shorted.

                Capacitors+current limit will signifigantly limit the average energy, while allowing the high peak energy needed to unshort the cells.

                A welder could EASILY put enough average energy into a cell to boil it internaly and cause it to explode in seconds.

                On a subnote, I have PERSONALY had a nicad battery pack last 20 years, and then it only died because of lack of use and me getting tired of unshorting the cells every couple months.

                Nicads LOVE to be used, I highly doubt they have any 'cycle' limit, And I will guarentee you a properly discharged and charged nicad used every day, will outlast one used occasionaly.

                What is properly discharged for a nicad? FULL discharge, Nicads HATE to be recharged before fully discharged, because discharging them actualy removes crystals that form on the plates, without a full discharge, the crystals grow bigger and bigger every discharge cycle.

                Its basicly recommend that nicads get fully discharged at least once a month, Reguardless of use. Studys have shown nicads 'abused' by allowing them to fully discharge (Devices left on overnight by accident, etc), lasted way longer then those that where babied (Recharged before full discharge, never allowed to fully discharge)

                This means use your nicads till they can't even spin the drill anymore! Never charge them up before that... Infact....

                its known that a very slow (1/10c or less, basicly only about 100mA or less) discharge to 0.4v per cell, actualy improves capacity on tired nicads!! (Best to be done on a per cell basis, so you don't apply any reverse current on any cells that discharge fully first, but then thats also why you use a TINY current)

                Also, Any '10hour'+ nicad charger likey trickles them with absolutely no intelligence. NEVER leave your nicads in such a charger, as they will destory them with overcharging. Infact most intelligence chargers have a limited 'float' mode that will also destory nicads over time.

                For the TLDR version:

                1: Never charge Nicads before fully discharged. As in won't even turn the drill over with no load on it discharged.
                2: Never leave Nicad in charger.
                3: Fully discharge your nicads once a month. Don't use your cordless tools enough for that? Buy li-ion instead. They may only last 3~ years, but thats longer then you'll get outta lightly used nicads!
                Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

                Comment


                • #9
                  Originally posted by Westline
                  What can I say My Dad is one of those guys that leaves the Batt in the charger till he remembers to take it out .... Could be in a hour could be next week.

                  Kobus
                  Nicads are a royal PTA no matter how they're handled, unless they're used regularly. They don't like sitting idle much better than they like sitting in a charger for prolonged periods. Contractors that use them every day and charge them every night will see much longer longevity than an occasional user. The Engineering dept where I work get about 5 years lifespan on the HT Nicads they carry.

                  That said, I've kicked some of them back to a lesser life with capacitive discharge.

                  Comment


                  • #10
                    Black_moons,
                    I will not question your having a NiCd last 20 years as I have had them last 10+ years. I will very much dispute your comment about memory effect on NiCd batteries and also the cycle-life of a NiCd. I have sold and disposed of literally thousands of NiCd batteries used on older two-way radios and flashlights. I can almost set a reorder schedule for the radios used by my police customers as the officers all work 5 shifts a week and charge the radios after every shift... 5 cycles per week X 52 week a year = 260 cycles per year X 2 years = 520 cycles = New Battery time.
                    Also the chemistry in a NiCd battery is the same now as it was 30 years ago. Please do your homework before misleading others.

                    Now NiMh is more like what you describe except it to has a finite cycle life.....
                    Robin

                    Happily working on my second million Gave up on the first

                    Comment


                    • #11
                      Originally posted by rdfeil
                      Black_moons,
                      I can almost set a reorder schedule for the radios used by my police customers as the officers all work 5 shifts a week and charge the radios after every shift... 5 cycles per week X 52 week a year = 260 cycles per year X 2 years = 520 cycles = New Battery time.
                      Also the chemistry in a NiCd battery is the same now as it was 30 years ago. Please do your homework before misleading others.

                      Now NiMh is more like what you describe except it to has a finite cycle life.....
                      Thats what they are doing wrong. They could easily get 5 to 10 years if they run the radios dry before recharging instead of after every shift, Or at the very least, once a month.

                      http://en.wikipedia.org/wiki/Memory_..._memory_effect
                      Please do your own homework before insulting me by saying I am misleading others when you are guilty of it yourself.

                      "True memory effect is specific to sintered-plate nickel-cadmium cells, and is exceedingly difficult to reproduce, especially in lower ampere-hour cells. In one particular test program—especially designed to induce memory—no effect was found after more than 700 precisely-controlled charge/discharge cycles. In the program, spirally-wound one-ampere-hour cells were used. In a follow-up program, 20-ampere-hour aerospace-type cells were used on a similar test regime. Memory effects showed up after a few hundred cycles"

                      You won't see memory effect in any 'consumer' device using consumer cells, And even if you where using the sintered plate aerospace cells, I doubt you could ever come close to the precise charge/discharge cycles needed to make memory effect show up.
                      You will see damage from not fully discharging nicads, Its the full discharge that actualy corrects the crystal growth.
                      Its lack of full discharge that will quickly ruin a nicad.. In about ohhh, 2 years reguardless of use, that is now refered to incorrectly as 'memory effect'
                      I bet if they simpley let the radio run dead at the end of shift THEN recharged it, they would easily double thier battery life, even though they would be wasting (partial) cycles.

                      PS: At first, I thought li-po where a ripoff for consumer power tools due to the 3~ year battery life. Then I realised with the way most people treat there nicads, they don't even get that long out of them.
                      Last edited by Black_Moons; 12-08-2011, 08:17 AM.
                      Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

                      Comment


                      • #12
                        Originally posted by rdfeil
                        Black_moons,
                        I will not question your having a NiCd last 20 years.....
                        Also the chemistry in a NiCd battery is the same now as it was 30 years ago. Please do your homework before misleading others.
                        Now NiMh is more like what you describe except it to has a finite cycle life.....
                        This is an excellent discussion because many of us have experienced the frustration of a cordless power tool fail prematurely.... at the worst possible time. My dewalt cordless drill motor failed me after Wilma blew a branch through my bedroom window. It was like someone was standing outside the window with a fire hose! Our weather people told us that Wilma was going to be a none event, so no preparations were made...Uh! While the wife held a flashlight on the window I resorted to using my old Yankee pump drill to board up the window from the inside. This tool's batteries never run out!

                        Anyway, your information and data are appreciated but that remark and tone are not. There are limitless ways of debating without throwing insults around.
                        Last edited by Chris S.; 12-08-2011, 11:18 AM.

                        Comment


                        • #13
                          Can we shift gears here to what would be the ideal battery charger for a typical high current power (NiCad) tool? After the experience that I described with Wilma I've thought that I should really find some time to design and ideal charger. I'm thinking about using a Picaxe to emulate a near daily discharge and charge cycle but I would like to do this while milking as many cycles out of a pack that I can.

                          The electronics and programming is not an issue for me but I would like opinions, other than my own, as to what level of discharge, charge rates, cool down periods and cycle initiations would milk the most life out of them.

                          All opinions are welcome, even if I think it's all wet!

                          Comment


                          • #14
                            At several TV stations where I worked we constructed a combination "discharge then charge" device for NiCads. It would first fully discharge the battery packs and only when they had reached a preset, low Voltage would the charger be connected. This greatly improved the life of the 24 Volt battery packs (belts) that the news departments relied on. Such devices have been available commercially, but they often are only for certain styles of battery packs.

                            At at least two of those stations we had a work station where the battery packs were regularly rebuilt. We purchased new cells and replaced the bad ones. You can buy replacement cells from electronic supply houses, but in the present day, the most economical source for such replacement cells may be the bargain, import tools being sold. You can often get two battery packs with a new tool for less money than one replacement pack would cost. You would need to work out a way to open the bad packs in a manner that would allow them to be reassembled after replacing the cells. You would also need some skill at soldering.
                            Paul A.

                            Make it fit.
                            You can't win and there is a penalty for trying!

                            Comment


                            • #15
                              Originally posted by Paul Alciatore
                              You would also need some skill at soldering.
                              Paul, thanks for your input but it doesn't answer any specifics such as the best discharge rate. Do I program it to periodically suck an amp or two out of them or a constant 100mA drain?

                              Electronics soldering is not an issue for me. I still consider my solder joints an art form, even with these old eyes. Prior to PC boards I was teaching Mil Spec wiring and soldering. I'm absolutely anal about it.

                              Comment

                              Working...
                              X