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Semi OT: NiCad Battery life

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  • Semi OT: NiCad Battery life

    I have a Dewalt 12v modewl DW 980 cordless drill driver. It is 5-1/2 years old and had moderate use. It seems like I have to swap out and charge the batteries just about every time I use it.
    Also my son has a second newer one of the same model.
    1) how long do these battery packs typicaly last?
    2) I am considering getting one of the better chargers that condition the bateries. Are these worth the money? Do they realy extend battery life has anyone here owned and used one?
    3) I know some guys on the board have rebuit packs. Is this worth the trouble?
    4) Ideas/Suggestions?
    Last edited by Tin Falcon; 03-31-2007, 02:01 PM.
    Ad maiorem dei gloriam - Ad vitam paramus

  • #2
    I would go with a rebuilt pack. I used to deal with hundreds of hand held radio nicads. We had the conditioners that would discharge and recharge and display the amp hour capacity. Sometimes that would work, sometimes not. I saw some batteries last for several years and some that didn't last a year.


    • #3
      Standard rating for most nicad types under ideal conditions is around 500 discharge/charge cycles. The better ones might make 1000. Power tools are hard on batteries because of the heat buildup caused by high current draw. Also, many of the cheap battery chargers have no temp sensing and will keep charging the batteries until they overheat and vent, which is the kiss of death.
      Last edited by Evan; 03-31-2007, 02:48 PM.
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      • #4
        Power tool batteries are the one thing in which you get what you pay for, in that the dearer units have inbuilt temperature monitors to turn the charge off before it damages the battery.
        As Evan says most should be good for about 500 charge/discharge cycles but this number will tend to include all those just incase charges given usually because you have forgotten if it was charged.
        The other annoying fact is that as the capacity of the cells increases so does their self discharge characteristics(ie will discahrge by itself if left unused)
        If you can get rebuilt packs for a reasonable amount go for it.
        When I have bought drills I try and get one that has 3 battery packs with it as the packs will last longer if they are allowed to cool after a charge which will not happen if you only have 1 or 2 packs.
        I have tools I don't know how to use!!


        • #5
          Tool batteries

          I am having a set of batteries rebuilt, that are for my 3/8 drive cordless impact. These batteries new are from $70, to $80, depending on where you purchase. I am getting the rebuilt ones for $40 each and the warranty is the same. The dealer told me that they put all new cells in the pack. So am going this route, this time.

          I have Makita, Ryobi, and Black and Decker cordless units. I was getting new 9.6 volt Makita batteries for around $25, the other day I noticed that at now at around $33. This is for an older drill that I have had for some years.

          I did purchase two batteries from Home Depot for the Ryobi for about $25 each. I will be checking on the rebuilt ones for this application the next time I need batteries. This is the 14.4 volt model.

          I do like the convenience that cordless allows, but it is pricey since the batteries don't last very long.


          • #6

            FWIW,i'have also found that some batteries show a rather optimistic amperage .
            This is particularly so with chinese batteries.I bought some "2500 mah" batteries ,and found the real amps to be more like 1600.
            Most of the cheaper brands like Ryobi do seem to use these cells.
            The old story,I guess.You get what you pay for.
            As a stopgap measure i used to replace just the dead cell in a pack,but this is just a temporary fix.You might get another year out of a pack this way if you're lucky.More often,a month later,another cell will die,and you're back where you started.


            • #7
              Its not only the batteries that are a bit on the cheap side, its also the motors in the cheaper drills. I was once side tracked by a Nutool 18volt drill which I assumed would have more power than my 9.6v Hitachi, boy oh boy was I in for a shock -absolutely no power even with twice the voltage. I still have it but havent used it for years. Have invested in middle of the range drills Bosch or Hitachi for preference.
              I think the motor efficiency is a little better in the more expensive drills which will give more power at the drill and longer battery life.
              I have tools I don't know how to use!!


              • #8
                I got almost 10 years life with moderate use overall. I think I shortened their life by usage.....

                One thing that kills them dead in short order is running them until, the drill won't turn. That reverse-charges some cells, and they croak early.

                As soon as you see a lack of power, swap and charge.

                I didn't do that all the time..... you know, one more screw, and a ladder or three flights of stairs to swap.....

                Keep eye on ball.
                Hashim Khan


                • #9
                  I have a Bosch and have good had good luck by using two batteries. I never ever charge the one on the drill until I can tell the drill is starting to run slow. Then I change batteries and get the dead one on charge right away as it isn't a good idea to store them in depleted condition. The cells internal resistance will only cause them to loose more energy until the finally are flat and one cell reverses polarity.

                  I wouldn't have a problem rebuilding my battery packs when they finally croak. You can buy the c-cells with the spot welded tabs on them and extremely simple to solder them up.
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                  • #10
                    Actually, the story is that NiCd don't care about being stored flat or charged.

                    I'm not sure I agree, but it may be true.

                    They won't reverse in storage, only if there is discharge current thru the entire pack.

                    Keep eye on ball.
                    Hashim Khan


                    • #11
                      It's true that storing flat won't hurt them. They had that problem on Skylab years ago. The batteries (nicads) had been flat for years and they managed to recover them.

                      The biggest problem with nicads is venting from overheating. If the battery is warm from use it should be allowed to cool before charging. The main reason cells go bad other than venting is the growth of internal whiskers of metal that short out the cell. These can sometimes be removed by charging a big capacitor to 12 volts or so and applying to the individual cell in the charging direction.
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                      • #12
                        For what my own limited experience is worth..

                        I needed to replace the 14.4 volt NiCd packs for a couple of Milwaukee tools recently.

                        My Milwaukee charger is an auto-charger able to (acc'd’g to the template) accommodate NiCd and NiMH batteries. What makes a charger automatic is, as was mentioned, a temp sensor built into the battery pack that will regulate the charge. One thing that might be considered when replacing/rebuilding is the milliamp/hour (mAh) rating of the cell/pack. This is a figure that you can often improve upon if you rebuild the packs instead of buying them new. Generally, it seems, the OEM replacement will be of the same amp/hr rating as your original. But cell technology has improved dramatically in just a few years. Your charger can charge a higher number, but may take a little longer to do it.

                        My 14.4 milwaukee was originally a 2400 mAh NiCd pack. As I said, the charger would accommodate NiMH so after quite a bit of research, I decided that NiMH had enough advantages over NiCd for me to go that route. I went to my local Batteries Plus and had one of the packs professionally rebuilt. They stocked Chinese pedigreed non-branded "sub-c" cells with which to rebuild their packs. This is already kind of taking a chance on quality, but I decided to go ahead for comparison's sake. They were labeled 3300 mAh NiMH sub-c cells. They did the rebuild for about sixty dollars. This represented only a ten to twenty dollar savings on the OEM unit, but was an improvement in performance. I got the pack back within two days.

                        As I researched more, I found many conflicting opinions, pros/cons. Someone observed that the higher the mAh rating, the more likely that internal shorts will occur with use. These 'internal shorts' are what is responsible for the eventual degradation of the cells - and probably a good reason to avoid stalling your tool at full charge whenever possible. As I said, after weighing a few dozen pros/cons I decided that the NiMH has sufficient advantage over NiCd that it's worth extra cost. I'd encourage anyone to check out the facts/opinions for themselves and make a choice.

                        You will also find a great deal of comment on various ways to rehabilitate your worn out packs through various "zapping" contraptions and the like. There may be a very marginal benefit to this, but most of what is happening is the following. Your charger, (in fact most chargers - even your automatic car battery charger) needs to "sense" a very small charge when connected to a battery in order to start doing its job. A good battery pack, even if worn down completely, will maintain enough charge to wake your charger up. When your pack is shot, it no longer has even this nominal little charge and the charger will fail to even begin charging when you slide the pack onto it. When someone "zaps" his cell with whatever means he's found posted on the internet, and then slides the cell into the charger, PRESTO, the charger sees the little juice he's put in it and starts charging away. The pack hasn't really seen much repair. The charger will do its best to recharge the bad cells, and they will run the tool a bit, but they'll still be basically worthless.

                        So, using my Batteries Plus pack as a benchmark, I went online to see how well I could do the job on another one myself. First I had to disassemble the pack. My Milwaukee comes apart very easily with six screws. I've heard that some other brands require more manhandling and breaking of plastic welds and such, so this is just another part of deciding if it's worth the effort for your tool. Most of these packs use a "sub-c" sized cell. Sub-c means that the cell is slightly physically smaller than a standard c-cell you'd buy at the grocery store. They are always 1.5 volts, so my 14.4 volt pack was comprised of 12 of them.

                        Basically you won't, yet, find NiMH cells rated in excess of 3000 mAh on the market. This may be due to that possibility of them being less robust (that internal shorts thing) at this point along the technological curve. I'll just have to keep my eye on the Chinese ones from Batteries Plus but, hell, 3300 mAh was probably a typically exaggerated number for a non-branded item anyway. They are probably just 3000 real mAh cells (hopefully).

                        As soon as I realized that 3000mAh was the best I could do by buying my own cells I was beginning to think that I wouldn't do much better pricewise/shipping/labor etc than could be had at Batteries Plus, until I started to come across some sales items. One good source was at Click on Special Offers. They sell Panasonic (reputed to be the very best) sub-c with tabs (needed for diy'ers to connect them with) 3000mAh NiMH for 3.00 dollars/ea. This is a very good deal for such a high quality branded cell. That puts my cost per pack at 36.00 +ship for a real leap in performance over the 2400mAh NiCd that came with the tool.

                        I ordered the cells and they arrived promptly. Using the old pack as a guide, I soldered the tabs together, slipped the thermistor temperature sensor back in between the cell bodies exactly as it had been in the old pack, and reassembled it all. Half an hour total. Does the thermistor perform the EXACT same function with the NiMH as it had with the NiCd? Of course not. Milwaukee would have put one of a very slightly different value in it's place to match the new type of cell behavior precisely. Does it really matter? So far, so good - the charger seems to function automatically quite well. I'm extremely happy with my results so far. These new cells are much much better performers in power and longevity (time between charges) than my originals had ever been while new. And I haven't yet noticed a difference between the Panasonic and the Chinese cells (although I wouldn't bet much on the Chinese cells being equal in longevity - we'll have to wait and see).

                        So there's my little story. Hope it helps/encourages someone. Next big thing is going to be lithium ion cells anyway. But by that time we’ll all be ready for new tools. I don't know. This Milwaukee just seems to keep soldiering on. And I realize I'm brand new to the board and this is an awfully long post, so to allay any suspicions I'll tell you sincerely that I haven't anything to do professionally with nicadlady or milwaukee tools! I was just so frustrated with the lack of info out there about diy'ing hand tool cells when I went looking for it that I felt like I ought to share.
                        Last edited by mtcw; 04-04-2007, 11:10 AM.


                        • #13
                          When someone "zaps" his cell with whatever means he's found posted on the internet, and then slides the cell into the charger, PRESTO, the charger sees the little juice he's put in it and starts charging away.
                          Not entirely correct. "Dumb" chargers don't care what the condition of the batteries are and are the type commonly sold with cheap battery tools. I have "repaired" many nicads with the 'zapping' technique and when it is successful you can often hear a faint 'pop' from within the cell. It won't last as long as a new cell because it only removes the end of the 'whisker' that was shorting the cell and there are likely others near to making contact. It will fix perhaps 30% of shorted cells well enough to last another season. It must be done to individual cells, not the entire pack.
                          Free software for calculating bolt circles and similar: Click Here


                          • #14
                            Hey, Thanks for taking the time to type that MTCW. I, for one at least, appreciate your summary of the process.

                            I may look into trying to resurrect my two long-dead Porter Cable batteries.
                            Since they died I've just been using a 19.95 Harbor Freight item. My use is so sporadic I don't view it as real cost effective to invest much in battery powered tools.
                            Lynn (Huntsville, AL)


                            • #15
                              Just to add a tidbit or two to the story, some chargers are responsible for the packs going bad early. Some will discharge the battery if it's left in the charger, and power is turned off. That happened to my friend, and since then both his batteries have died, and so the drill went to the graveyard. Not naming names, but it was a brand name, and two years old.

                              A couple of chargers I've had occasion to check out couldn't read the sensor in the pack, due to poor connections. One of my bosch packs is like this, and it doesn't get charged properly. I can hook it up to my power supply and charge it fully, but then I'm not using the sensor in it. I have to monitor the pack for temperature rise myself. Another charger had a poor connection to the terminals (no doubt caused by constant flexing as the packs are inserted and removed).

                              Sometimes I think it's a toss up- go with a basic charger and while it may need 8 hrs to charge, there's less to go wrong with it. Or go with a 'smart' charger, get a reasonably short charge time, and hope it keeps working properly.

                              Because I'm an electronics sort, I can keep track of how well my various chargers and packs are working. The bosch batteries are about 10 yrs old now, and still give good life, though not quite like new. I do have to see about repairing the one pack. They also seem to hold a charge while not in use for a good length of time.The makitas I've used are good this way. I have 2 cheap drills that continue to amaze me with their performance (5 or 6 yrs old now), and a few sears and panasonic models which were given to me because they died for some reason. They all have different characteristics in use- the sears I find excellent for driving small screws because the clutch mechanism works really well. The panasonic is the most powerful, closely rivalling the bosch, though the bosch breaks its gear teeth with the slightest shock load. It's really a piece of dogship in that regard. The two cheapos stand upright easily with little tendency to fall over even with a weighty drill bit in the chuck. These are the first ones I reach for almost every time I need a drill.

                              The panasonic seems to have the potential to handle even more power than it currently does because the gear train is ruggedly built. This is the one I would convert to neodymium magnets should I become inclined to do as a project one day.

                              Last point, on the subject of motors- some use the basic three slot armatures and are probably the least efficient and powerful for their size. Some have five or seven slot armatures, which are better all around motors, more efficient and powerful. I don't know how one would determine this when checking out new drills to buy, (unless it's actually stated in the literature) but it does make a sizable difference in how well and how long the drill performs on a charge. If you can get to see the exploded diagram you should be able to tell this, even if it's not stated anywhere.
                              I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-