replacing batteries in Norelco shaver
in [Repair]
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From: Darmok on 28 Aug 2005 13:30 On Sat, 27 Aug 2005 08:13:30 +0900, H. Dziardziel <hdzi(a)zworg.nospamcom> wrote: >On Thu, 25 Aug 2005 18:55:43 -0400, Darmok ><cooncat.spam(a)gmail.com> wrote: > >> > >Charging in only 20 minutes is a 3C charge rate ie, three times >the cell mAh capacity. Shaver NiCads would be in the 500m-1000Ah >range. NiMh 2000-2600mAh AAs can handle that 1500-2000mA charge >rate but must not go over full charge or will be destroyed. > >The question is: is that a timed 20 minutes or a "smart" 20 >minutes? If timed and one starts with fully discharged cells >then all is well. NiMh have no memory effect so can be charged >and dicharged from-to any level But, if a smart charger is used, >it may not properly detect the NiMh charge state and keep charging >past fully charged. > > For say, 1500mAh cells, that would take about one hour however so >manul timing would suffice. Monitoring the cell temperature is a >good idea. Some heating while charging is normal for NiMh but >after full charge is reached it quickly ruins the cells. > Well, I did as someone suggested, and "Googled" for "Norelco battery replacements". I found a place that carries replacements for almost all versions of the Norelco shavers. When I looked up my model number (4845XL) it showed them as a pair of AA NiMH batteries! When I looked at the actual cells in the shaver, they were a pair of 600mah Ni-Cds. So, since I have a lot of NiMH cells around (for digital cameras and hobby use), I decided to solder in a couple of them and see what happens. The first thing I noticed was that, for the first time in years, the RED charge LED came on (for a few minutes) as well as the GREEN LED. It then proceeded to charge for about 20 minutes, then the GREEN LED began flashing, and I knew charging had stopped. The case of the shaver felt warm, but not as warm as when there were Ni-Cds in there. I've been using it now for a couple days, and it has plenty of zip, and sounds real good (by the pitch of the motor). BTW, I assume that there is some kind of "smart charging" going on, as if I were to plug it in after only a couple days, it would shut off (green LED blinking) after only a few minutes. Maybe its voltage based? I guess I'll know how well, this works after some time has expired, but for now, it appears to be working well. BTW, I have 2 Norelco shavers, and this is the older of the 2. I use one until it runs down, then grab the other one, and put the exhausted one on charge. Thanks again .. Bill, KB8EB
From: Doug McLaren on 30 Aug 2005 01:28 In article <1125024813.133598.112080(a)f14g2000cwb.googlegroups.com>, <electricitym(a)yahoo.com> wrote: | The main complication would be very short battery life. As you hinted at, that depends on the charger. Most cheap rechargable appliances have a slow charger that charge the battery at around C/10. If you replace 600 mAh AA NiCds with 2400 mAh AA NiMH cells, the charger will work just fine, except that it's now charging at a C/40 rate -- which is slow enough that the incresaed self discharge of the NiMH cells will become an issue, but it'll probably work just fine. (It might not ever fully charge the batteries though. But it should be OK anyways.) You really only have to worry about the charger if it 1) only charges for X hours, which would mean that it won't fully charge the new, larger battery unless you unplug it and plug it back in after X hours, or 2) is a fast peak-detecting charger, as NiMH cells have a similar peak to NiCds, but it's smaller. In my experience, most cheap devices that have NiCd or NiMH cells have slow chargers that will work fine with either. Only the higher quality ones have things that actually detect when the battery is actually fully charged -- things like better power tools and the like. (And of course, anything with LiPo cells. Overcharging them is bad. But LiPo cells don't fit within the `NiCd or NiMH' classification I mentioned earlier.) -- Doug McLaren, dougmc(a)frenzy.com It's hard to be nostalgic when you can't remember anything. --Unknown
From: Doug McLaren on 30 Aug 2005 01:34 In article <G7SQe.3025$Nx.1762(a)tornado.texas.rr.com>, Doug McLaren <dougmc(a)frenzy.com> wrote: | Most cheap rechargable appliances have a slow charger that charge the | battery at around C/10. Of course, since the original poster says it charges the batteries in 20 minutes, obviously it doesn't fall into this category. It would be best to replace those batteries with similar batteries. Modern NiMH cells will tolerate overcharge almost as well as NiCd cells, but they don't like being charged at over 1C rates, except for the sub-C cells which can go a bit higher, probably 2C. As another poster suggested, if they're sub-C cells, get them at a hobby store that sells R/C stuff. You can buy them online too easily enough -- www.radicalrc.com is one of my favorite places. Places like Batteries Plus probably have what you need too, but their prices are generally quite high. -- Doug McLaren, dougmc(a)frenzy.com "The wheel is spinning but the hamster is dead."
From: Doug McLaren on 31 Aug 2005 12:48 In article <od41h1pv0n8po9320qbfgnr9ummai9drfc(a)4ax.com>, H. Dziardziel <hdzi(a)zworg.nospamcom> wrote: | On 27 Aug 2005 05:04:45 GMT, Jim Yanik <jyanik(a)abuse.gov.> wrote: | | >> For say, 1500mAh cells | | A typo, "1500mAh cells" should read "1500mA." Are you sure? 1500 mAh seems right to me. You're talking about the capacity of the cell itself, not the discharge rate, right? Capacity is given in mAh. Charge/Discharge rates in mA. | Unlike NiCads, NiMh are exothermic while charging so will get | warm, especially at this rather high charge rate.. NiCds get warm during charging too. Just not as warm, due to their generally lower internal resistance. | Once fully charged however the temperature (T) rises sharply after | the very small voltage drop that indicate full charge. Same with NiCd and NiMH cells -- it's just that with NiMH cells, the voltage drop is smaller. | NiCads, being endothermic are more reliably temperature end of | charge detected since the T change is sharper. In either case, | _hot_ cells indicate overcharging Endothermic? No way. Apparantly there is an endothermic component to the chemical charging process (and I see references to that in many places) but the current going through the internal resistance will generate heat as well, and from what I've seen, the overall temperature _increases_ as you charge, even for NiCds, during the entire charge cycle, even when you're not charging at an extremely high rate. (Of course, if you're charging at a low rate, any temperature changes are hard to detect, at least until the cell is fully charged, where it becomes much easier as all energy is going into heat, not just some.) Perhaps at low charge rates the endothermic component is slightly stronger than the exothermic heating, but if you're charging a NiCd battery in 20 minutes -- at a 3C rate -- no way. It's going to get warm. -- Doug McLaren, dougmc(a)frenzy.com Baby carrots: vegetarian veal
From: H. Dziardziel on 2 Sep 2005 05:34
On Wed, 31 Aug 2005 16:48:11 GMT, dougmc(a)frenzy.com (Doug McLaren) wrote: >In article <od41h1pv0n8po9320qbfgnr9ummai9drfc(a)4ax.com>, >H. Dziardziel <hdzi(a)zworg.nospamcom> wrote: > >| On 27 Aug 2005 05:04:45 GMT, Jim Yanik <jyanik(a)abuse.gov.> wrote: >| >| >> For say, 1500mAh cells >| >| A typo, "1500mAh cells" should read "1500mA." > >Are you sure? 1500 mAh seems right to me. You're talking about the >capacity of the cell itself, not the discharge rate, right? > The 1500mA was an estimated 3C charge rate for the original NiCads, hence the following words "..that would take about one hour.." (to begin to fully charge the new high capacity NiMh etc). >Capacity is given in mAh. Charge/Discharge rates in mA. > Well, I do believe that strikes a note but thanks for the reminder to be more alert. Sigh. >| Unlike NiCads, NiMh are exothermic while charging so will get >| warm, especially at this rather high charge rate.. > >NiCds get warm during charging too. Just not as warm, due to their >generally lower internal resistance. > >| Once fully charged however the temperature (T) rises sharply after >| the very small voltage drop that indicate full charge. > >Same with NiCd and NiMH cells -- it's just that with NiMH cells, the >voltage drop is smaller. > >| NiCads, being endothermic are more reliably temperature end of >| charge detected since the T change is sharper. In either case, >| _hot_ cells indicate overcharging > >Endothermic? No way. > >Apparantly there is an endothermic component to the chemical charging >process (and I see references to that in many places) Yes.and it's significant but I don't claim to understand the electrochemical.theory behind it,. Good NiCads stay pretty cool even at high rates. By the way, Li-ion are also somewhat endothermic until nearly fully charged. > but the current >going through the internal resistance will generate heat as well, and >from what I've seen, the overall temperature _increases_ as you >charge, even for NiCds, during the entire charge cycle, even when >you're not charging at an extremely high rate. (Of course, if you're >charging at a low rate, any temperature changes are hard to detect, at >least until the cell is fully charged, where it becomes much easier as >all energy is going into heat, not just some.) > >Perhaps at low charge rates the endothermic component is slightly >stronger than the exothermic heating, but if you're charging a NiCd >battery in 20 minutes -- at a 3C rate -- no way. It's going to get >warm I'm warming to your point. Regards. .. |