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| Ban of non-rechargeable batteries |
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| GlennSprigg:
--- Quote from: Zero999 on July 04, 2020, 01:24:45 pm --- --- Quote from: GlennSprigg on July 04, 2020, 12:10:51 pm --- --- Quote from: Zero999 on July 04, 2020, 11:43:45 am --- --- Quote from: GlennSprigg on July 01, 2020, 12:41:57 pm ---The 'problem' I have at times with 'AA' 'Rechargeables' is in the likes of some Cameras etc. Rechargeables are typically 1.2v instead of 1.5v. So "Low Battery" comes on too early!!! :-\ --- End quote --- That's because the device is poorly designed and depending on the current draw, could be wasting as much as half the capacity of alkaline cells. A properly designed device should operated down to at least 1V per cell. I hate this kind of junk. --- End quote --- I think it depends what the original cct was designed for. I was talking about a lot of equipment designed for 'AA' batteries, (ok, often old), that when powered with '1.2v' is quickly underpowered... --- End quote --- What sort of device was it: high or low power drain? I would expect a higher power drain load to work better down to lower voltages, than something with a very low current draw. Alkaline batteries typically have a relatively high impedance, compared to NiMH, so a 1.5V battery will quickly drop to 1.2V, with any significant load. If I remember rightly incandescent torches (flashlight) used to use a slightly lower voltage rated lamp, than the battery voltage, so a two cell unit would typically have a bulb rated to 2.2V, rather than 3V. Lower powered devices will probably do poorer on lower voltages, because the cell voltage should remain higher, at low current draws, but I still hope most will function down to 1.2V, with no problem. I think there's a lot of badly designed products out there, built down to a price. I've seen LM78L05 regulators used in devices powered by 9V alkaline batteries, when a low-dropout regulator should have been used instead. Quite often this increases the cost of ownership, compared to spending a little more on the device itself. --- End quote --- Hi there, 'Zero999'. Sorry about the delay. Only on forum every 2 or 3 days!! :( The main item I was talking about, is my Kodak Z710 digital camera, which I like.... It's not a junk cheap product, (or wasn't..), and has a fantastic proper main lens. I understand that such rechargeable batteries have better 'current' abilities, even when dropping to 1.2v, especially with repeated use of the 'Flash', but even new (charged) rechargeables only give me about 15 shots with the flash! :palm: |
| TimFox:
--- Quote from: james_s on July 06, 2020, 05:21:36 am --- --- Quote from: tooki on July 05, 2020, 09:07:24 pm ---And long term, the electrical grid is extremely accurate. --- End quote --- It is in much of the world, but not everywhere. Most of the old Soviet digital clocks used a crystal timebase for that reason. The person with the clocks is in India, I have no idea how stable the power grid frequency is there. --- End quote --- Frequency stability is very important with systems interconnected in an electrical grid, but is not so important with isolated distribution systems. This situation varies even within individual countries. |
| SiliconWizard:
--- Quote from: Zero999 on July 04, 2020, 08:55:27 pm --- --- Quote from: SiliconWizard on July 04, 2020, 06:25:28 pm --- --- Quote from: Zero999 on July 04, 2020, 01:24:45 pm ---I think there's a lot of badly designed products out there, built down to a price. --- End quote --- Very true. --- Quote from: Zero999 on July 04, 2020, 01:24:45 pm ---I've seen LM78L05 regulators used in devices powered by 9V alkaline batteries, when a low-dropout regulator should have been used instead. Quite often this increases the cost of ownership, compared to spending a little more on the device itself. --- End quote --- I suppose you're talking about the case where the user uses rechargeable 9V batteries instead? I don't quite remember how low a typical 9V NiMh battery can go for instance? Something like 6V or 6.5V? Then yeah, a 78L05 wouldn't cut it. A better approach (although a bit more expensive usually due to the inductor and more expensive regulator) is to use a buck converter, instead of typically dissipating almost 50% in the regulator itself: (9V-5V)*I. Loosing almost half of the capacity of the battery just to shave maybe one dollar, probably less? Eek. --- End quote --- I'm talking about alkaline batteries. If your device won't work at 7.2V, then it's wasting a large proportion of the battery life of a 9V alkaline. Here's some tests showing the discharge curves of some 9V alkaline batteries. https://www.powerstream.com/9V-Alkaline-tests.htm Always design for a lower cut-off voltage of 6V and not only will the device work off NiMH, but it will also make full use of ordinary alkaline batteries. --- End quote --- I see, and agree with the general idea. Of course always design you power supplies so that they can work over the full operating voltage range of the batteries it's made for. I haven't used 9V batteries in designs much at all, so I wasn't expecting them to still hold a significant charge when their voltage is below ~7V, but thinking about it, it makes sense. I guess they often are made of the equivalent of 6 1.5V cells? And yeah, 1.5V alkaline cells still typically hold a significant charge down to 1V or even 0.9V. Anyway, as I said for this particular example, using a linear regulator is itself a bad idea as far as capacity is concerned. The chunk of the capacity you're going to waste just by dissipating power (6V to 9V down to 5V) will be much more significant than what you're going to waste if it stops working at around 7V or so. Of course if you don't have a choice, it's better to use an LDO. But it's even better to use a switching regulator here, if you can. |
| Zero999:
--- Quote from: SiliconWizard on July 06, 2020, 03:12:21 pm --- --- Quote from: Zero999 on July 04, 2020, 08:55:27 pm --- --- Quote from: SiliconWizard on July 04, 2020, 06:25:28 pm --- --- Quote from: Zero999 on July 04, 2020, 01:24:45 pm ---I think there's a lot of badly designed products out there, built down to a price. --- End quote --- Very true. --- Quote from: Zero999 on July 04, 2020, 01:24:45 pm ---I've seen LM78L05 regulators used in devices powered by 9V alkaline batteries, when a low-dropout regulator should have been used instead. Quite often this increases the cost of ownership, compared to spending a little more on the device itself. --- End quote --- I suppose you're talking about the case where the user uses rechargeable 9V batteries instead? I don't quite remember how low a typical 9V NiMh battery can go for instance? Something like 6V or 6.5V? Then yeah, a 78L05 wouldn't cut it. A better approach (although a bit more expensive usually due to the inductor and more expensive regulator) is to use a buck converter, instead of typically dissipating almost 50% in the regulator itself: (9V-5V)*I. Loosing almost half of the capacity of the battery just to shave maybe one dollar, probably less? Eek. --- End quote --- I'm talking about alkaline batteries. If your device won't work at 7.2V, then it's wasting a large proportion of the battery life of a 9V alkaline. Here's some tests showing the discharge curves of some 9V alkaline batteries. https://www.powerstream.com/9V-Alkaline-tests.htm Always design for a lower cut-off voltage of 6V and not only will the device work off NiMH, but it will also make full use of ordinary alkaline batteries. --- End quote --- I see, and agree with the general idea. Of course always design you power supplies so that they can work over the full operating voltage range of the batteries it's made for. I haven't used 9V batteries in designs much at all, so I wasn't expecting them to still hold a significant charge when their voltage is below ~7V, but thinking about it, it makes sense. I guess they often are made of the equivalent of 6 1.5V cells? And yeah, 1.5V alkaline cells still typically hold a significant charge down to 1V or even 0.9V. Anyway, as I said for this particular example, using a linear regulator is itself a bad idea as far as capacity is concerned. The chunk of the capacity you're going to waste just by dissipating power (6V to 9V down to 5V) will be much more significant than what you're going to waste if it stops working at around 7V or so. Of course if you don't have a choice, it's better to use an LDO. But it's even better to use a switching regulator here, if you can. --- End quote --- Yes, alkaline 9V batteries are made of six 1.5V cells. I forgot to say, NiMH has a much lower impedance, than alkaline, so if a device is properly designed, the lower voltage shouldn't be a problem. http://adventuresinarduinoland.blogspot.com/2011/02/easy-nimh-discharge-curves_08.html http://lipobatterymanufacturers.weebly.com/lipo-battery-manufacturer-blog/lipo-vs-nimh-batteries |
| helius:
--- Quote from: helius on July 02, 2020, 12:30:43 am ---I have tried some experiments with recharging alkaline AAs (not Duracells, that would be futile, but Hitachi Maxells). Even when using very slow charging at 100 mA, and a very conservative termination of 1.55 V, there was slight leakage on 1 cell out of 4. The alkaline cells that were intended for recharging would have had different geometry to handle gas generation and so on, and even those were prone to leakage, one reason they didn't last long on the market. --- End quote --- I have done a further experiment on some nickel oxyhydroxide cells (Duracell PowerPix, made in Japan). Since the nickel chemistry has a higher open-circuit voltage, I used a termination of 1.7V and 200 mA. Results were okay at first, but the cells spilled their guts after a few weeks in storage. These are definitely not candidates for recharging. Interestingly, the spilled electrolyte is opaque white, whereas liquid leaking from alkalines is clear. |
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