Unused Li-ion battery pack
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From: William Sommerwerck on 4 Oct 2009 07:58 > Why don't UPS manufacturers use a decent > charging circuit in their SLA-backed UPS's? What are the differences between decent and indecent charging circuits?
From: who where on 4 Oct 2009 09:38 On Sun, 4 Oct 2009 06:24:04 +0000 (UTC), "Geoffrey S. Mendelson" <gsm(a)mendelson.com> wrote: >who where wrote: > >> That was one reason for the selection to be available. Unfortunately >> (as I mentioned earlier) laptop manufacturers have one objective - >> maximum runtime for minimum cost. > >And weight. If cost and reliability were more important, they would use >nickle metal hydride cells. The cells are almost indestructable, easy to >charge, have no reputation of early failure or catching fire, and so on. >They can be reconditioned by draining them completely, which they actually >seem to do well with unlike any of the lithium cells. and invariably a much higher self-discharge rate, although more recently this has improved a lot (although *after* Li-Ion gained widespread acceptance). >Somewhere along the way, people decided that expensive lithium cells were >"in" and nickle metal hydride cells were for flashlights and $10 MP3 players. Weight and volumetric superiority were the main attractions, particularly for cellphones. You could fit about twenty of my Nokia GSM phone's pack inside the NiXX pack for my old Motorola analog flip. >This is IMHO one of the great failings of portable device design in this >century. What surprises me is that no one has picked up on this in the >"climate change" crowd, lithium cells use rarer materials and are much more >dangerous to the environment if dumped in the trash, which is where most of >them end up. (or worse, a recylce heap in China.) which is the *same* as dumped in the trash :-( Don't get me started on CFL's ...
From: who where on 4 Oct 2009 09:40 On Sun, 4 Oct 2009 04:58:52 -0700, "William Sommerwerck" <grizzledgeezer(a)comcast.net> wrote: >> Why don't UPS manufacturers use a decent >> charging circuit in their SLA-backed UPS's? > >What are the differences between decent and indecent charging circuits? Quite simple really. Decent ones recharge the SLA's with a sensible regime that supports longevity while providing a reasonable recovery after disharge. Indecent ones overcharge the SLA's and fsck them.
From: Geoffrey S. Mendelson on 4 Oct 2009 10:04 who where wrote: >>Somewhere along the way, people decided that expensive lithium cells were >>"in" and nickle metal hydride cells were for flashlights and $10 MP3 players. > > Weight and volumetric superiority were the main attractions, > particularly for cellphones. You could fit about twenty of my Nokia > GSM phone's pack inside the NiXX pack for my old Motorola analog flip. That's not really fair. My Motorola flip used 6 volts, and needed about 1 amp to transmit while you were speaking. It used the AMPS system which was basicly FM radio. It also needed 50ma on standby. My current cellphone (a really cheap Alcatel GSM) has a 450ma 3.6 volt battery. In Nimh terms that would be 3 cells each 1/2 AAA size. Not much bigger or heavier, if at all then the lithium battery in it. It would also be ok to run it down to zero, and with the new cells last a year without discharging (or about a week in the phone, even with it off), and go through 1,000 cycles before dying. As for relative size, you could put 5 or 6 of the Alcatel phones in the 1600mah pack for the flip. I actually had a lithium battery for it, it was the size of the 600mah nicad, but held 1000mah. Cost around $100. Geoff. -- Geoffrey S. Mendelson, Jerusalem, Israel gsm(a)mendelson.com N3OWJ/4X1GM
From: Jeff Liebermann on 4 Oct 2009 13:09
On Sun, 04 Oct 2009 11:07:27 +0800, who where <noone(a)home.net> wrote: >On Sat, 03 Oct 2009 10:27:21 -0700, Jeff Liebermann <jeffl(a)cruzio.com> >wrote: > >>Yep. Seen any Li-Ion battery chargers that have a settable EOC (end >>of charge) adjustment? I haven't. > >Yes, the design I did allowed selection of 4v10 and 4v20 EOC. User selectable? That sure would be nice. If so, that's the first charger I've seen that offers any manner of early EOC control by the user. Sometimes, it's internally selectable by a jumper, pot, or component selection. However, I've never seen it user accessible much less properly documented. >(Technically it isn't the EOC point, rather the transition from CC to >CV charging. True end-of-charge is generally triggered when the >charge current at constant voltage tapers off to a predetermined >figure like 10% of the CC rate. But it does set the final charged >state and voltage). I think (not sure) that simply disabling the CV part of the charge cycle would be sufficient to stop charging at about 80% of full charge. >>One could program it to stop >>charging at perhaps 80% of charge, and somewhat extend the life of >>batteries that are in 7x24x365 laptops. Also useful for the spare >>batteries that I carry in the bag. Left fully charged, they also tend >>to die early. > >That was one reason for the selection to be available. Unfortunately >(as I mentioned earlier) laptop manufacturers have one objective - >maximum runtime for minimum cost. Yep. The math for calculating how far down a Li-Ion battery pack is discharged is fairly simple if I make a number of assumptions. Load can be estimated by removing the battery, and running the laptop solely on the charger. Measure the charger current while using as much power as possible (full LCD backlight, run a DVD movie, no CPU slowdown). It's usually fairly close to the current rating of the charger. If you're lazy (like me), just use the charger current spec. Estimating the average load and duty cycle is not easy. I use 10% of maximum, which is probably wrong for many applications and users, but is a fair starting point. I'm also ignoring charger efficiency which I assume is fairly high. Using a handy IBM Thinkpad R40 as an example, the charger is rated at: 16v 4.5A. 16v * 4.5A = 72 watts. Using my 20% duty cycle guess, we have an average load of 14.4 watts. The battery is rated at 14.4v 4000ma-hrs or: 14.4 * 4A-Hr = 57.6 watt-hrs. So, if we fully charge the battery, and run it to depletion, we can theoretically have: 57.6 watt-hrs / 14.4 watts = 4 hrs. My R40 typically will run about 2 hrs which is down to perhaps 50% of full charge. I should probably do the same calculation with one of the new Netbook computers, which is more sensitive to battery selection but are also conveniently rated in hours of operating time. Most of the vendors use MobileMark 2007 ($400) software for determining their battery run time under a controlled work load: <http://www.bapco.com/products/mobilemark2007/index.php> See <http://www.bapco.com/support/technical_documents/Mobilemark2007_Whitepaper.pdf> Section 2.5 and 4.4 have battery run time criteria which is rated down to 7% of battery capacity. Little wonder they get inflated run time numbers. Note: Run time = how long the laptop or battery will run. Life time = how long the battery will last before replacement. -- Jeff Liebermann jeffl(a)cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |