battery chargers, again
in [Design]
|
From: Tim Wescott on 28 Sep 2009 10:04 On Sun, 27 Sep 2009 21:16:46 -0700, John Larkin wrote: > Last time a car went dead in the garage, my wife's Fit, I hacked up a > charger from an old DSL wall-wart and a sabre saw as a series current > limiter. The garage geometry makes it essentially impossible for us to > push a car uphill to the street to jump it. Now The Brat left her Echo > in the garege for a month or so and it went dead, too. So I figure it's > time to buy a real charger. Went to Kragen Auto Parts and bought two > (one for here, one for Truckee) chargers. They are all "smart chargers", > namely switchers with electronics, these days. > > The battery is really dead, 1.8 volts. The first charger hums and > outputs nothing. Tried the next one: it hummed for maybe 3 seconds then > sparked and smoked inside. > > Went back to Kragen and traded up, two better chargers. Neither > charges... no current, battery steady at 1.8 volts. Both have their > "charging" LEDs off and "charge complete" LEDs lit. > > Back to Kragen, 3rd time, got all my money back. Passed by Bob Pease's > place all three trips, same collection of rusty VWs everywhere. > > A charger that puts zero amps into a dead battery does that by design, > and there's only one reason to do that: to convince people they need a > new battery. Kragen's sales pitch was exactly along those lines; "Tt > won't charge, so all the cells are shorted." > > So I went to work and nabbed a cute little Lascar bench power supply. It > current limits at 1.2 amps, so I just cranked it up. The battery went > instantly to 16.5 volts, then settled down to 12 or so in a few minutes, > and is creeping back up. > > Interesting. > > So I guess I'll buy a couple of 3 amp or so lab supplies, with nice volt > and amp meters, instead of battery chargers. They're handier to have > around anyhow, cost about the same as a "good" charger, and aren't booby > trapped. > > What Kragen is doing is fraud. > > John I've never had a battery come back from being that dead, and I've had numerous chances to try it (I'm stubborn that way). You'll be lucky to see 12V out of it with the charger disconnected, and I doubt that you'll see that after the first time you touch the key. If you _do_ get the car started it'll just be an opportunity for you daughter to get stranded some place. One new battery is cheaper than one tow truck ride. Do the math. -- www.wescottdesign.com
From: John Larkin on 28 Sep 2009 10:08 On Mon, 28 Sep 2009 12:32:42 GMT, Jan Panteltje <pNaonStpealmtje(a)yahoo.com> wrote: >On a sunny day (Sun, 27 Sep 2009 21:16:46 -0700) it happened John Larkin ><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in ><8ec0c5lnkt6gq1f9g4jl1o56c4n3uhlg97(a)4ax.com>: > >>So I went to work and nabbed a cute little Lascar bench power supply. >>It current limits at 1.2 amps, so I just cranked it up. The battery >>went instantly to 16.5 volts, then settled down to 12 or so in a few >>minutes, and is creeping back up. > >That is the right way to do it. >Put a dide in series, not sure if those like 12 V reversed. A diode prevents back-driving the supply if it's connected right - and that probably doesn't matter - but doesn't protect against reverse connection. But I know how to do that. John
From: John Larkin on 28 Sep 2009 10:09 On Mon, 28 Sep 2009 09:20:24 -0400, PeterD <peter2(a)hipson.net> wrote: >On Sun, 27 Sep 2009 21:16:46 -0700, John Larkin ><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: > >>Last time a car went dead in the garage, my wife's Fit, I hacked up a >>charger from an old DSL wall-wart and a sabre saw as a series current >>limiter. The garage geometry makes it essentially impossible for us to >>push a car uphill to the street to jump it. Now The Brat left her Echo >>in the garege for a month or so and it went dead, too. So I figure >>it's time to buy a real charger. Went to Kragen Auto Parts and bought >>two (one for here, one for Truckee) chargers. They are all "smart >>chargers", namely switchers with electronics, these days. >> >>The battery is really dead, 1.8 volts. The first charger hums and >>outputs nothing. Tried the next one: it hummed for maybe 3 seconds >>then sparked and smoked inside. >> >>Went back to Kragen and traded up, two better chargers. Neither >>charges... no current, battery steady at 1.8 volts. Both have their >>"charging" LEDs off and "charge complete" LEDs lit. >> >>Back to Kragen, 3rd time, got all my money back. Passed by Bob Pease's >>place all three trips, same collection of rusty VWs everywhere. >> >>A charger that puts zero amps into a dead battery does that by design, >>and there's only one reason to do that: to convince people they need a >>new battery. Kragen's sales pitch was exactly along those lines; "Tt >>won't charge, so all the cells are shorted." >> >>So I went to work and nabbed a cute little Lascar bench power supply. >>It current limits at 1.2 amps, so I just cranked it up. The battery >>went instantly to 16.5 volts, then settled down to 12 or so in a few >>minutes, and is creeping back up. >> >>Interesting. >> >>So I guess I'll buy a couple of 3 amp or so lab supplies, with nice >>volt and amp meters, instead of battery chargers. They're handier to >>have around anyhow, cost about the same as a "good" charger, and >>aren't booby trapped. >> >>What Kragen is doing is fraud. >> > >Regardless, any LA battery that is discharged to 1.8 volts is >basically finished anyway. It may recharge, but I suspect it won't >last long. Disagree. I'be done that too many times. > >The fact that the Kragen chargers recognized the battery was too >discharged to be considered serviceable (which is what they were >thinking...) is one that the owner must decide. The flip side of that >coin is that if your Kragen charger did charge the battery, then the >battery failed shortly afterwards, you'd have thought the charger was >at fault. They realized that (and that customers would be claiming >that the charger 'ruined' their battery, and demanding new batteries) >and instead built the system you bought. > >OK, in the end: I use an *old* non-automatic charger. Doesn't care, >doesn't measure, it just tosses volts to the battery (like your bench >charger). I'm happy with it, and had good success with it charging >batteries. Sometimes old technology is great. > >John, you are skilled enough to build a charger! Just do it... <g> I'm skilled enough to buy a B&K or whatever bench supply from Digikey, too. John
From: Phil Hobbs on 28 Sep 2009 10:08 Spehro Pefhany wrote: > On Mon, 28 Sep 2009 09:53:48 -0400, Phil Hobbs > <pcdhSpamMeSenseless(a)electrooptical.net> wrote: > >> John Larkin wrote: >>> Last time a car went dead in the garage, my wife's Fit, I hacked up a >>> charger from an old DSL wall-wart and a sabre saw as a series current >>> limiter. The garage geometry makes it essentially impossible for us to >>> push a car uphill to the street to jump it. Now The Brat left her Echo >>> in the garege for a month or so and it went dead, too. So I figure >>> it's time to buy a real charger. Went to Kragen Auto Parts and bought >>> two (one for here, one for Truckee) chargers. They are all "smart >>> chargers", namely switchers with electronics, these days. >>> >>> The battery is really dead, 1.8 volts. The first charger hums and >>> outputs nothing. Tried the next one: it hummed for maybe 3 seconds >>> then sparked and smoked inside. >>> >>> Went back to Kragen and traded up, two better chargers. Neither >>> charges... no current, battery steady at 1.8 volts. Both have their >>> "charging" LEDs off and "charge complete" LEDs lit. >>> >>> Back to Kragen, 3rd time, got all my money back. Passed by Bob Pease's >>> place all three trips, same collection of rusty VWs everywhere. >>> >>> A charger that puts zero amps into a dead battery does that by design, >>> and there's only one reason to do that: to convince people they need a >>> new battery. Kragen's sales pitch was exactly along those lines; "Tt >>> won't charge, so all the cells are shorted." >>> >>> So I went to work and nabbed a cute little Lascar bench power supply. >>> It current limits at 1.2 amps, so I just cranked it up. The battery >>> went instantly to 16.5 volts, then settled down to 12 or so in a few >>> minutes, and is creeping back up. >>> >>> Interesting. >>> >>> So I guess I'll buy a couple of 3 amp or so lab supplies, with nice >>> volt and amp meters, instead of battery chargers. They're handier to >>> have around anyhow, cost about the same as a "good" charger, and >>> aren't booby trapped. >>> >>> What Kragen is doing is fraud. >>> >>> John >>> >> Or just get a nasty big iron Craftsman charger off eBay. Two >> transformer taps, rectifier, thermal cutout. >> >> Cheers >> >> Phil Hobbs > > Many of the the newer battery chargers seem to do this.. they refuse > to charge if the battery is very dead. It's in the preferred algorithm > description for NiMH batteries too-- I just had to modify a charging > algorithm because people make mistakes and occasionally kill batteries > below the minimum charge voltage per cell and you need to be able to > override the (usually microcontroller-based) smart charger. And had > the same problem recently with a commercial charger for a stacker > (sort of a little fork lift). The deep discharge Marine duty battery > was too dead for the dumbf*ck little LM339 circuit to turn the SCR on. > At first we thought it had failed.. One of the problems with our software-intensive era is that the behaviour of ordinary objects has become arbitrary, like software, instead of merely ornery, like physics. It's nice to warn people, but building something that refuses to do the job it's built for is poor engineering. (Of course our current plague of tort lawyers is partly responsible, but only partly.) Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal ElectroOptical Innovations 55 Orchard Rd Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
From: Jim Thompson on 28 Sep 2009 10:53
On Mon, 28 Sep 2009 09:53:48 -0400, Phil Hobbs <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >John Larkin wrote: >> Last time a car went dead in the garage, my wife's Fit, I hacked up a >> charger from an old DSL wall-wart and a sabre saw as a series current >> limiter. The garage geometry makes it essentially impossible for us to >> push a car uphill to the street to jump it. Now The Brat left her Echo >> in the garege for a month or so and it went dead, too. So I figure >> it's time to buy a real charger. Went to Kragen Auto Parts and bought >> two (one for here, one for Truckee) chargers. They are all "smart >> chargers", namely switchers with electronics, these days. >> >> The battery is really dead, 1.8 volts. The first charger hums and >> outputs nothing. Tried the next one: it hummed for maybe 3 seconds >> then sparked and smoked inside. >> >> Went back to Kragen and traded up, two better chargers. Neither >> charges... no current, battery steady at 1.8 volts. Both have their >> "charging" LEDs off and "charge complete" LEDs lit. >> >> Back to Kragen, 3rd time, got all my money back. Passed by Bob Pease's >> place all three trips, same collection of rusty VWs everywhere. >> >> A charger that puts zero amps into a dead battery does that by design, >> and there's only one reason to do that: to convince people they need a >> new battery. Kragen's sales pitch was exactly along those lines; "Tt >> won't charge, so all the cells are shorted." >> >> So I went to work and nabbed a cute little Lascar bench power supply. >> It current limits at 1.2 amps, so I just cranked it up. The battery >> went instantly to 16.5 volts, then settled down to 12 or so in a few >> minutes, and is creeping back up. >> >> Interesting. >> >> So I guess I'll buy a couple of 3 amp or so lab supplies, with nice >> volt and amp meters, instead of battery chargers. They're handier to >> have around anyhow, cost about the same as a "good" charger, and >> aren't booby trapped. >> >> What Kragen is doing is fraud. >> >> John >> >Or just get a nasty big iron Craftsman charger off eBay. Two >transformer taps, rectifier, thermal cutout. > >Cheers > >Phil Hobbs And a hydrometer so you know what condition the battery is really in. ...Jim Thompson -- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | Coming soon to the elementary school in your neighborhood... I pledge allegiance to Dear Leader Barack Hussein Obama and to the community organization for which he stands: one nation under ACORN, unchallengeable, with wealth redistribution and climate change for all. |