Diodes for 12v battery charging
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From: Paul E. Schoen on 31 Jan 2010 20:58 "Jamie" <jamie_ka1lpa_not_valid_after_ka1lpa_(a)charter.net> wrote in message news:Hqo9n.37422$RS6.13180(a)newsfe15.iad... > Paul E. Schoen wrote: >> >> >> The picture of the rectifier shows a three-lead TO-220, but description >> says two-lead. >> >> Drop will decrease to about 0.3V at low current when regulator goes into >> float voltage mode. >> >> You might be able to cannibalize a Schottky rectifier from a computer >> power supply. Maybe a three-lead diode which can be used in parallel for >> even less voltage drop. >> >> Here is the manual for a 7A Harbor Freight charging unit: >> http://www.harborfreight.com/cpi/ctaf/manuals.taf?f=form&ItemID=96728 >> >> Paul > Many sights use generic images for their parts. They look at the TO-220 > and think they're all the same. > > AS far the manual, it really does not give much info to break down the > circuit how ever, it does state (+.5) above 14V, so I think it should > still charge the batteries, just maybe a little slower, which could be a > good thing if it's left to keep the units at float. The higher the current rating of the Schottky diode, the lower will be the voltage drop at a certain current. Here is a diagram of a typical 200W computer supply: http://www.pavouk.org/hw/en_atxps.html The output rectifier is a D83-004 which is rated at 30A. At 6A, or 3A through each in parallel, the voltage drop is just about 0.35V. http://pdf1.alldatasheet.com/datasheet-pdf/view/61331/FUJI/ESAD83-004.html So it might be worthwhile to take apart some junk computer PSUs to get these diodes. However, you can get an MBR4060 from Mouser for $2.60 each. Dual 40A 60V. Another idea to try is a set of three relays which take turns connecting the regulator to each of the three batteries. And you can add a small diode and resistor across each contact so that bateries not directly connected will still get a trickle charge. At least in this way the charger/controller will be able to interact with the battery in the way it was designed. Paul
From: Jasen Betts on 1 Feb 2010 05:42 On 2010-02-01, Paul E. Schoen <paul(a)peschoen.com> wrote: > Another idea to try is a set of three relays which take turns connecting > the regulator to each of the three batteries. And you can add a small diode > and resistor across each contact so that bateries not directly connected > will still get a trickle charge. At least in this way the > charger/controller will be able to interact with the battery in the way it > was designed. I second that, any passive scheme can be defeated by a shorted cell in one battery. (or an open cell if you charge in series) OTOH if you can get theee independant 14+V outputs from the solar panel you could set up each with an independant charge circuit. that would be another way to go, or just get three solar panels... --- news://freenews.netfront.net/ - complaints: news(a)netfront.net ---
From: ian field on 1 Feb 2010 09:34 "Stumpy" <perilmung(a)spamnet.con> wrote in message news:icmdnc4L8dZok_vWnZ2dnUVZ_rydnZ2d(a)earthlink.com... >>> >>> I don't even know how that 45volt rectifier could be used as a diode. >>> This is a link to the regulator I have. >>> >>> http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=96728 >>> >> >> >> If you put diodes in series with the output of the regulator, the volt >> drop of the diodes might result in under-charging. >> >> The ideal solution would be to give each battery its own regulator. >> >> If you only want to use one battery at a time then you can connect the + >> terminal with an alligator clip, if you want the full capacity from all 3 >> batteries at once, you'll need output isolating diodes to feed the + >> terminals to your load - these diodes will need to be rated considerably >> more than 7A !!! > > I'm getting confused. The 3 batteries are in 3 separate vehicles. It > might be convenient to have no diodes so that the other 2 batteries could > act as "jumpers" when starting one, but then I would risk having one > battery fail and drain the other 2 during a possible 2 month period with > no attention. It seems safer to isolate the batteries from each other, yet > allow a single solar panel to charge all 3 simultaneously. > > I assume that a 25 watt panel would supply ~2 amps at 12 volts .:. the > Radio Shack diode > http://www.radioshack.com/product/index.jsp?productId=2062591# would be OK > for charging and for reducing risk from an unexpected discharge. I was > looking for some confirmation because I am a trial and error sort of > fellow and an error can mean a bad trip and added expense. > > Thanks for considering my problem. > The 1N5822 40V 3A shottky-barrier diode would probably handle as much current as your speaker wire. Personally, I'd go for a bit bigger safety margin like the devices here; http://uk.farnell.com/jsp/search/browse.jsp?N=500006+1004178+5056622&Ntk=gensearch_001&Ntt=shottky+barrier+diode&Ntx=mode+matchallpartial&No=0&getResults=true&appliedparametrics=true&locale=en_UK&catalogId=&prevNValues=500006+1004178&filtersHidden=false&appliedHidden=false&originalQueryURL=%2Fjsp%2Fsearch%2Fbrowse.jsp%3FN%3D500006%2B1004178%26Ntk%3Dgensearch_001%26Ntt%3Dshottky%2Bbarrier%2Bdiode%26Ntx%3Dmode%2Bmatchallpartial%26No%3D0%26getResults%3Dtrue%26appliedparametrics%3Dtrue%26locale%3Den_UK%26catalogId%3D%26prevNValues%3D500006%2B1004178 If you want to charge 3 batteries in parallel, it would be better to feed each battery with its own regulator. If you want to split the current with a diode to each battery (from a single regulator) you will need a regulator that allows you to adjust the output upwards to compensate for the diode volt drops. If each battery is used individually, that's all you need to do, if you wanted to use all 3 batteries in parallel, you'd need 3 more (much higher current) diodes to combine the three batteries into the load - it would sort of defeat the object of the first 3 diodes to then strap the 3 batteries together in parallel.
From: Stumpy on 1 Feb 2010 10:50 > > The higher the current rating of the Schottky diode, the lower will be the > voltage drop at a certain current. Here is a diagram of a typical 200W > computer supply: > http://www.pavouk.org/hw/en_atxps.html > > The output rectifier is a D83-004 which is rated at 30A. At 6A, or 3A > through each in parallel, the voltage drop is just about 0.35V. > http://pdf1.alldatasheet.com/datasheet-pdf/view/61331/FUJI/ESAD83-004.html > > So it might be worthwhile to take apart some junk computer PSUs to get > these diodes. However, you can get an MBR4060 from Mouser for $2.60 each. > Dual 40A 60V. > > Another idea to try is a set of three relays which take turns connecting > the regulator to each of the three batteries. And you can add a small > diode and resistor across each contact so that bateries not directly > connected will still get a trickle charge. At least in this way the > charger/controller will be able to interact with the battery in the way it > was designed. > > Paul Those relays sound like a fun project, but too sophisticated for me. Where do you guys post diagrams of your circuits? If Sci. E. B. is text only is there a companion group for binaries?
From: ehsjr on 1 Feb 2010 11:43
Stumpy wrote: >>The higher the current rating of the Schottky diode, the lower will be the >>voltage drop at a certain current. Here is a diagram of a typical 200W >>computer supply: >>http://www.pavouk.org/hw/en_atxps.html >> >>The output rectifier is a D83-004 which is rated at 30A. At 6A, or 3A >>through each in parallel, the voltage drop is just about 0.35V. >>http://pdf1.alldatasheet.com/datasheet-pdf/view/61331/FUJI/ESAD83-004.html >> >>So it might be worthwhile to take apart some junk computer PSUs to get >>these diodes. However, you can get an MBR4060 from Mouser for $2.60 each. >>Dual 40A 60V. >> >>Another idea to try is a set of three relays which take turns connecting >>the regulator to each of the three batteries. And you can add a small >>diode and resistor across each contact so that bateries not directly >>connected will still get a trickle charge. At least in this way the >>charger/controller will be able to interact with the battery in the way it >>was designed. >> >>Paul > > > Those relays sound like a fun project, but too sophisticated for me. Where > do you guys post diagrams of your circuits? If Sci. E. B. is text only is > there a companion group for binaries? > > I'll bet the relay project is something you could tackle, with a little help. Regarding schematics, there are a number of possibilities: http://tinypic.com/ Spice lists a.b.s.e (alt.binaries.schematics.electronic) ASCII art For example here's ascii art showing the diode isolation you mentioned: ------------ | Solar +|------+--->|---[Battery1]---+ | Controller | | | | | +--->|---[Battery2]---+ | Harbor | | | | Freight | +--->|---[Battery3]---+ | Model (?) | | | -|----------------------------+ ------------ Each approach has its pluses and minuses. For example the ACSII art above must be viewed in fixed font such as Courier. Ed |