Diodes for 12v battery charging
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From: Jamie on 31 Jan 2010 15:08 Stumpy wrote: > I put in a 12v solar panel to charge up 2 ATV's and a mini tractor. Ran > some speaker wire and battery clips to charge all of them in parallel. The > tractor battery seems to not hold a charge very well. I'd like to add 3 > diodes to protect the other 2 batteries in case at night with no input > current, the low battery would siphon off power. > > The setup is in a very remote location with no power lines and I've > misplaced to specs for the panel and the 7amp regulator, but they both came > from Harbor Freight. The bigger battery is 14 amp-hr, the 2 smaller ones > are 10 amp-hrs. > > Can someone please suggest an appropriate diode to purchase at Radio Shack > or Fry's that will handle up to 7amp and not waste too much charging > ability? > > http://www.frys.com/product/1003123?site=sr:SEARCH:MAIN_RSLT_PG from Fry's NTE6083 Make sure you mount these to a heat sink. Also, not sure about your charging unit, it may be regulating voltage to a close degree. You'll get a slight drop in voltage to the batteries if the charge regulator does not ramp up to maintain current. Drop will be around .7 volts.
From: Stumpy on 31 Jan 2010 15:40 >> >> Can someone please suggest an appropriate diode to purchase at Radio >> Shack or Fry's that will handle up to 7amp and not waste too much >> charging ability? > > http://www.frys.com/product/1003123?site=sr:SEARCH:MAIN_RSLT_PG > > from Fry's > NTE6083 > > Make sure you mount these to a heat sink. > > Also, not sure about your charging unit, it may be regulating voltage > to a close degree. You'll get a slight drop in voltage to the batteries if > the charge regulator does not ramp up to maintain current. > Drop will be around .7 volts. > 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 Harbor Freight doesn't seem to carry the solar panel any more. I guess I'll just gamble with a 2 legged diode. http://www.frys.com/product/1001633?site=sr:SEARCH:MAIN_RSLT_PG http://www.radioshack.com/product/index.jsp?productId=2062591#
From: Paul E. Schoen on 31 Jan 2010 16:00 "Jamie" <jamie_ka1lpa_not_valid_after_ka1lpa_(a)charter.net> wrote in message news:G8l9n.11539$3n2.9167(a)newsfe01.iad... > Stumpy wrote: > >> I put in a 12v solar panel to charge up 2 ATV's and a mini tractor. Ran >> some speaker wire and battery clips to charge all of them in parallel. >> The tractor battery seems to not hold a charge very well. I'd like to >> add 3 diodes to protect the other 2 batteries in case at night with no >> input current, the low battery would siphon off power. >> >> The setup is in a very remote location with no power lines and I've >> misplaced to specs for the panel and the 7amp regulator, but they both >> came from Harbor Freight. The bigger battery is 14 amp-hr, the 2 >> smaller ones are 10 amp-hrs. >> >> Can someone please suggest an appropriate diode to purchase at Radio >> Shack or Fry's that will handle up to 7amp and not waste too much >> charging ability? > > http://www.frys.com/product/1003123?site=sr:SEARCH:MAIN_RSLT_PG > > from Fry's > NTE6083 > > Make sure you mount these to a heat sink. > > Also, not sure about your charging unit, it may be regulating voltage > to a close degree. You'll get a slight drop in voltage to the batteries > if the charge regulator does not ramp up to maintain current. > Drop will be around .7 volts. 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
From: ian field on 31 Jan 2010 17:43 "Stumpy" <perilmung(a)spamnet.con> wrote in message news:JPydna-tG9vXQfjWnZ2dnUVZ_oWdnZ2d(a)earthlink.com... >>> >>> Can someone please suggest an appropriate diode to purchase at Radio >>> Shack or Fry's that will handle up to 7amp and not waste too much >>> charging ability? >>> >> I assume by the application that they are lead acid batteries. I am never >> comfortable charging LA batteries in parallel because of the different >> states of discharge when you put them on charge. >> Your batteries are close to the same capacity so I suppose that you can >> get away with it. You need to know the maximum charging current you will >> be using and select a diode with about a 50% safety margin. >> BTW: What is "speaker wire" What I really am saying is gauge your wire >> appropriately. >> Tom > > They are all lead acid batteries and physically about the same size. I > was planning on putting a diode on each individual battery so that it > could not be drained if another one took too much current. It's > embarrassing that I don't remember, but I believe that the panel is 25 > watts. The system is simply supposed to maintain charge on reasonably new > batteries. The "speaker wire" is probably 14 or 16 gauge. I am unable to > go check because of distance. Want to get parts before the next 3 day > weekend. Can't run to the store very easily .:. any minor modification > takes ~ 3 months to plan and try out. > The answer to your question; "what type of diode", the best choice would be a shottky-barrier type as it has a lower forward volt drop than standard silicon. If you are using a regulator to give the correct charging voltage for the battery, you will have to take into account the diode volt drop. You quote a figure of 7A and say you are using "speaker wire", If I were you I'd check it isn't getting too hot when there's plenty of sun on the solar panels! Thicker wire would drop less voltage at full current and reduce power lost heating the wire.
From: ian field on 31 Jan 2010 17:53
"Stumpy" <perilmung(a)spamnet.con> wrote in message news:uMqdneRXuN4kd_jWnZ2dnUVZ_sednZ2d(a)earthlink.com... > > >>> >>> Can someone please suggest an appropriate diode to purchase at Radio >>> Shack or Fry's that will handle up to 7amp and not waste too much >>> charging ability? >> >> http://www.frys.com/product/1003123?site=sr:SEARCH:MAIN_RSLT_PG >> >> from Fry's >> NTE6083 >> >> Make sure you mount these to a heat sink. >> >> Also, not sure about your charging unit, it may be regulating voltage >> to a close degree. You'll get a slight drop in voltage to the batteries >> if the charge regulator does not ramp up to maintain current. >> Drop will be around .7 volts. >> > > 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 !!! |