2016-02-20 Charge Car Battery Faster

I needed to pick some grapefruit from the tree, and I borrowed the picker pole from a friend.  I put it in my Civic and got home, took it out and picked some ruby red grapefruit.  Man, were they Delicious!

So Monday I got in the car, and CLICK!  It wouldn’t start.  Then I noticed the dome light was dimly lit.  Apparently I hit the switch a few days ago when I was taking the picker pole out.  One would think that with all this high technology in the car they would put a sensor into tell you that the light was still on!  To make matters worse I was in a hurry to get to a hot lunch date, so I left it until later.

I had the same problem with the light above the rear view mirror and I solved it by putting in led lights so they wouldn’t run the battery down so fast.  But I never considered the dome light above my head.  I thought it was automatic, and came on whenever the door was opened.  And it fades out slowly, which led me to believe it was controlled by something more intelligent than a switch.  But it turned out that it has a 3 position switch; on, off and auto.  I must’ve bumped it to the on position.

I thought about what I should do.  Jam a piece of plastic in it so it can’t move?  it should be easy to remove if I need to put it back the way it was.  Not necessarily permanent, it could come loose.  Mess around with the wiring?  Too permanent.  But I will definitely put LED lights in it.

But back to the present problem.  I need to get the car running, so I have to charge the battery.  I have two 3 amp power supplies, one of them I’ve used before to charge the battery.  They are both constant voltage, constant current regulated PSes.  But it takes several hours at 3 amps, and I need to speed up that time.  I just got some big 35 amp Schottky diode rectifiers that I can use to prevent the power supplies from fighting each other.  Without diodes, the power supplies will not each put out 3 amps.

So I took two of these old rectifiers and screwed them both into the same nut.   The threads are the cathodes and go to the positive of the battery.  The pigtails each go to one of the power supply’s positive lead.

I clipped them together with multiple alligator clip leads to be safe, and placed them on top of a piece of bubble wrap on the battery.  I turned the PSes on and adjusted them for 14 volts and 3 amps, and checked to see if anything was getting hot.  Okay, so a few hours later, I checked the battery, and it measured a bit under 13 volts, still not fully charged but enough to start the car!

Anyone can make something similar with the diodes out of a PC power supply.  There are some high current Schottky diodes mounted on the heat sink, which have two diodes marked on the case.  It takes a lot of heat to unsolder some of these big parts.  But if you use them, they would stay cooler if they were left on the heat sink.  For currents of a few amps, the bridge rectifier will work.   Connect the plus to the battery and the AC ‘~’ to the plus of the two power supplies.  The minus is not connected.  It might get hot, so check it, and add a heat sink if necessary.

I got the Schottky diodes from Electronic Goldmine.  I also bought a 15 volt, 13.4 amp power supply from them when it went on sale.  Now I can use it to charge the battery.  But I’m hoping that this will never happen again once I put the LED lights in.  But I’ve learned to never say never.

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