Another battery charger question

Thanks for all the replies and knowledge. My other battery charger is a one pound electronic machine. It works OK, supplies 2, 6 and 12 amps and has all sorts of buttons and lights! What it won't do is charge a totally dead battery...thus repairing the old Craftsman. It displays: "BAD BATTERY" and I have to hook-up jumper cables from another vehicle to get a few percent of a charge to get the electronic charger to work.

I also confess I don't know enough about electronics. Is there a good book to start with that isn't too stupid yet not over my head? I think I can still learn stuff.

Reply to
Tom Gardner
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I went through this when stranded at a remote cabin with a car with a dead battery. Most of these smart chargers have some stupid secret code to "rejuvenate" a totally dead battery. You may have to push multiple buttons, hold for several seconds or whatever, and no way to figure it out without the manual. I had to play with that unit for MANY minutes before I was able to translate the Chinglish instructions into the right buttons to make it start charging.

Jon

Reply to
Jon Elson

That sounds like it should be a winner.

There may be an "idiot's guide", but I'd hesitate to recommend it without reviewing it.

Reply to
Tim Wescott

I learned electronics in the Army, without textbooks or homework, which was nice. There are some courses on the Internet and Radio Shack has books, but I doubt you'll find anything that takes you from beginner to fixing an antique battery charger. jsw

Reply to
Jim Wilkins

The reason they won't charge a dead battery is the "polarity protection" circuit to prevent hooking the charger up backwards and doing damage to either the charger, the battery, or both.

Reply to
clare

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Reply to
Jim Wilkins

Comparing to piping, hydraulics, fluidics, pneumatics...

Volts are pressure Amps is flow Resistance is opposition to flow, a restriction in the line. Power (watts) is the product of flow and pressure.

Rectifiers are like check valves. capacitors are like storage tanks, accumulators or air tanks. transistors are like pilot operated valves

AC would be kind of like a piston pump with no check valves, the power goes one way and then the other. So. using this back and forth fluid could drive a piston one size that is connected to a different size piston, either increasing pressure and decreasing volume, or increasing volume and decreasing pressure. That would be kind of like a transformer, it takes alternating current to make it work. So if you transformed your pumps force and pressure, it could be changed after the transformer by adding check valves at that point.

The old fashioned battery charger transforms the line voltage to a lower voltage at a higher current. Then a rectifier causes it to flow only one way into the battery.

Magnetic field going through a wire induces a voltage in the wire, not sure what that would compare to in hydraulics. The magnetic field inducing voltage has to do with transformers, motors, inductors, antenna, and other.

RogerN

Reply to
RogerN

You never know, though. With old farts like Tawm...there may be enough other, and relevant, experiences to make connections.

Reply to
Larry Jaques

The charger was bought new in '75...is it an antique now? I have a LOT of miles on it...consider the cars I had in college...

Reply to
Tom Gardner

Good article! Thanks!

Reply to
Tom Gardner

Good analogies Roger!

Reply to
Tom Gardner

The water analogy of pressure = voltage, flow = current is useful when you are first learning about Direct Current circuits, but it falls apart quickly for Alternating Current because moving water's inertia isn't the same as inductance, and we don't have the hands-on intuitive experience with AC reversing flows that we do with DC garden hoses.

The analogy that helps me with AC is imagining the pistons and crankshaft of an engine. The height of one piston represents the constantly changing voltage of one phase of the power line. If it was an equally spaced three-cylinder radial engine the other two pistons would be the other phases. The three pistons (voltages) combine their push in sequence to force a steady circular rotation of the crankshaft, which was Tesla's inspiration for introducing AC to spin motors without needing troublesome brushes.

This makes more sense if you understand sines and cosines.

Residential single-phase 120V is a one-cylinder engine and 240V is an opposed twin, like a BMW motorcycle. Since they can hang at top dead center they need a temporary circular push to start in the right direction, the reason why single phase AC motors need starting circuits but three phase ones don't.

.jsw

Reply to
Jim Wilkins

Toro has some good educational stuff on their website, including a basic primer aimed at teaching technicians enough "electricity" to troubleshoot mower and tractor wiring:

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They also have a hydraulics primer that is pretty good:
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Thanks for all the replies and knowledge. My other battery charger is a one pound electronic machine. It works OK, supplies 2, 6 and 12 amps and has all sorts of buttons and lights! What it won't do is charge a totally dead battery...thus repairing the old Craftsman. It displays: "BAD BATTERY" and I have to hook-up jumper cables from another vehicle to get a few percent of a charge to get the electronic charger to work.

I also confess I don't know enough about electronics. Is there a good book to start with that isn't too stupid yet not over my head? I think I can still learn stuff.

Reply to
Carl Ijames

But past a certain point, the analogy doesn't hold water - - - - .

Reply to
clare

Water hammer, ie. the inertia of the fluid moving through the pipe. Its not a perfect analogy, but then none of this electricity is like water and pipes is perfect, but it conveys the general behavior.

Jon

Reply to
Jon Elson

Right, but if you are out in the woods with a dead car battery, you need it to pump a little current into the battery to start the voltage rising. If you get the load that drained the battery turned off, and put a couple hundred mA into it, it won't hurt anything. if the polarity is indeed wrong, the alternator diodes will keep it from rising above about 1.4 V. If the polarity is right, the voltage will keep rising, and eventually the charger will decide to let you have rated current into the battery.

Jon

Reply to
Jon Elson

If you are out in the woods with a dead car battery the limitations of an automatic charger don't matter. Revive the battery with another vehicle or a portable jump starter. jsw

Reply to
Jim Wilkins

If you're interested in battery charger electronics you can look up some voltage regulator circuits. You can use an adjustable voltage regulator, such as an LM317, by setting the output voltage to what you want the maximum charge voltage to be, you can use it to charge a lead acid battery. By adding a resistor, low ohms and enough power for an amp or so, you can have the regulator lower the charge current while the battery gets nearer to full charge, like the lead acid battery chargers do.

I read some interesting charging information about the "Battery Tender" maintenance charger, useful if you want to keep your seasonal batteries in good condition through the off season. I found a PDF file that, on page 4, shows the voltages that the battery tender operates at, "absorption charge" to 14.5 and maintenance charge of

13.2V.
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Also, something I was interested in for boat batteries. Get a gasoline small engine and mount an automotive alternator, then you can have a portable battery charger that should be capable of some fairly high current. For Gunner's 8V batteries, I read about modifying the voltage regulators for alternators (the kind that have external regulators). IIRC, the basic idea was to control the output by controlling the power going to the rotor. That way the alternator, with the right voltage regulator, could be used to charge 8V batteries on up to 48V golf cart or fork truck batteries.

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RogerN

Reply to
RogerN

If you start playing with homebrew battery chargers this is a good meter to monitor the voltage:

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Digital meters aren't reliably accurate to one count, so "13.8V" could be anywhere from 13.70 to 13.99. This one should reduce the uncertainty to 13.79 - 13.81. Mine is quite accurate but I can't promise another will be as close.

The lighter plug is safer than clip leads and you can put an outlet for it in the homebrew charger's front panel, or use the lighter outlet in the vehicle. This device is powered from the 12V input and unlike a DVM doesn't have internal batteries to run down if left on for days. It draws 8mA from the car battery, most of that probably for the display's useful backlight. jsw

Reply to
Jim Wilkins

If the second battery has a reasonable charge and the dead battery isn't shorted, it SHOULD work every time.

Reply to
clare

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