MTFCA Forum

Following the discussion about using the magneto to charge battery, why can't a wire resistor of equal cold resistance of a 1156 12.8 volt bulb be used? As for overload or short protection a fuse in series. The diode from google search, is a 1N5402 diode which is rated at 3 amps and 200V peak repetitive reverse voltage.

3 amps is a bit lite. 5 amps would be a minimum in my mind. The units I have built put out 3-4 amps from a hot magneto.
I also used both filaments or they blew bulbs.

Ron Patterson's or John Regan's answer at the end of this thread answers the question as to why a bulb and not a resistor: https://www.mtfca.com/discus/messages/4 ... 1416288062

Scott_Conger wrote: ↑

Thu Aug 03, 2023 2:49 pm

Ron Patterson's or John Regan's answer at the end of this thread answers the question as to why a bulb and not a resistor: https://www.mtfca.com/discus/messages/4 ... 1416288062

This doesn't answer my question. There are industrial grade resistors that will change resistance - temperature variables - as variables change. Also what is the average life of a 1156 used a a current limiter?

Bulb life?
I have one on my T that has not been replaced yet.
Around 10 years.

This doesn't answer my question.

actually, Patterson's and Regan's answers answer your question EXACTLY, and very directly, about the use of a fuse rather than a bulb and why it would be a terrible if not completely ineffective choice.

I can only lead the horse to water...

I can only lead the horse to water...

Yes, but some time, that wack with a 2x4 (not one of those 1.5″ x 3.5″), can make a difference.

So, what is the life or hours of a 1156 as a current limiter?

So, what is the life or hours of a 1156 as a current limiter?

Excluding infant mortality, I think that would be entirely dependent on the current input, and it would be a current limiter right up to the point of failure - unlike a fuse, which can potentially allow a significant though brief surge of current before failing.

In a functional circuit and no problems as mentioned above, John has given some idea as to what can be expected.

FWIW - Per John's statement, at least as of 2014 when he made it, his kit did not use an 1156 bulb

I'm not sure I want any part of this fireplug as no one has expressed a goal on this lamp life thing...but for the sake of maybe helping, here goes.

Just looking at the lamp it's the voltage that goes through it that determines life...the amps are not necessarily the first order failure.

Lamp life and everything associated with lamp characteristics do NOT follow straight line calculations. There are some plug-n-play calculators to help with the variables question. Some lamp house offer 3-D interactive charts to make guesses.

I'm a simple guy...I'll use the format for 'rerates' from the 1930's before all of the PhD's chimed in. This is how all of the WW2 airplanes were 'rerated' for life, illumination, amp draw, etc when there were limited lamp choices and lots of voltage choices.

The chart may help the OP in his quest. A quick comment on an 1156. --- At 19V of Magneto, lamp life is statistically ZERO...like in poof (and why magneto rated lamps never really working in the first place) . The original rated current had increased by 25% and the illumination was 4 times greater than at control voltage.

This 'calculator' for rerating is what was used at the Naval Research Center...all of the Anti-Submarine Projects, all of early LAMPS projects, the original and subsequent Centrifuges, etc. There are other 'theories' and other 'publications'...I always use this one!

(PS...tongue in cheek, but also true from a differing angle...go with a 12V nominal LED equal to 1156. The forward voltage to fire should become stable at 10V on, and not flicker until it sees perhaps to 30V??????

Really, George, did you really even remotely suggest an LED in place of an incandescent light bulb in the charger circuit? I realize that you said "tongue in cheek" but then immediately followed up like it was a viable alternative. Of the 2 jobs that bulb is doing, neither is "light" and as for the 2 jobs it is supposed to do, an LED doesn't remotely compare in resistance or current attributes that exist in the incandescent bulb.

I'm really wishing I had not weighed in on this in the first place, but since I did, I'll leave with this:

For future readers - I am not an electrical engineer, but the guy who designed the circuit is - he has explained in plain and simple language how it works and what it does, and why the incandescent bulb he chose accomplishes those tasks. His words are expressed succinctly in the thread I posted above. Based on his words and description, I would say: "no, replacing the lightbulb on a MAG charger circuit with an LED is not an advisable thing to do"

Hold on. May be George M. has a point.

When the supply of incandescent 1156 bulb are depleted what will be a replacement?

There are 1156 LED bulbs available. And by design they have a current limiting resistor.

"The 1156 single-contact bulb uses powerful LEDs to emit up to 420 lumens of illumination. LEDs are covered by a plastic lens. It has a tower-style design with a BA15S 15-mm bayonet base for easy plug-and-play installation—just twist to lock in place. The energy-efficient LED bulb uses only 3 watts of power."

I’ve been using just a diode on my 13 to charge the battery. I’m running a “Tru-Fire” ignition and signal and brake lights. Charging a “Seadoo” battery.

Les Schubert wrote: ↑

Fri Aug 04, 2023 1:13 pm

I’ve been using just a diode on my 13 to charge the battery. I’m running a “Tru-Fire” ignition and signal and brake lights. Charging a “Seadoo” battery.

Well, thats interesting.

What does you magneto put out voltage wise pre diode?
What voltage battery? How many amps charge?
Doesnt the light bulb regulate the amperage down to a safe & sane level?
Is your mag output weak to the point regulation is not necessary?

As an electronic simpleton with severe MEGO, the magneto battery charger was easy for me. I just did what John Regan said.

Will the 6 buck generator cutout diode sold by model t parts suppliers work in the battery charger application.

Art Mirtes

I am about to find out and do not see any reason why it should not work.

There is a 1156 bulb in the light.

J1MGOLDEN wrote: ↑

Fri Aug 04, 2023 6:02 pm

I am about to find out and do not see any reason why it should not work.

Jim,

I see some lettering on that diode - any chance you could let us know what it is?

FYI the ideal 'cutout' diode would be a mid to high-current schottky type, which is not the right thing for your half-wave magneto rectifier.

Luke.

FYI
I made one of John's Chargers per his sketch years ago. It worked quite well....UNTIL -- I inadvertently let one of the wires rest on top of a spark plug wire. (I have my device under the hood, not wanting to be distracted watching the 1156 bulb increase and decrease in brightness with the revolutions of the engine).
Anyway...the diode was fried.
Bought a new diode....pretty inexpensively, I think (I read Steve J's posts intently)
Diode is 6 A10 DC from MGS Max Gain Systems, Inc. https://mgs4u.com/product/6-amp-1000-volt-diodes/

BEWARE: keep the "device" wires as far away from the Hi Voltage spark plug wires as possible, otherwise you'll fry a $.40 DIODE AS I DID.

As cheap as the diodes are, I'd be inclined to take 4 of them and connect 2 pair in paralell and then connect both pair in series. I'd use the 1157 bulb varistor set up and clip a spare bulb to the assembly.

Holy cow, you guys are working awfully hard at "improving" a two component design that already has proven outstanding field service life and essentially idiot-proof safety parameters.

Doesn't gravity need improving or something else that all mankind can make use of? I hear the Monongahela Iron Ingot factory is looking for an improved iron ingot design

A lot of effort and technology has been devoted to countering or even canceling gravity.

As for iron ingots, isn't it time that iron "pigs" actually look like pigs?

Scott_Conger wrote: ↑

Fri Aug 04, 2023 9:53 pm

Holy cow, you guys are working awfully hard at "improving" a two component design that already has proven outstanding field service life and essentially idiot-proof safety parameters.

Doesn't gravity need improving or something else that all mankind can make use of? I hear the Monongahela Iron Ingot factory is looking for an improved iron ingot design

Interesting statement about "improving" designs.

Not to take away from Ron Patterson's etal two component design, but a review or a Electronics Illustrated, January 1967, article about low cost battery chargers, there is a discussion about constructing a small battery charger using a diode and either a light bulb or a resistor as a current limiter. If interested pages 74-77. Oh, the author was Herb Freidman.

Wasn't the ECCT an improvement over a tried and tru HCCT or the Buzz Box? And yet I still stand behind the simple non chipped Buzz Box.

I've used an 1157 bulb and socket to charge small lead acid and Li batteries using older battery chargers that lack appropriate settings for such batteries.

With a discharged battery, the bulb glows bright and as the battery comes up to charge, the bulb goes dim.

I use a tail/brake light socket, which is convenient and which also allows choosing 3 different charge rates:
High, using both filaments.
Medium, using the brake light filament.
Low, using the tail light filament.

The Diode is a 1N1183A and the one that Snyders was selling as a kit with directions and may still sell.

The earlier editions of the MTFCA Electrical book also had that one, if I recall correctly.

Later editions deleted it!

With this one the current flows in the direction of the arrow.

Some of the older other diodes had the current flow opposite of the arrow direction.

I made several Model A Diode Cutouts before I recognized my problem.

I didn't, but John Regan told me, I had to read the diode spec sheet for each diode type.

An original ammeter with two short test leads can be used for a quick test to identify the diode polarity issue.

You clip one lead to the yellow battery wire.

You clip the other lead to the Bat terminal on the Cutout or the connection from the Mag.

If there is any current flow showing on the ammeter, your diode is in backwards and has to be reversed or your battery is in backwards with a positive ground and has to be reversed.

An original ammeter with two short test leads can be used for a quick test to identify the diode polarity issue.

You clip one lead to the yellow battery wire.

You clip the other lead to the Bat terminal on the Cutout or the connection from the Mag.

If there is any current flow showing on the ammeter, your diode is in backwards and has to be reversed or your battery is in backwards with a positive ground and has to be reversed.

I use a $9 H/F meter, Check with the red/black leads, reverse them . That will tell you flow direction.

J1MGOLDEN wrote: ↑

Sat Aug 05, 2023 10:29 am

The Diode is a 1N1183A and the one that Snyders was selling as a kit with directions and may still sell.

Thanks Jim,

That diode has vastly more capacity current-wise than is needed, however it's potentially close to spec from a (reverse) voltage perspective. While it'd probably work ok it isn't what one would normally specify for the task you're wanting it to employ it in - those that Dave showed would be more like it.

Interestingly it's not necessarily ideal for a 'cutout' diode either. To be clear, it's not that it won't do the job and I'm certainly not advocating you throw it away, however it will have more loss and could generate more heat than you'd get from a schottky type. On the other hand given the relatively low currents involved it's hardly likely to matter much, and I expect they're cheap and plentiful (and robust) so there are compensatory factors

Luke.

I am planning to try a diode from a GM alternator. They seem to be robust and reliable. I haven't seen one fail since the 1960s. Does anyone we forsee any problems.

Art Mirtes

Art,

Without a part number it's not possible to say definitively but it's likely to be capable of handling the current draw, whether it'd cope with the reverse voltage over time is perhaps less certain.

Like JIm's component most of these diodes are designed for high-current but low-voltage use, whereas in the case of a magneto charger you have low-current, with a higher applied voltage. It's not a particularly high voltage in the grand scheme, but let's say you get to 30V or 40V input, and/or there are a few spikes on the line as a result of the T's generally harsh electrical environment, and you apply this to a diode that's only rated for say 50V, you're getting uncomfortably close to its maximum...

In circuit design it's normal to over-specify such components in order to allow a healthy margin and ability to cope with minor events where things exceed expected parameters for a brief period. If you've a component that's only just rated for the regularly applied voltage it could well deteriorate over time and fail prematurely.

In your case the diode may be fine, but you need to bear in mind that in its normal environment it wouldn't be anticipated to have more than say 18V applied to it, certainly not twice that. To be sure, if you were able to let us know the part number it may be possible to check the rating to see if it'd be ok for your proposed use.

Luke.