DC Voltage Output

[StarTech]

That one thing Briggs doesn't do and that is to keep charts and service manuals up to date. That's why I posted the supersede list so each of the previous number could be check against the chart. Some of the service info has been outdated for some time.

In this case it is just better to install a 9+ amp AC stator and used the rectifier/voltage regulator if the customer is wanting to do anything other than recharge the battery. Something like the tri circuit stator.

It is like the Briggs engine spec charts that are out of date. I have a personal copy of the non Vanguard chart that I have made numerous notes on as new updated SB and DSB info was published.

 

[Fish]

I call them "vrrrroooom meters".....

 

[Telesis]

With all do respect to txmowman and ozpete, it is not true that all alternators put out 26v minimum. One need only look at the chart I shared earlier, and specifically the 3rd row. You will note that the AC voltage output is shown in the chart. Those 4 put out 14VAC at WOT. If you'd like a more complete discussion, please refer to the excellent B&S "Engine Alternator Repower Guide". Just Google that and look on page 10 of the manual. [I didn't include a link because who knows how long it would be good for!] That section discusses testing AC voltage output of the various alternator types. The table on p 10 shows the wide range of voltages, depending on type. This is my 'go to' manual for all things 'alternator-related' for B&S engines.

[the manual is too big to upload here and I was not able to successfully open any of the manuals in Rivets' link provided in an earlier post. probably just 'old-man' syndrome on my part, lol!]

FWIW! Merry Christmas to all!

 

[bertsmobile1]

That one thing Briggs doesn't do and that is to keep charts and service manuals up to date. That's why I posted the supersede list so each of the previous number could be check against the chart. Some of the service info has been outdated for some time.

In this case it is just better to install a 9+ amp AC stator and used the rectifier/voltage regulator if the customer is wanting to do anything other than recharge the battery. Something like the tri circuit stator.

It is like the Briggs engine spec charts that are out of date. I have a personal copy of the non Vanguard chart that I have made numerous notes on as new updated SB and DSB info was published.

Alternators were another "mystery to me " when I kicked off.
However while the part numbers are allover the place, the colour codes are fairly consistent so the chart was printed out A2 size, laminated & stuck on the inside door of the electric stuff cupboard
So I can work out what stator goes on which mower.
However I only stock two B & S stators , the late model 9 amp & 20 amp
If a replacement stator is required then I upgrade most of the unregulated ones to current regulated specs which down here is cheaper than chasing up old duel or tri circuit stators

 

[txmowman]

With respect to Telesis, it was a "minimum" of 26 volts. Charging coils are limited by the size of the windings, the number of windings, the magnet strength and the rotating speed of the magnet. Unregulated is typically 30 to 40 volts, AC. It is then the regulators job to rectify to DC and charge the battery. When the battery is charged, the DC voltage goes to ground.

 

[txmowman]

The minimum is 26 volt because when converted from AC to DC, the voltage is cut in half. Half of 26 is 13, obviously. 13 volts is more than the 12.7 (roughly) to fully charge the battery. Typical DC from the regulator is in the 14 volt +/- area. Most regulator specs are up to 15 volts max.

 

[StarTech]

Well trying to explain this is going to be well over the heads of most. Plus it take several days of reading on my part to fully familiarize myself with the formulas (heck it been 40+ yrs since I knew these by heart.) But I do have my ARRL manuals on the shelf for reference

But txmowman your understanding of rectified DC circuits is lacking. Even your theory is off several volts. You got RMS voltages being converted to pulsing DC voltage ((0V to peak (RMS - rectifier voltage drop). First you must consider peak AC voltage, voltage drop the rectifier, the capacitance in the load, along with other factors.

Here is an example of what is actually at your 120 vac wall plug. It varies from zero to about 170v peak (or about 340 volts peak to peak) 60 times a second or 50 times a second outside the US. This why it can easily kill you along the amp capacity.

The reason Briggs don't give a voltage rating is that an unregulated DC circuit voltage is quite varied depending a which factors are present at the time of the voltage measurement.

 

[Hammermechanicman]

What really happens is the spinning magnets are giviving a motivational speech to the electrons which makes them march back and forth and the diode picks out the good ones from the bad ones while the full wave regulator converts the ones with bad karma to good ones and then tells them all to go wait in the battery. It's not that complicated.

 

[StarTech]

Then comes along Covid-19 and some are just dropping dead along the way so they can't volt even if they make it to storage.

 

[Telesis]

Just to be clear txmowman, please take a look at the references I cited. They specifically state those particular units put out unregulated 14VAC. That's the stator output prior to any rectification or regulation. As Star indicated, your meter typically is reading RMS (root mean square) volts. [It may or may not be 'true RMS' depending on the quality of the meter, a detail that's not extremely relevant here. There is also something called 'average volts' which is also a detail we'll leave out here for brevity]

To convert from RMS volts to peak (of the AC) volts, you multiply by 1.414, which is the square root of 2. [I'll leave the formula details out] So, 14 x 1.414 = 19.8 (Vp) What that means is the unregulated AC voltage coming out of the stator goes from 0 to a positive peak of 19.8 volts down to 0 continuing to a negative peak of -19.8 volts and back to 0 in a sinusoidal fashion before being rectified and/or regulated. So Vp-p (voltage peak to peak) is 19.8 x 2 = 39.6 VAC

Again as Star indicated, the 120VAC you measure in your home is an RMS value. To find the peak(Vp), 120 x 1.414 = 169.7. Vp-p = 169.7 x 2 = 339.4

What does all this gibberish mean? Simply that a stator that puts out an unregulated 14VAC can be simply half-wave rectified with a single diode and with that 19.8 volt pulse, be able to charge a battery. There are caveats to this again which are beyond the scope of this discussion but suffice it to say this is the typical configuration used in the lower charging current (3 amp) systems.

Hope this helps!