If this post looks familiar to some of you, that is because I previously put it up on the picoauto.com board.

I am trying to get a charge reading on an old (1953) Chevrolet truck with a 6 Volt system. I am using a Picoscope 4425 with TA167 probe, set to 200 Amp scale. Pattern shows an average reading of 100 mV, which as I understand it translates to a charge rate of about 10 Amps. I suspect I am not getting much out of the generator/regulator combination but this seems awfully low. Am I looking at this correctly?

I do understand that the Pico software may not be compatible with the old systems, but would like to make it work if possible.

Here is what the pattern looks like:

https://photos.smugmug.com/Cars-and-Trucks/Trucks/53-3100-Truck-Shared/i-hztGBZq/0/628f4f8a/M/IMG_5540-M.jpg

Any help or suggestions greatly appreciated!

Bruce Jones wrote on Oct 23^rd, 2020 at 8:56am:

I do understand that the Pico software may not be compatible with the old systems, but would like to make it work if possible.

Bruce, not a software engineer but doubt it cares if it is an old system. I have used it on skylite openers at work to test the MA draw on our openers, low voltage batteries, but again JMO.?

Maybe another channel also adding voltage. Don't know much on 6 volts, had an NAA tractor but did not put out much more than 8 when charging as I recall. Most 12 V run high 13 or 14, not sure on this?

Larry

Bruce Jones wrote on Oct 23^rd, 2020 at 8:56am:

If this post looks familiar to some of you, that is because I previously put it up on the picoauto.com board. I am trying to get a charge reading on an old (1953) Chevrolet truck with a 6 Volt system. I am using a Picoscope 4425 with TA167 probe, set to 200 Amp scale. Pattern shows an average reading of 100 mV, which as I understand it translates to a charge rate of about 10 Amps. I suspect I am not getting much out of the generator/regulator combination but this seems awfully low. Am I looking at this correctly? I do understand that the Pico software may not be compatible with the old systems, but would like to make it work if possible. Here is what the pattern looks like: https://photos.smugmug.com/Cars-and-Trucks/Trucks/53-3100-Truck-Shared/i-hztGBZq/0/628f4f8a/M/IMG_5540-M.jpg Any help or suggestions greatly appreciated!

Define your probe as a current probe and you will see the actual current
Do not forget to zero your probe

Bruce Jones wrote on Oct 23^rd, 2020 at 8:56am:

If this post looks familiar to some of you, that is because I previously put it up on the picoauto.com board. I am trying to get a charge reading on an old (1953) Chevrolet truck with a 6 Volt system. I am using a Picoscope 4425 with TA167 probe, set to 200 Amp scale. Pattern shows an average reading of 100 mV, which as I understand it translates to a charge rate of about 10 Amps. I suspect I am not getting much out of the generator/regulator combination but this seems awfully low. Am I looking at this correctly? I do understand that the Pico software may not be compatible with the old systems, but would like to make it work if possible. Here is what the pattern looks like: https://photos.smugmug.com/Cars-and-Trucks/Trucks/53-3100-Truck-Shared/i-hztGBZq/0/628f4f8a/M/IMG_5540-M.jpg Any help or suggestions greatly appreciated!

Define your probe as a current probe and you will see the actual current
Do not forget to zero your probe

Thanks for the advice Logic and StitchB.  When adding a second channel trace I get about 7.5 volts at the battery.

I checked the charging current with my inline tester and got pretty consistent results, so I believe I am close on my interpretation of the scope trace.

https://photos.smugmug.com/Cars-and-Trucks/Trucks/53-3100-Truck-Shared/i-hmxSPPF/0/96ee4ee1/M/IMG_5619-M.jpg

I think the strange pattern on the Picoscope is a reflection of arcing at the brushes in the generator.

Bruce Jones wrote on Oct 24^th, 2020 at 1:19pm:

When adding a second channel trace I get about 7.5 volts at the battery.

Bruce, never was aware of it till late but a lot of folk still use 6 volts here ran in series on some systems here in the farm rigs and motor homes. Until I owned the tractor had no intro to them and on the tractor positive ground, still makes me scratch my head some.

So thanks for the post, and would be curious what the voltage is at the Gen and not the battery. But again not around them a lot, 7.5 sounds pretty good IMO.

Larry


'

Is that photo a pattern of key on, cranking, revving??

6V is very inefficient i.e. low voltage and high current

So if you have 7.5V above idle it's good. Some I used to adjust to 7.5-8V just so the lights are brighter

Have you thought of clamping the battery lead off the generator?? to see true output

And if you suspect brushes are worn, not sure if there's a inspection hole in the generator to see if there's arcing inside

Good luck with these old systems

P.S. love the old snappy MT500, haven't seen one is ages

autosparky:

That is the pattern taken from the BAT lead off the regulator, during crank (big dip at the start) and run at about 600RPM.

Generator is Delco 1100018, and regulator is Delco 1118827, which are the correct ones for my 1953 Chevrolet 1/2 ton truck.  The output capacity of the pair (per original specs) is a maximum of 45 Amps.

Voltage at the generator is 7.4V at 600 RPM.  Same at battery.  Could be a little higher I guess, but I am not real concerned because the truck cranks right up.  Having #1 gauge battery cables doesn't hurt.

I am guessing the reason for the low amperage reading I am getting is the fact that the battery is fully charged (6 Volt Optima red-top).

Yes, the MT500 is a dandy unit.  Just got to keep a supply of fresh 9V batteries handy!

Thank you for getting back to me.