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Old car weirdness
Mr Whippy - 19/8/23 at 04:57 PM

Hi,

So on the ancient one, the electrics are a bit wonky. It's a great combination of no proper current regulation (movable 3rd brush nonsense), a generator that doesn't produce anything on idle (about 10amps peak) and 6v electrics. It's the same setup on later Model T's which is a bit shameful for car of the 30's, bad Ford, you total cheapskate!

Due to the lights being like candles I got LED headlights but these flicker and flash quickly at idle but are steady at higher speeds. What's got me confused is when I put the multi meter over the battery instead of showing 6 or 7 volts, it goes nuts just all over the place. I can't understand how the voltage is varying so much and when I test it on the Fiesta its normal, even at faster speeds the voltage reads (on is not reading) the same dumb thing. Obviously not many people will have experience with such systems but I have to admit am I bit lost.

If anyone has experience with this crappy system and what's going on, ideas would be appreciated. Thanks.

40inches - 19/8/23 at 06:09 PM

How about a 6 volt alternator (ducks for cover )
https://www.instructables.com/Install-a-6-volt-alternator-on-your-old-car/

smart51 - 20/8/23 at 08:14 AM

LEDs will cut off quite sharply if the voltage drops too low, where incandescent bulbs "slur" the voltage dropouts somewhat. You could see if you can find some LEDs with a lower minimum voltage, that might be the easiest solution. Another would be to fit a secondary battery to power the lights. You would feed that through a diode from the main battery. That would hold up the voltage a bit. Find a diode with a very low forward voltage.

gremlin1234 - 20/8/23 at 08:37 AM

are you trying to use led headlights designed for a 12v system?

you can get them designed for 6v working
maybe look for some motorcycle ones
or
https://www.classiccarleds.co.uk/collections/6-volt-collection

obfripper - 20/8/23 at 01:49 PM

Have you tried your meter in a manually set range (the unstable voltage can confuse some meter autoranging), or with an averaged display mode (not all meters have this function), or borrow a moving coil type meter, as this will damp any jitter in the voltage due to the cutout.

There is no output regulator with this type, but there is an upper voltage cutout, if this is set incorrectly or has contact corrosion/wetting/arcing damage it will cause under/over charging issues.
I would estimate this to be set for a max of 7.2v (older manuals will probably give a higher voltage, but this will slowly kill your battery), and should buzz when the engine is revved with the charging system not under load, but be quiet with the engine at idle and a load present.
It's of the age that the cover should be removable for servicing/adjustment, most of the above faults can be rectified or adjusted out.


Dave

Mr Whippy - 20/8/23 at 04:29 PM

quote:
Originally posted by smart51
Another would be to fit a secondary battery to power the lights. You would feed that through a diode from the main battery. That would hold up the voltage a bit. Find a diode with a very low forward voltage.


I was thinking something along those lines myself but had not considered a diode with the additional battery. Funnily enough I have a couple of 6v gel battery's spare for my rc boats, so may give this a go first. The LED's are special 6v versions and probably work fine on cars with regulators. The voltage cutout is working fine and the battery is charged well with no signs of over charge. It's the sudden drop at idle that seems to be the problem and how to keep the voltage up for the LED's when the generator isn't charging.

Mr Whippy - 20/8/23 at 04:32 PM

quote:
Originally posted by obfripper
Have you tried your meter in a manually set range (the unstable voltage can confuse some meter autoranging), or with an averaged display mode (not all meters have this function), or borrow a moving coil type meter, as this will damp any jitter in the voltage due to the cutout.

There is no output regulator with this type, but there is an upper voltage cutout, if this is set incorrectly or has contact corrosion/wetting/arcing damage it will cause under/over charging issues.
I would estimate this to be set for a max of 7.2v (older manuals will probably give a higher voltage, but this will slowly kill your battery), and should buzz when the engine is revved with the charging system not under load, but be quiet with the engine at idle and a load present.
It's of the age that the cover should be removable for servicing/adjustment, most of the above faults can be rectified or adjusted out.


Dave


I was wondering if a coil meter would behave a bit better. My digital ones are quite cheap so I don't have any special features. I don't think its over voltage as the battery is doing very well. Thanks for the suggestions.

coyoteboy - 21/8/23 at 01:28 PM

Instead of a battery, just drop in a big 1F capacitor like the audio guys do. You're just trying to flatten the ripple/drop-out, not power something long term.

That said, if you're using a battery (as opposed to some other strange archaic system I'm not aware of) you should have a smooth voltage at the battery regardless.

[Edited on 21/8/2023 by coyoteboy]

gremlin1234 - 21/8/23 at 03:08 PM

quote:
Originally posted by coyoteboy
Instead of a battery, just drop in a big 1F capacitor like the audio guys do. You're just trying to flatten the ripple/drop-out, not power something long term.
[Edited on 21/8/2023 by coyoteboy]

I think 1F is overkill, a 1,000uF electrolytic across the meter should be fine for smoothing changing dc Volt readings.

coyoteboy - 21/8/23 at 03:20 PM

quote:
Originally posted by gremlin1234
quote:
Originally posted by coyoteboy
Instead of a battery, just drop in a big 1F capacitor like the audio guys do. You're just trying to flatten the ripple/drop-out, not power something long term.
[Edited on 21/8/2023 by coyoteboy]

I think 1F is overkill, a 1,000uF electrolytic across the meter should be fine for smoothing changing dc Volt readings.


I wasnt talking about the meter, I was talking about his original problem with headlights flickering and I suspect a 1000 mic is too small to deal with that.

Ultimately though I think it has a bigger problem if the voltage variance is so pronounced.

[Edited on 21/8/2023 by coyoteboy]

gremlin1234 - 21/8/23 at 03:31 PM

quote:
Originally posted by coyoteboy
quote:
Originally posted by gremlin1234
quote:
Originally posted by coyoteboy
Instead of a battery, just drop in a big 1F capacitor like the audio guys do. You're just trying to flatten the ripple/drop-out, not power something long term.
[Edited on 21/8/2023 by coyoteboy]

I think 1F is overkill, a 1,000uF electrolytic across the meter should be fine for smoothing changing dc Volt readings.


I wasnt talking about the meter, I was talking about his original problem with headlights flickering and I suspect a 1000 mic is too small to deal with that.

Ultimately though I think it has a bigger problem if the voltage variance is so pronounced.

[Edited on 21/8/2023 by coyoteboy]

yes, I agree
1000uf would only work for making the meter easier to interpret,
and yes 1F might help overall, but better to find/solve the underlying fault.

edit, we have been approaching this from different directions, which is what technical forums like this are useful for ;-)

[Edited on 21-8-2023 by gremlin1234]

Mr Whippy - 21/8/23 at 04:01 PM

Thanks for the info. However its not really a fault as such but only what happens when it tries to run LED's, with the normal dull bulbs there's no flickering as they take so long to respond. Its a crazy old system, long since abandoned for many good reasons Unfortunately just converting it to a regulator system, heaven forbid 12v's would cost several hundred.

coyoteboy - 22/8/23 at 05:52 PM

quote:
Originally posted by Mr Whippy
Thanks for the info. However its not really a fault as such but only what happens when it tries to run LED's, with the normal dull bulbs there's no flickering as they take so long to respond. Its a crazy old system, long since abandoned for many good reasons Unfortunately just converting it to a regulator system, heaven forbid 12v's would cost several hundred.


I don't think it's normal to have that much variation, your incandescent won't last long even if they do have enough thermal mass to stay lit. I really wouldn't expect that much variation unless the battery is gunned or the connections are high resistance. Even with poor alt regulation of expect the battery to carry the bulk of the spikey loads and hold the voltage up. But then wee 6v batteries are only small I suppose.

Mr Whippy - 23/8/23 at 12:09 PM

quote:
Originally posted by coyoteboy
quote:
Originally posted by Mr Whippy
Thanks for the info. However its not really a fault as such but only what happens when it tries to run LED's, with the normal dull bulbs there's no flickering as they take so long to respond. Its a crazy old system, long since abandoned for many good reasons Unfortunately just converting it to a regulator system, heaven forbid 12v's would cost several hundred.


I don't think it's normal to have that much variation, your incandescent won't last long even if they do have enough thermal mass to stay lit. I really wouldn't expect that much variation unless the battery is gunned or the connections are high resistance. Even with poor alt regulation of expect the battery to carry the bulk of the spikey loads and hold the voltage up. But then wee 6v batteries are only small I suppose.


No it's not normal at all, unless you have a dynamo with 3 brush pickup and no regulator I've found a good website that explains how convert the existing dynamo to use a regulator and that's probably the best solution. will let you know if it works

Thanks.