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Hi there, I have a Lambretta LI150 series 3 6v original points system, Italian. It has a battery which powers the brake light, side light and horn. Don’t use it much but the battery goes flat within a couple of hours of fitting after charging. I just took it out for a spin and the lights now only appear to work when the battery is disconnected. Wondering if it could be the regulator as at one point this for quite hot. The fuse isn’t blowing which is strange as if there was a short I would have thought this would happen. Have checked the wires and continuity to the headset which appear fine. I fitted a new switch when the scooter was rebuilt which is an original too. Hope this all makes sense, any ideas?

Sounds like the recent freezing temperatures may have damaged the battery cells which is very common. They take a charge but don't hold it long. I have my batteries fully charged and in the airing cupboard. Test the voltage across the battery.

I did charge the battery and left it a few days on its own where the charge stayed at about 6.5 volts? Am I missing something

jonalabaster wrote:Hi there, I have a Lambretta LI150 series 3 6v original points system, Italian. It has a battery which powers the brake light, side light and horn. Don’t use it much but the battery goes flat within a couple of hours of fitting after charging. I just took it out for a spin and the lights now only appear to work when the battery is disconnected. Wondering if it could be the regulator as at one point this for quite hot. The fuse isn’t blowing which is strange as if there was a short I would have thought this would happen. Have checked the wires and continuity to the headset which appear fine. I fitted a new switch when the scooter was rebuilt which is an original too. Hope this all makes sense, any ideas?

I assume that your regulator is the Ducati 6V black box with an internal fuse?
If this fuse isn't blowing it may still be getting hot if something is drawing current from the battery. Have a feel.
Does the battery connection spark when connecting it up indicating that there is a fault or something is switched on?

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this is the regulator which is the original Ducatti 6V version. Yes when the battery is connected it sparks. I'm wondering whether it could be the horn causing the issue as it is an AC horn but the wiring diagram on page 265 (Appendix 14) of Stickys shows it seems to be powered by the battery??

Cheers

I would suspect power is some how bypassing your switch and making your scoot permanently live also are you sure when it's running it producing enough power to run lights etc and charge the battery?

hi
had a similar problem with my standard 6v li150 DC
the battery would discharge quite quickly. after about three new batteries in the period of about 2yrs i bought a new regulator and have had great charge and same batt for three years or more.
you say yours has an AC horn??
should be a DC i think.
hope this helps

lam1962brettagg wrote:hi
had a similar problem with my standard 6v li150 DC
the battery would discharge quite quickly. after about three new batteries in the period of about 2yrs i bought a new regulator and have had great charge and same batt for three years or more.
you say yours has an AC horn??
should be a DC i think.
hope this helps

This seems to make most sense to me so I’ll get one ordered. The horn is the original, but I may order a new DC one as this makes sense based on the wiring diagram. Cheers

put a volt meter across the battery and rev the engine.....you should be getting a tad over 7v. if less you're regulator is suspect, likewise anything over 8v would point to suspect regulator.

Ah I see. A 4 pole system.
These old selenium based rectifiers were never very reliable any way.
If I'm reading the drawing correctly, then the headlamp is AC straight off the generator and everything else is DC via the rectifier, battery and inductor. Long time since I worked on a 4 poler so I stand to be corrected.
Rimini still do these regulator boxes for about £100. Ouch.
Perhaps you can get creative by just replacing the old selenium rectifier array with a more modern silicon rectifier diode. Maybe something like the RS Stock No.544-5802 can be successfully grafted in its place? Less than £3. Gotta be worth a try.

MickYork wrote:put a volt meter across the battery and rev the engine.....you should be getting a tad over 7v. if less you're regulator is suspect, likewise anything over 8v would point to suspect regulator.

Ok tried this and the battery (which is now charged) stays at 6V doesn't move. Thanks for the advice, new rectifier on order. Cheers

Fast n Furious wrote:Ah I see. A 4 pole system.
These old selenium based rectifiers were never very reliable any way.
If I'm reading the drawing correctly, then the headlamp is AC straight off the generator and everything else is DC via the rectifier, battery and inductor. Long time since I worked on a 4 poler so I stand to be corrected.
Rimini still do these regulator boxes for about £100. Ouch.
Perhaps you can get creative by just replacing the old selenium rectifier array with a more modern silicon rectifier diode. Maybe something like the RS Stock No.544-5802 can be successfully grafted in its place? Less than £3. Gotta be worth a try.

Love the idea, having looked at this I think this may be above my pay grade on grafting it onto the existing wiring loom. The £3 price tase looks much more welcoming than the new rectifier though . Is it simple to graft this on?

Thanks again for all the help

It would need a little revision to my earlier statement but yes its easy enough to do with some basic tools.
The rectifier is the bit made up of multiple stacked plates. This bit needs to be removed leaving the 2 connections ready to connect to the new rectifier.
The original rectifier was connected up as 4 stacked diodes in a series /parallel arrangement as shown in sticky's manual.
Selenium diodes could only handle about 20 volts so they connected 2 in series to handle the incoming voltage with 2 in parallel to handle the current.
These diodes would have a forward voltage drop around 1 volt. So 2 in series would drop about 2 volts.
Modern Silicon diodes only drop around 0.6 volts. So if the same arrangement was made using silicon diodes then the output voltage would be a little higher.
From a practical point of view it would work better to use a bridge rectifier ( RS Stock No. 145-1568 ) as these can easily be mounted with a nut and bolt. (This is the same bridge rectifier as used with some Lambretta 12v positive earth conversions.) This rectifier has 4 tabs. Forget the AC connection tabs and just tape these up to insulate them as they wont be needed. Connect the wire that leads to your generator to the negative terminal of the bridge and the other wire to the positive side of the bridge.
Check the voltage across the battery with the engine revved up. If it doesn't exceed 7.5volts then it will be ok and not cook your battery.
Gotta be worth a try for less than a fiver.

Thanks for all the help will try the RS option first

I tried a test tonight. I disconnected all wires from the rectifier then added one back at a time to see which one led to the sparking when the battery was connected. It appears to happen when I connect the brown lead which comes from the Stator plate to the rectifier. When I connect any of the other leads individually there is no spark but the battery circuit works for brake light etc. It's only when connected to the stator that the sparking happens.

This is all with the scooter turned off though, I guess this still points to the rectifier as this connects to the battery through the rectifier to the brown wire of the stator and I guess indicates the diodes are letting current through incorrectly?

I did take the rectifier apart when I assembled the Scooter, however this was over a year ago so would have thought I would have had problems sooner if I had put it together incorrectly?

Cheers all

Wierd, stripped Rectifier. Jiggled it a bit (technical term) put back together and now there is no longer a short. I guess this is why I love Lambrettas

Unfortunatley, Lambretta's do have nasty habit of unjiggling jiggled fixes.