Battery drain

[Mollbhan]

I have a 48 G80 fairly recently overhauled and acquired by me. The battery (new) will drain completely flat in a few days because of the current drain through the wassell rectifier, a new rectifier did not help, wiring seems fine and the battery charges ok, disconnecting the live wire to the rectifier will stop the drain. Is this just a consequence of fitting modern electronics to a simple antiquated system?

[g80csp11]

Id start by disconnecting the red and black lead from the rectifier unit , charge the battery and see if it still goes flat
That will eliminate the charging system
check that your stop light switch is not stuck on as that is normally connected directly to the battery and will not show on the ammeter

a start then you know where to loo

[clive]

The Walsell rectifier (voltage control unit?) Will be feeding power through the dynamo primary field. It does not take much but enough to flatten the battery in a few days. The original voltage controller disconnected the battery when the revs dropped. Other makes of electronic unit also do so. Easiest and cheapest solution install an on off switch next to the battery in the circuit and remember to switch off. Probably safer too.

[Groily]

This isn't a problem confined to dynamo systems though - for a long time the regulator / rectifier supplied with the widely-acclaimed Alton alternator allowed some of the same, until a better unit was adopted a few years back. In those cases, a switch was essential, they say.

I have been using Altons for about 30 plus years. The wiring diagram was clear from the outset that you needed to switch off when storing the machine. By and large they have been very long lasting if expensive to purchase. There was a period when the plastic internal gears were not up to the job, long since redesigned. I am still using the one that I first bought after reconnection of an internal wire that broke. I have gone through a number of dynamos on other bikes during this time and the repair costs are probably comparable!

[jackstringer]

Could a relay not be a better option rather than a switch. Though it does add a layer of security.

EDIT: Though it looks like Lucas SSB103 might suit as period looking type switch. Supposedly an battery isolator switch for an Austin.

[clive]

I have been using Altons for about 30 plus years. The wiring diagram was clear from the outset that you needed to switch off when storing the machine. By and large they have been very long lasting if expensive to purchase. There was a period when the plastic internal gears were not up to the job, long since redesigned. I am still using the one that I first bought after reconnection of an internal wire that broke. I have gone through a number of dynamos on other bikes during this time and the repair costs are probably comparable!

[Groily]

Summat odd has happened here Clive with our texts muddled, bits disappeared and quotes not highlighted. (I've never had an Alton - let alone for 30 years!)

But yes, nothing whatever against Altons in case you thought I was picking holes in what was just an aside really about battery cut-outs, as this is a dynamo regulator problem, not a rectifier thing.
Loads of Altons out here in the land of their birth and they work a treat. Many friends swear by, etc.

[clive]

Weird or what Groily. I am a moderator and must have pushed the wrong button! Apologies

[Mollbhan]

There seems little doubt that the battery drain is taking place somewhere in the charging system, I will fit an on off switch on the handlebars taking a lead from the ammeter, that should isolate the rectifier. Thanks for the advice.

[Radcap]

I have a similar problem.
I built my own loom and have 3 fuses.
One for charge circuit
One brake light
One for other lights.
My drain is via the dynamo.
I remove the charge circuit fuse if im not using the bike for a few days.