Charging problem with cyclon battery

[bikerbob]

I have an A7 1956 which was not charging, problem initially was the dynamo but that is now sorted and dynamo is now giving out correct power. It was still not showing a charge on the ammeter this was down to the previous owner getting the D&F terminals mixed up on the voltage regulator sorted that out yesterday and was showing a good charge on the ammeter with the lights on. Today went out started the bike and no charge showing on the ammeter switch the lights on and they are very bright ammeter struggles to stay on the positive side with increased revs. With the engine stopped the lights are dull particularly the front side light but comes bright with the engine running the headlight becomes dull and then really bright with engine running depending on the revs. Now it has a Cyclon battery fitted 6v-8.0Ah and the reading from the battery off the bike is 6.38volts with a multimeter, when on charge with a motoblat charger it is reading 7.28 volts is this normal and is the problem a battery one or a voltage regulator one the regulator is new. Thanks

[a101960]

You do not say what type of regulator you are using.  If you are using a mechanical regulator be aware that Cyclon batteries are not suitable for use with these chargers. Cyclon batteries should be charged with an electronic regulator. How are you measuring your charge rate? I assume you are putting a multi meter across the battery terminals with the engine running. A reading of around  6 .3 volts for a fully charged 6v battery with no load on it is about right. You should see between 6.8 and 7v when the engine is running on fast tick over. A mechanical regulator cut out should operate between  6.3 and 6.7 volts according the BSA service sheet. Outside of those limit’s the cut out will need adjusting. The cut out operating voltage is determined by measuring the output voltage of the regulator at terminals E &D on the regulator. If your battery is fully charged then the ammeter will not indicate a charge until the battery voltage drops below the threshold  of  6 volts. However, from what you describe it would seem that the charging circuit is doing its job. I would suspect that the battery is unserviceable. A reading indicating a nominal 6 volts can be had from a U/S battery, but the voltage will start to drop quite quickly when you apply a load. Also check all your lamps to see how many watts that they are collectively consuming. The dynamo is a willing animal and it will keep on trying to supply enough current to meet the load that is being demanded of it. The problem is, that if the battery is not 100% then it is a bit like trying to fill a bucket with water that has got a whacking great hole in it. Also check that you have a really good earth path for everything. Especially check the battery to frame earth, and try running a separate dedicated earth from the headlamp. I suspect though that the battery is the problem, and if you are using a mechanical regulator then you need to fit a lead acid battery. A mechanical regulator is not sensitive enough and it will cause premature battery failure.

[bikerbob]

Thanks for the reply. The bike has a new manual regulator fitted  the 6.8 volt reading was taken with the battery on the bench, fitted to the bike without the engine running and the headlight and speedo and tail light on the voltage drops to 5.00volts. with pilot light speedo and tail light it reads 5.73 volts. with the engine running at a fast tickover the reading is 7.2 volts no load. With the headlight speedo and tail light 6.4 volts with pilot light speedo and tail light it reads 6.9 volts. All readings taken with a multimeter. So it looks like the battery is the problem so what amperage battery should I go for.

[a101960]

The original battery fitted to the A10 by BSA was 6v 12 amp hour. The dynamo maximum out put is 60 watts, so you need to make sure that the total current draw with all lights operating is less than than 60 watts. Original headlamp bulb will consume 30 watts main beam, 24 watts dipped beam. Original tail lamp 6 watts, and brake lamp 18 watts. Pilot bulb was also rated at 3 watts. I am not sure what the speedo bulb was rating is. My guess is it will be be between 1 and two watts.