Forum

[jefrs]

I'm not disputing whether a 14Ah (that's amp-hour) ES battery will work in an Interceptor (although bikes of that era were often 6V, notwithstanding 12V conversion), it will probably work quite well. I would however be ready to use a charger on it from time to time.

Do not confuse a battery's power (watts) with its charge capacity (amp-hours), a more powerful battery is needed to turn an electric starter (ES), so they need to be able to churn out more amps (x Volts = Watts). They invariably have greater charge capacity than the other flavour, but just because it has "14Ah" written on it doesn't mean it can put out 14A current (that might buckle its plates). A bigger battery like this requires a greater charge current (amps) to charge it properly, something that the old school Lucas generator may well not be able to provide. To charge a "12V" lead-acid we need 14V or a little more from the generator. It's not just a case of putting back what you use, there are losses involved, you have to put more in than you take out.

[Dennis C]

The CCA (I won't explain it as you know everything) of a 14ah battery would normally be around 190 amp's.

Putting thing's simply consider a battery to be a container for electricity, like a water tank, a charging circuit a float valve and the bikes electrics a tap, as long as the float valve let's more water in than the tap let's out the tank will never empty regardless of whether it contains 10 gallons of a 100 gallons, despite loss due to evaporation.

[Adrian]

1966/67 seems to be when the British manufacturers were changing from 6V to 12V Lucas systems, and a quick check of the S1A parts book on-line shows the 12V zener diode and heat sink, so that's an original set-up. I can't see an Interceptor's requirements outstripping a healthy RM21 or RM19 alternator's output unless you start fitting things like (illegal) 100W headlamp bulbs. So picking up on Dennis' illustration, the Interceptor alternator should be more pumping more in through the float valve than the tap can draw off (which sort of makes the Zener diode or modern reg/rectifier the overflow pipe).



My father swapped the bike battery on his BMW R80/7 outfit for a car battery in the boot of the sidecar, the alternator kept it charged just fine.



A.