The less power your bike takes from your battery the longer it's life will be, as constant charging and discharging will buckle the plates and then you have a dead battery.

If you can kick start your bike so much the better, your battery life will be long, if you need a battery at all. But you may well find that you can not kick it over as the compression maybe too high, and electric start is your only option.

Amps x Volts = Watts

As the Ruggerini RD211 work shop manual states, the alternator (under the flywheel) kicks out: 17amps / 12 volts / 280 watts @ 3000 rpm. After doing the maths it is 24 amps not 17 as stated in the Ruggerini manual.

The Ducati made regulator / rectifier is 24 amp so the 17amp could be a typing error in the manual, or it could be referring to only the B+ (battery) connection of the reg/rec and not including the L connection. Sadly I do not have a working Ducati Ruggerini reg/rec to check, but if this is the case and B+ is 17amp then L must be 7amp which works out to 84 watts, about right for a small street sweepers lights.  

Battery

So this tells us we need a battery that is a possible 24amp, but maybe only a 17amp as Ruggerini has stated. A modern Harley Davidson alternator kicks out 32 amps, and their hi amps gel battery works very well. So well in fact it started my engine with a flat battery that was left for a few hours (a flat battery will regain a small charge all by it's self after a period of time). So this tells us that the battery does not have to be so big and powerful to start the engine, but maybe it does have to be big and powerful to take the punishment from the reg/rec

My thinking is this; a Harley battery costs £120 and it's big and heavy, my bike has all low power led lights, and uses 38 watts max with the lights on etc, so the remainder of the 280 watts is recharging the battery, 242 watts. So why do we use a slow trickle charger like an Optimate, just to rip the guts out of the battery when using the bike.

It may seem that I'm going over the top here but this led parking light is only 0.1 watt as apposed to the 4 watt of a standard bulb. It will not burn out and it is anti vibration. Now fitted and working after modding my Harley light switch, it looks really good as it gives off a dull blue light.

Normal tail bulbs are 21 watt & 5 watt break light, led's are only 1 watt. That's a massive saving on power. Together with the led indicators that's a saving of 60 watts. And with a led parking light in the head light, you can run the lights all day and not worry about the state of the battery.

Harley  sportster head light, can be had for around the same price of a cheep Chinese Bates import. Don't buy a sealed beam as you can't change the bulb if it blows.  

This is a Suzuki GT50 switch, it has four positions, C / Ignition / Lights / Park. it has 11 wires from it and can be wired as a 5 pole switch. Perfect for the custom build, just remove the wires you don't need. This replaces my three pole Harley switch.

I have wired it like this:

Position 1 - 2 pole Bat, Aux

Position 2 - 4 pole Bat, reg L, Lights, Aux

Amended. I wasn't sure the the wires could take the lighting power on main beam, so I replaced or doubled up the wires.

Well I have used the bike with this battery at night, around 250 miles with no problem at all. In the morning it fired the bike up with ease.

So I'm happy so far, how long will it last we shall have to see.