also when using a sealed lead acid battery (SLA)
they need to be kept at a minimum charge of 12.6 volts, otherwise they will prematurely fail.
a good capacitor can be left uncharged for 10+ years , start up the bike and it will recharge in under 20 seconds and be ready to use.
i have a pic comparing some batterys etc
left back battery-
12v 7AH SLA battery. dimensions are 150mm wide, 65mm deep, and 100mm high
this weighs 2.54 kgs, and cost around $30
centre back battery-
12v 2.9AH SLA battery, dimensions are 80mm wide, 55mm deep, 110mm high
weighs 1.3kg, cost around $25
right rear battery-
6V 4.5AH, approx same dimensions as the 12V, 2.9AH above, but with almost twice the capactiy.
weighs about 1.25kg, cost around $20
front left capacitor-
pic for size reference only, 40 Volt maximum, 27,000uf, screw on terminals, 60mm high, 45 mm wide (a bit bigger than a 'D' cell battery)
weight 130grams, cost around $15 for a decent brand if sourced from O/S, or about $40 locally
front right capacitor-
pic for size reference only, 40v maximum, 10,000uf, solder on fly leads, height 50mm, 35 wide (around same size as a 'C' cell battery)
weight 100grams, cost around $10 locally, or about $5 from O/S