The Optimate 4 is an excellent solution. I fixed the fused 'Tail' connection direct to the battery and keep the charger permanently plugged in whilst the beast is sleeping. Then when we go riding I fit an Optimate USB into the 'Tails' SAE plug for phone charging etc. The USB plug also guards against battery discharge cutting off after a set time or when the battery reaches a certain level, protecting against inadvertant discharge should you leave something connected. I also ran a seperate direct battery connection under the Tupperware to the handlebars and into a Wunderlich Media Bag, again usng Optimate cabling and a USB protected outlet to charge a Power Bank and Phone contained in the Media Bag. As an added bonus my Tyre repair kit has a Air compressor which fits straight onto the SAE plug if needed avoiding the use of Crocodile clips etc. Hope this helps.
Regards,
Tony