Electrics question (not Honda!)

[MarkCR750]

Hi all, my wife has just become the proud owner of a Piaggio x8 125 automatic scooter so that she can join me on rides (slow ones!), she will also use it for work, because it’s auto it can’t be bump started and although the battery seems good and charges fine it concerns me that if it did ever go flat she’d be stuck!, I’ve got a good motorbatt battery that is surplus to requirements so I’m thinking of fitting it in the huge underseat compartment as a back up, initial thoughts are to connect it to the original battery with an isolator switch in the positive lead and charge it separately using my optimiser every few weeks, then if the original battery goes flat she can lift the seat, turn the isolator and off she goes.
Second thought is just to connect it to the original battery with no isolator so that the bikes charging system charges both batteries, as you can tell I’m useless with electrics so would the second option work, or would it strain the bikes charging system?, I’m preferring the first option as it leaves the second battery completely stand alone, I would appreciate your thoughts, thanks Mark.
PS if you’ve ever been on a scooter forum you’ll know why I’m not asking on one of those, what a bunch of numptys!

[mike the bike]

Wire them in Parallel.  The alternator will keep both batteries charged.

[hairygit]

Or use a "Split Charge Relay" as loved and used by the caravanning fraternity. It charges the main battery first, then once that is fully charged charges the second. You have a changeover switch to put the second battery into use if it's needed for starting.

[K2-K6]

https://www.workshopping.co.uk/product/electrostart-batteryless-power-start-800a-12v/E-START800/?utm_source=google&utm_medium=shop&utm_campaign=feed&gclid=EAIaIQobChMIwon-5dyi2gIVrr3tCh399QHQEAQYASABEgKbRPD_BwE

It won't make use of your spare battery but I've one of these, above link.

It's just a bank of capacitors that you charge when needed (even from a battery that won't start the motor if it's got 5volts in it)
Connect it,  push start button,  wait for leds to light up,  then start the engine.
Can be charged from USB,  cigarette lighter, other vehicle battery. You don't have to maintain it at all. Useful on your other bikes if needed.

[MarkCR750]

Thanks for the replies, a few good options then.

[Bryanj]

Not a good idea to have two different types or ages of battery permanently connected together

[ogri211]

I think you would be better with your first Idea, if you are using a motobatt these keep their charge very well even over the winter, you may have a problem connecting it in parallel as the voltage on the motobatt is slightly higher being a gell battery, but I think the biggest problem would be if there was a drain or short circuit on the original circuit and your backup battery was connected it would flatten that one as well defeating the purpose, another idea would be a small set of jump leads.

[Rozabikes Tim]

Hi all, my wife has just become the proud owner of a Piaggio x8 125 automatic scooter so that she can join me on rides (slow ones!),

Don't do yourself down, surely the old CR is up to it Mark!
I love these technical questions,  you always learn something to store in the old memory banks.

[MarkCR750]

Hi all, my wife has just become the proud owner of a Piaggio x8 125 automatic scooter so that she can join me on rides (slow ones!),

Don't do yourself down, surely the old CR is up to it Mark!
I love these technical questions,  you always learn something to store in the old memory banks.

Ha, yes no matter how hard I try I can’t keep up with her 🙂👍