Inverter recommendation advice

i have seen an article or post recently about this very subject (perhaps in MMM) but I can't for the life of me remember where. I think the answer may well be that what you want is practicable but that you will need a pure sine wave inverter i.e. a better quality and therefore more expensive. I think the voltage on your bike battery will be at least 24v. It is important to ensure that the cable connecting your inverter to the leisure battery is thick enough

This is only a partial answer but it may help.  

agree with the above...i do charge two electric bike batteries from our 500w 'quasi' sine inverter....one at a time, when no ehu is available.

one is a Bosch and the other Panasonic, they both run ok.

i have experimented with this process and can see (in sunshine) the SP seems to be providing sufficient power so as not to reduce the capacity of the twin 95ah batteries.

the inverter is mounted within 1 ft of the batteries (in our battery compartment) via the supplied thick leads (dont use a 12v socket, wire it in properly) and i have run an extension 240v output cable to the rear garage for convenience, although any locker will do.

set it up and (say) run one for an hour and then check the batteries, repeat as necessary to acheive full charge. this will convince you (or otherwise) that the process is sound and that the batteries can cope with the demand.

good luck.