Simple issue: Solar power charger and inverter concurrently on battery

[Guldborg]

Hi electric people, I have a couple of questions, that you maybe able to help with:

I have a garage without power and have therefore made a setup with a 60 Ah car battery, a 300 W 12V-220V inverter with power outlet for a lamp and want to add a 18 Watt solar power charging-array.

1) Can I connect the solar power charger (incl. regulator) and the inverter to the battery at the same time without hazards?

From invertere manual: "Disconnect AC inverter before using a battery charger (...) Failure to disconnect the inverter prior to connecting af charger may result in an input spike which will damage the inverter. CONNECTING THE INVERTER'S INPUT TO A BATTERY CHARGER WILL VOID WARRENTY AND MAY DAMAGE INVERTER".

Can 'input spike' also occur when connecting a continuesly charger as the 18 solar power charger? Please note, the charger has a regulator. Is it likely for the inverter to be toasted, if I connect both units simultaniously - and as you see charge an discharge at the same time?

The idea is to have this setup on all the time, so the battery will be charged slow, nice and easy after any use (discharging). Is it possible?

2) My inverter is always ON, because the lamp is movement sensitive. The battery has already been drained after a couple of weeks (haven't bought solar power charger yet). The inverter lights a small green diode when ON.

How much kWh does it 'cost' to have the inverter on standby? How can I measure? Shall I look for a specific spec in the manual?

Hope for help.

Best regards,
Jens Guldborg
Odense, Denmark

NB: Danish links!
Inverter: http://www.harald-nyborg.dk/merinfo.asp?varenr=6656&Grp=&n=10
Solar power charger: http://www.batteribyen.dk/18w_solar_panel_kit_inkl__laderegulator-p-4676.html?cPath=521_529&osCsid=7a278925bbfafbef25698f2915f12d92