Security lighting

I personally think you are cutting it to close to the maximum the unit can put out. You could do it but buy the 120W globes. Should be fairly easy to find. Also I wonder how long the battery would last running the inverter.
I don't know how practical it is but you can buy electronic kits which converts a 18W fluro into a 12 volt light. with Triphos tube in it it is as bright as a normal fluro and only runs about 1.5A on a 12 volt supply. You should be able to get the electronic units from Dick Smith perhaps. I'll see what I can find out and I will get back to you.

Regards
Sparkie

More mucking about but this could also work:

PIR sensor for an alarm system (eg Jaycar CAT. NO. LA5036, 9-16V operation)
Relay
12V lights

You may need to include a timer circuit to hold the relay on for some predetermined time rather than just being on whilst there is movement.

Could be done for less than $50 all up using some 12v downlight globes.

Adrian

If you are using a PIR sensor to spot crocs you could be wasting time and money.. PIR stands for Passive Infa Red and work on heat movement... Crocs are cold blooded and move pretty slowly and as such I would put money on it that they would slide straight past your security have a bite to eat and then slide back to the water without the lights coming on..

An option you could play with would be microwave sensors but stay away from dual tech sensors as both technologies have to trigger and again will probably let the buggers slip right through..

A string with a tin can with marbles in it might be just as useful as running a lighting set up..

You will also find that a 300w invertor will probably have a 500w max rating anyway so it would work but you would be better of with flouros at any rate in my opinion.

Cheers

To just clarify, last year we were camped at Kalumburu and had our tinnies parked on the beach. We were well back etc but one of the other campers heard something at night and thought their tinnie was banging in the surf. When they got there it was a croc that was probably attracted to the bait we had in the tinnies. My thought was that our next camp will be a little closer to the tinnies (yeah I know don't leave the bait in there this time) so I thought some early warning system may be useful.

I'm not that worried but it's the others that seem to have issues like what happens when nature calls in the middle of the night and all those type of irrational questions. Told them not to worry no respecting croc would hang around if they dropped their dacks but they think I'm making light of their concerns.

Kind regards