Is a 45 W MagSafe Charger going to work for MacBook model A1181 (2007)?
...or I need 60 or 85 W charger?
Does 45 W MagSafe only work for MacBook Air or also for other Apple Macbooks?
Apple says 60W. Page 7 of this pdf manual.
45W is just for the MacBook Air
The only real issue is sometimes if the battery is completely drained, you must wait 2-5 minutes for it to charge up before the machine will even boot. You can use it with any MacBook Pro etc even 17" but for sure you will see this issue and hate it at the larger/ higher newer models.
Much longer charging times for battery also. 30-70% est.
But in fact, because of the slow charging, may make batteries last longer.
Won't damage anything in laptop.
Very very small risk of damage, short or failure in the adapter itself. Like 10%. Fire risk? 1/100,000 or less I would estimate. And I know a little about these things. Still hard to say.
One other issue is having my techs scream that they killed a laptop... When it's just they are trying to boot a 17" with a 60 or 45 watts power adapter. Sooner or later, if there is even one non-85 watt in the shop or home. This will happen.
Don't be cheap. That's for windows users. :-)