UPS as inverter

Alot of the cheaper UPSs don't have a high duty cycle, they count on the fact that the battery will go dead within X minutes and design the UPS to survive X+5 minutes (for example).

If your UPS has the option of adding battery packs then it should be fine (and probably also too big to keep in your car). If it has a fan then it might be OK. If its a good brand or you add a fan then its worth a shot.

Of course all of that only really applies if your putting a fairly high load on it, if you just want to run a fluro light or an FM radio you shouldn't be pulling enough power for it to even warm up.

-- Michael Heydon

Depending on the model it may need the battery for loading and proper function

Apart from the duty cycle consideration, it shoud be fine. I use one to run my Weller iron in the field. The only downside is the ferkin annoying beeping because it's upset at having no mains input. (The beeper is ferkin hard to get at to disable elegantly).

Be aware that they DO pull a decent bit of current @12V and cig-lighter outlets often provide poor contact.

The one I tried to do that with had a 'safety feature' that inhibited the inverter unless the mains had been supplied and then cut off, the solution to that was to make a blocking oscillator with the centre-tapped secondary of the small mains in transformer and power the BO via a push button to fool the control circuit into thinking mains was supplied and just failed.

Mine has a battery start button which I presume does what you've described. Anyway, thanks for all the replies everyone, I found the battery for it was only $20 at jaycar and so have decided to use it as a UPS and buy an cheap inverter if I need it. Normally I like to hack something together even if it costs more and doesn't work as well but decided to be sensible for once :-)

Michael

One of those "battery start buttons" would have been very handy on mine, I had to hack the circuit and figure a way to start the UPS remote from any mains supply.

My motorcycle had a badly designed lock which got road grit in the keyhole, so one morning I went to get the bike out and couldn't unlock it. This meant using the angle-grinder in the garage where there's no mains supply, while my purpose was legitimate it does hint at why UK supplied UPSs have this inhibit.