12v on arduino

i have a few lead-acid batteries lying around here i want to use to power my arduino, but they’re 12 volts batteries.
the arduino diecimila specs say that the best voltage is from 7 to 12 volts, but most people use a 9v supply and some people say that the arduino will get a bit hot when using a 12v supply.

so, is a 12v lead-acid useable?, or should i use a voltage regulator to regulate 12 volts → 9 volts?

so, is a 12v lead-acid useable?

Yes, no problems. I’ve used 12V SLAs, 13.8V ham type power supplies, and vehicle power, among other sources, to power arduino circuits.

some 7805s (but not all!) are rated up to 35V input.

The higher the input voltage, the more heat generated by the regulator. A heat sink maybe called for if you draw lots of current and have a high input voltage (but not with a typical arduino circuit and a 12V supply).

-j

The higher the input voltage, the more heat generated by the regulator.

This is USUALLY the real problem, rather than the rated max input voltage of the regulator. Since it can be difficult to add a heatsink to the SMT regulators on modern arduinos, one relatively easy solution is to use a three-terminal “pre-regulator” like 7808 or 7809 (8V and 9V regulators, respectively) with arbitrarily large heat-sink…

Also, thanks to portable electronics, it’s pretty common to find automotive voltage converters on the surplus market that are switching regulators (probably?) and may even offer a bit of extra protection against the hostile automotive environment. For instance, Here’s a useful looking one from BG Micro