I used a battery to drive a rb133 board. It worked for a while until the battery voltage becomes too low, then the board stopped working even when I connect a good DC power.
Any idea what happened? My theory was that somehow the software or the memory got corrupted with low voltage. Is this a typical behavior with routerboard when the power is too low?
What should I do to make the board work again – reload the software or do something else?
Thanks a lot for your help.
Jin 
Try using a serial cable and connect to it…
Well, a normal serial cable wont bring him nowhere…
He needs to use a so called ´nul´ modem cable to connect to the router. (http://wiki.mikrotik.com/wiki/Serial_Console)
And to be complete, we can tell QpoX that that cable has to be connected to a PC and then with a terminal program he can login the router and do a netinstall. (http://wiki.mikrotik.com/wiki/Netinstall)
I think this is a bit more of a help to QpoX.
If that is not helping, I would suggest to write support an e-mail.
And it’s called “null”
Now WirelessRudy read http://forum.mikrotik.com/t/rb-411-eth1-problem/20975/4 before you act like a “smarty”…
Well, if you are such a ´smarty´, why this stupid advice to someone with a genuine question.
If pointing to correction spelling errors and calling people names is the best you can add to this forum you’d better go to a grammar forum or so… 
We don’t need such wise guys like you on this forum and I don´t like to be called names by someone that obviously fit that profile himself…
It’s still a serial cable… And people should know when connecting between 2 devices you need cross cable’s…
And i did NOT call you any names! but a feature, that you are…
But if you wanna fight, it’s fine with me… or should we just stop here? and help him?
Greetings!
Usually, a voltage too low to power the ICs on the board will cause irreversible damage if allowed to continue for any time at all. That is why I use a battery backup (UPS) on mains power, or Low Voltage Disconnect for solar, on all my equipment.