# Help With Very Simple Battery Back-Up



## maddy (Oct 30, 2010)

I would like to set up a very simple battery back-up system to run a laptop computer (65 watts) and satellite modem (80 watts) during power outages. I would like to be able to run the computer and modem for at least two hours before having to worry about recharging anything.

I have researched this a bit, and I think I need a deep cycle battery and an inverter. However, I am overwhelmed by all the technical details and could use some recommendations about exactly which components to buy. What should the capacity of the inverter be? What capacity (amp hours) for the battery? 

Is there an additional component I need to alert me to when the battery has been run down by 50 percent and needs to be recharged? What type of battery recharger would you recommend? 

Thank you for your help!


----------



## ace admirer (Oct 5, 2005)

A good Deep cycle battery would be nice and at least 200 watt inverter (constant, not peak rating). a good modern inverter will have a low battery warning and at some later point in time auto cut off. You will need a good modern charger (smart charger). depending on battery, you could probably run a few hours (roughtly 6 to 8 hours) with being to harsh on the battery life (if i am wrong i hope others will chime in)


----------



## cmcon=7 (Mar 7, 2010)

I use a cheap 300 watt inverter that screams when the battery gets low,and shuts off @11.5v
my net book em250 uses about 10 watts running, yours is probably much less than what is posted on the power supply.
with a group 27 battery you should get 10- 20 hours or more,and a 2amp automatic charger should keep it up between outages


----------



## TnAndy (Sep 15, 2005)

Instead of inverting the DC to AC, and then using a transformer to change it back to DC....with all the losses associated with this......you might want to look at using it directly.

If your devices use a wall charger, look on it and see what the output is. May well be 12v DC, or some DC voltage.....in which case, simply use a DC to DC converter to get the voltage right, and not bother with the DC to AC back to DC route.


----------

