Building A UPS

At least that is what I think I am looking to build...

I need to make sure that my servers and networking equipment stay on during power loss or power fluctuation. This happens about once a month where I live, and causes me whole lot of grief.

UPS does not seem economical.

So I started scouting inverters on eBay and figured that if I can put the following 3 pieces together and some automatic power source switching I should do well.


For this project I have:

3 car (12V) batteries
Car battery charger
[will buy] 1000-2000 continuous power inverter(s)

I also have a [POS] 700VA APC UPS that I cary in my trunk in case I need a [very short] boost to my mobile electronics. I prefer to keep it in my trunk, but am debating on sacrificing it if necessary.


Basically this is what I want to happen:

My P4 servers ATX (2), my 2U Cisco switches (2) my 2U routers (2), my DSL modem need to automatically switch to battery power when the lights go off, or any sort of power fluctuation happen (including surges of course).


I'm relatively new to these things, but love to get my hands dirty, please give me some ideas!


This is my first post btw, and it is good to be here! Hi everyone!

The simple truth is it will cost much more to build than buy a UPS. They're pretty cheap thesesdays.

What I am looking for costs between 700-900USD on eBay. Those UPSs use proprietary batteries. The capacity of car batteries is much larger and they are more flexible. Because I can add batteries and inverters to the system it makes it much more scalable on-the-cheap if I for example decide to tie in the pair of massive cisco switches that consume 2000W each. Powering those alone via UPS would cost me ~2500 if I find a great deal on eBay.


I'm interested in the switching circuit: the one that can switch from AC power to DC power. Can you help?

Hi party,

from your description it is not quite clear to me if you want to build an on-line UPS.

I have an off-line UPS which works fine if there is a distinct power failure. It happens very often that switching different supply lines to mains there are power fluctutations (ripple on and off) which make the UPS fail. (It doesn't know when to take over).

Consequently the connected PC fails, too.

The off-line UPSes take over within 8 to 10ms, which is just withing limits. 5ms should be achieved for safe operation.

On the other hand using an on-line UPS will increase the amount on your electric bill considerably.

Boncuk

Offline Powersupply Is What I Need

Offline Powersupply Is What I Need:

I would like the batteries to kick in when the power fails or fluctuates.

Thanks for the description of choices.

Anyone?

Car batteries are not designed for cyclic deep discharge/recharge. They will not last very long after the first couple of deep discharges.

You could look at "leisure" batteries which cost around twice as much but are designed for cyclic charge/discharge.