Battery backup for pump and heater. How do I calculate the size I need?

[Newreeflady]

I will preface this with the statement that I didn't do well in EE. haha.

So, I want to have a battery backup that will support my heater and pump for a decent amount of hours (haven't decided yet, depends on the relative power and price of backup units.)

Trying to keep running:
-MJ900 8.5w pump
-Visither 50w heater

But, I don't know how to figure how many hours a given system will run 58.5watts for. (I guess I need watt-hours?)

Here's a product i'm looking at, rated at 180 watts, but I don't see how many hours! Anyone care to enlighten me? compusa apc backup

Thanks!
Angela.

 

[chucksta1]

I do believe the formula for watts is based on voltage times amps.

1 amp times 120 volt = 120 watts. The 180 watt rating is the max output ( think 250 watt power supply for a basic PC)

the setup you have will have a variable life dependant on ambient temperature, as it will affect the duty cycle of the heater.

Or, you could go to the company's web site and e-mail tech support.

Or, you could get two and plug one device into each. The pump will run for days, your milage may vary on the heater.

Or, someone who knows electrical conversion formulea could chime in and help.

Good luck.

 

[Newreeflady]

Thanks.

Does anyone use one of these? I guess I could e-mail the company, but I figured I wouldn't be the only one using something like this and maybe someone had experience with a battery backup.

Anyone?

-A

 

[BC Sparky]

Usually these type of units are rated in AMP Hours. As mentioned Volts X Amps= Watts. Therefore Watts/ Volts= Amps. Amp hours ratings tell you how many amps the unit will supply for "X" hours. For example- your demand would be (worst case= heater on) just under 1/2 Amp. A unit rated at 2 Amp hours at 120V would power your set up for about 4 hours (again- heater on). The 180 W they are talking about is is the maximum output at any certain time (180Watts/ 120Volts= 1.5A maximum draw). Something to keep in mind when purchasing- most of these units automatically shut down when the batteries have been drawn down by 80%.

 

[Newreeflady]

Man, this retarded unit doesn't say how many amp-hours. I am going to have to call I suppose. Thanks for the info on the 80% drain shut down, too.

Thanks,
Angela.