How long 1 cir. pump run on car battery?

I need to be able to run a taco 700 cir. pump on a battery just wonder if you have an idea how long a pump could run on a good car battery? or should I have couple of them, Just one pump with an inverter

You need to make a lot of assumptions to figure this out. First let's assume you're using a 40 Amp-Hour battery that hasn't degraded in capacity at all. Next let's assume that your power inverter is 90% efficient, and that your taco pump draws about 80 watts (this varies depending on the head).

80 watts / .9 efficiency = 89 watts needed from the battery by the inverter
89 watts / 12 volts = 7.4 amps drawn by the inverter
40 Amp-Hours / 7.4 Amps = ~5 hours

Note that this would be under ideal conditions, and I wouldn't be surprised at all if in reality you got an hour or two less than that.

Thanks for the info on this, it gives me a good idea now what I need to do,,

You can also buy DC circ pumps. I've used these on solar systems powered from a 30W module, or power them from a battery. That would save the cost of the inverter and the efficiency loss thru it. Not as powerfull as that 70W pump, but it may be enough for your application.

Bob, thanks for always posting such interesting hydronic toys!

Has Laing always been a part of Xylem or is this something new? Also, have you ever used the El Sid pumps?

Noah

maybe a year or more for the Laing/ Xylem partnership?

I have not used the El Sid. I have used and removed a handful of the Marsh 809 12V DC pumps. Very durable, noisy and not as efficient as the ECM based Laings however.

FWIW, sometimes I can buy a comm truck battery for as much money as a car battery.