Need help with design for solar/battery bank for pool heater.

[Moofer]

I have been trying to figure out the best way to heat up my pool. I have a rooftop solar system that works when my pool pump runs. Unfortunately the power demands of the 3/4 HP pump are very high. The electric bill is overwhelming.

I want to run a couple golf cart batteries or other 12V deep cycle batteries to a 12V marine style bilge pump. I would charge the batteries with the solar panels.


The existing roof top system is about 300 square feet of skinny black rubber hoses. On a sunny day the water comes out pretty hot. If I can run the solar heater for a longer period of time the pool will get warmer earlier in the season, and stay warmer later in the season.


The roof is about 14 feet up, so the pump would have to push the water up 14 feet. I may not be able to find a pump that can do that, or it might take too much power.....but I could set up a secondary system at ground level.

I don't expect to move a whole lot of water. The pump I currently have moves 500 gallons per hour. It say 12 V, but I couldn't find the amperage or wattage listed.




Originally I planned to run the solar panels directly to the pump, and whenever the sun was out, the pump would run...? Not sure if that would work or not...It would take a lot of solar generated watts to make it run. The batteries would provide enough reserve so the pump could run for 4 or 5 hottest hours a day.


Am I on the right track? Any suggestions for panels or other ideas that would work better?

[Mike90250]

Simple way is to use a "linear current booster" to assist the pump, run direct from solar PV panels, and once the pipe is full, and both ends stay submerged, the water will stay in place like a siphon, and the pump just moves it.

[Moofer]

You mean that would do the job of the batteries then...?

I found the pump draws about 1.9 amps. Do i need a particular amperage converter?

[Mike90250]

When the sun is not shining, and the hot water panels are not heating the water, why would you need the pump?

The instructions for the booster in my first message
http://www.solarconverters.com/ppt7.htm indicate it should easily work with your smaller motor. You could give the mfg a call http://www.solarconverters.com/contact.htm
and find out for sure.

My concern is that the pump motor is a brushed unit, and that eventually, the brushes will wear out with weeks of 6-7 hour daily run times.

Pump is 12V @ about 2 amps, so any 50-100W panel should be fine, the boosters job is to manage the power flow.

[Moofer]

that sounds good.

here was my thinking.....

I expected the panels to charge the batteries all day. But I would only run the little circulating pump during the hottest hours of the day, say from 11 to 3.


I thought I could get away with fewer and cheaper panels....

But if that current booster will make the pump run whenever the sun is out....well that sounds even better.