#### Bryan Sloan

##### New Member

- Joined
- Sep 10, 2020

- Messages
- 9

Wanted to power a 1.4 amp 75 Watt air pump for my pond. Didn't need it to run 24x7, so I chose a run time of 8 hours per day.

I followed Will's video on how to size a system, factored in 30% oversized arrays to reduce battery cost, and then rounded up.

3x Rich Solar Monocrystalline 200 watt panels

1x Renogy 60A MPPT Charge Controller

2x VMAX SLR125 SLA Batteries

1x GoWISE 600 Watt Pure Sine Wave Power Inverter

1x Hiblow HP 100LL Air Pump

Checking my work on how long the system will run, I get

2 batteries x 12 volts x 125 amp hours / 2 (50% discharge rate for SLA) / 2 (days of autonomy) = 750 watt hours

750 watt hours / 75 watts of usage = 10 hours of run time

Am very happy to confirm I get a full charge every day with my pump timer set to run 8 hours.

Lesson learned #1 - The system ended up beefier than I expected. I started out thinking a 75 watt load was nothing and a single solar panel would do the trick. However, the math taught me different.

Lesson learned #2 - This one took me about 3 days to ponder and then I had to laugh at myself. I measured 6.49 amps between the batteries and the Inverter. My pump is rated at 1.4 amps. Thinking disaster until the answer hit me days later. 6.49 amps at 12v is the same as 1.4 amps at 120v. Sigh........

I have the air pump split to feed two aerators on each end of the pond.