Solar shed 24Vdc and AC grid 110V

Solar shed 24Vdc and AC grid 110V

A small solar shed setup for a barn, a shed or a green house. Build with both low voltage batteries (24Vdc) and an AC inverter (110Vac) to use grid like power for some powertools.

The setup is re-build with the following parts:

  • Four 12-Volt batteries that hold 90Ah each, 2 series in parallel, this was only two 12-Volt batteries 125Ah each
  • Four 100Wp solar panels with 17.3V/5.78A output in series
  • A new model EPsolar Tracer2210CN MPPT charger controller
  • Two different panelmeters to keep track of the PV-output and the battery charge level
  • A 6HE DIN-rail enclosure for the breakers and panelmeters
  • Two 20A circuit breakers for the charge controller
  • One 63A circuit breaker for the inverter

Why re-build ?

As you might have noticed this is about the same shed in the “various parts” section, but it was a real example yet and after 5 years in need for an update/re-build.

Most of the material, like the breakers an panelmeters will fit very nicely in a 6HE (6-single phase MCB – Miniature Circuit Breaker box with DIN rail) enclosure.

EPsolar Tracer2210CN » 12/24Vdc - 20Amax
EPsolar Tracer2210CN » 12/24Vdc – 20Amax

The brand new Tracer2210CN has no load output, so it’s nessecary to connect the inverter directly to the battery in this case. Two wires of 8 AWG take care of that since the distance between the batteries and the enclosure is just a few feet. In the previous setup it was a 60A on-off charge controller that had a load output, so some changes need to be made.

From on-off charging to MPPT, what does that bring ?

The biggest change here is putting the four solar panel in series instead on the 2 series of 2 panels switched in parallel. The input on the new Tracer2210CN can handle upto a 100Vdc, so 4x 17.3=69.2-Volts won’t be a problem. This also keeps the output current limited to 5.78-Amps, the same as from a single panel.

Mainly early in the morning, later in the evening and during cloudy days this will be a large difference. Before the voltage drops below 30-Volts will take much longer now, so more output. MPPT takes care of the rest, a max. of about 11.5-Amps has ever reached the batteries, a disapponting (24×11.5/400) = 69% efficiency flowed into the batteries before. This will become 99.5% with the new controller.

The distrobution box:

As mentioned before everything has to fit in the distribution box. Now the battery wires are the most critical, so we start of wiring from the higgest to the lowest current before we finally distribute to the small panelmeters. So 8 AWG to the 63A breaker, than with 10 AWG through the 20A breaker.

The output of the 20A breaker is already pretty save compared to the batteries short circuit current, so from here we’ll go to the charge controller and distribute into 2 smaller 24-Volt outputs using a 15A dual row connector.

The panelmeter for measuring the input can support upto 30-volts, but just to be on the save side, let’s install a small 24-12V DC-DC converter a feed it 12-Volts.

Total performance update:

The yeild of the solar shed should increase by about 25-30%, this means we can also store more energy. Batteries that already needed replacement will be upgrade from 125Ah to 180Ah too, so storage will increase from 3kWh to 4.32kWh.

Combined battery back
Combined battery bank for our solar shed example

Be sure to wire batteries “over the diagonal” and do not connect the load to a single string of batteries.
A bigger storage would have been golf cart batteries that hold 6-Volt and 210 or 225Ah, that would also require four pieces in series this time to reach 24-Volts in total.

Please refer to our battery wiring page for more info about putting batteries in series, parallel or combined.