Photovoltaic carts

Motivation: why build photovoltaic carts?

These photovoltaic carts were built for emergency backup power during a major earthquake. Some advantages of this setup include:

  • Modular: The carts are bolted together. They can be disassembled and reassembled.
  • Movable: The carts can be moved to a safe area away from danger or to a triage area (in the event of a mass disaster).
  • Durable: The carts are designed for outdoor use.
  • Reliable: These carts were built with high quality components with long warranties and low maintenance.

The entire build is comprised of the following:

  • Outback Power Flexmax 60 MPPT charge controller (inside Hoffman utility box).
  • Outback Power VFXR3524A-01 24V 3500W inverter (inside one of the Ameresco 4BS2000BP battery boxes).
  • Outback Power MATE 3S monitor and controller for Outback inverter and Outback charge controller. The MATE 3S also monitors the battery bank state of charge.
  • Midnite Solar MNPV3 PV combiner box containing three 150V DC, 15A circuit breakers (between photvoltaic panels and charge controller).
  • Midnite Solar MNDC125PLUS battery disconnect with 150A DC circuit breaker (between battery bank and inverter).
  • Midnite Solar Baby Box with 60A DC circuit breaker (between battery bank and charge controller).
  • Hoffman A20R208HCR NEMA 3R electrical enclosure (housing to protect charge controller).
  • Wiegmann RHC121206 NEMA 3R enclosure (housing to protect MATE 3S controller),
  • GE TLM812RCUP 125A A/C breaker box with two A/C 15A circuit breakers.
  • Three Ameresco 4BS2000BP NEMA 3R aluminum battery boxes (each box can hold four Battle Born BB5024 LiFePO4 batteries).
  • Eight Battle Born BB5024 LiFePO4 batteries each rated at 24V and 50Ah. The eight batteries will be wired in parallel with a total capacity of 400Ah.
  • Two outdoor GFCI (ground fault circuit interrupt) rated 15A A/C electrical outlets in weather resistant cases.
  • Lots of 2 inch, 1 inch, and 3/4 inch diameter non-metallic, liquid tight PVC conduit to protect internal wiring from outdoors.
  • Superstrut (14 gauge, 13/16 height, galvanized B-channel) struts cut to length to create the cart.
  • Redwood 2x6 lumber for cart structural support, attachment of electrical boxes, and wheels.
  • Powertec model 17050 solid rubber caster wheels. Wheels are 6 1/4 inch diameter. Each wheel is rated for 330 lb. As each cart has four wheels, the maximum weight capacity per cart is 1,320 lb.

Wiring diagram of entire build (involves three large solar carts).

This schematic diagram represents what the completed build will look like once finished (revised).

Specialized tools used in this project.

Here are specific electrician tools that were very helpful on this project:

  • Gardner Bender UL locknut wrenches. These are very useful for tightening the locknut retainer rings around conduit fittings.
  • Klein Tools cable cutter model 63050. Very smooth cutting action. These cutters are excellent for smaller diameter wire.
  • Greenlee cable cutter model 718. These cutters make cutting 4/0 AWG wire easy.
  • Klein Tool ratcheting wire crimper model 3005CR. Very useful for smaller wires like 10 AWG.
  • Thomas & Betts TBM5-SV ratchet crimper. These crimpers really do a great job of crimping large lugs on 4/0 and 6 AWG wiring.

My first book on Solar Energy.

Solar Energy By Example is my work-in-progress book [restricted access].

Latest news

My photovoltaic cart system has been running reliably since June 29, 2020.

February 25, 2024

February 21, 2020

Solar cart number 3: Installed Outback Power inverter and a Midnight Solar DC Disconnect breaker box containing a 125A DC circuit breaker.

Note: I temporarily put a battery inside to test the inverter and AC outlets. The AC outlets testing was a success!

February 19, 2020

Solar cart number 3: Installed main electrical wiring (from inverter to AC breaker box) and firmly attached conduit to cart.

February 9, 2020

Front and rear views of all three large solar carts.

February 8, 2020

On large solar cart three, installed 12 AWG wire (hot, neutral, ground) inside the GE TLM812RCUP 125A AC breaker box to two GFCI-protected electrical outlets. Each electrical outlet is on its own 15A circuit breaker. Next step will be to install the AC mains electrical from the inverter to the circuit breaker box.

December 15, 2019

Inside large solar cart one, two battery jumpers were built using 4/0 AWG welding wire to wire two Battle Born 24V LiFePO4 batteries in parallel. This brings capacity up to 100Ah at 24V.

December 14, 2019

The second large large solar cart features a used ReneSola 250W type panel. The two 250W panel carts are wired in parallel. The two smaller solar carts are on separate circuits to recharge Goal Zero Yeti devices.

November 22, 2019

In the photos below, a steel backing plate is installed inside the large solar cart's battery box. A Midnight Solar Baby Box with 60A fuse and a Dinkle 6AWG pass-through terminal block are then attached to the backing plate. The other end of the 6AWG wire will be connected to the battery terminals.

November 16, 2019

In large solar cart one, 6AWG copper welding wire is installed at the photovoltaic fuse box and the charge controller.

NOTE: The breakers in the second photo below were replaced with 15A breakers instead.

November 11, 2019

In large solar cart one, 1-inch diameter Liquidtight flexible conduit is installed from the Midnight Solar combiner box to the Hoffman electrical enclosure and from the Hoffman electrical enclosure to the Ameresco aluminum battery box. The second plug conduit connector on Ameresco battery box will be used to connect the battery box to an Outback Systems inverter.

August 9, 2019 - October 12, 2019

In large solar cart one, the Midnight Solar combiner box, the Hoffman electrical enclosure, the Flexmax charge controller, and the Ameresco aluminum battery box are installed.

August 9, 2019

In the photo below, the second (smallest cart to the right) and third (largest cart on the left) solar photovoltaic carts were built. The carts still need to be plugged into a charge controller and a battery array.