Small portable set-up 12/24Vdc – 110Vac Grid.

Small portable set-up 12/24Vdc – 110Vac Grid.

Sometimes it’s easy to just have a small portable solar setup. It can be used as an emergency backup or just to power some tools in the back of the garden. So-called solar generators are available in many sorts, some mounted on wheels for easy transport. To give you an idea, we offer a set of plans to build your own.

List of parts that come to mind:

  • A small plastic enclosure as a control box to build all the small stuff in.
  • 100-200Wp solar panel (2x 100Wp) (Externally connected to the box).
  • 60-125Ah Deep Cycle Marine Battery (Externally connected to the box).
  • 300-1000W Inverter 12Vdc -> 110Vac (Make the connections directly on the battery !)
  • Some panel meters to monitor solar power and battery voltage.
  • 20A Battery Fuse or DC-breaker.
  • LED indicator light green.
Example 02: A 12Volt DC to 110Volt AC inverter
Example 02: 12Volt DC to 110Volt AC inverter

Small 300watt inverter
Small 300watt inverter

The Charge controller

BSV20A Charge controller for 12/24Vdc
BSV20A Charge controller for 12/24Vdc

The BSV-20A charger controller can operate on both 12 and 24V. In this setup we use it primairily as a 12V controller. The two 100Wp /12V (in reality 12V panels usualy provide something like 18V x 5.55A) panels put in parallel will exceed 11 amps so a 20A charge controller is required. This charge controller has a lot of build-in security features, but we simply want a circuit-breaker, that can also be used to swich-off the battery.

This controller looks very simular to the older OMP12 model (only 10 Amps) and many others out there, so be sure you buy the right one.

All the loose parts are fitted into a small plastic enclosure of 7.87″ x 4.72″ x 2.95″. The solar panels are connected with special solar connectors, the so called MC4 chassis connectors. These are in male and female versions so accidently switching polarity is not possible in any way.

 

volt-amp-meterBoth the panel meters are fitted in the enclosure. The combined volt-/ampmeter requires a shunt, these meters are available up to 10 Amps without shunt but that sadly isn’t sufficient here.
The battery is connected directly to the charge controller with the 20A circuit-breaker in the positieve line. Please note this is a DC-breaker for solar systems, not to be confused with a regular 20A AC-household breaker. In case of short circuit this will trip and can also be used to switch-off the battery.

The “load” connections on the charge controller can’t be used to connect the AC-inverter since the load can only be 12V x 20A = 240W. So the solution is to connect the inverter directly (with short thick cables) to the battery. The low-battery load-cut-off protection of the inverter won’t switch off the inverter this way but if the battery voltage drops below a certain level the inverter will shut of by itself.

So what can we expect ?

This small portable unit can store about 750Wh (in 60Ah battery) or 1500Wh (in the 125Ah battery), the battery however shouldn’t be completely discharged however, with deep cycle batteries go up to 50% maximum. Then we have 375/750Wh available. This is more than sufficient to use some powertools like a powerdrill or a jigsaw. Even a small circular saw can be used. A 1000W inverter can handle enough output in most cases. For just running your radio and charge your phone this might be a bit overdoing it, but it’ll surrely work.

Most parts we used in this setup can be purchased on Ebay and are pretty cheap, so the whole setup can be easily made and extended.

Some extra’s we can connect to the load-connections is a indicator light and a double or quadruple 12Vdc to USB connector, useful when phones need to be charged.

2x USB output from 9/12/24/36Vdc
2x USB output from 9/12/24/36Vdc

 

4x USB output from 12/24 or 36Vdc
4x USB output from 12/24 or 36Vdc

In our small case is one extra PCB (Printed Circuit Board) that we haven’t addressed yet. It’s a small step-down converter that makes the 12V for the light. This might seem strange since we have talked about building a 12V system from the start. However all the used products can handle 24Vdc except for that little Led indicator, so why not make it a 12 or 24V mini system, by adding this simple Step-down converter (approx. $1,00) we can make it versatile.

Small DC-DC step-down inverter.
Small DC-DC step-down inverter.

Just remember you need different panels (or just put two 12V panels in series) and use a different AC-inverter in case it’s going to be a 24V system.

Specs: on 12Volt:

  • Solar panel max. voltage 25V
  • Solar panel max. current 20A
  • Solar panal max. power 240Wp

Specs: on 24Vdc:

  • Solar panel max. voltage 36V
  • Solar panel max. current 20A
  • Solar panel max. power 480Wp

Mounting the PV panels on a cart or make them foldable seems like a good idea, but is kept outside this small tutorial.


Downloads


Part 2: Extend to 24-Volts

Assembly, comes soon