The microgrid is supposed to consist of many components and should have a number of devices connected to it. So one of the obvious questions is: how do we connect those components together? And one very obvious part of that questions refers to the type of plugs we use to do so.
There are a number of different connectors out there that are used for DC power, for different voltages and purposes. Let's take a look at some and their advantages and disadvantages.
- DC barrel plugs They have the DC right in their name, and are used for all kinds of devices. They are very common, but also come in a variety of different sizes.
- Car cigarette lighter plugs
Used to connect to the normally 12V DC onboard systems in cars. Also very common, but there's a lot of low quality plugs out there.
There's a smaller variant based on the ISO4165 standard as well
One example of many different battery connectors mostly used in the RC world. Small and sturdy, some can carry quite a bit of current (or at least that's the theory)
- XLR-4 The 4pin variant of XLR plugs is sometimes used to carry 12V. But it also has numerous other uses.
- MC4 connector
These connectors are mostly used for solar systems. The connector only has a single pole, but they are pretty weatherproof.
- SELV connectors There is an IEC directive for DC connectors, IEC 60906-3:1994. They look sturdy, and there's special keying in the connectors for different voltage levels. They are also incredibly hard to get a hold of.
- Speakon Not quite a standard DC power connector, the Speakon plugs can carry decent DC currents, and have a good locking mechanism. But they are normally used for connecting speakers, so there's a certain risk of connecting two very different systems to each other, and in the meantime breaking both.
- Anderson Powerpole Powerpole connectors are common in the amateur radio community, and come in different sizes/current ratings. The bigger connectors have a coloring scheme for different voltages.
Nowadays, USB connectors are the standard connectors for low-current 5V DC connections.
- Screw terminals Too obvious to not mention, there's always the possibility to use screw terminals. Good for more permanent connections, but not exactly what we're looking for here I guess
There's also a list on wikipedia on DC connectors, which has some of the connectors that I mentioned here.
Now where does this leave us? Well nowhere really. So far, we haven't found the ideal connector, especially for higher grid voltages such as 48V. The most common ones like DC barrel plugs or the car lighter plugs are great if we want to support connecting all kinds of DC consuming devices, but they are not ideal for connecting different components of the grid together.
For the consume01 unit, we chose car lighter plugs for connecting devices, because that's what most devices on hand are using. For the grid side, we went with a Speakon socket, because of the locking mechanism (and because that's what we had on hand). Ideally, we would've preferred a SELV socket, but they are hard to come by. Another good alternative might have been Powerpole.
So we'll be using Speakon for most of our grid connections for now, because that's a sweetspot of features, availability and price, but we'll keep an eye out for better alternatives.
Updates: Picture & link for the SELV connector, and addition of the ISO4165 plug