Specifications

How to match your battery and solar panels

Battery and Solar Panel Specifications

Ecoflow has a really good in depth description of connecting batteries and solar panels

Lets sort out all the specifications and how to buy the right battery and solar panels. This will be the most technical part.

In the list of specifications of the battery will be a rating for the PV input. There may be more than one connection for PV (solar panels). The rating on the inputs may be the same or different. 

Lets look at the Pecron E2000LFP:

Voc 12V~18V / 100W Max /7A Max. 

2 x Voc 32V~95V / 600W Max / 15A Max

Looks like it has 3 spots to connect solar panels. A little one (Voc 12V~18V / 100W Max /7A Max) and two bigger ones (Voc 32V~95V / 600W Max / 15A Max)

Lets look at the bigger ones. Each one can accept:

Voc 32V~95V which stands for Voltage Open Current. Voltage is like water pressure measured in Volts (V). The solar panels must provide at least 32V and at most 95V

600W Max which stands for the maximum power. Power is how much can be done at once measured in Watts (W). The total of all solar panels plugged into this outlet must not exceed 600W. This is the easy part. If you have 200W panels you could only have 3. 3 x 200W = 600W

15A Max which stands for maximum current. Like water, current is how quickly electricity flows. It is a function of power and voltage. Power = Voltage times Current. W = VA

We need to look at the specs on the solar panels:

Maximum Power(Pmax) 100W

Maximum Power Voltage(Vmp) 17.9V

Open Circuit Voltage(Voc) 18.8V

Maximum Power Current(Imp) 5.72A

Short Circuit Current(Isc) 6.2A

Maximum System Voltage(Vmax) 1000VDC

There are two basic ways to connect solar panels, in Series or Parallel. 

Here is a Series connection. One is connected to the next and the first and last are connected to the battery

Series Connection

In a series connection, the voltages ADD and the current is the same for them all. So in this configuration for these 4 panels:

The Voltage is 17.9 x 4 = 71.6V

The Current is 5.72A

Recall that total power is Voltage times Current or 71.6V x 5.72A = 409.5 (a bit more than the 4 x 100W that the panels claim to output)

Look at the battery again:

The voltage needs to be 32~95V so 71.6V is in that range.*

The current need be less than 15A so 5.72A is great

Maximum power is 600W so 409W is fine

* You actually should check that the Open Circuit Voltage(Voc) is not over the maximum for your battery as well. Recall it is Open Circuit Voltage(Voc) 18.8V so 4 x 18.8V = 75.2V so that is still fine

Here is a parallel connection. All the batteries are basically connected to the battery directly. 

Parallel Connection

In a Parallel Connection, the Current ADDs and the Voltage is the same

The Voltage is 17.9V

The Current is 4 x 5.72A = 22.88A

Recall that total power is Voltage times Current or 17.9V * 22.88A = 409.5 (the same power as the series connection, which is expected)

Looking at our battery, this will not work at all:

The voltage needs to be 32~95V so 17.9V is too low.

The current need be less than 15A so 22.88A  is too high.

Maximum power is 600W so 409W is fine.

Connectors

The batteries that come from the battery manufacturer often have the right connectors to connect directly to the battery but they assume you will only use ONE.

Most other solar panels have an MC4 Connector below

Many batteries input are an XC-90 (or its lower power sibling the XC-60) connector below

So you would need some sort of adapter because the solar panels don't plug in directly. Something like

If you buy the solar panels and battery from the same place, they will often deal with the connectors and can also provide extension cables. If not, be careful to get the right connectors because they can be difficult to find in Cuba though many people sell the MC4 connectors now and can put them on for you.