Series is like a column of 10 people in line at a traffic light in a single lane. The light turns green and all the cars start moving at the same time, no problem and all 10 people get to move. But…if car #3 does not move (gets shaded) then all the cars behind it also cannot move and only three cars were able to move forward and produce motion. Benefit is that you only have to have a single lane with a narrow road to carry the traffic.
Parallel is like the same 10 cars at a traffic light but they each have their own separate lane (10 lanes side by side). When the light turns green, all the cars begin to move forward except car #3. The remaining 9 cars are still able to move forward and produce motion. This comes at a cost of having to have a wide road which takes up more room.
Now this is all completely non technical but my attempt to explain it in simple terms so for all the engineers out there go ahead and post more technical explanations that most will not understand : )
You are already connecting your panels in Parallel so no explanation needed.
To connect your panels in Series, do the following:
Don’t use your parallel branch connectors. They are not used at all in series connections.
Take panel #1 and take either of the two wires and lead that wire to the only wire on panel #2 that it will snap into. Take the remaining unconnected wire coming from panel #2 and connect it to the only wire on panel #3 that it will snap into.
This will leave you with a disconnected wire coming from panel #1 and a disconnected wire coming from Panel #3. These two disconnected wires are what you connect to your EB150. You may have extension cables leading to your EB150 which is fine.
You should get the best results by using the panels in series and they are simpler to connect this way.
Series gives you more electrical pressure which is easier to transmit over your wires.
Parallel gives you more volume of electricity but less pressure. This is harder to transmit over the wires and requires larger wires. You are also limited by the volume of electricity your EB150 (amperage) can accept and when you wire three panels in parallel you are likely exceeding this maximum and not receiving all the available charging power.