I am trying to connect a solar panel array in parallel with a LiPO battery. The battery voltage that I want to match is 18.5V (Voltage of 6S LiPo battery). The solar panel array has an output voltage of 18.368V. What is the safest way to combine the power from the battery and the solar array to send into an electronic speed controller?

 

I am trying to connect a solar panel array in parallel with a LiPO battery. The battery voltage that I want to match is 18.5V (Voltage of 6S LiPo battery). The solar panel array has an output voltage of 18.368V. What is the safest way to combine the power from the battery and the solar array to send into an electronic speed controller?

If you want to "OR" them together as alternate sources, you can do that by putting a diode in series with each one. That prevents any reverse current. The load will draw current from whichever source has a greater EMF at the moment. It will even draw from both at times.

This arrangement will not charge the battery from the panel though, and there is a voltage drop across the diodes. Using Schottky diodes will minimize this power loss.

If you want to charge the battery, you'll need a more elaborate setup including a battery charge regulator to protect it from over-charging.

 

Is that panel voltage the open circuit reading?
If so, it will not supply very much current at that voltage. You will need to go to a higher voltage panel and as wayneh points out, some sort of regulator is needed. It is very dangerous to try to charge LiPo batteries without the correct charge controller. Think fire and explosion type dangerous!