For some applications you may wish to add cable extensions to the RDE300 PV cables in order to reach PV modules located farther from the RDE300 unit.
When extending the PV cables on either the PV1 or PV2 channel of RDE300, observe the following requirements:
- Keep the maximum cable length from the RDE300 unit to any PV module less than 20 meters.
- Ensure that the PV cables run along a straight path. Do not coil up the cables at any point.
- Ensure that the positive and negative cables of a PV channel are paired closely together. Do not run the positive and negative cables along different paths.
- If you have too much extra cable length you must shorten the cable.
If the above instructions are not followed, the IV measurement circuit may not operate properly.
In addition:
- Ensure that your RDE300 unit has the latest firmware. See RDE300 Series Firmware Update.
- Ensure that you are using the latest version of the RDE300 Series Engineering Client Software for configuring the RDE300 unit.
- Using the RDE300 Engineering Client Software, program the RDE300 with an estimate of the cable resistance for your PV cable extensions. This value is used to correct the IV measurements at each point in the IV curve for voltage drops along your cable. To estimate cable resistance, use your choice of online calculator (e.g. search "cable resistance calculator") and perform a calculation for your cable gauge and length. Enter this value in the RDE300 Engineering Client Software on the PV Device Calibration tab for each channel (PV Channel 1 or PV Channel 2).
- Using the RDE300 Engineering Client Software, in the PV Channel Configuration tab, set the IV sweep direction to "Voc to Isc".