RS485/Modbus RTU topology and termination

Ev Charging Question
1

Hello,

We are currently deploying a multi-TeltoCharge installation with dynamic load balancing over RS485 / Modbus RTU.

Our current test setup consists of:

  • 2 TeltoCharge chargers

  • 1 smart meter

  • one charger configured as Master

  • the second charger configured as Slave

Communication and dynamic power balancing are working correctly and appear stable.

However, while planning to expand the system with approximately 10 additional TeltoCharge chargers, we encountered a concern regarding RS485 bus termination.

We observed that:

  • each disconnected TeltoCharge charger measures approximately 120 Ω between RS485 A/B lines;

  • this suggests that each charger has an internal active termination resistor;

  • we could not find any documentation describing how to disable this termination (DIP switch, jumper, software setting, etc.).

The RS485 network is installed according to standard best practices:

  • twisted pair cable is used;

  • all chargers are connected sequentially in a daisy-chain topology;

  • no star topology is used;

  • the planned installation includes a relatively long RS485 segment with many chargers.

Our concern is that if every charger contains a permanent 120 Ω termination resistor, the total bus load becomes excessively low and communication stability may be affected.

We would appreciate clarification on the following questions:

  1. Is RS485 termination enabled by default in every TeltoCharge charger?

  2. Is there an official method to disable the termination resistor?

    • DIP switch

    • jumper

    • software configuration

    • any other procedure

  3. What is the maximum recommended number of TeltoCharge chargers within a single RS485 segment?

Thank you in advance for your support.

2

Hello,

Thank you for reaching outl. Could you confirm what is your current model of the stations that you have and the ones that you are planning to install? There a few key differences between EVC1 and EVC2 models so it’s important to be clear of the model that we are working with.

Sincerely,

Dominic

3

Hi!
All stations EVC121000000, all mounted, just having issue wiring them.
Sincerely,

Egidijus

4

Thank you for you response. For EVC1 device, based on your inquiry type maybe you could send us email with detailed installation plan? As there a few things that may need to be addressed based on the signal cables length and systems amounts. Maybe you could send us the scheme with detailed information such as lengths between stations and we could provide information this way? You can send this directly to our support email: support.energy@teltonika.lt

5

Thank you for your response and for looking into this in more detail.

We appreciate the willingness to review the installation layout. However, we would also like to point out that the question regarding RS485 termination in larger TeltoCharge installations may be relevant for many integrators and installers, not only for our specific project.

At the moment, our planned RS485 topology is as follows:

  • Total number of TeltoCharge chargers: planned expansion to approximately 12 units

  • RS485 topology: sequential daisy-chain

  • Cable type: twisted pair

  • Cable routing: from one charger to the next sequentially (no star topology)

  • Smart meter placement: located between the first and second charger

  • Distance between chargers: varies from approximately 1 meter up to 30 meters

  • Total RS485 cable length: below 200 meters

Simplified topology example:

Master Charger
|
|---- Smart Meter
|
Slave Charger 1 ---- Slave Charger 2 ---- Slave Charger 3 ---- … ---- Slave Charger 11

The concern comes from the fact that every disconnected TeltoCharge unit appears to measure approximately 120 Ω between RS485 A/B lines, which suggests that every charger includes permanent RS485 termination.

Because of this, we would like clarification regarding:

  • the intended RS485 topology for larger installations;

  • whether termination can or should be disabled on intermediate chargers;

  • and how Teltonika recommends implementing larger RS485 charger networks.

Thank you again for your support and guidance.

Best regards

6

I just wanted to follow up on this topic. It has been more than two weeks since I provided the requested installation details, and I have not yet received any feedback.

Could you please let me know whether there are any recommendations available regarding RS485 termination and topology for larger TeltoCharge installations, or when such guidance might be expected?

Considering that installations with more than two chargers are likely quite common, I assume there should already be some established best practices available.

Thank you.