Precharge circuit - Expansion board settings


I have three relays (T+, T- and precharge) and want to control them. What are the settings, that T- relay is closed with precharge resistor and after the calibrated time, T+ is closed, Precharge is opened and T- stays closed? In critical failure, all relays should be opened.

It is clear, that the precharge relay will be set to “Critical Precharge Timer”. But for T- and T+ there is some information missing. Could you help me with that?


Hi Kuchengeschmack,

The setting you are looking for regarding T- is Critical Traction Before Prechg, shown below:

As for T+, you are likely looking for Critical BattOk

Here’s a diagram that illustrates what I think you are looking to do:

Let me know if you have any other questions, and sorry we didn’t get to this sooner!

Perfect, this is exactly what I searched for. The system overview was clear to me but I did not found it in the wiki. If it is not included in the wiki, could you just add it there? This will be really helpful for the people :slight_smile:
One further question: is there a safety check with the voltage at the contacts from the hybrid inverter before the T+ relay switches to ON state? Or is it just a simple timing sequence that it follows?

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Hi Kuchengeschmack,

It is just a timing sequence, but if you know the size of the capacitors in your inverter, and the resistance of your precharge circuit, you can calculate the charge time to always allow enough time for full pre-charge. And if in doubt, just set it to a larger value.

I’ll add it to our wiki when I get the chance :slight_smile:. My diagram was made in apprehension of that, but there are a few things on my list first.

Where can the timings between Crititcal Precharge timer and Critical BattOK be configured?

Hi Kleini,

This can be found in Control Logic > Critical > Extra Parameters:

Thank you very much. I didn’t search there in that depth.

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