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House battery project is almost done but the required terminating resistor is AWOL. I only have a couple 100s and lots of 470s. I could get close by paralleling 2 100s and put another 100 in series --> 150 Ohms. Or parallel four 470s --> 118 Ohms.

I don't know about the tolerances for Modbus termination. Anyone know if a single 100 Ohm resistor has a chance of working?

Edit: Cable length is about 29 ft (~9 meters) Cat6

House battery project is almost done but the required terminating resistor is AWOL. I only have a couple 100s and lots of 470s. I could get close by paralleling 2 100s and put another 100 in series --> 150 Ohms. Or parallel four 470s --> 118 Ohms. I don't know about the tolerances for Modbus termination. Anyone know if a single 100 Ohm resistor has a chance of working? Edit: Cable length is about 29 ft (~9 meters) Cat6

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[–] • 1 pt

Frankenresistor will become a problem long term

Higher inductance? I'd agree, use it until you get a proper 120 ohm to drop in place.

[–] • 1 pt

There will be a slight change in cross-sectional inductance as well as a new parasitic capacitance that forms between the resistors. But since RS-485 is current loop, the inductance and capacitance changes will only be a problem at very high frequencies, which is unlikely to be the case here. Ultimately my concerns with the Frankenresistor are those related to their connection. Though OP used 60/40 Sn/Pb solder, there is the chance that cold joints will change the resistance/impedance of the compound resistor over time. It's probably not a major issue at all, but if it's for some critical industrial control application, I would definitely change it out as soon as possible with a good high quality, tight tolerance metal film resistor just to avoid liability issues that could pop up in a failure incident investigation.