rockyeades
New Member
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- Mar 21, 2022
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Can I use a cat5e ethernet cable in place of an RS485 cable to parallel 2 HQST 40amp charge controllers? HQST has removed RS485 cable from its catalog.
RS485 or cat5e ethernet cable
- Thread starter rockyeades
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wildbillpdx
Solar Enthusiast
My understanding is that you should be able to use Cat5. Just try it...don't think you'll hurt anything. Maybe others have a different answer.
Should be fine; make sure you use a twisted pair. Over what distance are you connecting? Shielded Cat5e would be better if distance is a long way or there is a lot of interference from other circuits.
During installation testing, I ran RS485 over about 50m of Cat5e with no issues.
During installation testing, I ran RS485 over about 50m of Cat5e with no issues.
I have a similar question regarding connecting an LG battery to a Growatt inverter. It calls for RS485. I tried a Cat5 cable from my computer cable bin and it doesn't seem to work (I might have a setting wrong). When you say make sure to use a twisted pair, does that mean that the pinouts are not the same, even though they are the same connector? The distance is about 6 feet.
DougfromdaUP
Solar Enthusiast
Your cable choice depends on the distance and data rate. I installed lots of shielded twisted pair audio cable (like Belden 9451) for runs of a couple of hundred feet or so For controlling equipment. If you’re going a long way, like 500 feet at a moderate to high rate, look for better cable. At six feet you , could probably use zip cord if you could fit it into the connector.
If you’re having trouble with a short cable make sure you are using the right connector pins.
If you’re having trouble with a short cable make sure you are using the right connector pins.
Not sure what you mean. The cable I'm using is a standard ethernet cable. Does that mean the pins are different for RS485?
DougfromdaUP
Solar Enthusiast
I think you’ll have to check the device drawings, or hope for someone with more knowledge than me to respond. Most of the equipment I installed used screw terminals and half duplex, so I’m not able to help with what inverters use. Sorry.
Hedges
I See Electromagnetic Fields!
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I do use RJ45 jacks and CAT cable for RS-485 with SMA. Running slow, 1200baud. Supposed to be good for 1200 meters.
TX+/TX- should be on a twisted pair, some color and same color striped wires. Then ground on some wire.
Occasionally a cable has different wire to connector pin mapping from common, and some are crossover. Look through transparent connector or buzz it out.
Pullup, pulldown need to be supplied by something on the bus, and terminators at both ends.
SMA recommends CAT5 shielded cable.
TX+/TX- should be on a twisted pair, some color and same color striped wires. Then ground on some wire.
Occasionally a cable has different wire to connector pin mapping from common, and some are crossover. Look through transparent connector or buzz it out.
Pullup, pulldown need to be supplied by something on the bus, and terminators at both ends.
SMA recommends CAT5 shielded cable.
I finally found something on youtube that shows how to connect the battery. Even though the LG battery has a RJ45 jack, that's not where you connect the comm. Just to close the loop in the rare event someone else needs to do it, here is the way they say to do it. HOWEVER, while this did get the battery and inverter to talk to each other, the inverter app was saying there was a wiring error with the battery. There wasn't. (I've read others having to update the firmware when adding a battery, so maybe that still needs to be done as I haven't been able to get rid of the error message).
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