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Chris Michael avatar image
Chris Michael asked

Cyrix-Li-Ct not charging house battery in RV

Hello. I have an RV with a standard lead acid battery connected to the alternator, which is then connected to a Cyrix-Li-Ct. The Cyrix-Li-Ct is then connected by about 15 ft of 2 gauge wire to the house battery, which is a Renogy 100ah LiFePO4. I'm trying to diagnose why the house battery never seems to charge from the Cyrix-Li-Ct. The voltage from the starter battery seem to be in line with the spec sheet when the alternator is running and I have a ground wire ran back to the starter battery on the 86 Bat terminal. I've verified that the house battery has a proper ground to the system. Are there any additional troubleshooting tips that I can try? Thanks!

Cyrix Battery Combiner
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zhenders avatar image zhenders commented ·

I have the same question. When I check the voltage on the 30 post (LiFeP04 battery bank) I see the voltage at 13.04 volts. When I check the voltage on the 87 post I see 4.2 volts. I start my truck and I see 13.9 volts and about 10 seconds later I see the voltage drop to 13.10 volts when the batteries combine. I think I may need to increase the wire gauge from my truck battery to the Cyrix?

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ejrossouw avatar image
ejrossouw answered ·

I'd check the basics as below. Assuming a couple of things given no schematic, I'd suspect voltage drop has something to do with it the given length and AWG

https://docisolation.prod.fire.glass/?guid=9d9ec711-4d98-41f5-1af0-3595facddea3

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Chris Michael avatar image Chris Michael commented ·

I'm getting a Symantec link validation error when trying to open your hyperlink.

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Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

A cyrix-li-ct needs a + from the BMS on contact 85.

If there is no + the cyrix will not close.

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skipcool avatar image skipcool commented ·

Hello,

My supplier sold me a superpack battery (with internal BMS) and a Cyrix-li-ct to connect both start battery (lead) and leisure battery (super pack) to the engine alternator.
As the 85 signal "+" is mandatory, what the required tension is to be able to charge both battery?
Thanks,

Cyril

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