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Schneider Conext SW4048 - Remote Solar Generator/Charger Setup and Neutral-Ground Bond

Hello! I am a new member, and I have only our anecdote to offer. I think RCinFLA is correct that the SW408 manages neutral AC input connection within the inverter. Our SW4048 also has intermittent grid support, 120v only on L1. There is no neutral-ground bond in our inverter subpanel. Our grid input is active most of the time for battery charging and pass-thru, but we sometimes disconnect grid input during electrical storms or occasionally to experiment with grid outage scenarios (e.g. how long could we keep the freezer going?) In January there was a 3-day grid outage, and while we were off-grid there were no apparent end-load issues, bad smells, loud hums/clunks, fires, etc. Perhaps by sheer luck, our system has been stable since 2018. We don't have any 240v loads, although we may add HVAC to the subpanel next year. That may uncover vulnerabilities in our current system.

We had to reduce our grid input to 120v because the SW charging parameters were not compatible with our repurposed Chevy Volt lithium batteries, which have a nominal voltage range of 38-48v. The SW charger could theoretically overcharge batteries, even with (wonky) AC Support Mode and a BMS with 13amp shunt. To fix this vulnerability, we added a SSR on L1 input only, controlled by battery voltage per our Midnite Classic aux1 port. We opted against a dual-pole relay for full 240v L1-L2 grid support due to advice from someone who had already tried that in a similar scenario. With L1 grid input only, batteries recharge at approximately 1500w, and it seems like pass-thru can add another few hundred watts when needed. Thus far, problems from L1-only input are that when batteries get below 44v and charger is subsequently switched on, the inverter clunks repeatedly, throws a "battery below voltage" fault, and won't charge the batteries. Because of this, we have to keep our battery reserve higher than we would like, as they can theoretically provide solid power down to 38v. Could this charging limitation be related to not having a neutral-ground bond in our solar subpanel?

Thanks!
 
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