Builiding of a complete 6kW PV inverter with MPPT chargers

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KeepIS Guru Joined: 13/10/2014 Location: Australia Posts: 1634	Posted: 01:41am 06 May 2024       @ -dex- I somehow missed your post of the circuit layout Posted: 06:18pm 02 May 2024. The Kilovac or equivalent you show between the DC bus and MPPT bus is the way I think it should be done, everything I/we do is aimed at protecting the LiFePO4 banks, IMHO the MPPT regulators can look after themselves. You have fuses on the MPPT outputs but I have breakers, some of my MPPT controllers are Auto voltage sensing, which is a pain, they need to be isolated from the Arrays to setup correctly, and supposedly need to be powered off after updating settings - I'm guessing as a precaution to ensure the installer actually set and saved the settings correctly. You look to have everything set up correctly and in a similar fashion to mine.   nickskethisniks said   One thing to do is to set absorb voltage very low and time short, so it's not immediately a problem as there is extra capacity to charge. Yes I agree, not only is my absorb low, but my bulk charge current of a "max" 30A per bank is reasonably low and hardly ever reached, as I never discharge much below 60% SOC, my average charge is around 10A per bank and drops quickly. The max SOC I aim to reach at the end of the day is around 90%, but can be as low as 80% on overcast rainy days. You might need to top charge/balance once a year when doing this as there can be a slight memory effect, but it's completely eliminated with one top balance, do NOT confuse this with the old memory effect of LI.   The bulk charge rate and max SOC you select is of course, totally dependent on the system design parameters for your installation, solar array size, battery size, and your power usage, there is "NO" one size fits all. If you are looking for long term LiFePO4 battery life - The aim should be to not have the batteries sit above 90% SOC for too long. Most recent data again supports what a lot of off grid users also found, LiFePO4 likes to be on a discharge cycle as soon as possible after the charging cycle is close to completion, and there is no need to fully charge a LiFePO4 bank every day, both of these ideas were suggested a long time ago and crapped on back then. Apology -dex- as this is partly off topic in your thread. . Edited 2024-05-06 13:10 by KeepIS