Hooking up to existing Midnite Solar Kid Controller.

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SV Serenity

May 2, 2021, 9:49:35 PMMay 2
to electrodacus

Trying to make sure the Electrodacus will work for my planned setup.
I have 400w Solar through a Kid Solar Controller. Other charging sources are an AC based charger that can be configured to approximately the right voltages and eventually an alternator through an external regulator (current setup wont work). Primary charging is through the solar.
These are going to be feeding 600Ah of 12v LiFePO4 batteries in two banks each with their own controller. A 400Ah bank and a second 200Ah or 400Ah bank (all 200Ah cells). I have the cells ordered. Measured usage shows the solar can provide adequate charging vs/usage during cruising.
The plan would be to have the charging sources cutoff before the BMS does (85%-90% or so).
The Kid has the ability to do load diversion for when the batteries are full if needed. This is on a sailboat.The batteries will also be used to start the diesel (25hp) when needed. There will be a constant 3A load or so for the instruments when cruising.
Thank you for input and ideas.

Dacian Todea

May 3, 2021, 12:15:18 PMMay 3
to electrodacus
The SBMS0 needs to be able to control ON/OFF all charge sources and separately all loads the voltage settings on the charger is fairly irrelevant as the SBMS0 needs to be able to completely turn OFF the charger when any cell gets to say 3.55V (default for LiFePO4).
Why do you have so many separate batteries ? You are not allowed to parallel LiFePO4 batteries only individual cells can be paralleled. If all your cells are 200Ah and same model why not build a single large battery that is made as groups of 3 cells in parallel then 4 of those groups in series for a 600Ah battery?
The BMS is the one that needs to stop the charging and you can set the SBMS0 to stop charging at 85% if that is what you prefer but after the first charge that needs to be done to 100% for SOC calibration.
If this is your solar controller https://www.midnitesolar.com/pdfs/10-268-1_REVT_Kid_Manual.pdf then it seems it has an Aux input that can likely be programed to turn OFF the chagring when the SBMS0 says so. It should have a mode where charging is OFF unless the SBMS0 provide a signal to Aux pin that is OK to charge. For some reason for me the search function is not working in that pdf manual. You will need to find what the setting is or ask the manufacturer how to integrate with a BMS.

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