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Everything in this article assumes you have already assessed your daily power requirements (DPR). The article will stipulate a DPR of 1,000Wh (1kWh). This 1,000Wh will be the base of all our calculations below.
We will assume lithium = the common LiFePO4 and not any other form of lithium chemistry.
'Dwellers contemplating large currents relative to capacity (“C rates”) might have to oversize the bank to get sufficient throughput, and/or choose a chemistry with lower resistance. FLA are famously stingy with current, AGM good, and Lithium excellent.
The simplest model assumes the bank will be charged then all the loads will be run from the bank.
In real life sometimes loads are running while the system is making power.
You may want to add a section to your DPR spreadsheet to account for load use while solar is present, etc. In extreme cases only a very small bank may be required if most loads are effectively run off the panel.
Charging can be very predictable or highly unpredictable. More predictable charging allows smaller battery banks, and less predictable charging may require bigger banks unaffected by PSoC to cover the variability.
Lead chemistries typically have minimum charging current requirements to stay healthy
If we cannot meet minimums the bank should be downsized (or charging increased)
Note: Lithium has no minimum charging current
Battery chemistries typically have maximum charging currents that can stress charging systems (particularly alternators via combiners):
If the alternator can only safely provide 50A of charging to the house bank this would limit us to a 166Ah AGM bank (166Ah x 0.33 = 50A).