I'll be taking delivery of 400ah of 48 volt lifepo4 in a couple months, so I've been studying as much as I can in advance. Based on what the consensus seems to be regarding maximizing cycles, my plan is to charge to no higher than 80% SOC and discharge to no lower than 20% SOC, I understand that deducing SOC from voltage is a challenge due to the extremely flat charging curve.

So here is my question: Given that charge current drops as the battery voltage approaches the charge voltage, doesn't this provide a good way to deduce SOC? For a given charge voltage, that is, doesn't the current (the battery's "acceptance") reflect the battery's SOC pretty accurately? I've seen specs that say, e.g. "for a 90% SOC, terminate charging when current falls to .005 C." For my 400ah bank, that would mean halting charging at 2a (with charge voltage set at manufacturer's recommendation). So doesn't it follow that stopping at 80% SOC would mean stopping at some higher amperage, e.g. 4a? If so, I wonder why there aren't tables that let you estimate SOC based on current at given charge voltages and for given Ah capacities.

I'm not an EE, so I realize this mightn't make sense. Happy to be educated! Thank you.

BTW--I found PNjunction's 07-12-2019, 05:08 PM post on bulk/absorb/CC/CV extremely enlightening, and I hope he weighs in on my post.

So here is my question: Given that charge current drops as the battery voltage approaches the charge voltage, doesn't this provide a good way to deduce SOC? For a given charge voltage, that is, doesn't the current (the battery's "acceptance") reflect the battery's SOC pretty accurately? I've seen specs that say, e.g. "for a 90% SOC, terminate charging when current falls to .005 C." For my 400ah bank, that would mean halting charging at 2a (with charge voltage set at manufacturer's recommendation). So doesn't it follow that stopping at 80% SOC would mean stopping at some higher amperage, e.g. 4a? If so, I wonder why there aren't tables that let you estimate SOC based on current at given charge voltages and for given Ah capacities.

I'm not an EE, so I realize this mightn't make sense. Happy to be educated! Thank you.

BTW--I found PNjunction's 07-12-2019, 05:08 PM post on bulk/absorb/CC/CV extremely enlightening, and I hope he weighs in on my post.

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