diy solar

diy solar

Usable LifePO4 Range

caymaanedge

New Member
Joined
Jul 19, 2020
Messages
124
I have 680ah of 12v LifePO4 batteries. Changing at 14.6v per specifications and they are settling fully charged at 13.4v
I have the Victron Smart Shunt installed and am using the blue tooth app to monitor. My issue is the state of charge does no reset as it is recharged. So I'll draw down 100ah overnight and once the solar kicks in and the voltage rises the SOC% continues to decline.
So, I need to keep playing to figure that out, but in the meantime I am looking to manually calculate the SOC based on voltage. Like a little chart showing voltage and corresponding available AH. Ideas?

TIA
 
Please download this PDF resource which contains not only assembly info but charging info, voltage charts & more.
Luyuan Tech Basic Lifepo4 Assembly Guide

NOTE for CLARITY:
LFP Full Voltage Range is from 2.500Vpc to 3.650Vpc (This is the Gross range for LFP)
The Curve from 2.500-2.950 is Very Steep as is the Curve from 3.450-3.650 and is generally what people reserve off for long life & less stress.
LFP Working Voltage is from 3.000-3.400 with 3.200Vpc being Nominal. and THIS is what delivers the Amp Hours that the cells are rated for.

Examples using EVE-280AH cells
NOTE that from 2.500-2.950 _and_ 3.400-3.650 only represents roughly 5-7% of GROSS CAPACITY
Grade B / Bulk cells will test out around 270-280AH from the Gross voltage range and therefore deliver less from the Net Working Range (which is the Flat Voltage Curve) On average people are reporting 272-275AH when they do tests..
Grade A Cells will test out at 285-290+ AH Gross and are quite capable of delivering 280AH from their Net Working Voltage range.

* Properly Matched & Batched cells will have similar IR (Internal Resistance) through their entire Voltage Range during load & charge. Matching & Batching is a long process that tests cells at different loads at different voltages through cycles. This ADDS COST to the cells. MOST Vendors selling "Matched" cells are not in fact doing proper matching, they just test the cells with for Voltage & IR at the standing resting/storage voltage which is essentially worthless as cells can become runners at certain voltages if they differ too much from their fellow cells.

Hope it helps, Good Luck.
 
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