LFP’s Voltage Curve…
As I’ve previously posted, my 200a drop-in LFP battery bench tested at 215a (so about 7% more than the shelf rating), yet I was able to brew Keurig coffee at 125a even at zero % SOC, without a single low voltage alarm on either the inverter or the Victron BMV 712…
I have no way to know how ubiquitous this ‘over capacity’ feature might be regarding other vendor’s LFP’s, but in this case (possibly unique - I donno?) it nearly translates to 100% of advertised rating as potential usable capacity…And this kinda explains my buddy’s scenario when using his single 100a/h LFP he inadvertently ran his air cond down to 6% SOC without a low voltage alarm (was at a dang 6% before noticing SOC!)…
So (speculative forensics here only), although his Victron was displaying 6% SOC, then based upon my above example (same maker battery, assuming 7% surplus), in reality he may have had about 13% SOC (say, < > 6a + 7a) still remaining reserve…In retrospect (admittedly assuming such…), his voltage at that time was likely at around 12.0v - thus, explains why no low voltage alarms…
Voltage/SOC chart link:
https://footprinthero.com/lifepo4-battery-voltage-charts
Whether or not this potential (say unadvertised?) over capacity is a wider-spread feature among other battery makes (??), still, it’s this nearly flat voltage characteristic that provides LFP’s their far greater usable capacity, and though often somewhat difficult to convey, where actual practice very much mimics ‘a near’ shore power experience…
It would be interesting to hear other LFP users points of view!
3 tons
I have no way to know how ubiquitous this ‘over capacity’ feature might be regarding other vendor’s LFP’s, but in this case (possibly unique - I donno?) it nearly translates to 100% of advertised rating as potential usable capacity…And this kinda explains my buddy’s scenario when using his single 100a/h LFP he inadvertently ran his air cond down to 6% SOC without a low voltage alarm (was at a dang 6% before noticing SOC!)…
So (speculative forensics here only), although his Victron was displaying 6% SOC, then based upon my above example (same maker battery, assuming 7% surplus), in reality he may have had about 13% SOC (say, < > 6a + 7a) still remaining reserve…In retrospect (admittedly assuming such…), his voltage at that time was likely at around 12.0v - thus, explains why no low voltage alarms…
Voltage/SOC chart link:
https://footprinthero.com/lifepo4-battery-voltage-charts
Whether or not this potential (say unadvertised?) over capacity is a wider-spread feature among other battery makes (??), still, it’s this nearly flat voltage characteristic that provides LFP’s their far greater usable capacity, and though often somewhat difficult to convey, where actual practice very much mimics ‘a near’ shore power experience…
It would be interesting to hear other LFP users points of view!
3 tons
