Battery Rating vs Capacity Monitoring
Some things: Shipping batteries in the US requires the Watt-Hour rating to be marked on the battery, and the rule is to use the "nominal" voltage. So LFP uses their 12.8v figure for that 100AH x ...
Forum Discussion
I think you have a misunderstanding of how a battery is rated in Watt hours, to provide an accurate ratings you need to measure how much energy is provided by the battery, just as you would for Amp hours. Now for regulatory reasons, often the 'nominal' voltage is just multiplied by the Amp hour rating, but this is an approximation at best.
To determine the Ah capacity you discharge the battery (at a specified rate and specified temperature) until it reaches a specified end point while at the same time measuring the current and integrating over time. That is how a manufacturer knows their battery is a 100Ah battery. Same deal with Wh, you measure the power the battery provides during discharge (Watts) and integrate over time.
PS the fully charged resting voltage of LiFePO4 is 3.2V/cell ~ 13.2V not 13.6V.
To determine the Ah capacity you discharge the battery (at a specified rate and specified temperature) until it reaches a specified end point while at the same time measuring the current and integrating over time. That is how a manufacturer knows their battery is a 100Ah battery. Same deal with Wh, you measure the power the battery provides during discharge (Watts) and integrate over time.
PS the fully charged resting voltage of LiFePO4 is 3.2V/cell ~ 13.2V not 13.6V.
