Watt Hrs vs Amp Hrs
This article helps explain these ratings and raises a question wrt battery charging older vs newer LFPs too. Not sure if this also applies to other battery types or if it matters with any when you me...
Forum Discussion
How do you operate in Watt Hrs? Do you have a battery monitor that does that instead of AH?
How do you get started? You have to enter a "full" amount for capacity at 100%.
An LFP rated at 100AH says it is rated at 1280 Watt Hrs . Turns out that is using the "nominal voltage" of 12.8v BUT
they also say the resting voltage at 100% is 13.6v which would be 1360 watt hrs. They say 40% SOC is 13.1v. 40 x 13.1 = 524 Watt hrs, and
524/1360 = 38.5% so about 40.
Meanwhile a 100AH 12v FLA batt says resting "full" is 12.73v so that is 1273 Watt hrs. 40% SOC is 11.96v = 478 watt hrs and 478/1273 = 37.6%
I don't know the rated watt hrs for the FLA, but it seems your watt hr monitor should be using the resting voltage when full as the capacity.
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BTW, that Battle Born LFP claims their battery has "2 to 3 times the power of the same size FLA."
I don't see how 1360 is even 2 times 1273 so that claim is sort of amazing? They also claim the same for its "energy density"--which is fine in that the same size FLA weighs more. 50 lbs vs 31 lbs so not even half the weight but whatever.
Is that as bogus as it looks to me, or am I just not understanding what they mean?
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So what do folks who monitor by Watt hrs really do? Does your monitor keep track of the battery's actual voltage? How? It needs the resting voltage, but you always have a loaded voltage of some amount while camping.
It would need the shunt ammeter to keep track of the amps, but what does it do with the time? The AH counter uses amps and time, but how would the monitor track watts vs time matching the amps with the voltage (which it only has the loaded voltage for)?
How do you get started? You have to enter a "full" amount for capacity at 100%.
An LFP rated at 100AH says it is rated at 1280 Watt Hrs . Turns out that is using the "nominal voltage" of 12.8v BUT
they also say the resting voltage at 100% is 13.6v which would be 1360 watt hrs. They say 40% SOC is 13.1v. 40 x 13.1 = 524 Watt hrs, and
524/1360 = 38.5% so about 40.
Meanwhile a 100AH 12v FLA batt says resting "full" is 12.73v so that is 1273 Watt hrs. 40% SOC is 11.96v = 478 watt hrs and 478/1273 = 37.6%
I don't know the rated watt hrs for the FLA, but it seems your watt hr monitor should be using the resting voltage when full as the capacity.
-------------
BTW, that Battle Born LFP claims their battery has "2 to 3 times the power of the same size FLA."
I don't see how 1360 is even 2 times 1273 so that claim is sort of amazing? They also claim the same for its "energy density"--which is fine in that the same size FLA weighs more. 50 lbs vs 31 lbs so not even half the weight but whatever.
Is that as bogus as it looks to me, or am I just not understanding what they mean?
-------
So what do folks who monitor by Watt hrs really do? Does your monitor keep track of the battery's actual voltage? How? It needs the resting voltage, but you always have a loaded voltage of some amount while camping.
It would need the shunt ammeter to keep track of the amps, but what does it do with the time? The AH counter uses amps and time, but how would the monitor track watts vs time matching the amps with the voltage (which it only has the loaded voltage for)?
