LFP on Shore Power with Inverter/charger?

BFL13 wrote:
Steve, thanks for the clarification. I was using CCA because it is the only thing I can think of with battery ratings that are a measure of its power. FWC said a battery's power is its max current at its nominal voltage (if I got that right) so 800CCA is twice the power of 400CCA.

I don't know where an RVer cares about power as such. Ads saying a battery has "twice the power" got me wondering what that is supposed to mean. Seems to be "Sales" talk. ?

That Odyssey 31 hybrid battery that allows a high draw makes that claim, and ISTR LFP ads saying that too.

Another puzzle is how they do AH with LFPs, but that only matters to those who operate them trying to keep track of usage while camping if they even do that.

EG, The blurbs say don't use Peukert, but still say the LFP is 100AH because they ran it down at 100 amps in 1 hour so that is 100AH. Then they sort of dance around saying it also takes 20 hours to run it down at 5 amps, so that is 100AH at the 20 hr rate. But no Peukert here folks! :) It makes your head spin.

Then they start in with the Wh, but use the 12.8 nominal voltage to get the AH. OR----did they get the AH first and then invent the Wh????

In the previous example, it was 1536 Wh and 120 AH at 12.8v

The battery is full at 13.6v so that is where you have to start. Either:

A. the battery is really 1536/13.6 = 113AH , or
B. the battery is really 120AH so x 13.6 = 1632 Wh

Which is it? If you are monitoring by Wh usage or AH usage, I would think that is important for setting up your monitor.

Not a clue. so Steve, what are you going to do for operating your "280AH" battery for setting up a monitor? Just curious on my part, but other LFPers might be interested. ?

oh where to start, so many questions at once haha..

the first thing you have to come to terms with when dealing with LFP is it isnt lead acid. every other battery flooded, agm, SiO2 and so on is a lead based tech. Most Lithium batteries dont fall into the voltage specs that are simular to the lead based batteries but LFP comes very close. close enough we can use it interchanagbly. having said that its overall volatage is a little higher so conventional ways of measuring wont quite work, and some of the conventions we are use to are out the window. there is pretty much zero Peukert effect with the LFP chemistry so for all intensive purposes you don't worry about it. this is a bonus of LFP as you can run high loads with out losing AH.

As for the 20 hour rate, I imagine there must be a standard voltage that the test is done at but I am not totaly sure on that.

I will probably use the cheepest monitoring thing I can find on Amazon that is LFP compatable. I have a little 50 buck version of the Victron in my camper that says it is LiFePo4 compatable so if that works Ill grab another. plus the few BMS setups I have narrowed my choices down to have bluetooth and an app I can check out the other battery info with. so far it looks like I am going to go with the overkill BMS but there are a couple other ones I am trying to find out more info on.

Steve