LiFePO4 - SOK or Renogy.

3 tons wrote:

BFL13 wrote:
The claim is about charging efficiency making for less time to absorb the same number of AH when being charged. For FLA's here is what the Trimetric monitor's manual says:

" technical note: Some people familiar with batteries will be surprised that the suggested "efficiency factor" is as high as 94%. Without going
into all the details here, there are two reasons for this: (1) The number entered in the TriMetric is not true battery efficiency, or energy efficiency, (which is often quoted at 70-80% for lead acid batteries) but charge efficiency. Charge efficiency (the ratio of total amp-hours you get out divided by total amp-hours to charge the battery) is always greater than energy efficiency. (2) What is entered in the TriMetric is not even the overall charge efficiency of the battery, but the charge efficiency while the battery is not at the top of charge, and not gassing. A battery is not charge efficient while at the top of charge, so if this part is excluded the battery is very charge efficient. (We have measured this to be 95-98% with Trojan wet cell
batteries.)"

So the FLA's is variable over the SOC range, being high until gassing starts (above 80% SOC ), then going worse, with a suggested average of 94% overall.

Let's say the LFP's factor is 100% (it's not) and the FLA's is 94%, and you charge until your "uncorrected" AH counter says you put in 100AH before amps taper in either case.

The LFP will have absorbed 100AH, and the FLA will have absorbed 94AH

That means the LFP is 6% "faster" based on the relative charge efficiencies. (not "3 x faster")

You also know that on solar with its low amps wrt size of bank, the low charging rate means with the FLA that the absorption stage begins in the 90s % SOC zone, while the LFP's starts some where higher in the 90s zone, so not much difference.

With a 200AH bank, the 90s zone is 20AH wide, and if the different starts of Absorption are 5% apart (93-97 say) that is 10AH where the the LFP is "faster". OK, say the solar is still doing 20 amps with LFP and tapering with FLA for that 10AH. with average amps 10 with the FLA. Twice as fast for LFP! What is that in minutes?

It takes 30 min to do 10AH with 20 amps. It takes 60 minutes to do 10AH with 10 amps, so 30 minutes faster to do the 93-97 part.

So if the whole day on solar with 200AH starting at 50% (100AH down) to do a "50-97" is the scenario with solar averaging 20 amps (it will be up and down and whatever all day of course, but say it averages 20--so must be a fairly high amp controller with lots of watts panel), then:

50-93 (86AH) at 20 amps takes 4 hrs, 20 minutes for the LFP and 6% more time with FLA, so 16 minutes longer approx = 4 hrs , 36 minutes.

Now, to get past 93% up to the 97% it takes 30 minutes longer so the difference to do a 50-97 is now 46 minutes. FLA total time 5hrs, 6 min or 306 minutes so 46/306 is 15% faster, with 9% of that for the 93-97 part.

When did 15% become "3 x faster"?

and if you got to 97% at 4 pm with LFP would you notice that you did that instead of at 4:46 PM given how variable solar amps are?

Would you pay maybe $1,400 for the two LFPs instead of say $400 for a pair of 6s to save 16 minutes to do a 50-93 on solar? Obviously, many people are doing just that.

“That means the LFP is 6% "faster" based on the relative charge efficiencies. (not "3 x faster")”

Huh?? Understand that the notation you’ve cited never mentions the element of time. It does mention Charge efficiency which is merely a ratio of how many amp/hrs you get out vs how many amp/hrs you put in, thus it has nothing whatsoever to do with comparing 3x or 6x faster charge recover times per battery type...How does one conclude data that isn’t there??

3 tons

Again - Per trimetric’s technical note above (which never mentions the element of time) can someone explain (by extension...) the premiss suggesting how it is that charge efficiency is related to faster charge recovery times per battery type??

Lost for logic in the NV desert...

3 tons