LiFePo4 vs Lead Acid...Some points of interest.

full_mosey wrote:

time2roll wrote:
LFP is faster in all conditions. Not even close enough that you would need to time it. There is no "fair fight" as LFP is whole different class.

Here is a 'fair' fight.

Cycle the LFP at 10% - 90% and the FLA at 50% - 90%. Do this until the FLA dies. Install the LFP as a replacement for the dead FLA and continue on your merry way.

The LFP features I am looking forward to:

1. the practically unlimited cycles without any full charges,
2. replacing 400lbs of AGM with 100lbs of LFP.


HTH;
John

BINGO Sir!!

Just an occasional full charge to allow for cell-balancing and for a periodic meter resynchronization is all...

Battery University seems to be having problems--I get "overloaded" error.

It was BU-409 if you Google for that and if you can get it.

Wait till you see the article whenever if gets back on before insisting on the 97% idea. You also have the second quote about 60%. No reason to think that person is a liar.

Even with the 60% end of Bulk at 1C, the times came out as shown, so there's that. The long absorption time after the 60% is still fairly short so you can see where the time-savings occur if you look.

If you compare charging efficiencies then use 99% for LFP as the BU article says and use 94% for the FLA like Bogart does for the Trimetric monitor (Bogart explains how they got that number in their user's manual.

That means a 5% time saving average for the LFP along 0-100 from charging efficiency.

What is missing from the BU I think, is the wiring and BMS on the LFP cells, which add R and could increase "LFP" times. No idea how much that would be. That BB tester guy mentioned that and said some have better wiring than others. Something for a roll-your-own guy to consider perhaps.

BFL13 wrote:
The Battery U link has a charge time graph (scroll down) that has what I need to make a time comparison to do a "0-90". Obviously the "90-100" times are of great interest, but I don't have that for FLA. Their graph does go to 100 on the capacity curve.

I will use my ugly graph figures without inflicting the graph on folks again, unless you all insist. I have it for a 55 amper on 220AH doing a 50-90 which is a 25% charging rate, so that makes it convenient. I just need to do it in proportion for a 100AH batt, easy! Same times at the 25% rate doing 25 amps on 100AH as 55 amps on 220AH.

The FLA Bulk ends at 72% SOC and tapers to 90%. the Batt U graph shows the time for when the capacity reaches 90% on their 100AH batt. It shows Bulk ending at 60% SOC then amps taper.

(Howls of outrage from the usual suspects!--so take that up with Batt U , not me)

So FLA first:

0-72AH at 25 amps = 2.88 hr = 173 min
72-90AH tapering = 86 min
Total time 0-90 = 259 min = 4.32 hr

Now the LFP:

0-60 at 100 amps = .6 hr = 36 min
60-90 tapering amps = 39 min
Total time 0-90 = 75 min = 1.25 hr and 4.32/1.25 = 3.46 times faster
It would look worse for the FLA if we added the 90-100 part.

What about a 40-90 though, perhaps more typical of camping?

FLA : 40-72 at 25 amps = 1.28 hr = 77 min
72-90 still 86 min
Total = 163 min = 2.72 hr

LFP: 40-60 at 100 amps = 12 min
60-90 still 39 min
Total = 51 min = .85 hr and 2.72/.85 = 3.2 times faster

So if you added the 90-100 times it would be more like the 4 times faster claim for a 0-100 looks like. (if anybody would ever do that with an FLA!)

EDIT--in real life an RVer might have a 100a charger and be used to doing 50-90s with his 460AH bank of FLAs. He might wonder how much gen time he could save getting the same AH restored (that matched his AH usage) if he switched to LFP.

Now he can't use the 4 times faster as with 1C vs .25C. He has to do a whole set of calculating to see how much gen time he would save with how many AH of LFP instead of his 460AH of LFP, assuming he will still use his 100a charger.

non of this makes any sence, first off your link doesnt work so I cant see the graph, also why are you tapering at 60% for the LFP, they will go from 0 to ~ 97% on bulk with no tapering. you only need a single stage charger if you are happy with this and you can still get it to 100% with that same single stage charger. if you are using a 1C charge rate you can charge a LFP in 1 hour maybe a couple min longer. this isnt conjectur, its in the manufactures specs for the LFP cells. the only issue a camper will have is getting enough charger power to hit that 1C rate, which if you build any significant battery you wont do it. so a 280 AH at 0.25C is quite possible, that would be 70 Amps of charging so a larger converter would do it or a combanation of converter and solar, or larger solar. I get 22 amps off my one panel camper so if I add another I am up to 44 on a good day. so realy it is about how fast can you replace you overnight use. my one panel does it by noon (havent sat and watched to see when I hit 100%, and it would do that with LFP or FLA batteries. by switching to LFP I go from two 6V GC to one battery that is a little smaller than one of the GC and weighs about 1/3 of what was is there now.oh and has 2.8 times the usable AH. so how does this benifit me, well it lets me move the battery into a indoor space that isnt used right now (so no more worries about tempature) it will free up an out door storage space so I will be able to put some stuff in there instead of in the door on the floor. and if I do hit a run of bad weather, I have the capacity to go about a week with no sun...

Steve

time2roll wrote:
LFP is faster in all conditions. Not even close enough that you would need to time it. There is no "fair fight" as LFP is whole different class.

Here is a 'fair' fight.

Cycle the LFP at 10% - 90% and the FLA at 50% - 90%. Do this until the FLA dies. Install the LFP as a replacement for the dead FLA and continue on your merry way.

The LFP features I am looking forward to:

1. the practically unlimited cycles without any full charges,
2. replacing 400lbs of AGM with 100lbs of LFP.


HTH;
John

time2roll wrote:
LFP is faster in all conditions. Not even close enough that you would need to time it. There is no "fair fight" as LFP is whole different class.

That is kind of the point I was indirectly trying to make. I am not sure who would care if there is a specific case where it is 'only' 3 times faster to charge as opposed to 4 or 5 times faster.

This reminds me of the whole MPPT vs PWM discussion from several years ago, where there were a few holdouts arguing that under a very specific set of circumstances PWM was actually more efficient than MPPT. Only in that case we were arguing over a 20%-30% difference in performance, now we appear to be arguing over a 300% - 400% difference in performance.

LFP is faster in all conditions. Not even close enough that you would need to time it. There is no "fair fight" as LFP is whole different class.

time2roll wrote:

BFL13 wrote:
So if you added the 90-100 times it would be more like the 4 times faster claim for a 0-100 looks like. (if anybody would ever do that with an FLA!)

You might find FLA is just as slow at 2% as it is at 98%.

Yes BTDT with a guy at the campground with dead batts. Got them going and they only took a few amps at first then amps slowly rose to normal acceptance. ISTR you can even get reverse polarity if you start at zero?

I saw something about LFP wanting a slow start till a higher SOC not hit with 1C right off, but that might have been a low temp thing, can't remember.

Pretty hard to set up a "fair fight" with practical scenarios. My edit at the end of the times post about the RVer wanting less gen time is apt I think. You could do the times for that.

Kinda funny to watch some folks relentlessly swinging at Windmills:

https://theflatearthsociety.org/home/

I guess I don't really understand your point? What is the big picture message you are trying to convey?

Yes, if you arrange the starting line and goal posts just so, and use data from a different battery chemistry it could be that lithium will charge slightly less than 4x faster than lead acid. But why is this important?

BFL13 wrote:
The Battery U link has a charge time graph (scroll down) that has what I need to make a time comparison to do a "0-90". Obviously the "90-100" times are of great interest, but I don't have that for FLA. Their graph does go to 100 on the capacity curve.

I will use my ugly graph figures without inflicting the graph on folks again, unless you all insist. I have it for a 55 amper on 220AH doing a 50-90 which is a 25% charging rate, so that makes it convenient. I just need to do it in proportion for a 100AH batt, easy! Same times at the 25% rate doing 25 amps on 100AH as 55 amps on 220AH.

The FLA Bulk ends at 72% SOC and tapers to 90%. the Batt U graph shows the time for when the capacity reaches 90% on their 100AH batt. It shows Bulk ending at 60% SOC then amps taper.

(Howls of outrage from the usual suspects!--so take that up with Batt U , not me)

So FLA first:

0-72AH at 25 amps = 2.88 hr = 173 min
72-90AH tapering = 86 min
Total time 0-90 = 259 min = 4.32 hr

Now the LFP:

0-60 at 100 amps = .6 hr = 36 min
60-90 tapering amps = 39 min
Total time 0-90 = 75 min = 1.25 hr and 4.32/1.25 = 3.46 times faster
It would look worse for the FLA if we added the 90-100 part.

What about a 40-90 though, perhaps more typical of camping?

FLA : 40-72 at 25 amps = 1.28 hr = 77 min
72-90 still 86 min
Total = 163 min = 2.72 hr

LFP: 40-60 at 100 amps = 12 min
60-90 still 39 min
Total = 51 min = .85 hr and 2.72/.85 = 3.2 times faster

So if you added the 90-100 times it would be more like the 4 times faster claim for a 0-100 looks like. (if anybody would ever do that with an FLA!)

BFL13 wrote:
So if you added the 90-100 times it would be more like the 4 times faster claim for a 0-100 looks like. (if anybody would ever do that with an FLA!)

You might find FLA is just as slow at 2% as it is at 98%.