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

BFL13 wrote:

For example--- I have notes of one of my recharges in the 5er up-Island where there is a two-hour gen time rule 9-11 am. I set-up for that so I would not run out of AH. Quick version:

personaly I think no generator time should be allowed, but thats just me. with the price of solar right now, why would you not have a bunch of panels on there and charge all day long?

Steve

"one huge thing your missing is that your going off sales info"

So you didn't read my posts? :(

Good point you made about using FLAs now in the 5er and what would go better with LFPs instead. There is more than generator time savings to it all of course.

For example--- I have notes of one of my recharges in the 5er up-Island where there is a two-hour gen time rule 9-11 am. I set-up for that so I would not run out of AH. Quick version:

Temp 3C/35F, Bank about 600AH in the cold (est--came out more like 584)
26% charging rate with 150 amps of adjustable voltage chargers, set to 15.2V, Trimetric down 292AH at the start, 12.1 v "resting" so about 50%

0900-0931 Constant 150 amps (fiddling with voltage as temp comp some)
Amps tapered at about 61% SOC at 0931
0931-1100 amps down to 65 amps Trimetric says down -78AH, so 214AH restored and at about 87% SOC of 584AH

So how could that have gone better with LFP? Still need about 220AH usable that I can restore in 2 hours of allowed gen time.

It would not take as many AH in the bank, it was just over freezing, so you have the LFPs in where it is warmer.

I think you would want to pick an SOC operating range to fit that 220AH into. Then you could say how many AH of LFP you need.

eg if you picked 20-90 for 70% range, then if 70 is 220, then 100 is 314AH.

Now you need charging rate for 220AH in two hours on 314AH (you would not have 314 of course-some thing near that.)

Pretend constant amps for the 20-90, never mind Battery University--what do they know? :)

So two hours 220AH is 110/314 = 0.35C so you are good with that, being under 0.5 and you still have the 150 amps chargers and the gen.

You have lots of choices--use a higher charging rate and less gen time or whatever you think works for you with the LFPs.

--That is what I meant earlier by saying an LFP buyer would need to do some math for his own scenario.

BFL13 wrote:


LFP specs say 1C is possible but recommend 0.5C. FLA can be charged at .3C, not just .25C. What is "valid"? 1C vs .25C or .5C vs .3C?

.

one huge thing your missing is that your going of sales info. no seller who has to honor warenty is going to say, go ahead and charge at 1C all you want. the prismatic cells I am looking at are rated up to 5C as long as you have a solution for the heat it will create. they can do 1C all day long. so 1C charge rate will completly refill the battery from 0 to 100 in 1 hour. but lets try a different angle here to see if you are just looking at it differently. lets talk usabal AH and keep that as the comparason.

so I have four 235ah 6V batteries in my 5th wheel right now which gives me 235 usable AH. lets say I have a LFP that is 235AH so that is 235 usable at a 0.25C charge rate it will take me 4 hours to recharge my LFP, I can tell you from experiance with that charge rate it takes a lot longer than that to charge the Golf cart batteries, we are looking 6 to 8 hours and that is only to 80% now are the batteries acepting the full charge, nope I have a temprature compensated system so if the temp starts climbing the amps are cut down to prevent dammage to the batteries. it does kick in charging my FLA batteries, but at that rate it wouldent cut in on the LFP so if you factor in the adsorption which could be another 4 to 6 hours to get up to 100 then ya the same system will replace the AH drawn about 4 times faster.

there does come a point where if you drop the charge low enough though they would be closer togeather in time, but if you go and spend the money on LFP why would you not upgrade the rest of your system to take advantage of them?

to me it seams you are basing everything on having a 20 to 40 amp charger on a larger fla bank. I have a 40Amp converter in my camper right now, but as soonn as the LFP battery gets installed that is going up to a 90 amp. can I use 90 amps right now with 210 AH of GC batteries... nope it will just taper amps like crazy so I left it at 40 for now.

so your trying to compare a setup that shouldnt be compared. if I ran a genny instead of solar, which to me if you are spending the money to reduce genny use why wouldnt you add solar and scrap that noisy thing in the first place ;) solar is now dirt cheep, for 600 cdn I bought and installed a complete 325 amp split cell 24volt pannel, the wires, the controler and some other knick nacks. a second panel will only be 200.00 which I will add when I switch to LFP. so right now I have 210 AH (105 usable) with up to 24 amps charging from solar and up to 40 amps from my converter. when I put in the 280AH usable LFP battery and add a second panel and chage out the charge section of my converter, I will have up to 50amps from my solar, and 90 amps from the converter. so doing the same type of camping replacing the used capacity every day will be very fast.

its all relitive, they can accept a higher charge rate so take advantage of it. if I went SiO2, I would never be able to add a second panel and I would have to restrict the output of my converter to 25 amps, every battery tye will have advantages or disadvantages its just how you view them and what your willing to do to take advantage of the good things or minimize the not so good things...

Steve

full_mosey wrote:


I could revise the former test as:
Cycle the LFP at 10% - 50% and the FLA at 10% - 50%. Do this until the FLA dies. What do you believe would happen to the FLA if it were reharged at 10% - 50%. Quick death?

Now, try working your calculations again with valid criteria.

HTH;
John

heck you get a FLA down to 10% and it is probably already dead. lost a couple when I first started camping that way.

Steve

. “It’s like déjà vu but all over again.” – Yogi Berra

3 tons

After endless excursions into deceptive time wasting rabbit holes, what is the point here - character rehabilitation??

3 tons

I agree the depleted to full test is not valid but that is how they do it to get their 4 x claim. That is where the sales guys get to put "4 times faster" in their ads.

Meaningless when FLA stays above 50% so it loses half the range where it could be taking in high amps. If you started both off at 50%, that is not fair to the LFP.

I don't have a valid comparison to cover all scenarios, because they don't have the same operating SOC ranges for one thing. LFP is faster if you do supply more amps than the FLA can absorb.

LFP specs say 1C is possible but recommend 0.5C. FLA can be charged at .3C, not just .25C. What is "valid"? 1C vs .25C or .5C vs .3C?

Solar is not so clear with its low amps, the FLA can take them in, and the LFP is stuck with the same amps (can't make the sun shine brighter) so hardly any difference. You need to get more panel watts same as you would need a bigger amp charger to exploit the LFP advantage, but if you are getting to full by 2PM most days you might wish to spend your money on something else. Or you might want more battery AH in the same space, or more cycle life. It is all up to the individual and his own scenario.

BTW that BU-409 link was working this morning, I haven't checked it lately.

full_mosey wrote:


I could revise the former test as:
Cycle the LFP at 10% - 50% and the FLA at 10% - 50%. Do this until the FLA dies. What do you believe would happen to the FLA if it were reharged at 10% - 50%. Quick death?

I like this test. We can even spot the FLA 500 cycles. ;)

BFL13 wrote:
Always suspecting the sales hype, so want to verify the claims and see if possible where they got their numbers. In this case it is true that 1C with LFP is 4 x faster than with FLA doing depleted to full. ...

The premise is wrong because you have added 'full' as a constraint.

Perhaps you have not fully grasped a point I made in my recent post. To wit, "1. the practically unlimited cycles without any full charges,".

There is no penalty for partially charging an LFP. All I need to do during a recharge is ensure that the LFP will have enough capacity to last until the time I plan the next charge. There is no 'full' goal.

I could revise the former test as:
Cycle the LFP at 10% - 50% and the FLA at 10% - 50%. Do this until the FLA dies. What do you believe would happen to the FLA if it were reharged at 10% - 50%. Quick death?

Now, try working your calculations again with valid criteria.

HTH;
John

Well it seems there’s been a lot of attempted mythology disseminated on both LiFePo4 and SiO2 battery formats..This is why discernment is important when it comes to acceptance of information...A few post speak for themselves...


3 tons