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

FWC wrote:
You certainly can choose to stay within some limited range, but there is no real need to do this, unless you are hoping to get > 3000 or so cycles. I do think you are making things much more complicated and confusing than they need to be, and posting some very misleading claims.

Hey B-F-L, since you are a staunch SiO2 battery avocate, and since you have (per your loooong LFP disparagement crusade...) purposefully disseminated a faked manufacturers construct concerning LFP vs FLA (SiO2) charge profiles (this, an established fact), kindly take a moment to explain why someone might be inclined to invest in what appears an ongoing troll??... I’m all for fun, but in the end I just don’t get how this misinformation gamesmanship serves anyone well - but thats just my humble opinion...

3 tons

Right, a full-timer wants lots of those cycles he paid for, so he might get a 500AH bank and use a 100 amp charger (if no solar adding to that) and get more cycles using the 0.2C rate and not so deep a DOD

Weekend warrior could plan to use 0-100s with a smaller bank in AH, since he knows he will never use so many cycles, but he needs to equip for the needed C rate (minus 10 amps very time the furnace comes on during the recharge, adding to gen time, same as with FLAs)

Lots of things to figure, but IMO it would be good to have some camping off-grid time to know what you want your LFPs to do. Then do the math and build your system. It is the same with FLAs but the cost of getting your math wrong is not nearly so severe.

You certainly can choose to stay within some limited range, but there is no real need to do this, unless you are hoping to get > 3000 or so cycles. I do think you are making things much more complicated and confusing than they need to be, and posting some very misleading claims.

BFL13 wrote:

FWC wrote:
There is nothing here that is specific to lithium in any way. Unlike lead the 'operating SOC range' doesn't matter at all for lithium, you can bounce between 0% - 100%, 0% - 50%, 30 - 80%, all you need is the capacity.

Well several folks on here have said they plan to stay in mid-range. Itinerant1 has warned to stay between the knees and that he usually stays above 35%

Doesn't change anything. You pick your own SOC range and go from there.

I don't go out of my way and use the mid range area it just happens 35% SOC seems were my use gets down to before it starts charging (1,280w solar goes along way even in winter) Many times over the years I've been in the 25% SOC range, that's always morning after making 2 pots of coffee (12c Mr coffee) and using the microwave for 5 minutes making breakfast.

Edit: 55-60% is my evening time SOC during winter months (mid Nov, Dec, early Jan) when I'll run the gen for an hour or so for a hold over charge. So morning time after the mentioned above morning routine they'll be enough power. I don't skimp on my power use.

FWC wrote:
There is nothing here that is specific to lithium in any way. Unlike lead the 'operating SOC range' doesn't matter at all for lithium, you can bounce between 0% - 100%, 0% - 50%, 30 - 80%, all you need is the capacity.

Well several folks on here have said they plan to stay in mid-range. Itinerant1 has warned to stay between the knees and that he usually stays above 35%

Doesn't change anything. You pick your own SOC range and go from there.

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". 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."

Don't forget that 90 amper is not PF corrected. A 2200w can run a 75 amper, but not a 90 amper. Can you carry along a Honda 3000? I so, no problem

time2roll wrote:
In a bit less space and bit less weight than the 4x GC2 I currently have I believe I can fit 1240 Ah and leave the generator at home.
That is 5.5 days of 220 Ah usage.

The 100AH drop-ins are mostly G27 size but half the weight, no idea how big the DIY LFPs are.

That 229 down was on the second day, but I needed a top up next day, did another day no gen, (four nights camping) and did the full recharge/recovery at home plugged in.

Whatever, IMO a sharp pencil is required for your math. If you get it wrong and don't have enough AH after trying it out off- grid, you can't just go to Walmart and get another LFP for $100.

There is nothing here that is specific to lithium in any way. Unlike lead the 'operating SOC range' doesn't matter at all for lithium, you can bounce between 0% - 100%, 0% - 50%, 30 - 80%, all you need is the capacity.

In a bit less space and bit less weight than the 4x GC2 I currently have I believe I can fit 1240 Ah and leave the generator at home.
That is 5.5 days of 220 Ah usage.

StirCrazy wrote:

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

That was in a provincial park in January under lots of trees. No solar.
I have lots of solar for when out in the open off grid. See photo in profile for that park site, but that was in March

FWC-"I am not sure why a lithium buyer would need to do any math. In EVERY case the lithium charges faster than lead. Not to mention the half dozen other advantages"

I said he needs to pick an operating SOC range that covers his daily usage and calculate how many batteries he would need to stay under a preferred C rate. Seems pretty obvious.

Yes, you could have put 300Ah into a LiFePO4 battery in those 2 hours, more if you had a larger charger. Or even better, put your 220Ah back in a shorter time and given everyone a few more minutes of peace and quiet.

I am not sure why a lithium buyer would need to do any math. In EVERY case the lithium charges faster than lead. Not to mention the half dozen other advantages.

BFL13 wrote:
"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.