LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

[john61ct]

Originally Posted by PacificGreen

I believe I'm interpreting the .3C of 180ah correctly for charge rate at 54Amps and that the cells should not have current applied beyond a 54Amp charge rate.

I don't see that last, how do you figure?

I don't recall seeing maximum current Capacity sizings for charge sources. Batteries pull Amps based on Voltage, sources don't push Amps, right?

My guess would be that "recommended" 54A would be either

a starting point for the user to get reasonably fast charging, or

a point within a range where they think longevity is (likely) extended.

If my "between .3 and .5 of C" holds, then either would apply.

[PacificGreen]

I'm sure they have C ratings for both charge and discharge as is evident by most every battery specification and documentation I've ever read. This is especially important with charging lithium batteries and also discharging them.

Here Jack works with the same cells:

http://evtv.me/2012/07/calb-ca180fi-new-lifepo4-cell/

"We are accustomed to things after 3.00v moving pretty rapidly, particularly at 100 amps. It would appear in this case that they move VERY rapidly at 3.10v. And indeed, CALB indicates that on these new cells, 3.10v indicates 90% discharge."

So now what did Jack know about the batteries that the manufacturer didn't manage to include in the datasheet.

He charges at 100 amp only for convenience and notes that after hitting 3.6 volts the current reduction for constant voltage must be turned down quickly.

[john61ct]

yes but I'm saying in the absence of words like "minimum" or "maximum" a single "recommended" number is most likely "anywhere around this is fine".

And note some manufacturers, especially less expensive Chinese ones, apparently either aren't keeping up with the real-life experience with this relatively new chemistry gained over time by objective testers like Maine Sail and Calder, or are lying their as$es off.

It is true at the high end some top vendors have different specs allowed for by the intelligent chips in each cell, but otherwise I think LFP is LFP, and unless a trusted authority tells me otherwise, current availability "between .3 and .5 of C" is the default no matter the brand, and then only an ideal suggested for longevity.

Every such source raves about the very fast gennie runtimes enabled by LFP's huge acceptance rate, and I don't recall one yet warning about reduced longevity from feeding what the bank wants at too fast a rate. Not saying it's not possible, but I'm pretty sure a 600A alt isn't going to damage even an "undersized" 600AH bank.

Would welcome being corrected on that if I'm wrong.

And of course with LFP money at stake, excellent charge control, temp regulation etc is assumed. . .

[PacificGreen]

Also to consider was Jack discharged above the max recommended documentation as well to make an efficient smooth graph. If discharged at the 54 amp .3C rating 2.9 volts or 3.0 volts would be more realistic for the 80% 90% cutoff values.

[PacificGreen]

Originally Posted by john61ct

yes but I'm saying in the absence of words like "minimum" or "maximum" a single "recommended" number is most likely "anywhere around this is fine".

I can see on these specs it fails to list minimum or maximum or even optimal as is used in Winston battery specks all three in fact. So this can cause some usage confusion.

Originally Posted by john61ct

And note some manufacturers, especially less expensive Chinese ones, apparently either aren't keeping up with the real-life experience with this relatively new chemistry gained over time by objective testers like Maine Sail and Calder, or are lying their as$es off.

Let's add Joe to the list here as he has used his batteries for 4 years and apparently gone over the vague .3C charging specification.

It is true at the high end some top vendors have different specs allowed for by the intelligent chips in each cell, but otherwise I think LFP is LFP, and unless a trusted authority tells me otherwise, current availability "between .3 and .5 of C" is the default no matter the brand, and then only an ideal suggested for longevity.

Sure I can relate.

Every such source raves about the very fast gennie runtimes enabled by LFP's huge acceptance rate, and I don't recall one yet warning about reduced longevity from feeding what the bank wants at too fast a rate. Not saying it's not possible, but I'm pretty sure a 600A alt isn't going to damage even an "undersized" 600AH bank.

I think and as Jack in the video dialog points out some valid points on acceptance charge especially in terms of the calb 180 is that they rise very quickly to the 3.6v and even to the 3.5v upper knee and then recommends only charging these cells to 3.45 volts and calling it done simply because of how fast they climb. Now to your point using your conditions above Firstly I've never seen a 600Amp alternator. Lets be specific and say a 120A alternator and even that is over a recommended .3C rate charge. Also consider does the alternator have the ability to drop the current and maintain a constant voltage especially in batteries that approach the upper limits of their acceptance quickly as these cells do. Not dealing with fictional 600AH bank. Then the question remains and one that I have as well is "What if any damage can be done to the cells by not charging with CC/CV?" I like many others now simply charge until 3.5 volts or less and don't worry about any CC/CV in the charging.

Would welcome being corrected on that if I'm wrong.

And of course with LFP money at stake, excellent charge control, temp regulation etc is assumed. . .

I'd like to also say that if you go out everyday in your new chevy volt or nissan leaf and drive it with a lead foot you can expect to have problems. Not saying that it can't be done and isn't but certainly it is not a wise thing to do for longevity sake. I guess the same could be said for charging to some degree in instances where the charging is not monitored explicitly to correct for CC/CV and that the reductions happen at the correct time.

[john61ct]

Originally Posted by PacificGreen

Here Jack works with the same cells:

http://evtv.me/2012/07/calb-ca180fi-new-lifepo4-cell/

You do realize this is from a very long time ago, true infancy of LFPs rollout?

And no point at all talking about "too much current available" in this context, because

3.6V is crazy too-hot as far as I'm concerned, how to murder your pricey bank, get a very small fraction of its potential lifespan.

And for what, a gain of under 1% extra SoC?

I think the only reasons we see such abusive levels still floated (see what I did there? 8-) is

dishonest low-end vendors **really** want the market to think LFPs can just be plugged into existing charge sources designed for Lead

and people referencing old "box-opening" reviews rather than following reports more recently published based on longer-term real-world testing.

So sure, I totally believe you could come up with a bank-damaging scenario between a 600A alt and a 600AH bank at a 3.6 charge voltage.

But it's the volts are the problem.

And I would bet real money .5C is no problem with the right protection circuitry in place.

I recall seeing that even 4-5C(!) is safe, but perhaps that is "won't blow up the boat" safe rather than acceptable for longevity.

Just in case you haven't read MS's provisional notes in progress, not saying this specific issue is settled there, just highly recommend http://www.pbase.com/mainecruising/lifepo4_on_boats

[john61ct]

I'm sorry if I was unclear, but the **only** issue I was addressing here is your statement that 54A could be a maximum charge rate for a 180AH LFP.

That 3.6 is a not-healthy charge voltage for LFP longevity is I admit less mainstream, but I trust Maine Sail and others on that.

[PacificGreen]

I do realize the age of the video for sure but the references to it are still valid to Joe's cells. Certainly though I have been mistaken when in reference to the .C rate of charge for the Calb 180's because .3C x his original 700ah capacity should have allowed him to safely charge at 170 amps.

Now though does the optimal or maximum .C charging rate at all deteriorate over time after repeated fast charges and should it be reduced as batteries age?

and people referencing old "box-opening" reviews rather than following reports more recently published based on longer-term real-world testing.

Yeah don't blame me for Joe's dead cells I'm not here to argue. Of course I've read the compass marine material and I am posting to the end of a thread I have mostly completely read over the last five years.

I am simply here to consider and answer and perhaps add some insight into the longevity and use of Joe's calb 180 cells that the video directly addressed in a very learned manner in exploring the underlying potential of the calb 180 cells.

You can note though how in draw down tests and management of the Compass Marine bank and I think he notes it on the previous page:

These cells have:


--Never been floated, they get charged, then discharged
--Only absorbed to a net 8A > 10A of tail current at 13.8V -14.0V
--Not charged above 14.0V unless for testing purposes (I now have a few other banks for that)
--Max charge rate at approx .3C
--Stored at 50% SOC when not being used or cycled
--Stored in 40-60F +/- temps when not being used or cycled
--Only very rarely exceeded 80F
--Highest voltage they have ever seen was 3.8VPC while top balancing initially.

So that leads me to believe that for longevity sake high charge rates might very well be avoided when possible. I'm now suggesting that if as a bank ages after high charge rates that perhaps more longevity can be squeezed from a bank by reducing or abstaining from high charge rates especially if charging to the upper knee 3.5 volts. Theoretically speaking there is only so much chemical left in the battery and preserving or utilizing what is left may be prudent in some cases.

Also and from my learning bank of smaller calb 72 ah cells they do get hot comparatively speaking in terms of my larger format 400 ah Winston cells. I can put the temperature gauge on my big cells and they never deviate from 20 degrees Celsius but I'm sure and only Joe would know what his running cell temperatures during a charge cycle at 170amps and therein you may also find reason for premature failure over anticipated life cycles albeit perhaps he lost 500 not sure. Joe?

[john61ct]

>Jack in the video dialog points out some valid points on acceptance charge especially in terms of the calb 180 is that they rise very quickly to the 3.6v and even to the 3.5v upper knee and then recommends only charging these cells to 3.45 volts and calling it done simply because of how fast they climb.

Sorry, are you talking about first charging to 3.6, then cutting back at some point to 3.45? I haven't seen that, is it supposed to buy you a shorter charge cycle to get to 100% - which is bad for the bank?

Just set V to 3.45, OK 3.50 if you're less risk averse, then when current drops stop. That's all.


> does the alternator have the ability to drop the current and maintain a constant voltage especially in batteries that approach the upper limits of their acceptance quickly as these cells do.

Obviously that's the VR's job, and yes Balmar's MC-614 is the one I'd give the job to.

I used 600 as an example, if that is safe, then a normal ~200A unit is covered eh?

Nice thing besides precise customization of charging setpoints, their "belt manager" lets you scale back the available amps, for example if you want more HP left for propulsion.



> "What if any damage can be done to the cells by not charging with CC/CV?" I like many others now simply charge until 3.5 volts or less and don't worry about any CC/CV in the charging.

Yes, I thought that was now established as the norm.

There is NO reason to charge to 100% full from the POV of bank health.

Doing so out of "AH greed" is not harmful, as long as you're shortly USING that power, not letting the bank sit there full

AND you keep charging volts in the above range, MUCH lower than what most vendors think is best.

Look at Sterling - excellent chargers otherwise - sets their "canned profile" for LFP at: murder!

But as with Balmar's VR, he gives you the option to micro-manage your own setpoints.

That capability is now a pre-requisite for any charging source investment, if it ain't got that it better be very cheap and good in every other way!

My next mission is a list of bank combiners that let you change the setpoints and delay timers. . .

[john61ct]

Originally Posted by PacificGreen

in instances where the charging is not monitored explicitly to correct for CC/CV and that the reductions happen at the correct time

Personally, if you can't afford good charge regulation you shouldn't even consider LFP, because you'll never get your money's worth out of them.

Like flaunting huge diamonds around Paris without a proper security detail.

[PacificGreen]

So the .C rate of charge is based off in this case .3C of the 180ah cell and that equates to 54Amps. .3C of his 700ah pack is 210 amps.

But in this case Joe is stating he now does not have the 700ah variable and more and in fact his .3C of his pack is now 120 amps only. Obviously now he is over his C rate for charging yet continues to charge at 170 amps.

Thus the question for those using LiFeP04 batteries as propulsion or house banks is:

Should the C rate for charging be adjusted as a bank is used based on it's usage history or exhibited traits accordingly?

[PacificGreen]

Now I'm sure Joe bought the best money could buy in terms of the charger he selected. I know it was one I seriously looked at. But in this case did it help or hinder his batteries and is it yet as his cells age?

Now so far as having CC/CV charge regulation in regards to large expensive lithium battery packs I would surmise everyone has a volt meter for their bank and a handheld one for their cells and if there is ever doubt they quickly verify with a hands on approach. I know I do.

That is not to say we will be robbed of our batteries for not having the latest and greatest in CC/CV charging gear. I'll go back to the cell log debate on that one and T1Terry.

More often than not it is the reliance on the automation of some of these systems that and especially in this case the ability to float that apparently perhaps lost a user some 500 hypothetical cycles. My impression is Joe hasn't been back in civilization for four years or at least back to the forum here during that time because the cells worked so well and he only realized in the last year for the most part on route to Compass Marine that perhaps there may be some issue with his cells.

[PacificGreen]

Also and as demonstrated from Jack in the video as these particular calb 180 cells hit the upper knee they had to manually adjust the current on their power supply to keep up. So with this particular cell would it be wise to have something automated looking after the top end of a charge? I submit that no it would not and that such a charge should only occur with the security detail present - namely the all knowing and learned owner and master of the vessel.

[john61ct]

Originally Posted by PacificGreen

I do realize the age of the video for sure but the references to it are still valid to Joe's cells.

My point is that the community's knowledge base is still in early stages NOW, just the fact it's from 5 years ago, and he's charging at >3.6V immediately means I take anything there with a pound of salt wrt longevity.


> Now though does the optimal or maximum .C charging rate at all deteriorate over time after repeated fast charges and should it be reduced as batteries age?

Excellent question. I'm betting keep it constant is fine, but then I'm betting much higher than .3C isn't a problem in the first place.

> calb 180 cells

Again I question your focus on a specific model. Once you're above the "cheapo Chinese low-quality" bar, and not yet in the silly "drop-in" or stratospheric cost cell-embedded custom control chips - IOW where sane plebs shop - I really think LFP is LFP, most of these issues are predestined by simple chemistry.


> perhaps more longevity can be squeezed from a bank by reducing or abstaining from high charge rates especially if charging to the upper knee 3.5 volts.

But why 3.5 if you think that's pushing it, what are you gaining by not using 3.45?


And yes, heat kills. Back to quality charge regulation, I wholeheartedly endorse scaling back Amps available as a function of higher temperatures.


> You can note though how in draw down tests and management of the Compass Marine bank and I think he notes it on the previous page:

> --Max charge rate at approx .3C

Ok I did misremember that. Funny, because in reading later stuff I concluded I would prefer even slightly more conservative Voltages, but here his Current max spec is at the bottom of my noted range.

I'm guessing that's not yet been tested, say .3C vs .5 (or even higher?) for longevity. Just because he set that limit for purposes of that test series, doesn't mean he did so because of evidence that higher current rates hurt longevity as much as over-voltage.

Maybe the​ man himself will come by, in the meantime I'll let it rest.

[john61ct]

Originally Posted by PacificGreen

Obviously now he is over his C rate for charging yet continues to charge at 170 amps.

Only if you think your excellent (but tangential) question

Originally Posted by PacificGreen

Should the C rate for charging be adjusted as a bank is used based on it's usage history or exhibited traits accordingly?

Has already been answered as Yes.

To me the primary question is:

Is there evidence of a lifespan reduction resulting from high current availability ( > .3C) while charging?

Is the difference between .3C and .5C significant?

How many X% DoD cycles are lost going to 1C? 2C?

For someone firing up an expensive (600A 8-) and annoying fossil-fuel genset expressly to recharge the bank, it may well be worth dropping from say 4000 cycles down to 3500 to shorten runtimes.