Most useful article I've ever found on LFP battery charging

[Maast]

Came across this as a reference in a thread, it's possibly the most useful article I've ever came across about LFP charging regimes. Evidently there actually is a well documented memory effect on LFP cells and that always holding charge voltages low to avoid overcharging the cells is counterproductive. The author recommends a periodic full charge and discharge to 'recondition' the cells.

Marine lithium batteries in operation | Nordkyn Design

This article details the relations between voltage, state of charge, current and temperature for lithium iron phosphate (LFP or LiFePO4) battery banks.

nordkyndesign.com

 

[upnorthandpersonal]

Cold temperatures are known to be detrimental to the cells if they are exposed to charging. Cycling performance tests at varying temperatures showed the apparent existence of a threshold below which capacity fade with cycling suddenly accelerated. This threshold appeared to be above the temperature of 0°C often suggested as limit for recharging, but the data available was limited and the exact details of cell manufacture are likely to influence this value.

Emphasis mine.

I figured this was the case. I always have my cut-off temperature well above 0°C, preferably at 5°C or even higher. Seeing people putting it right at 0°C seemed a bit off.

 

[Maast]

Supporting documentation, info-dense read though. Oh the irony, we still need what is effectively a "equalization" charge periodically and I have no idea of how to automate that with my Midnites. I might have to rig something up with a power supply and long duration time delay relay control boards for once a month or so after the system gets inspected by the county after install is complete.

 

[gnubie]

Really has me wondering how the all-in-one MPPs handle lithium charging now. They should be able to watch the battery current directly.

 

[Maast]

Everything the author writes on the subject is gold and I wish I'd come across it a lot sooner.

Like this one on LFP battery bank assembly: http://nordkyndesign.com/assembling-a-lithium-iron-phosphate-marine-house-bank/

Or anything on the subject of LFP batteries: http://nordkyndesign.com/category/marine-engineering/electrical/lithium-battery-systems/

 

[Maast]

I think I'll just attach a PSP-300-48 power supply to a standard high reliability timer and set it to one day a month but otherwise keep the charge profile down to 3.4v

 

[Dzl]

Came across this as a reference in a thread, it's possibly the most useful article I've ever came across about LFP charging regimes. Evidently there actually is a well documented memory effect on LFP cells and that always holding charge voltages low to avoid overcharging the cells is counterproductive. The author recommends a periodic full charge and discharge to 'recondition' the cells.

Marine lithium batteries in operation | Nordkyn Design

This article details the relations between voltage, state of charge, current and temperature for lithium iron phosphate (LFP or LiFePO4) battery banks.

nordkyndesign.com

I have that website bookmarked, but have yet to read the article(s) in full.

Coincidentally, this article which is the 'most useful article on lithium batteries' that I've come across so far, also touches on some of these same issues. The author does a full capacity test every 50 cycles and after 772 cycles has what appears to be slightly greater capacity than when he began testing. His hypothesis as to why there has been no capacity loss is that the every 50 cycle full charge and discharge helps keep any potential memory effect to a minimum. I'm oversimplifying a bit, but I think that is the gist of it, and it seems to corroborate the theory from the article you cited.

 

[upnorthandpersonal]

Time to buy some of those cells off of Aliexpress and set up a test set-up for myself I think.

 

[Steve_S]

I have that website bookmarked, but have yet to read the article(s) in full.

Coincidentally, this article which is the 'most useful article on lithium batteries' that I've come across so far, also touches on some of these same issues. The author does a full capacity test every 50 cycles and after 772 cycles has what appears to be slightly greater capacity than when he began testing. His hypothesis as to why there has been no capacity loss is that the every 50 cycle full charge and discharge helps keep any potential memory effect to a minimum. I'm oversimplifying a bit, but I think that is the gist of it, and it seems to corroborate the theory from the article you cited.

The link to MarineHowTo you provided IMO should be a MUST READ like the Nordkyndesign ones... Sure explains a LOT and makes no bones about it.... IN particular how & what a BMS is supposed to do and best charging profile info...

 

[SolarRat]

Like I've been saying, todays charge controllers are just lead acid chargers with just enough user adjustable settings so they can slap a "for lithium" label on them...

LFP is still in it's relative infancy. There's a lot we still don't know, and the ones "in the know" are not giving up their trade secrets so easily. I've been reading the links above the past few months and those guys grasp a lot of the challenges, but even they are still learning and are not always 100% correct (but probably a lot closer than most).

Battery manufacturers hold all the secrets. They don't care about us DIYers. They sell to huge companies, not just the batteries but charger design info too. They are not freely giving this type of information to you or I...or Victron, MPP Solar or Epever for that matter.

 

[gnubie]

It's an interesting point. Victron has its own range of lithium batteries. If the lifepo4 charging profile in their SCCs cause the sort of damage the article suggests is possible, that will mean there could be a substantial number of warranty claims. At least Victron will honour the warranty and will be around to do it.

 

[SolarRat]

It's an interesting point. Victron has its own range of lithium batteries. If the lifepo4 charging profile in their SCCs cause the sort of damage the article suggests is possible, that will mean there could be a substantial number of warranty claims. At least Victron will honour the warranty and will be around to do it.

Victron doesn't make their own batteries. They use CALB or Winston cells (I forget which). The BMS they use was also probably recommended by or designed by the battery manufacturer. Did they also help design their charge profiles?...not sure

 

[gnubie]

Who said they did? They have their own range, ie a product line.

 

[SolarRat]

Who said they did? They have their own range, ie a product line.

Just clarifying for the majority that probably don't realize that.

If a Victron has a bad cell, who eats the warranty cost, Victron or Winston?

 

[SolarRat]

My guess is the manufacturers are not responsible for lost capacity due to memory effects (would fall under "improper charging").

IF there is even such a thing as a memory effect on lithiums?...

 

[gnubie]

Yes, it is IF at this point. My point was that if Victron has range of lithium batteries and a range of SCCs with lifepo4 profiles specifically to charge their lithium batteries, improper charging shouldn't be an out, unless of course the charging profile has been modified or not used.

 

[SolarRat]

Victron only warranties their batteries for 2 or 3 years. IF memory problems are real they probably won't be pronounced enough to trigger a warranty claim in that timeframe. Getting 5 years out of a quality LFP should be easy with any CC from a decent company...but will they still be going strong at 10 years without some end-user help? Most people who post about their 10 year old battery banks are way above the average user in terms of electrical expertise and test equipment. They've surely done capacity tests throughout the years which exercised the banks.

 

[Steve_S]

One of the,main reasons that Victron, Trojan, Rolls Surette LFP Battery packs cost as much as they do, they buy guaranteed & tested cells that meet "their specs", not just some random pull off the assembly line. They stand behind the product they stick their label on and they eat the cost "if" it is a Warranty issue but NOT if it is a User Abuse issue. IN the case of Victron, they have their profiles setup to match their LFP offerings which can be tweaked.

LFP has no memory it is NOT NimHi, NiCad or those other horrible batteries of the past which did set a charge memory. Again the old wives tales progress to new batteries & new chemistries... hen of course the FUDster's push such as an argument against Renewable Energy. What is a FUDster, it is someone or some group pushing "Fear, Uncertainty & Doubt" in regards to any technology or science. It can be highlighted quite well by the Anti-Tesla goons who attack everything out of context to portray things negative and to keep people from considering an EV...

 

[upnorthandpersonal]

Please read the article. There might very well be memory effects, even if they're not as pronounced as on other chemistry. However these memory effects do occur in specific circumstances, and if batteries are charged wrong, these might very well cause issues. This has nothing to do with FUD. I've been reading the nordkyndesign articles for the past day or so, and they are very well written and properly sourced with references and I don't see any obvious bias.

 

[SolarRat]

I remember what a FUDster is. You called me one when I warned you to stay away from Shun-Bin..... Sometimes FUDsters are correct.