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

[goboatingnow]

Originally Posted by diugo

Could you please cite any "scholarly material" on LFP cell aging that did not study cells that were also heavily cycled? My understanding is that the SEI layer protects the anode---and since shallow cycling and/or low currents preserve this protective layer, that may suggest increased longevity.

I have my university library journal access tied to my office iMac and also where I keep my research articles. Given were off till the 3rd of Jan , I might not get them for a while

Ah no , I'll be in the office over the break , ill post some article references

But from my online links here's one good overview http://www.mdpi.com/1996-1944/6/4/1310/pdf

The interaction of the SEI layer is quite complex. Formation of a stable SEI is necessary to prevent decomposition , and it is formed within the first 5 or so cycles. And such layers are required for longevity as you say

Paradoxically the layer also adds the ageing issue , as it continues to grow , especially under high voltages or high SOC , as the layer grows it clogs the graphing anode, causing reduced intercalation and isolating sections of the anode electrically , as a result Li transport is slowed and some areas of the anode are lost. Over time this is what generally contributes to the ageing of a LI cell.

Hence at medium SOC the SEI layer growth is at a minimum and degradation is slowed. Which is why it's recommended for storage conditions

Heavy cycling causes anode bulging and contraction , which causes fracturing of the layer , which then results in contamination and a further contribution to capacity loss and ageing.

This is all a bit of simplification as there are further interactions in the electrolyte / electrode boundary and various additives are added to the electrolyte to extend lifetimes etc.

So yes the SEI layer is both required and a contributor to ageing

Dave

[DotDun]

Originally Posted by bethflkys

I’m planning to replace this setup with a Sterling Power 210 amp max ProAlt C Alternator to Battery Charger and a Sterling Power 60 amp ProCharge Ultra battery charger. Sterling promises both of these will charge LiPo4 batteries as well as AGMs and LA batteries.

In your learned opinions, are these a good choice for someone who wants to make the switch to lithium down the road? I understand I’ll have to add some other gizmos when the time comes; I am just trying to improve my current situation while keeping my battery options open for the future.

Kinda a loaded question? It's like asking Apple if the latest iPad will run all the apps that come out 3 years from now.

The main points I take away from all the blather.

- Li and La are 2 different technologies. So much so that existing chargers made for La may actually be detrimental to Li. Expect to change existing methods/equipment including shorepower chargers, solar regulators, smart alternator regulators, and especially OEM fixed voltage alternators.

- Li takes a different care and feeding, so much different that habits everyone is used to for La (constant float charge, etc.) must change. And we all know how hard it is to change the habits of curmudgeonly old sailors. Li appears to be more finicky compared to the care/feeding of La.

-Li is still new to the marine industry, hence prices have not yet stabilized towards the commodity stage. Expect that how much you pay today, will be significantly less in a year or two. This is true for not only the batteries themselves, but all the required support equipment. When West Marine, Walmart, Costco, and Sam's Club start selling large Li batteries, prices will stabilized.

-Be grateful for those that spent the big bucks during the early testing. They've actually saved the rest of us a lot of money!!!

IOW, changing from La to Li is more radical than simply changing the cells. Don't believe anyone that says otherwise.

[Joe Parklane]

Ouch, I have followed these posts with much greater interest than understanding. Particularly damage from float charge. My very limited understand is that I am damaging my LFP04 bank by having the a 100% SOC while at the dock on Mains with the Victron chargers set a 13.4 volts and 65 amps (so to provide power to the DC systems we use, e.g. water pressure, head system, lights, KVH sat dish).
What follows is a very minimal recollection of the initial setup of my dual Victron multis charging system. "..."...This low voltage "float" setting was selected to not overcharge as the voltage was too low for the cells to accept any amperage which just spills over to house DC system....". We live on the boat full time so need to power those mentioned necessary DC loads.
My questions:
Is this is harmful to the long term life of the bank and to what degree chronologically?

Is a solution to discharge the bank to 50% SOC and isolate it from any charging source/demands and supply house DC demands from an alternative charging/power supply source e.g. Sterling Power 60 amp charger(other suggestions?) which is claimed to function as a power supply? This charger could also serve as a backup should the Victron Multis fail. Obviously this is just throwing more money at an already expensive system.

I'm not sure if the Multis can function as a DC power source without reprogramming, which is a daunting task considering that the current Multi LI profiles took several days and conference calls to Holland and eventually remote programming by Victron Holland to effect. I have e-mailed Victron asking if it is possible that the multis can act as a DC power source with no battery in system without reprogramming.

Fretting in New Bern

[deckofficer]

Joe,

Others are better versed than me on our LiFePO4 cells, and I'm sure they will chime in but until they do, your float at 13.4 volts pack is 3.35 volt cell voltage and IMHO that is fine. I use a charger for EV LiFePO4 use and it charges at 14.6 volts for a faster charge time but at that voltage I wouldn't float.

[bill good]

It has always been a no no to float li batteries & it is imho the part of the charging phase that will do most damage i.e. CV. All the charge curves show approx the same time after the constant voltage is applied so why not follow the specs & ensure there is no float charge ever applied to this family of cells in exess of the specs period. The CC phase is shown normally .5C as a common factory spec & many applications will require a different charge rate BUT the CV part is not messed with at all. In simple terms the static field causes damage effect without current flow being able to be detected.

Merry Xmas Bill

[senormechanico]

Joe,
I'm doing the same thing with my home's 24 volt backup power bank. It has only about a half amp load when on standby. A wall wart with a regulated board attached is holding it at 26.8.
If that's a problem, we're going down together !

Bill,
If the static voltage is the same as the resting voltage, how can that be? Just asking.

[deckofficer]

This is what I do know, our cells after a charge will hold 3.35+ volts for a very long time (months) on their own. So if the charger is set at 13.4 volts for a 4 cell bank or 26.8 volts for an 8 cell bank, there aren't going to be any electrons moving.

[Maine Sail]

Originally Posted by deckofficer

This is what I do know, our cells after a charge will hold 3.35+ volts for a very long time (months) on their own. So if the charger is set at 13.4 volts for a 4 cell bank or 26.8 volts for an 8 cell bank, there aren't going to be any electrons moving.

I removed my cells from the boat about 4 weeks ago and the raw cells are sitting on my bench waiting to be reassembled for more cycling. I just went down there and measured resting voltage at 52F after being off charge for approx 5 weeks.

The cells have 206 cycles and have not been either top balanced nor shunt balanced for 206 cycles...

If you program a float setting of 13.2V the charger will terminate charge until the bank voltage falls to 13.2v..

Cell #1 = 3.338V
Cell #2 = 3.337V
Cell #3 = 3.338V
Cell #4 = 3.338V

[bill good]

Looking for electron flow for a static charge?? It happens with a bang at the point of discharge when the gap is right!! There are papers written & photos taken of the partical movement under static conditions that do not occur without the charge present. Most phone & laptop applications will tell you to remove once charged to give the best life from batteries. But hay do what you feel is best for you. Every fire I have heard about that is not wiring related is failures while charging. If the manufacturer says disconnect at the end of charge, there is a good reason to do so & given the slow self discharge why would you do other than ensure a timed disconnect??

[transmitterdan]

Originally Posted by bill good

If the manufacturer says disconnect at the end of charge, there is a good reason to do so & given the slow self discharge why would you do other than ensure a timed disconnect??

Because for boats plugged in or using solar (and unattended) it's not easy to find a charger/power supply that will do that without external help. This extra connect/disconnect circuitry complicates the system, reduces reliability and increases the cost of an already costly technology. There is no shame in looking for an easy/cheap solution. It's what is needed for Li technology to gain wider acceptance.

[Joe Parklane]

Thanks for the responses however I'm still confused with regard to the 50% SOC for a "storage" harmless mode and then disconnecting the bank. This is a problem as we are living aboard static at the dock for the winter months cruising again in March. So looking for alternatives for while we are static. I guess I could continually cycle the batteries but hope for a better alternative. I can disconnect them via a rotary switch, however need to supply 12 volts for live aboard systems. So suggestions as to an alternative 12 volt power source would be great.

[Jd1]

Originally Posted by Joe Parklane

So suggestions as to an alternative 12 volt power source would be great.

Maybe this is too obvious but .... why not put in an inexpensive LA battery if you are concerned about floating the Li's. Just put in an A/B switch to select one or the other and possibly something to trickle charge the LA battery when you are swithed to Li mode. Keep the charger at the setting you are happy with and just disconnect the lithium system when in port for a longer time.
You could probably even get away with a small motorcycle battery (if your charger is ok as a power supply)

Personally I think (but don'y know for certain) that setting the charger voltage somewhere short of the upper knee (as you have it) should be fine.

[Maine Sail]

Originally Posted by Joe Parklane

Thanks for the responses however I'm still confused with regard to the 50% SOC for a "storage" harmless mode and then disconnecting the bank. This is a problem as we are living aboard static at the dock for the winter months cruising again in March. So looking for alternatives for while we are static. I guess I could continually cycle the batteries but hope for a better alternative. I can disconnect them via a rotary switch, however need to supply 12 volts for live aboard systems. So suggestions as to an alternative 12 volt power source would be great.

I use my LA start battery in the off season....

[css145hs]

I'm fairly far along in my LiFePo4 install on my liveaboard sailboat, and yet perhaps only half way there at the same time.

My current situation is "horrible" when on multi-day trips. I drag the existing batteries down to 50% twice a day just with basic equipment, auto pilot, night lights. They were here when I bought it and I don't think they are in great condition, so am always monitoring them and running the engine for two hours in morning and evening to compensate.

What's done so far:

- replaced 1500W 20gal hot water heater with isotemp 750W 11gal, and re-wired to allow both shore and inverter powered use, also now heats via diesel hydronic exchange (cabin heater) in addition to engine exchange
- new Magnum Energy 2000watt inverter, 100 amp charger, ARC50 remote and battery monitor
- Electromaxx 160amp alternator with serpentine belts and MC-614 regulator
- 420W (3x140W) solar on top of bimini arch, with Tristar 45amp MPPT controller
- Aquair 100 towed generator with D2B regulator (the D2B is new this year, it has dump loads and doesn't constantly connect/disconnect the generator)
- Duocharge to maintain start battery from house bank, all charge and load sources wired to house bank, starter still wired to start battery. New battery switch on/off/combine, don't need to twiddle with it 8x a day now.
- internal and external lights to LEDs (god what a savings that was for external lights)

What remains is that I haven't actually put the new batteries into this system yet, it's all still hooked up to 2 FLA 4Ds and a group 27. So far its felt like nothing has changed except my wallet ;-)

I have 5 100ah GBS 12V packs from elite power, and the accompanying balance boards and battery monitor (this is separate from the magnum monitor).

Everyone here seems to favor CALB, and even though it's a bit late for me, I wouldn't mind any major reasons why. I would have definitely preferred the lower CALB pricing than elite power's mark up. I almost went the direct from china route for GBS, but wasn't willing to risk it. It also wasn't significant given the total cost of this multi-month project, the cells are a small part.

Here is my new charging settings for the above equipment, once the Li go in, and is what I'm largely writing this for... as well as any other feedback you may want to add.

Magnum:
- LVCO to 12.9 (to turn inverter off), for charging set to do absorption at 13.8V and hold for 30 minutes, then turn off until bank falls to 13.0V and restart. Float is set to 13.2V but never happens automatically (Silent final charge mode on the magnum).

Alternator:
- 14.1V bulk, 13.9V absorption, 13.2V float, belt load manager to reduce field by 15%, bulk->absorb field threshold at 90%, float<->absorb at 80%, 14.4V max voltage, 14.3V temp limit, temp compensation turned off, reduce minimum times per stage from 18 mins to 6 mins
- temp sensor on the frame
- Maine/T1 I think have referenced lower settings on the MC-614 but the manual says 14.1 and 13.9 are the minimums for bulk/absorb. Does it actually let you go lower (I haven't tried yet)? I'm probably going to keep it here anyway, because it will better fit the AGM's profile just after starting the engine, and is still within the Li range.

Solar:
- Absorption until 13.8V then hold for 45 mins, float at 13.2V, equalize at 14.16V every 5 days for 15 mins
- When at the dock most of the time, shore power/magnum charger will mostly do nothing, as solar will top it off each day and the daily loads will not draw it down to the 13.0V level for the magnum to kick off a charge cycle. The magnum is there as a safety net against the solar not keeping up. My daily load at the dock is around 40 amp-hours (half fridge).
- The magnum and elite battery monitors need periodic topping above 14.08V to reset to 100% SOC, also the balance boards kick in at 3.55V or 14.2V, 14.16V is 3.54V so may cause a few boards to kick in if they are a little uneven (yes i know the error in the equipment makes this a bit moot)

Towed:
- 13.8V max charge voltage, equalization pulses periodically for 1 second (not configurable). equalization mode is max current for 1 second, the towed generator puts outs 40-60W sailing, its a 100W generator.
- This is a weird charge controller, its highly variable on voltage, on the premise that its less stressful to the battery. Given that its only used on multi-day trips and that I don't think the voltage will be able to rise much with 60W for 1 second, I'm thinking this is good, but it's probably the most questionable part of this whole setup.
- http://www.flexcharge.com/custom-1/N...ual%202012.pdf (page 8)

Duo:
- Forwards current from house to start when input voltage is 13.6V to 14.3V. My new starter battery is a mastervolt AGM (14.2V absorb, 13.8V float)
- This range means the start battery is only linked to the house at the very peak of charging and during the absorption hold period. It will also get the ~once a week equalization charge from solar at 14.16V
- Everything has temp compensation off, except for the duo which does have a temp sensor on the AGM start battery. Even without it, at these settings, I figure I'm good until about 95F, which in the seattle area is pretty rare

BMS:
- The elite power bms will be connected to two EV200s one for charge and one for load sources (for high voltage and low voltage bms alarms)
- The magnum inverter-charger will be on the charge side. My thinking is that the magnum has its own low voltage cut off (LVCO) at 12.9, and the only thing I'll even be inverting at measurable load away from the dock is the water heater which I'll be manually turning on/off anyhow. So better to have it be on the charge side, where I may not be on the boat at all and need it cut out.
- I'm not currently planning on doing long parallel strings of cells, as the balance boards won't connect to the bms easily then. So will instead have 5 parallel 12V batteries, each a series of 4 cells (which is also how they were shipped to me, so is easier). I expect a few here may advise against that, but I'm hoping at just 20 cells, keeping them in balance won't be much of an issue. Obviously if I observe that not working well then I'll revisit this and repack into 4 series of 5 paralleled cells.
- Also, I don't really know how to rewire that properly anyway, with proper fusing throughout the big cell block, so if someone wants to comment that be nice. I've seen various wiring diagrams and its not clear to me what makes one version better/safer than the others. I've been meaning to look into the EV forums as I'm sure they have this better documented.

Main points:
- No floating at night, pure discharge
- 13.2 floating during the day from solar, with a daily charge cycle in the morning/noon at 13.8
- inverter-charger as backup charge source when on shore power
- my daily cycle at the dock (90% of the year) will be 90-100% SOC
- when away from shore, my loads will be closer to 150amp-hours/day, my goal was to be able to go several days without sun or engine runs. i can reduce consumption if needed as well.

All this yields long life yes? Hope so.

Areas I'm concerned about:
- cell arrangement (4S5P vs 5P4S)
- D2B regulator's variable voltage, and its equalization mode
- use of AGM start battery mixed with Li house

BTW, thanks for reading if you got this far.

[Maine Sail]

Originally Posted by css145hs

Alternator:
- 14.1V bulk, 13.9V absorption, 13.2V float, belt load manager to reduce field by 15%, bulk->absorb field threshold at 90%, float<->absorb at 80%, 14.4V max voltage, 14.3V temp limit, temp compensation turned off, reduce minimum times per stage from 18 mins to 6 mins
- temp sensor on the frame


- Maine/T1 I think have referenced lower settings on the MC-614 but the manual says 14.1 and 13.9 are the minimums for bulk/absorb. Does it actually let you go lower (I haven't tried yet)? I'm probably going to keep it here anyway, because it will better fit the AGM's profile just after starting the engine, and is still within the Li range.

Yes the MC-614 reg can be programmed lower. The trick is you need to start at float and reduce it first then move up the chain. Each step needs 0.1V between it. I think I currently have mine programmed for 13.9V bulk and 13.8V absorption..