Best LifePo4 charge controller settings known to man for Maximum Service life and Minimum battery stress!!! 5,000-10,000+ cycles?

toms said:

I don’t have anything capable of separating out the busbar resistance from the IR of individual cells. I’d like to see the seperate resistance meters you use.

If a parallel pair show up a discrepancy, i will remove them both and check them. Until then i treat them as one cell.

At one stage my battery went over 6 years without me even looking at it - no way i’m taking it apart every 2 years ?

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You definitely got lucky and have good batch of battery cells that are within tight QC tolerances. High quality battery cells are easy to work with. What is your BMS and balancing method? I do prefer active balancers over passive types.

Samcat said:

You definitely got lucky and have good batch of battery cells that are within tight QC tolerances. High quality battery cells are easy to work with. What is your BMS and balancing method? I do prefer active balancers over passive types.

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I have set up dozens of systems like mine for other people - many are approaching the ten year mark with no issues.

Active balancers are fine, i’ve seen too many fail in a state that will destroy a cell though for me to leave one permanently on my pack.

Best way to balance is to use low current (ie low heat) resistors and bleed high cells whenever the battery is at constant voltage (and low current).

In a typical off grid house situation, the batteries spend a lot of time at “full” constant voltage setting. Even if you are only bleeding 0.5A to balance, you can get a few ah/day correction.

toms said:

I have set up dozens of systems like mine for other people - many are approaching the ten year mark with no issues.

Active balancers are fine, i’ve seen too many fail in a state that will destroy a cell though for me to leave one permanently on my pack.

Best way to balance is to use low current (ie low heat) resistors and bleed high cells whenever the battery is at constant voltage (and low current).

In a typical off grid house situation, the batteries spend a lot of time at “full” constant voltage setting. Even if you are only bleeding 0.5A to balance, you can get a few ah/day correction.

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Does this balancer have option to be disconnected from battery bank without pulling connector terminals. I.was researching but could not find any On/Off button.

toms said:

It is impossible to get imbalance with parallel cells. What you can get is different characteristics between cells that reduce the capacity of the stronger cell in the pair.

Cell balancing is surely one of the most misunderstood aspects of LiFePO4 battery construction. The amount of misinformation i see on this forum is staggering (especially with respect to parallel cells)

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with parallel cells, diagnosis while cell terminals are still bonded, seems difficult (impossible?)

still value to parallel cell arrangement

my ignorance of parallel cell behavior fuel my design requirement of one cell per voltage sense lead.

grateful for your insight. thank you ?

curiouscarbon said:

with parallel cells, diagnosis while cell terminals are still bonded, seems difficult (impossible?)

still value to parallel cell arrangement

my ignorance of parallel cell behavior fuel my design requirement of one cell per voltage sense lead.

grateful for your insight. thank you ?

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Best way to look at parallel cells is just to imagine them as a single cell.

It really is no different to how a manufacturer makes different size cells, there are simply more parallel plates inside the cell. With parallel cells half the cell is parallel externally instead of internally.

There is unfounded concern about rapid discharge between parallel cells in case of single cell failure. It is no different to a single cell suffering dendrite failure. The dendrite short circuits part of the cell and the rest of the cell has a short discharge of current that has the effect of open circuiting the dendrite (blows it like a fuse)

I haven’t seen a failure mode that results in prolonged high current discharge.

@toms ? agree with you on your statement.

toms said:

Best way to look at parallel cells is just to imagine them as a single cell.

It really is no different to how a manufacturer makes different size cells, there are simply more parallel plates inside the cell. With parallel cells half the cell is parallel externally instead of internally.

There is unfounded concern about rapid discharge between parallel cells in case of single cell failure. It is no different to a single cell suffering dendrite failure. The dendrite short circuits part of the cell and the rest of the cell has a short discharge of current that has the effect of open circuiting the dendrite (blows it like a fuse)

I haven’t seen a failure mode that results in prolonged high current discharge.

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Yeah, especially car companies put fuses on parallel cells so if a cell decides to puke and short out then it goes out of loop...

One ref of many:

I don't run multiple cells in parallel (yet hehe), but it seems like fuses would be a good idea for our community as well even though LFP are not at risk for thermal runaway, it could stop a glowing bus bar meltdown leading to a potential fire at worse case...

Samsonite801 said:

Yeah, especially car companies put fuses on parallel cells so if a cell decides to puke and short out then it goes out of loop...

One ref of many:

Fuse-wire for individual cells, DIY Tesla style

Tesla uses ultrasonic vibrations to connect a fuse-wire from the nickel-plated aluminum-core bus plates to each of the positive tips of the cells. I'm starting this thread to park information I find about using fuse-wire. This has to do with fire-safety, and is something that every battery...

endless-sphere.com

I don't run multiple cells in parallel (yet hehe), but it seems like fuses would be a good idea for our community as well even though LFP are not at risk for thermal runaway, it could stop a glowing bus bar meltdown leading to a potential fire at worse case...

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I think these fuses would help if a short circuit was caused by physical damage to the pack. I’ve seen many dendrite shorted cells, never seen (or heard) of one sustaining high current.

I’d be keen to see any real world examples of a shorted cell (not physically damaged) causing pack thermal damage. Very early on with LiFePO4 (twelve years ago), there was a lot of discussion regarding fusing parallel cells. The manufacturers i was involved with at the time advised me they weren’t required - nothing i’ve seen since has changed my mind.

@Will Prowse this Thread raises several issues which have bounced around forever. The Proverbial running around the Mullbery Bush which has created a moat due to wear, never ceases.

Would you consider making a Video concerning Parallel Cells ?
Showing how real "A Grade" cells in parallel behave through operation and how if 1 very weak Cell Paired with an "A" cell behave through cycles and IF the "Matched Pair" behaves better or worse between the "Odd Pair" and how their Voltages & IR are through the low to high SOC and under various loads & charge rates. Tricky and a Time Killer but I believe this would be a Very Valuable addition to your Video Library. I would suggest that using smaller <100AH cells would be prudent due to capacity & time to charge/discharge would eat up a boat load of time... maybe 50AH or less even would probably do just fine I would think.

Thanks in Advance for your consideration.

SOURCE: Battery University.

There is over a decade of real-world experience of how LiFePO4 cells act when in parallel, knock yourself out if you want to re-invent the wheel. (and yes - a decade ago people were using second hand EV cells - remember Thundersky’s? - in parallel for their house banks so the experience well and truly covers mismatched and dying cells)

At least i’m not seeing so many posts stating that parallel cells can have different voltages as was commonplace when i first started here.

@toms it does seem that cells from the past were better, not so many of today's claims of grade A which are of lesser quality or just rejects from the "A" batch.

I did enjoy reading and learning from old threads from the past that are gone from forums missing now.

Many new comers trying to reinvent the wheel that was tried and destroyed in the past. Sometimes setting up voltages for everyday use can be..... less is more. After 6+ years of everyday use I hope mine can live a useful life as yours and many folks from the past that don't even post on the internet. My batteries/ system acts/ delivery like they did when first installed.

Samsonite801 said:

Yeah, especially car companies put fuses on parallel cells so if a cell decides to puke and short out then it goes out of loop...

One ref of many:

Fuse-wire for individual cells, DIY Tesla style

Tesla uses ultrasonic vibrations to connect a fuse-wire from the nickel-plated aluminum-core bus plates to each of the positive tips of the cells. I'm starting this thread to park information I find about using fuse-wire. This has to do with fire-safety, and is something that every battery...

endless-sphere.com

I don't run multiple cells in parallel (yet hehe), but it seems like fuses would be a good idea for our community as well even though LFP are not at risk for thermal runaway, it could stop a glowing bus bar meltdown leading to a potential fire at worse case...

Click to expand...

Bus bars with Pyro fuses when become available for aftermarket will change how many you could do in parallel with no issues on safety. For EV they are down to 1mOhm resistance and have temperature probe also.

I usually if on the salvage yard will look to buy all of them they have at the time. And all of them are run on 12V DC if someone is interested. There is a lot of things that could be harvested for home battery banks . Just my loud thinking here.
Good luck hunting.

.......

We're still tossing around confusing 100 year old lead acid terminology.
New LifePo4 has 2 charging states, boost and float.
Let bulk/absorb go away.

robstrom said:

We're still tossing around confusing 100 year old lead acid terminology.
New LifePo4 has 2 charging states, boost and float.
Let bulk/absorb go away.

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Charge controller says absorption not boost.. same as most peoples charge controllers.

robstrom said:

We're still tossing around confusing 100 year old lead acid terminology.
New LifePo4 has 2 charging states, boost and float.
Let bulk/absorb go away.

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Personally, I like the idea of actually using technical terms to describe things instead of arbitrary industry invented meaningless terms.
1) Constant Current
2) Constant Voltage
3) Float

BentleyJ said:

Personally, I like the idea of actually using technical terms to describe things instead of arbitrary industry invented meaningless terms.
1) Constant Current
2) Constant Voltage
3) Float

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I agree CC is like Bulk and the termination voltage is when it transitions to CV (Absorb or sometimes called Boost) Float is a lower voltage form of CV often at a lower current. Only used with Lithium sparingly.

Ampster said:

Float is a lower voltage form of CV often at a lower current. Only used with Lithium sparingly.

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From what I’m reading I’m supposed to set a float voltage (if the charge controller has float) lower than the absorb voltage. So float would be used all the time. What do you mean by sparingly?

Cheap 4-life said:

So float would be used all the time. What do you mean by sparingly?

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Float is okay when supplied by solar because it turns off at sundown. It is typically used when there are loads and it keeps the cells from dropping below resting voltage. It is not needed all the time because Lithium does not self discharge as fast as Lead Acid.

Cheap 4-life said:

From what I’m reading I’m supposed to set a float voltage (if the charge controller has float) lower than the absorb voltage. So float would be used all the time. What do you mean by sparingly?

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Unlike lead acid, LFP doesn't "require" a float charge, but like @Ampster said, if you don't use the float on your solar charge controller you are not taking advantage of solar while the sun is out. Using float allows the power you consume during the day to be from the sun, rather than from your batteries.

Maintenance guy said:

No float charge. that is the third in the cycle. set it below absorption levels. the inverter manufacturers are killing everyones LiFePo4 cells prematurely using lead acid parameters.
Bulk, absorption only. Bulk is CC absorption is CV.
you can also lower your balance levels to coincide with the above parameters.

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Absolutely agree

There is no bulk or absorption phase or Float phase with lithium

There’s a CC phase and a CV phase , CV phase with system with simultaneous load currents should measure tail currents . No float on completion of charge cycle , charger should disconnect

Charge greater then .15C and less then 0.5C

Depth of discharge has major impacts in LFP life , more recharging time promotes SEI layer growth and degradation

Low DOD cycles are best , recharge as an when needed.

Goboatingnow said:

Absolutely agree

There is no bulk or absorption phase or Float phase with lithium

There’s a CC phase and a CV phase , CV phase with system with simultaneous load currents should measure tail currents . No float on completion of charge cycle , charger should disconnect

Charge greater then .15C and less then 0.5C

Depth of discharge has major impacts in LFP life , more recharging time promotes SEI layer growth and degradation

Low DOD cycles are best , recharge as an when needed.

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Wow. I'll just say there isn't much in that post that I agree with. I guess I'll leave it at that.

funny - chuckles.... just gotta....
Typical Day, my 30kWh bank is hitting Float by 13:00 hours. It trickles in 1 to 3 amps into the packs as the active balancers do their thing and get all the cells to <0.009V delta in all packs. The fridge or freezer kick on, and Float handles it and ups the Amps and the batteries are left alone. By 14:00 +/- all the battery packs will be static @ 3.415Vpc , not taking any charge or outputting anything UNLESS a Big Demand hits and Float cannot handle it, but immediately after, Float steps up and brings them back up "if they dropped".

Float is NOT forcing anything into the battery packs, it just allows them to be fully saturated to the target voltage I set (the top of the Working Voltage Range) and services anything called for by the devices in the house/shop.

CASE IN POINT: Got a new Washing Machine and was excited to try out this new High Efficiency machine (old one was a monster pig). Mid Day, Batts all sitting in float with a low delta and happy. So in goes a Load & on goes the machine \\YAY// and observing the Midnite Status Panel (software) it's still in float but hauling down 48A roughly from the panels, 0 to batteries and my lights are on in the house, the washer is humming along and the fridge kicks on and Float served it all... End of day as the sun starts to head for its nap, my Battery Bank finally starts to be used and it starts at 3.400Vpc per pack, with a Cell Delta <0.010 (my setting on BMS).

I've been at his quite some time and have done extreme tests including Hard Thrash Tests with Max Loading & Charging, even with different BMS' to STRESS THEM to the edge. I depend on my systems because I am quite Rural & Remote and "shit happens" so I leave nothing to chance if at all possible... to the extent that I have 3 ways to generate power, draw water, heat my home etc (It's an Ex Military Thing, triple redundacy - damned triplicate.... LOL)

I am SORRY TO SAY, but there is some Clear Buffoonery Posted into this thread that deserves nothing less than a good Beatch Slappery ! and I am BEING POLITE.

From the Whitepapers:

Charging a Pack with a CCCV charger and a BMS

Fully chanrging a Li-Ion battery pack with a CCCV (Constant Current / Constant Voltage) charger and a BMS requires three stages

1. Full charge: charger is fully on (CC), until a cell reaches its maximum voltage
2. Balance: charger goes off and on (CC), while BMS balances the cells, until all cells reach 100 % SOC
3. Top off: charger stays on (CV), while the current is reduced exponentially down to 0

The Constant Voltage of the charger must be set to CV = number of cells in series x max cell voltage.

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Wives Tales, along with Assumptions being turned into Conclusions and stated as fact only belong in the bottom of the Outhouse !