Real world efficiency of LiFePO4

[Jeremiah]

The largest impact to decreased longevity is not from bringing the batteries to empty or from charging back up to 100%. It is from charging at a rate higher than .5c (50 amps for a 100ah battery), this will have the biggest effect on diminished lifespan.

Right, because they are not giving the user access to the full bandwidth of the battery.

They could but they don't.

They do.

All Battle Born Batteries come with a built-in battery management system (BMS) that protects the cells for long-term cycling. The BMS protects against the following conditions:
High voltage: > 14.7V If an individual cell voltage exceeds a prescribed threshold during charging, the BMS will prevent a charge current from continuing. Discharge is always allowed under this condition

https://battlebornbatteries.com/wp-content/uploads/2019/09/Battle-Born-Manual.pdf

The time codes I posted earlier from WIll's tear down; he indicates that they use less of the battery bandwidth thus lengthening its life.
I think that's more than just the standard "keep the cells from exceeding 100%"
Still clear to me fellas; they aren't using all the capacity. Good design, just like Tesla does the same thing in their power wall design.
Please check Will's video I posted in the thread with the relevant time codes then we won't need to continue discussion what "BMS" stands for in this thread I appreciate you chiming in but I think I'm gonna go with Will's take on this one. Thanks fellas.

 

[ghostwriter66]

So I'm gearing up to jump in to LiFePO4 and as I calculate and estimate and my spreadsheet gets bigger and bigger, I'm wondering, how real are the charge / discharge efficiencies I read about online?
I'm looking to put together a 48v system; where my battery bank will stay between 25% and 80% SOC for longevity (may have to eat into 25% on rainy days).
What is a realistic % of energy loss going in to the battery bank and coming out I can expect if my charging rate will never exceed .17 C and my discharging rate will be around .26 C or less? I intend to ensure the battery bank stays bellow 25 degrees C.

It drives me crazy to see folks spend all this money on batteries and then NOT use them top capacity -- dude -- lifepo4 is designed to go 100% to about 5% ... so to play it safe -- set it for 95% down to 10% ... the way you are doing it you are leaving 45% on the table

 

[ghostwriter66]

So whats the concensus for realistic LifePO4 longevity and cost effectiveness? i.e. 20% down to 90% up?

HEAT is the #1 killer of LiFePO4 .. not charge cycles ...

 

[Jeremiah]

HEAT is the #1 killer of LiFePO4 .. not charge cycles ...

Yeah, I learned that. Literally as you were writing this I was writing to someone a PM asking about their Air conditioner solution for battery bank room something in the air I guess..

 

[Jeremiah]

It drives me crazy to see folks spend all this money on batteries and then NOT use them top capacity -- dude -- lifepo4 is designed to go 100% to about 5% ... so to play it safe -- set it for 95% down to 10% ... the way you are doing it you are leaving 45% on the table

I don't often have disposable income for investments like this living in the 3rd world now (my choice, not complaining). I'm just following @Will Prowse 's lead on his longevity video. is he really that off on his conclusions in that video? I've been spec'ing my system to last. I need it to last long and now the stuff is cheap and I actually have some loot so.... what's wrong with following the data that's out there to make it last longer?
If I was still doing software architecture consulting in the 1st world sure I wouldn't care. I'd eat through those puppies and just get more later. Now I need my things to last. That's why I'm planning to cycle between 25% to 85% on the LIfePo4 battery I'll be building.

 

[Ped]

Battleborn has you charging to 3.6v but somehow not getting the battery to 100%. And this achieved by preventing the internal cells from actually seeing the 3.6v. And this extra charge energy goes where?

 

[Jeremiah]

Battleborn has you charging to 3.6v but somehow not getting the battery to 100%. And this achieved by preventing the internal cells from actually seeing the 3.6v. And this extra charge energy goes where?

When Will concluded that they reserve some of the bandwidth it seemed to me it must be the same way Tesla reserves and upper and lower bound. Maybe the Battleborn cells go to 3.7 or 3.8 and that's where the outlier reserved area is (and also a bit at the bottom).
Seems strange to reserve some of the bandwidth but not at the top and bottom as the literature suggests preserves life.
Seems there is no disagreement that we should not be hitting 100% so I was trying to rectify that common knowledge with the CEO claim he wants people to charge theirs to 100%. Sounds like you're a BattleBorn user, perhaps you can solve this inconsistency for us.
Or maybe I was wrong and their capacity will be 25%+ less after 10 years so people will buy more. Planned obsolescence?
I haven't' seen anything to change the conclusion of Will and the literature that we should not charge to 100% (as someone in this thread suggested is no problem earlier-it is a problem if we like prolonged capacity).
The only thing that may change is if BattleBorn users should listen to the CEO's comment or not. I know WIll couldn't find where their cells are manufactured. it would be interesting to yank one of those cells out away from the BMS and see what it's charge range is. I posit it may surprise you.
One thing that seems uncontested is that we should not be charging our cells to 100% if we want prolonged life with less diminished capacities.

 

[Ped]

Tesla is not lifepo4.

Maybe the Battleborn cells go to 3.7 or 3.8 and that's where the outlier reserved area is (and also a bit at the bottom).

can you elaborate?

I haven't' seen anything to change the conclusion of Will and the literature that we should not charge to 100%

How do you plan to balance your cells?

Or maybe I was wrong and their capacity will be 25%+ less after 10 years so people will buy more. Planned obsolescence?

Or maybe youre wrong about not charging to 100%.

The only thing that may change is if BattleBorn users should listen to the CEO's comment or not. I know WIll couldn't find where their cells are manufactured.

Can you name any manufacturers that do not suggest charging to at least 3.6v? My 9 year old valence says 3.65v.

 

[Ped]

Lion energy

We recommend setting all voltages to 14.6 per UT in series or at least close to where it does not exceed 14.6V.

End amps or tail amps need to be set as low as possible and inverter low voltage needs to be set to 11.5V.

Trojan Trillium lifepo4



Renogy







All these companies and their planned obsolescence. Youd think itd be a terrible business model...

 

[Jeremiah]

Lion energy
...
All these companies and their planned obsolescence. Youd think itd be a terrible business model...

Well the literature put out there by marketing or whoever does not square with almost everyone's comments on this forum I've read about this topic (except you fellas for some reason think it's healthy to hit 100% all the time). I'm not sure why that's important for you but go for it.
I'll follow ghostwriter and will's lead on not hitting 100% as well as the peer reviewed lit. I've seen on this so far; mock me as you may sorry I'm not taking a user manual form a specific manufacturer as "proof" against scientific literature.
That said, I know there's a lot of mystery to LiFePO4 and it's not identical to other Li chemistries but the prevailing wisdom is "do not periodically" charge to 100% if you want to maintain capacity for the long term and by the way there is still this thing out there called Thermodynamics; nobody can have it all.
Regarding how you guys absolutely trust these business;
I don't have any beef with you guys, I just say "show me the data", not marketing hype. There's no reason where the same biz culture which has the gall to tell people "This lead acid battery will give you 200AH" which is such bull, would suddenly produce hyper ethical businesses just because they are involved in another batt. chemistry. Come on.
If you prove me wrong on this, then you'll have my gratitude.
Let's just please adjust the tone eh? We're on the same side here; nobody is making you wrong for purchasing Battle Borns.

However, the fallacy of Appeal to authority of a suit and assuming purer than the driven snow motives to business entities is a bit silly.
"show me the data" then we'll talk. Until then, continue charging to 100% if it makes you happy guys.
No need to thrust that on me and others like me who want maintained capacity and longevity.
This isn't a cult or something here; we can choose different strategies that fit our needs. Some can charge to 95% and that will greatly reduce the stress and build up of internal resistance in their cells. 10% to 95% is probably the best fit for those following the Pareto principle.

I'll personally go from 25%-85% or so; I need this stuff to last. If someone produces some scientific papers disproving this, well I don't mind being wrong on a technology that I literally just started learning about a month or so ago.
I'd be very happy if you show me a peer reviewed study that indicates it's best practice to always cycle from 0% to 100%; not marketing or a user manual; otherwise for some reason we're just dealing with an odd emotive reasoning right now that I don't understand.... though I'm used to dealing with this kind of stuff with other engineers so usually emotion doesn't enter into it unless it's in a meeting and becomes a "I'm smarter than you pissing contest."

Thanks for sharing your perspectives so far. I appreciate it even if I'm unconvinced. You took the time and effort.
peace

 

[Ped]

So its not planned obsolescence, just marketing?

 

[Jeremiah]

So its not planned obsolescence, just marketing?

Could easily be both. It's certainly not science unless you've got some actual science to share with me perhaps? We can read user manuals and marketing hype all day though if you like but I'll probably not participate. Just take a breath; nobody is attacking your intelligence here; I'm sure you're probably a clever kid.
No need to be unpleasant. It's a battery for crying out loud.

 

[Stupid Monkey]

Well at least somebody answered the question ... 92% - nothing to do with cycles, and all to do with charge/round trip efficiency ...

The round-trip energy efficiency of a LiFePO4 battery is over 90%. The charge process of lead-acid batteries becomes particularly inefficient when the 80% state of charge has been reached, resulting in charging efficiencies of 50% or even less.


I was looking it up also as my discharge capacity test failed, so I've measured the charge (before again measuring the capacity on discharge)

For ref my 24x BLS 150aH should have 11.5kwhrs .... they have already taken 12.0 and not charged yet .....

 

[ghostwriter66]

Until then, continue charging to 100% if it makes you happy guys.

stress and build up of internal resistance in their cells. 10% to 95% is probably the best fit for those following the Pareto principle.

I'll personally go from 25%-85% or so; I need this stuff to last. If someone produces some scientific papers disproving this, well I don't mind being wrong on a technology that I literally just started learning about a month or so ago.
I
peace

You do realize that going from 25-85% leaves 40% of your battery power literally "left on the table" ...

Sort of like wanting a Large pizza for supper but having to order 2 larges instead since you only eat half a pizza at a time ... sort of makes no sense ...

There is not a drastic difference from those of us that do this for a living running a cell 95% to 5% as to running it 85% to 25% ... the only difference is that you need allot more cells in order to make up for the energy that your not going to use because of these "safety" margins ...

The reason that I only go to 90% is that voltage-wise - the difference between 90-100 is literally a blinking of the eye and i just don't want to take that risk ... the same for only going down to 5 or so % .... but honestly if you have the money and doing your batteries 25-85% works for you then that's fine ... honestly the figures on how long these will last range between 2000-5000 cycles for literally the same battery made by the same company but for a different vendor ...

 

[Forbisher]

It drives me crazy to see folks spend all this money on batteries and then NOT use them top capacity -- dude -- lifepo4 is designed to go 100% to about 5% ... so to play it safe -- set it for 95% down to 10% ... the way you are doing it you are leaving 45% on the table

You know when the dude word comes out ghostwriter is ticked off.
Great advice!
Why buy twice as much LFP as you need?
That aint saving money and calendar aging will diminish capacity even if you only use 45%

 

[Forbisher]

OK so I just watched a video where Will tears down a BattleBorn and it turns out our theory was correct!
The battleborns absolutely have MORE capacity than they rate the battery for but the BMS keeps part of the bandwidth out of bounds.
That is why (as I postulated earlier in the thread), their CEO encourges people to cycle to 100% .. because the cells are NOT actually hitting 100%. The BMS is protecting that zone. It's a smaller margin than I thought but we also speculated that the warranty surely allows loss in capacity after 10 years.
At 6:38 Will concludes, "So with battleborn they overshoot the capacity so that they know that everybody will always have that capacity and they'll have an improved charge cycle life." That's exactly the point I was trying to get across (as a theoretical way to reconcile the Battleborn warranty with the scientific literature and sure enough; the 2 are not at odds!

You do a lot of guessing and speculating!
I called Battle Born for answers and they answered the phone.
103Ah maximum in their 100Ah labeled battery and they capacity test every battery they sell
When they get an occasional tested 99.x Ah battery it gets sold at a substantial discount just like their case blemished battery sales at $835.
If they sold a 120Ah battery it would be labeled as such.
There is no hidden capacity in their batteries as in the conspiracy theory promoted on this forum by member Jeremiah
They recommend discharging from the resting voltage of ~13.6v to 10v which is one 100% cycle even though inverters will usually cut off at a higher voltage.
11 volt cut off would be 95% discharge and would give a 3000 cycle life to about 80% capacity.
10 volts is the BMS low voltage disconnect.

Battle Born has been making LFP batteries under the Dragonfly brand for at least 10 years so they know what to expect for life cycles. Brandon was not sure on the 10 years, might be 15.

To be clear BB claims 3000 cycle life to 75% capacity when charging and discharging at a high 1C rate.
All of us with solar are charging much less than 0.5C or and discharging at much less than 0.5C so you will get more than 3000 cycles.

 

[Ampster]

And this achieved by preventing the internal cells from actually seeing the 3.6v. And this extra charge energy goes where?

I haven't followed this thread from the beginning so I don't know the context of your question.
Forgive me if my assumptions are wrong but to put some context into your question I can offer the following explanation.
If the cells are perfectly balanced the current tapers while the voltage remains the same. In that scenerio there is no extra charge energy because it is going into the cells at an ever decreasing amount.
If the cells are not balanced then when the first cell hits 3.6 the BMS turns on the shunt resistor and the current goes to heat and some is shared with the other cells that are not shunted. That is how the BMS keeps the first cell from going above 3.6 volts.

Does that make sense or did I miss something?

 

[Ampster]

That is why (as I postulated earlier in the thread), their CEO encourges people to cycle to 100% ..

My question may be a nitpick but does he actually encourage people to cycle to 100% or did he say they are designed so that people can go to 100% if they want to or need to? It is not like NimH where there is a memory effect and there were definite advantages to cycle 100%

 

[Ped]

My question may be a nitpick but does he actually encourage people to cycle to 100% or did he say they are designed so that people can go to 100% if they want to or need to? It is not like NimH where there is a memory effect and there were definite advantages to cycle 100%

To be charged to 100% to cell balance.

 

[Ampster]

That makes more sense but that does not imply that one needs to take them to the bottom. Balancing only happens at the top.
Thanks for clarifying.