Real world efficiency of LiFePO4

[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.

 

[Jeremiah]

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%

Since you didn't see the earlier part of the thread here's the brief recap:
I was just speculating to appease the fanboys since battery university and Will shared that you can greatly increase the lifetime of LifePO4 by not charging to 100% and not discharging to 0%. Ped was saying that BattleBorn encourages full cycling (as a challenge to the scientific data I was referencing). So to be diplomatic I was trying to reconcile what the data says about LiFePO4 capacity over time and what the BattleBorn fanboys were getting upset about (I never attacked that brand, why would I?)
My background is in a different area of engineering so I'm just learning like everyone else.

One guy bolted from the thread b/c the fan-boying became hostile in tone; inappropriate I would have moderated it if it were my forum but I suspect it's an issue of youth.
I'm still here because I'm also interested in reconciling the science with the "Battleborn phenomenon." The @Ped fellow shared a video and a time code (wrong time code they are discussing temp you have to watch a bit longer) where Will asks about battery life is it true that it's best not to charge to full capacity and the BattleBorn CEO says, "we want people to charge our batteries all the way" (paraphrase).
SO this was presented as evidence that the Video Will made discussing how to extend Lifepo4 battery life (not charging to 100% and not discharging to 0%) was somehow fallacious. So here we are... for some reason the @MBR fella is upset with me and my "speculating."
As a retired engineer I don't understand the passive aggressive shots about a product. It's not like I'm attacking Battleborn; I would never spend so much when I could build 4x the capacity for myself but I know not everyone is hands on into tinkering. I've accepted the claims at face value; I trust Will more though than I do fanboys though so I'll continue to approach my own upcoming LifePo4 system with a strategy to use 70% capacity to extend the life.

 

[Ped]

He cannot seem to grasp that the extra internal capacity is so the end user actually gets the full 100Ah without actually taking the internal battery below 10%, and not to magically hide the top end and force a faux top balance.

Its like a reserve on a fuel tank. Theres actually still fuel when the gas runs out. But you're still filling the tank to the top.

 

[zorlig]

He cannot seem to grasp that the extra internal capacity is so the end user actually gets the full 100Ah without actually taking the internal battery below 10%, and not to magically hide the top end and force a faux top balance.

Its like a reserve on a fuel tank. Theres actually still fuel when the gas runs out. But you're still filling the tank to the top.

You mean so it can lose more capacity before the warranty gets triggered (before it falls under spec?)? There is no protection to keep them from going below normal voltages that I'm aware of.

 

[Forbisher]

.

He cannot seem to grasp that the extra internal capacity is so the end user actually gets the full 100Ah without actually taking the internal battery below 10%, and not to magically hide the top end and force a faux top balance

Battle Born batteries are 103Ah because they have 120 cells and they capacity test them to check.

3.2V x 3.4Ah = 10.88wh per cell

10.88wh x 120 cells = 1305.6wh actual tested capacity in Will's tear down video.

Yeah Will said that was smart derating the 100Ah.

12.8v x 100Ah is 1280wh
So Battle Born underates their battery by about a whopping 25 watt hours
They could legitimately label their batteries at 103Ah but they stick to saying 100Ah.

The Battle Born tech laughed about them hiding or limiting battery capacity. Those 103Ah are available under their 100% discharge from 13.6 volts to 10 volts as proven in Wills capacity test.
I also think a 120 cylindrical cell battery is superior to a 4 cell prismatic battery that a lot of people here are assembling with a BMS.

 

[Jeremiah]

...
The Battle Born tech laughed about them hiding or limiting battery capacity. Those 103Ah are available under their 100% discharge from 13.6 volts to 10 volts as proven in Wills capacity test....

Great sense of humor on that tech! I can't wait to hear how this story continues to develop; tell him about how Tesla holds back a good chunk of AH, maybe we can get an actual engineer rofl-ing soon b/c it's j-u-s-t such an insane idea right? silly Tesla...what were those guys thinking? It's clearly a bad idea since a tech somewhere else laughed about it (this iteration of the story). I'm still laughing too, it's just sooooo funny to assume 2 good companies might have the same best practice. bwaaaaahaha. phew, time to breath.