Solar battery question/query

[bladerunnerpv]

Hi I can't quite get my head around the datasheet for the EVE cell...

Discharge test is for a cut-off volt of 2.5V at discharge current of "0.5 C" (Gen. Tech Param #4)

So it's discharge test is only to 2.5/3.2 V = 0.78 i.e. 78% ?
If I assume the volts is proxy for capacity then is nowhere near a depth of discharge of 90% (Scope of SoC has min 10%) it's a DoD of 22% or SoC of 78%??

How do read you the 0.5C ? Elsewhere the spec put (A) after the C, i.e. section 4.3, making me think Amps

Intrigued and concerned about battery storage now !

I see the FZSoNick goes to 100% discharge as they're using different chemistry in the cells. I was surprised to see the GivEnergy batteries quoting 100% DoD, whereas most seem around 85-90% DoD and wondered if they were the same, but they're LiFePO4

The Aussie report shows 80% capacity after 6000 cycles at 25 degC. and 80% capacity after 1000 cycles at 45 degC.

Hmmm the loft is looking iffy, but this is accelerated testing and not real life usage...

Is there a standard definition of "cycle" ?

Thanks for the link


Split from hi-jacked post

 

[johnb2713]

2.5v is the terminal voltage when the battery is flat, 0.5C relates to the discharge current, in my case, my batteries are 280A/h so the discharge current 0.5C would be 140A.

On my EV's and my house batteries I generally operate between 10% and 90% to increase life.

I don't think there's any major problem with temperature in UK lofts unless we get more days of 40 degC and above.

A cycle is from fully charged to fully discharged (2.5v) and back to full again, if yo discharge to 50% and then charge back to full thats counted at half a cycle.

 

[Ucatchmydrift]

Hi I can't quite get my head around the datasheet for the EVE cell...

Discharge test is for a cut-off volt of 2.5V at discharge current of "0.5 C" (Gen. Tech Param #4)

So it's discharge test is only to 2.5/3.2 V = 0.78 i.e. 78% ?
If I assume the volts is proxy for capacity then is nowhere near a depth of discharge of 90% (Scope of SoC has min 10%) it's a DoD of 22% or SoC of 78%??

How do read you the 0.5C ? Elsewhere the spec put (A) after the C, i.e. section 4.3, making me think Amps

Intrigued and concerned about battery storage now !

I see the FZSoNick goes to 100% discharge as they're using different chemistry in the cells. I was surprised to see the GivEnergy batteries quoting 100% DoD, whereas most seem around 85-90% DoD and wondered if they were the same, but they're LiFePO4

The Aussie report shows 80% capacity after 6000 cycles at 25 degC. and 80% capacity after 1000 cycles at 45 degC.

Hmmm the loft is looking iffy, but this is accelerated testing and not real life usage...

Is there a standard definition of "cycle" ?

Thanks for the link


Split from hi-jacked post

Sometimes companies, like stirling batteries list theres as having for example 5000 cycles at 100% dod. But in reality it seems that the battery capacity they list is about 20% less than the actual capacity so as they can list it as 100%dod, where infact its 80%dod just with a higher capacity than advertised.. Such as 150ah 5000 cycles at 100% dod, but, its actually a 170ah battery.

 

[Bob Smith]

Hi

I see the FZSoNick goes to 100% discharge as they're using different chemistry in the cells. I was surprised to see the GivEnergy batteries quoting 100% DoD, whereas most seem around 85-90% DoD and wondered if they were the same, but they're LiFePO4

What I have learnt from Sunsynk who also claims their LiFePO4 batteries have a DoD of 100% is that measure it on the useable capacity.
I take it a bit like a marketing trick.

Let's say the battery is 10kWh, and the usable capacity is 8kWh. They will hide 2kWh from the end user through settings etc... and then say this is a 8kWh battery with a 100% DoD. I know regarding the sunsynk that you can override the settings to really get and take from this "reserve" but this invalid the warranty.

Maybe GivEnergy use the same trick.

For the rest of your points. I am afraid, I cannot help you


One thing I struggle to find is the degradation rate. Even if the battery is used within its optimal characteristics after x years of use, the total capacity will be less than when the battery was new.

 

[johnb2713]

Hi

What I have learnt from Sunsynk who also claims their LiFePO4 batteries have a DoD of 100% is that measure it on the useable capacity.
I take it a bit like a marketing trick.

You seem to have a hang up on 100% discharged, I suspect you think that this level should have 0v across the terminals? 100% discharge on LifeP04 occurs at 2.5v and this is taken into account by the cell manufacturers. A 280A/h cell has 280 A/h capacity from full down to 2.5v.