LIFEPO4 Battery discussion thread

[denmendez65]

Oh, I thought we talking LFP.

No Andy's used 20A because that is 0.2C, his std test parameters.

Refer to post 796 for different C ratings.

No, I am talking LFP. I just said I go the idea from GELs and decided to check if it is a problem on LFP also. It is. You run the risk of damaging your cells pulling big loads at low SOC. The screen shot is for FLP.

 

[wingnut771]

No, I am talking LFP. I just said I go the idea from GELs and decided to check if it is a problem on LFP also. It is. You run the risk of damaging your cells pulling big loads at low SOC. The screen shot is for FLP.

and like I said, the big loads will be for a fraction in time and nothing to worry about. You not doing constant 1C discharge test. That is only possible with a 20kW inverter.

Anyway, LFP cells are rated at 6000 cycleas @ 1C to 100% DOD so gemini can suck my balls

 

[wingnut771]

No, I am talking LFP. I just said I go the idea from GELs and decided to check if it is a problem on LFP also. It is. You run the risk of damaging your cells pulling big loads at low SOC. The screen shot is for FLP.

Ask gemini why it says in the cell specs 6000 cycles @ 1C down to 0% and still have 80% SOH.

 

[denmendez65]

and like I said, the big loads will be for a fraction in time and nothing to worry about. You not doing constant 1C discharge test. That is only possible with a 20kW inverter.

Anyway, LFP cells are rated at 6000 cycleas @ 1C to 100% DOD so gemini can suck my balls

I don't know, man, Science Direct has a study on it. And found more on other sites. I will stick to 48 to 49 cut-off. Maybe do 48.6. I need that battery to last as long as possible.

 

[denmendez65]

Ask gemini why it says in the cell specs 6000 cycles @ 1C down to 0% and still have 80% SOH.

 

[wingnut771]

I don't know, man, Science Direct has a study on it. And found more on other sites. I will stick to 48 to 49 cut-off. Maybe do 48.6. I need that battery to last as long as possible.

View attachment 1912511

In the real world high discharge rates are not constant but only for a few minutes not 5 hours.

 

[wingnut771]

View attachment 1912514

View attachment 1912515

This is complete bullcrap:


Please find me an Andy video where this cell drop to 2.1V or 2.0V happens where BMS is not fast enough. I'll save you the time, thats never happened, but anyway, you do you, at least you not thinking about tubular lead acid anymore.

 

[denmendez65]

This is complete bullcrap:
View attachment 1912527

Please find me an Andy video where this cell drop to 2.1V or 2.0V happens where BMS is not fast enough. I'll save you the time, thats never happened, but anyway, you do you, at least you not thinking about tubular lead acid anymore.

You can't deny the temperature and clamping issue, though.

 

[wingnut771]

You can't deny the temperature and clamping issue, though.

I can.

Andy has covered those ones too.

 

[denmendez65]

This is complete bullcrap:
View attachment 1912527

Please find me an Andy video where this cell drop to 2.1V or 2.0V happens where BMS is not fast enough. I'll save you the time, thats never happened, but anyway, you do you, at least you not thinking about tubular lead acid anymore.

And this is the datasheet for a PACEBMS.

It will take 1 second before it reacts to an overdischarge event. Gemini wasn't talking nonsense, actually. A whole second of pulling a big load when the voltage of the cell is tanking...yeah, that doesn't sound good.

 

[denmendez65]

I can.

Andy has covered those ones too.

He is not doing 1C 0 to 100 though.

 

[wingnut771]

And this is the datasheet for a PACEBMS.

It will take 1 second before it reacts to an overdischarge event. Gemini wasn't talking nonsense, actually. A whole second of pulling a big load when the voltage of the cell is tanking...yeah, that doesn't sound good.

Luckily we are cutting off at 46V then (2.88V).

Here, just replace faulty cell with MB56:

 

[wingnut771]

He is not doing 1C 0 to 100 though.

Nobody does. So what are you worrying about when cell can handle 6000 cycles at 1C according to spec sheet?

 

[wingnut771]

He is not doing 1C 0 to 100 though.

Capacity would be the same though:

 

[denmendez65]

Luckily we are cutting off at 46V then (2.88V).

Here, just replace faulty cell with MB56:

After 1 second, that is. You have little headroom at 46, as your voltage is crashing before the BMS takes over. If you set it as the knee curve starts to dip (3.1 you have leeway.).

Maybe thats why the 49V that your CPT system has? And you couldn't drop it further?

 

[denmendez65]

Capacity would be the same though:
View attachment 1912539

After 3.1 look at how sharply the curve drops.

If you pulling a large load and you had it set at say 3 and under, 1 second is an awful time to wait while your cells are dipping that low.

 

[denmendez65]

After 3.1 look at how sharply the curve drops.

If you pulling a large load and you had it set at say 3 and under, 1 second is an awful time to wait while your cells are dipping that low.

 

[cavedog]

Was thinking of getting one of these small 12v solar inverters for my 12v cheapig battery. Run some lights, gate motor and electric fence

They go for about R1800 brand new.

 

[wingnut771]

After 1 second, that is. You have little headroom at 46, as your voltage is crashing before the BMS takes over. If you set it as the knee curve starts to dip (3.1 you have leeway.).

Maybe thats why the 49V that your CPT system has? And you couldn't drop it further?

It takes minutes to get from 46V to 40V.

 

[wingnut771]

Was thinking of getting one of these small 12v solar inverters for my 12v cheapig battery. Run some lights, gate motor and electric fence

They go for about R1800 brand new.

View attachment 1912545

View attachment 1912546

Where do you find these deals?