Battery doesn't seem to keep up after a few days

[shvm]

thanks @DIYrich - I do get to at least 13.6 before dusk; but again it's according to the charge controller. And I'm now learning that may just be inaccurate!

There is a very simple voltage current relationship to decide whether LFP is fully charged or not.
BOTH Current and Voltage is needed (calibrated reference).
Put simply, Current going into battery has to be less than 0.05 C at 3.625 V/Cell, for it to be considered fully charged.
For charging voltages lower than 3.6 V/Cell, this current has to be even lower and can be easily determined.

SOC indication based purely on voltage will simply drift over time for LFP.

 

[pollenface]

I believe the 60a renogy charge controller is not adequately charging your battery while using the factory Li setting. There is no absorption period which is needed to help balance cells.

I suggest changing to USER, if that's possible and adding 1-2hrs of absorption at 14.2v.

On the 4000w inverter comments, a fridge doesn't pull 300+ amps, don't sweat it.

 

[shvm]

There is no absorption period which is needed to help balance cells.

I suggest changing to USER, if that's possible and adding 1-2hrs of absorption at 14.2v.

That is for Lead Acid not LFP.
For LFP, there is something commonly termed as tail current parameter. It should result in the controller terminate charging automatically.
No need to mess around with absorption settings.

Look:

https://www.renogy.com/content/files/Manuals/RNG-LFP_Manual_V1.0.pdf

 

[mikefitz]

That is for Lead Acid not LFP.
For LFP, there is something commonly termed as tail current parameter

Solar controllers from Renogy and Epever do not offer tail termination, with these controllers and where you have variable solar charging current and power being taken from the battery , tail current termination is not possible or desired .
The low cost batteries often have unbalanced cells, by programming a suitable charge voltage and duration it will give time for balancing to take place.

 

[shvm]

by programming a suitable charge voltage and duration it will give time for balancing to take place.

There's no such thing as a "suitable charge voltage and duration" for LFP battery balancing.
LFP battery should be balanced after charging ends (top of SOC) when the Cells are resting. As simple as that.

Once balanced properly , I don't see a reason to even turn the balancer on for months assuming you're charging correctly.

So called reputed 'Experts' in this forum claiming LFP needs balancing after every charge cycle have obviously never seen a balanced pack behave.
Most don't even know the proper charging parameter for LFP to begin with.

 

[Quattrohead]

There's no such thing as a "suitable charge voltage and duration" for LFP battery balancing.
LFP battery should be balanced after charging ends (top of SOC) when the Cells are resting. As simple as that.

Once balanced properly , I don't see a reason to even turn the balancer on for months assuming you're charging correctly.

So called reputed 'Experts' in this forum claiming LFP needs balancing after every charge cycle have obviously never seen a balanced pack behave.
Most don't even know the proper charging parameter for LFP to begin with.

You show a basic misunderstanding of how these batteries work and what they need to remain healthy.
OP, is it possible the fridge is going through a defrost cycle when the battery does not make it ?

 

[shvm]

You show a basic misunderstanding of how these batteries work and what they need to remain healthy.

What is Your source?

 

[Q-Dog]

Hi all,
I've set up a small system of a few panels, LiFEPo4 battery, charge controller and inverter (more details on the system below). It's meant to power my full sized refrigerator in my kitchen indefinitely (I live in a hurricane-heavy area in Florida; it's not to save money but rather for assurance that we'll always be ok with food regardless of the weather).
I power my fridge with this little solar system just fine for a few days. When it gets dark at night, battery starts draining, but doesn't get completely discharged, and starts charging in the morning faster than it's being consumed, so I can see it climb back up to about 100% by around noon. I check again at 5:30 PM or so (when it starts getting dark), battery is at 100% - awesome. After about the 3rd day or so, battery was at 100% at 5:30 PM, but by 11 PM that night - it's completely drained and I have to chagne the fridge back to the grid. Am I missing something in my setup? Am I just assuming the battery can handle this when it really can't?
The set up is this: 4 Ecoworthy panels at 200w, 10.83ah (max) apiece in parallel, connected over 30 ft of 8awg copper wire controlled by a Renogy 60A MPPT Rover Li charge controller connected to an Ecoworthy 12.8v 200ah LiFePo4 battery, and output to a Gearzaar 4000w 12v to 110v/120v AC inverter. Wiring from battery to charge controller and from battery to inverter is also 8awg.

I'm just confused - I'd understand if on that 3rd day (sometimes it's the 2nd, sometimes the 4th, its not consistent) the battery just wasn't at 100% (according to the charge controller, that is) when the sun goes down around 5:30 PM - but each of those days I check, it's always at max capacity at that time, but somehow just suddenly can't power the fridge through the night, and dies about 5-6 hours into the no-sunlight hours. It makes me worried the battery is damaged somehow, but maybe I just need to learn more. Would I benefit from adding batteries to make a small bank of them maybe? Should I trust the battery charge percentage I'm reading on the charge controller? Thanks in advance!

My fridge runs a defrost cycle about every 20 hours, so sometimes while charging and sometimes while on batteries. Therefore it uses about 4% more of my battery capacity during nights when it runs the defrost. And I suspect your 800 watts of solar won't refill the batteries except on really perfect days.

 

[pollenface]

That is for Lead Acid not LFP.
For LFP, there is something commonly termed as tail current parameter. It should result in the controller terminate charging automatically.
No need to mess around with absorption settings.

Look:

https://www.renogy.com/content/files/Manuals/RNG-LFP_Manual_V1.0.pdf

No. I'm talking about LFP regardless of what is written in the Renogy manual.

 

[pollenface]

So called reputed 'Experts' in this forum claiming LFP needs balancing after every charge cycle have obviously never seen a balanced pack behave.
Most don't even know the proper charging parameter for LFP to begin with.

Everyone here is genuinely trying to help.

 

[shvm]

Everyone here is genuinely trying to help.

That I wholeheartedly agree!