Hi,

 

Thanks to feedback and input from persons on this forum I have my inverter/battery setup running well now after the installer had a few weird settings. (5KW deye with 2x 5kw dyness)

 

I have done way too much reading online about this matter and am once again looking for input on here from more experienced folk.

 

Everywhere I read, is all the same about prolonging your lithium battery life... main factors being temperature, charge and discharge at a low C rate, don't discharge too much and also don't charge too much (lots say don't go to 100%)

 

So, my question - whilst I am waiting for my panels, is it better to charge the battery to say 80-85% max and then for 4,5 hours loadshedding discharge it to 50% and then recharge again to 80-85% (via Time Of Use in work mode) OR charge to 100% and discharge to 70% during loadshedding then charge to 100% again (un-ticking time of use option in work mode, so basically UPS mode)

 

Or is it really horses for courses as when my solar comes, the solar will keep batteries at 100% anyway during the day if it's not load shedding?

 

Thanks again

 

 

Edited April 14, 20231 yr by flyfisherman

Based on the settings I use after much research about this topic (THANKS ANDY and some others)

Optimal charge/discharge rate for lifepo4 is 0.2C that combined with the correct top end voltage will give maximum life for the batteries.
If your BMS balance start voltage allows it then try keeping the voltages to max of 3.45v per cell. Note: some/many of these prebuilt batteries have a higher balance start voltage so you would need to adjust the upper voltage accordingly or adjust the BMS settings to allow balance start at a lower voltage.
Most households using 2X 48V 100AH batteries will only occasionally go above 0.2C like when the kettle, geyser or microwave run, and then usually only for a few minutes at a time and mostly only when solar is not not available to support the loads, nothing wrong with that.

As for DOD try never going below 20%, that bottom end is where a lot of the "wear and tear damage" happens.

Edited April 14, 20231 yr by WannabeSolarSparky

1 hour ago, WannabeSolarSparky said:

Optimal charge/discharge rate for lifepo4 is 0.2C that combined with the correct top end voltage will give maximum life for the batteries.

@WannabeSolarSparkyjust a few questions regarding your statement:                          1.How is cycle count calculated.

2. Why invest in a 1C Lfp if best to charge/discharge at 0.2C 

3. Cycle life stated from  manufacturers 3000 cycles at 80%dod or 15 year lifespan. Why would we charge/discharge a 1C battery at 0.2C to preserve the battery life beyond 15 years. With current load shedding cycles and moderate power consumption charging a [email protected] on a cloudy day is not going to cut it.

Just my 2cents

12 minutes ago, TaliaB said:

Why invest in a 1C Lfp if best to charge/discharge at 0.2C

Nothing stops anyone from using their batteries at 1C other than maybe the bms limits.
LiFePo4 battery cells are recommended by the actual cell manufacturers to run at 0.2C for charging and discharging.
They give these values for a reason, they usually know what's best for the cells they manufacture.

As for the companies that sell these batteries (The fully built ones), it all comes down to marketing and how they have setup their bms's
As of late most/many are now saying 6000 cycles, this is a new marketing phenomenon and maybe based on updated test results or just calculated/risk.

Daily use charge/discharge at full 1C continuous will ruin your battery in no time at all with all current LiFePo4 cells.

Gazillions of videos and tests available online about how these battery cells work and how to get the best service life out of them

Personally at R45k spent for my 2 batteries I would sure as hell like them to last as long as possible before replacing them and still staying safe and getting good use from them.

Each persons use case is different. My statements are always generalised and based on my personal use case and experience (See signature).

27 minutes ago, TaliaB said:

3. Cycle life stated from  manufacturers 3000 cycles at 80%dod or 15 year lifespan.

These are not cell manufacturers specs, these specs are usually from the companies who assemble cells into battery packs and are mostly marketing statements put on as "specs". Many will say 0.5C constant or lower as the normal use, that usually can/may get you to the stated 3000 cycles and or years. Again this is mostly sales/marketing stuff.

31 minutes ago, TaliaB said:

1.How is cycle count calculated.

Many many many debates online about how to do cycle counts. Again best would be to read up on the research labs who can point you to the "correct" way to determine cycles.

Again read my signature to get context fro any/all of my statements