Deye - Charging to 99%

[QB87]

Hi,

I have two 5kw Deye inverters in parallel connected to a single 10kwh lithium batter.

Any ideas why my battery is charging up to 99% even if my Time of Use is configured to 80%? This only happens during daytime when the system is powered by solar energy. It’s almost as if it is ignoring my SoC settings and decides to charge the batteries to full when on solar.

At night time, when charging from grid, the Time of Use SoC is adhered too.

The time of use schedule is followed and working. It’s only the SoC settings on Time of Use that is ignored when charging from solar.

Regards.

[mzezman]

The 80% is a maximum discharge% not a maximum charge % when there is PV. Read it as "discharge my batteries to the % set in TOU during that time" and then use grid or generator

Alternatively; use the grid or generator to charge my batteries to the % set in the TOU during that time

[Nexuss]

43 minutes ago, QB87 said:

Any ideas why my battery is charging up to 99% even if my Time of Use is configured to 80%? This only happens during daytime when the system is powered by solar energy. It’s almost as if it is ignoring my SoC settings and decides to charge the batteries to full when on solar.

Thats correct ,if there is lots of solar the batteries will charge fully you cant stop it from going to 100%.

[Kilowatt Power]

On 2023/04/29 at 3:47 PM, QB87 said:

Any ideas why my battery is charging up to 99% even if my Time of Use is configured to 80%?

Out of curiosity, why wouldn't you want your battery fully charged by solar? 

[QB87]

I thought charging lithium batteries to 100% decreases it’s lifespan? If that’s not true please let me know  

[mzezman]

36 minutes ago, QB87 said:

I thought charging lithium batteries to 100% decreases it’s lifespan? If that’s not true please let me know  

Keeping them charged at 100% isn't ideal.

If you do charge them to 100 try run them down as far as you can every few days 

[Bursu]

LiFePo4 batteries are NOT like your Li-Ion smarphone batteries.

1. LiFePo4 batteries have 4000 to 9000 charge cycles, depending on model. Your phone battery has 500-800 charge cycles.

They are less energy dense but have alot more charge cyles and are designed to be used 15+ years. 

2. LiFePo4 batteries do not need trickle charging from 90% to 100% like your phone does. LiFePo4 batteries can take the same rate of charging up to 100%.

3. Charging them to 100% allows the BMS to balance them in order to maximize their performance and prolong their life.

4. As long as you cycle them daily it's ok to charge them to 100%.

5. LiFePo4 batteries if stored for 10 years without ever charging them, they degrade about 20%. They still charge and hold about 80% of their initial capacity.

6. LiFePo4 batteries are less prone to combustion and thermal runaway. They tend to be cooler when charging, in comparison to Li-Ion batteries

Smartphone bateries if not charged for 10 years, degrade from about 60% at best, to complete capacity loss, depending on your luck.

 

 

Edited May 4, 2023 by Bursu

[Eurard]

There is no real benefit from charging a LiFePO4 battery the final 0.05V per cell.

3.6V per cell is actually better in the long run, which is 15s - 54V, and 16s - 57.6V.

Max is 58.4V on a 16s and that is taking the battery 3.65V to 100% capacity.

But yes for the BMS to balance an as suggested to charge them once or twice a year to full 100% until the current drops to near Zero.

For max lifespan to run the battery below 100% to just before bottom knee also prolongs life. In essence, just let the battery casually do its thing, dont strain the hell out of it, they do have electrodes that needs penetration, micro cracks etc etc happen.

 

PS are LiFePO3 a new type, I know of only LiFePO4 ... jk .. 

[Antonio de Sa]

12 minutes ago, Eurard said:

There is no real benefit from charging a LiFePO4 battery the final 0.05V per cell.

3.6V per cell is actually better in the long run, which is 15s - 54V, and 16s - 57.6V.

Max is 58.4V on a 16s and that is taking the battery 3.65V to 100% capacity.

But yes for the BMS to balance an as suggested to charge them once or twice a year to full 100% until the current drops to near Zero.

For max lifespan to run the battery below 100% to just before bottom knee also prolongs life. In essence, just let the battery casually do its thing, dont strain the hell out of it, they do have electrodes that needs penetration, micro cracks etc etc happen.

 

PS are LiFePO3 a new type, I know of only LiFePO4 ... jk .. 

In my case LifePO4  16S I get full charge at 3.53 V, anything above that the BMS goes into equalization mode and stops charging cell above 3,5 V see attached dashboard of the last 24 hours.

[apl60]

Could you configure this in the deye Inverter? And if so, how?

Otherwise, it should be possible in the BMS config...