Absorption time for growatt 5000es

[Hermanvanveen]

Hi there,

In the manual I could not find a possibility to program a specific absorption time for the growatt 5000es inverter. If I am not mistaken, Andy from the offgrid garage recommends 1 hour for this absorption period.

The combination will be: the 5000es with 16x eve 280 or 304 cells.


Does anyone have experience with such a combination and knows what the inverter uses as absorption time before it switches to fload mode?


Thanks

 

[gremlin66]

Hi , also have growatt es 5000 and JK BMS with EVE cells, have same issue if I set absorption to 3,45 like Andy looks like is not possible to set a time of 1 or 2 hours on growatt... I am currently working on best growatt settings in junction with JK. Working on it as I write this

 

[Hermanvanveen]

Well, I wish you all the best. I hope you will figure out a solution that works well. Please inform us about your discoveries!

 

[Hermanvanveen]

Maibe there are other people here on the forum who have suggestions?


It should be possible, since Will Prowse also used individual cells in combination with a mpp solar inverter (which is Voltronic like growatt)

 

[timselectric]

Growatt only has bulk and float. (which is absorption for LFP) float is continuous, as long as charging power is available.

 

[Hermanvanveen]

The question is: is the growatt unit capable to put the full 280ah into the cells?

Since you can not set a absorption time like the victron charge controller.

I just wonder what actually happens with the growatt unit during the "bulk/absorption" phase. The moment the cells reach their set 3,45 volts, does it keep it there for a while, or does it switch to the float setting right away?

 

[Pim57]

According to Andy from off-grid-garage there’s not much need for absorption time if charging to 3.45 V.

After reaching 3.45 V there’s only room for a few more Ah’s.

 

[Hermanvanveen]

Thanks for your reply.

The graph and table does not tell us that Andy didn't use any absorption time. Normally he set it to 1 hour if I am not mistaken. I doubt that he reduced this time to zero seconds for this test, but I could be wrong....

 

[Pim57]

In that video graph and table the absorption time is zero.

The test is how much capacity is in the battery when you charge with 5, 10, 20, 40 A and stop when the voltage reaches 3.3, 3.35, 3.4, 3.45 and 3.5 V.

Conclusion: there is no need to charge any higher than 3.45 V. The battery is >93% depending on the charge current.
If you charge with 0.05C (5A with 100Ah) and stop at 3.45 V the battery is 99% SOC.

And of course some absorption time will add a few extra Ah’s. In your case where no absorption time can be set in the SCC you could set the bulk/absorption voltage to 3.5 V to add a few more Ah’s.

 

[Hermanvanveen]

That's good news.

Thanks for the info.

 

[gremlin66]

First this is the parameter I have setup for Growatt and JK BMS, after I will explain why.
GROWATT: (program N°: value)
5: USE (not US2 like you might think)
19: 54.7 (3.418 per cell) about 100% SOC
20: 53.4 (3,337 per cell) FLOAT 92% SOC
JK: start balance voltage: 3,34 V
Explanation and my thoughts:
The first thing I checked was the battery voltage with a decent multimeter and compared to Growatt and JK then corrected JK voltage so it will match Growatt voltage (slight difference with multimeter, but not much...)
On Growatt if you set program 5 to US2 (Lithium without BMS communication port) program 19 and 20 have same value and FLOAT will not work, and since is not possible to set a time for absorbption is hard to balance the cells especially at 3,45 volt. So the first decision is if you want to float or not. At the moment I think float is good so I always have the battery full, especially because I will need the energy 24/7 (I need to heat the house also at night in winter with heat pump)
I don't want to stress the battery too much so for now I keep values low. The 3,34 volt on JK to start balance looks like is working fine at the moment, so I will not put it higher for now. In case I change something I will update this post or write a new one. Remember to turn off and on growatt Inverter when you switch from US2 to USE and set the float, otherwise will not start floating.
I am NO expert so this might be all wrong, but please let me know.

 

[timselectric]

The question is: is the growatt unit capable to put the full 280ah into the cells?

Yes
I do it every few days.

 

[Hermanvanveen]

@gremlin66

19: 54.7 (3.418 per cell) about 100% SOC
20: 53.4 (3,337 per cell) FLOAT 92% SOC
JK: start balance voltage: 3,34 V


Your internal jk balancer then balances for a charging period from 3,34 to 3,418 volt, correct?

Because when the unit switches over to the float setting, the voltage will quicly drop down to under your balance setting.


Is this enough time to balance your cells adequately?

 

[gremlin66]

I have connected everithing just 5 days ago and set the parameters today, so I will let you know in the next 1 or 2 weeks

 

[timselectric]

My current settings for Growatt and JK BMS.
Bulk 57v (3.56v per cell)
Float 56v (3.5v per cell)
Balance start 3.5v @ Delta of .003
The Growatt charges at full available rate, until 57v is reached. Then drops to 56v, and holds it there as long as a charging source is available. JK BMS balances cells until they are within the Delta.

 

[gremlin66]

My current settings for Growatt and JK BMS.
Bulk 57v (3.56v per cell)
Float 56v (3.5v per cell)
Balance start 3.5v @ Delta of .003
The Growatt charges at full available rate, until 57v is reached. Then drops to 56v, and holds it there as long as a charging source is available. JK BMS balances cells until they are within the Delta.

thank you, in case I will switch to your settings

 

[timselectric]

19: 54.7 (3.418 per cell) about 100% SOC
20: 53.4 (3,337 per cell) FLOAT 92% SOC

These settings are for charging.
But you are quoting resting SOC voltages.
These are two different things.

 

[timselectric]

This might help some people.

 

[timselectric]

thank you, in case I will switch to your settings

My settings are a bit aggressive. I would recommend that you see what works best for your setup.
My cells are very good quality. They don't seem to be stressed with the settings I have. I gradually tested many settings.

 

[Pim57]

My current settings for Growatt and JK BMS.
Bulk 57v (3.56v per cell)
Float 56v (3.5v per cell)
Balance start 3.5v @ Delta of .003
The Growatt charges at full available rate, until 57v is reached. Then drops to 56v, and holds it there as long as a charging source is available. JK BMS balances cells until they are within the Delta.

A float of 3.5 V will overcharge the cell !!

Overcharging means Lithium plating. The Lithium ions can no longer be stored in the carbon anode because all available places are occupied (the cell is 100% charged). The Lithium ions wil then convert to pure Lithium which is an one-way irreversible process. And thus you loose the ions hence capacity!

For float 3.35 V or 3.337 V is the best choice.