Proper process for balancing two Dyness batteries

[leon.davibe]

Yes, there is zero absorption time needed with LFPs.

yea if it hits 3.65v per cell
it stops absorbing amps

while we had stage 6 i set a high charge rate so the batteries would be full for every shedding

and it would be like minutes from inverter pushing 80A and down to nothing

 

[wingnut771]

It will just age the batteries differently

Yes, i can live with this and worry about it in 16 years time.

 

[leon.davibe]

Huh, how does that happen when charging at 57.6V?

the moment the system goes from charging to discharging ie cloud rolls over
and load exceeds solar

the spike dissapears quie quick and then almost no change for ages as it hits flat section of the curve

 

[wingnut771]

the moment the system goes from charging to discharging ie cloud rolls over
and load exceeds solar

the spike dissapears quie quick and then almost no change for ages as it hits flat section of the curve

So what? They are still 100% fully absorbed at 57.6V.

 

[denmendez65]

Huh, how does that happen when charging at 57.6V?

There was a power forum had a guy who asked why, when he disconnects the charger from his LFP bank, the voltage would quickly drop and stabilise. Quick google now and I see plenty others asking the same questions. Thats surface charge which quickly goes away when you remove a charger.

 

[wingnut771]

There was a power forum had a guy who asked why, when he disconnects the charger from his LFP bank, the voltage would quickly drop and stabilise. Quick google now and I see plenty others asking the same questions. Thats surface charge which quickly goes away when you remove a charger.

There is a difference between charge voltage and resting voltage that is all. The battery is still 100% full.

 

[leon.davibe]

So why bother with 57.6V if the BMS auto switches off the one battery bank and the inverter only charges the other? Its pointless.

the if else statemnents that the inverters uses can be quite stupid

ie the voltronic systems actually has a known bug
if the battery is at float voltage for a long time it will just stop charging the battereis and settle to float

so then you have a battery at 70% soc meeting float criteria and inverter doesn't charge the battery

lithium absorbs charge not pull charge

so if the inverter thinks the battery is full and pushes no current it does not charge full

the only way of getting it out of the funk is to lift the float voltage to bulk voltage
it pops out of the if else loop it is in and charges the battery again

these decices look clever but is actually really stupid or should i say their logic/programming is stupid

 

[wingnut771]

the if else staemnents that the inverters uses can be quite stupid

ie the voltronic systems actually has a known bug
if the battery is at float voltage for a long time it will just stop charging the battereis and settle to float

so then you have a battery at 70% soc meeting float criteria and inverter doesn't charge the battery

lithium absorbs charge not pull charge

so if the inverter thinks the battery is full and pushes no current it does not charge full

the only way of getting it out of the funk is to lift the float voltage to bulk voltage
it pops out of the if else loop it is in and charges the battery again

these decices look clever but is actually really stupid or should i say their logic/programming is stipid

Lets not insult deye inverters here now okay?

 

[leon.davibe]

We still disconnected the batteries for a LFP based BTU that was going into a Substation. Clearly stated in the user manual from the manufacturer.

yea often safety recomendations are inherited
now yes i ain't an electrical engineer and can't know what i don't know

so safest is always to heed manufacturer reccomendations irrespective of how stupid they sound
in case i don't know something

 

[leon.davibe]

Lets not insult deye inverters here now okay?

well from what i understand dey and sunsynk is quite good was more refering to voltronic but yea they are all in this if else valley some just more refined vs others

 

[SauRoNZA]

Some discrepancy will always happen with the SOC lights on the batteries in my experience.

In my case it’s usually the Master that goes lower first, I presume because it’s the first in the chain.

Right now my overall SOC is 43.6 and Master battery is at 1 + blinking light. All three others are at 2 + 1 blinking light.

SOH is 97% overall, but 3 of the four batteries are a year older than the 4th which includes the Master.

Current voltage is 49.9V.

 

[denmendez65]

the if else statemnents that the inverters uses can be quite stupid

ie the voltronic systems actually has a known bug
if the battery is at float voltage for a long time it will just stop charging the battereis and settle to float

so then you have a battery at 70% soc meeting float criteria and inverter doesn't charge the battery

lithium absorbs charge not pull charge

so if the inverter thinks the battery is full and pushes no current it does not charge full

the only way of getting it out of the funk is to lift the float voltage to bulk voltage
it pops out of the if else loop it is in and charges the battery again

these decices look clever but is actually really stupid or should i say their logic/programming is stupid

I would assume I have inherited this bug also since I have a Voltronic clone. Never had issues, my charging voltage is set to 29V (58 if I was 48V system) and float is 27.6V(55.2). Maybe I dont see this issue because my settings are "high"?

 

[leon.davibe]

So what? They are still 100% fully absorbed at 57.6V.

yea they are full at 57.6 and 53.6v like schrodingers cat
the soc voltage thing on lifepo4 is really a thing that can irritate the crap out of you

but yea that is why the 57.6v is a thing no matter waht if it hits 57.6 it is full

edit or 54.75/54v with 15s batteries which i have
always have to do the calculations still don't remember 16s battery voltages

 

[wingnut771]

Some discrepancy will always happen with the SOC lights on the batteries in my experience.

In my case it’s usually the Master that goes lower first, I presume because it’s the first in the chain.

Right now my overall SOC is 43.6 and Master battery is at 1 + blinking light. All three others are at 2 + 1 blinking light.

SOH is 97% overall, but 3 of the four batteries are a year older than the 4th which includes the Master.

and when you get to 10% none of them will have lights as they all bottom out together.

 

[SauRoNZA]

and when you get to 10% none of them will have lights as they all bottom out together.

Probably. Don’t remember checking because when that happens it all turns off and I’m left in the dark with bigger problems.

 

[wingnut771]

I would assume I have inherited this bug also since I have a Voltronic clone. Never had issues, my charging voltage is set to 29V (58 if I was 48V system) and float is 27.6V(55.2). Maybe I dont see this issue because my settings are "high"?

Do you ever see 29V on your batteries?

 

[wingnut771]

Probably. Don’t remember checking because when that happens it all turns off and I’m left in the dark with bigger problems.

15% then

 

[leon.davibe]

Some discrepancy will always happen with the SOC lights on the batteries in my experience.

In my case it’s usually the Master that goes lower first, I presume because it’s the first in the chain.

Right now my overall SOC is 43.6 and Master battery is at 1 + blinking light. All three others are at 2 + 1 blinking light.

SOH is 97% overall, but 3 of the four batteries are a year older than the 4th which includes the Master.

Current voltage is 49.9V.

yea i have grown to just ignore the soc discrepancies but yea 2 lights difference just does tickle me
i would dig arround just to be safe in case it is battery

since bad cells can cause quick drops in soc and then once the bms has learned the reduced capacity the warning signs go away

it would be a good idea with the 2 lights to just do a capacity test and see if the battery has degraded to the point of warrantee claim

just to sooth the voice in the back of the head

 

[SauRoNZA]

15% then

Been a while since I’ve been there but yes I believe so.

 

[SauRoNZA]

yea i have grown to just ignore the soc discrepancies but yea 2 lights difference just does tickle me
i would dig arround just to be safe in case it is battery

since bad cells can cause quick drops in soc and then once the bms has learned the reduced capacity the warning signs go away

it would be a good idea with the 2 lights to just do a capacity test and see if the battery has degraded to the point of warrantee claim

just to sooth the voice in the back of the head

I would only worry about that after 100% charging it for 24H.

If it then still deviates that far I’ll also consider it a concern.