SBMS - Solar BMS from electrodacus

[BruceS]

Dacian? You lost me now!
You'll need to get each cell up to 3.6V quite a bit to keep the capacity of the bank.
Multiply by 4 to get bank.

[froggy]

Sorry Dacian is the maker of the solar bms unit.
Are you saying set it at 3.65v or just charge them up to that occasionally?
What about bottom voltage, pretty sure it’s set to 2.8v

[T1 Terry]

Still haven't set up our solar system at the house so I haven't connected up the Electrodacus unit. I know it monitors the cell voltages and has a method of balancing, but it the end of charge or a timed charging halt triggered by a max cell voltage? The cell voltage is critical, control the max and minimum and the battery voltage will look after itself, let any cell rise above or fall below the safe voltage for an extended period will result in potential battery failure, so combined terminal voltage is not a suitable method of battery voltage control.

T1 Terry

[froggy]

Yes terry, it cuts out at 3.55 cell voltage but it is all customiseable.
He has it go down to 2.8 which I feel is a little low.

[T1 Terry]

Yes terry, it cuts out at 3.55 cell voltage but it is all customiseable.
He has it go down to 2.8 which I feel is a little low.

2.8v cut off is fine, reset to 3.6v HVC to allow the cells to reach saturation charge for their first charge. You will see the cells go out of balance once they start to approach fully charged but with the auto balance feature combined with the 3.6v charge cut should eventually get the cells fully charged. You will know they have not reached fully charged if the cell voltage drops a fair bit as soon ass the charge stops. Once they are full the voltage will remain above 3.5v when there is no load applied.

T1 Terry

[froggy]

They have already had a couple of charges to 3.55v will this matter?
The auto balance seems to be working well as they seem to range from about 4-70mv out of balance from highest to lowest.

[T1 Terry]

They have already had a couple of charges to 3.55v will this matter?
The auto balance seems to be working well as they seem to range from about 4-70mv out of balance from highest to lowest.

You should only ever see an out of balance when the cells reach 100% SOC because voltage has very little to do with the state of charge and the voltage will only climb once the cell won't accept any more.
Picture the first time you fill a water bed, how many times did you have to bleed the air out before the sloshing noises stopped? The initial fill of a lithium cell is similar, until all the pockets in the graphite have accepted their first linking to a lithium ion there will not be more lithium ions in the electrolyte than can be absorbed into the graphite and that means 100% capacity has not been reached.
It gets a heap more technical after that as to why this first charge being done correctly is so important but the end result is a less than optimal cycle life.

T1 Terry

[froggy]

Terry, do you suggest to leave hvc at 3.6 permanently or just first the first few charges if the latter what would you set it too?

[T1 Terry]

I still haven't read the manual, slack of me I know, but you only read the instructions when all else has failed and that hasn't happened yet
What settings have you used for the bulk charge voltage, absorption stage voltage and time and the float voltage? The high cell cut off should only ever be a secondary level protection required if the cell balance is excessive at the top end of the bulk charging cycle

T1 Terry

[froggy]

I still haven't read the manual, slack of me I know, but you only read the instructions when all else has failed and that hasn't happened yet [emoji1]
What settings have you used for the bulk charge voltage, absorption stage voltage and time and the float voltage? The high cell cut off should only ever be a secondary level protection required if the cell balance is excessive at the top end of the bulk charging cycle

T1 Terry

I may be looking in the wrong spot but i cant see settings to do with this, its not a conventional charger? I just assume it charges whatever the solar give it. I was of the understanding that it just cuts out when a cell gets to the set hvc.
Actually going back through the manual there was an end of charge setting, think ive got that at 3.60 and hvc as 3.62
Here is the standard settings screen