Bogart SC-2030 - not what i expected

[John Frum]

I did. I set it to 14.2V, but it kept pushing current as it passed that voltage until 3.65V again

4 scenarios come to mind.
1. your cells are not balanced and one of them is getting ahead of the others.
2. the charge controller is not calibrated properly
3. the solar charge controller is fubar
4. user error.

Suggest we make tests to scenarios.
Sorry if i missed it what is the pack voltage and what are the individual cell voltages?
If one of them is an outlier then It indicates #1.
The BMS protection circuit is tripping, confirm?

 

[grizzzman]

When the first cell hits 3.65 what do the other cells read?

 

[mkaye]

when the 1st cell hit 3.65V, i had 150mV difference between cells (as stated in earlier note)
it seems to better now as it is cycling a bit
more sun today, i'll be able to watch it

 

[grizzzman]

Sorry had to reread your first post. 150mV is a bit on the high side. It implies that the cells are not at the same charge level. Once again did you top balance the cells?

 

[fat_old_sun]

I did. I set it to 14.2V, but it kept pushing current as it passed that voltage until 3.65V again

I'm responding to this & a couple of your recent posts.

I think I have an explanation (speculation?) for what's happening. The controller (& the monitor) use time averaged values of voltage & current for switching from bulk to absorb. The BMS is using instantaneous voltage readings to decide when to shutdown. This difference causes the BMS to react before the controller when the voltage is rising.

The over-voltage shutdown feature of a BMS is to be used as a backstop to prevent a catastrophic event. Setting the trigger voltage for the shutdown too low can cause conflicts. I recommend increasing the BMS setpoint to 14.8V or even 15.0V. In addition to this, the pack has cells that are out of balance at the top end, causing the BMS to intervene too soon.

 

[grizzzman]

I'm responding to this & a couple of your recent posts.

I think I have an explanation (speculation?) for what's happening. The controller (& the monitor) use time averaged values of voltage & current for switching from bulk to absorb. The BMS is using instantaneous voltage readings to decide when to shutdown. This difference causes the BMS to react before the controller when the voltage is rising.

The over-voltage shutdown feature of a BMS is to be used as a backstop to prevent a catastrophic event. Setting the trigger voltage for the shutdown too low can cause conflicts. I recommend increasing the BMS setpoint to 14.8V or even 15.0V. In addition to this, the pack has cells that are out of balance at the top end, causing the BMS to intervene too soon.

Well with the BMS he has he could drop HVD to correct, but if cell imbalances are the issue I would suggest that you deal with that issue first.

 

[mkaye]

i discharged to 95% - now charging 20A+ - another 20min and should be full
BMS cell difference is 31mV - actual is 15mV
cell #2 is the highest (was the lowest during my 1st couple of tests)
i'm trying to watch to see what happens when i approach 14.2V

yes, i did top balance

i did notice that i had 60-100mV drop across my busbars when discharging 100A+ - need to clean & tighten or squeeze some copper pipe

 

[mkaye]

definitely a top balance issue
cell #2 would lag behind >3.5V - cell difference shot up over 200mV
i am top balancing - #2 took quite a bit of current to get it up with the other 3
all within 10mV now - leaving them on the charger @14.4V for a while
have to build a foam base for the cells now...

 

[grizzzman]

i discharged to 95% - now charging 20A+ - another 20min and should be full
BMS cell difference is 31mV - actual is 15mV
cell #2 is the highest (was the lowest during my 1st couple of tests)
i'm trying to watch to see what happens when i approach 14.2V

yes, i did top balance

i did notice that i had 60-100mV drop across my busbars when discharging 100A+ - need to clean & tighten or squeeze some copper pipe

If you plan on pulling 100+ amps. I would suggest copper to reduce cell heating.

 

[mkaye]

i am using the Xuba busbars - copper with plating - should have ordered more to double up

all cells in parallel with P/S @3.62V - will let them sit overnight

 

[Bogart Engineering]

280AH 12V system
yesterday i got to do a full charge using my solar panels and the SC-2030
i had:
P1 "Charged" setpoint voltage @14.4V
P2 "Charged" setpoint amps multiplier @2%

P1 & P2 are used to calculate %Full based on the battery reaching P1 and current below (P2 * battery capacity)

others set to Bogart recommended for LFP

what happened?
i saw 8A charging current from my 2 rooftop panels
the voltage climbed to 14+, current stayed at 8A
finally 1 cell got to 3.56V and the relay opened - charging was still 8A!
at this point there was 150mV difference in the cells - i may need to top balance again
so, even tho i reached 14.4V, i still get full charging current until the BMS steps in
when the relay opened charging current dropped to 0 and i met the 100% FULL condition

the good thing is that when the BMS closes the relay again @3.55V the SC-2030 won't turn on charging again until <98%

i then set P1 to 14.2V - same behaviour, BMS had to step in as current was still 8A as it passed 14.2V

bottom line: you need the BMS to stop charging from the SC-2030

i really didn't want the BMS to be my high voltage cutoff, but i don't see any other way
if someone from Bogart can step in explain how i can do this better - please do


i also have a PD replacement P/S for the original WFCO
i moved the jumper to LI and it charges correctly
i.e. CC mode until close to 14.4V and then CV until 14.4V with current dropping appropriately

mark

Please contact us by email - bogart at bogartengineering dot com

 

[Bogart Engineering]

Do you have the monitor because I believe that is required for custom profiles or lifepo4?
Can remember exactly but I was annoyed that I would have to buy another part to make things work.

There's an advantage to our approach of using the monitor to measure battery voltage, instead of having the charger measuring it. The monitor measures the voltage directly at the battery terminals. A charger sits upstream of the battery on a high current path and measures the voltage at a different point. At peak charging current, the voltage measured by the charger can be 0.3 to 0.4 higher than what's measured at the battery due to factors like wire gauge, length.

 

[grizzzman]

Hands down the Bogart system is much better at knowing at "system" voltage/Amps/Amp/hours. Then the Chargery's attempts at watt hours and it's percent of pac SOC. Of course the Chargery with out question has it's place.( Cell level control ) Temp controls etc.