Renogy Rover 40A not disconnecting at high voltage.

[Johannlog]

Hi, I am using Renogy Rover 40A MPPT.
However this SCC is not disconnecting when the LFP batteries reach high voltage.The BMS keeps shutting down due to high voltage however I would like the SCC to shut off before the voltage reaches BMS HVD.

(Using 2p8s 24v Chargery BMS8T-300 BMS,)

I set the Renogy settings as directed in the manual for a 24v lithium system.

 

[Whinny]

What battery type is set in the controller, you may need to set a custom profile....look at page 28....

https://www.renogy.com/content/RNG-CTRL-RVR40/RVR203040-Manual.pdf

 

[Johannlog]

What battery type is set in the controller, you may need to set a custom profile....look at page 28....

https://www.renogy.com/content/RNG-CTRL-RVR40/RVR203040-Manual.pdf

I set it to "Li" since I'm using LFP batteries.

 

[Whinny]

Rover will boost at 14.4 when set to Li-is that too high for you?

 

[shadowsteve]

If you cells get out of balance a bit as they charge you could get an overvoltage trip on a single cell.

I run a 40A on a 12v system and I adjusted the boost voltage downwards as the BMS (JBD) was hitting cell overvoltage. I charge to 13.8v now. I assume for your 24v you just double all the numbers

 

[Johannlog]

If you cells get out of balance a bit as they charge you could get an overvoltage trip on a single cell.

I run a 40A on a 12v system and I adjusted the boost voltage downwards as the BMS (JBD) was hitting cell overvoltage. I charge to 13.8v now. I assume for your 24v you just double all the numbers

Okay, I will try lowering the boost...
Yes, double the numbers for 24v systems.
14.4v x 2 comes out to 28.8 which I think is too high or really close to too high. The max the battery could reach I believe would be 29.2v (3.65vx8) for LFP batteries.

 

[time2roll]

Li goes to 28.8 and might be a bit much. Try GEL at 28.4

 

[Johannlog]

Li goes to 28.8 and might be a bit much. Try GEL at 28.4

I've got boost set to 13.8 (×2=27.6v) and it's still not disconnecting before the BMS... maybe I should lower the boost some more?

 

[Johannlog]

I've got boost set to 13.8 (×2=27.6v) and it's still not disconnecting before the BMS... maybe I should lower the boost some more?

I noticed that the Renogy SCC is reading the battery at about 0.5 volts lower than the SCC so I am adjusting the boost (calibrating the SCC an additional bit lower from 13.8 to 13.2).
I'll see how it goes when the sun comes out again.

 

[time2roll]

Yes. If you know the cut off go one-tenth lower.
I assume you have a high cell causing the BMS cut off.

May want to bleed off some voltage from the high cell as you watch it rise tomorrow.

 

[Johannlog]

Okay, here's what the cells read

 

[Johannlog]

I'm thinking your right! Noticed the image attached above of the chargery BMS was just after the alarm and shut down, the cell difference was 37mv and the diff of cell voltage was set to 30 in the BMS so it maybe shut down because of the cell diff?
I have adjusted the cell diff to 55mv now

Yes. If you know the cut off go one-tenth lower.
I assume you have a high cell causing the BMS cut off.

May want to bleed off some voltage from the high cell as you watch it rise tomorrow.

 

[time2roll]

Actually the cells look close now but watch them as they go above 3.450
What is the cell max and the battery max setting in the BMS?

 

[Johannlog]

Actually the cells look close now but watch them as they go above 3.450
What is the cell max and the battery max setting in the BMS?

 

[shadowsteve]

I noticed that the Renogy SCC is reading the battery at about 0.5 volts lower than the SCC so I am adjusting the boost (calibrating the SCC an additional bit lower from 13.8 to 13.2).
I'll see how it goes when the sun comes out again.

My Renogy is off on it's voltage readings as well

 

[Johannlog]

Same problem again today.
Here's what I have set the SCC Renogy at today.
Boost 13.4v (26.8)
Float 13.2v (26.4)
But when the sun had been out for serveral hours the SCC finally reached about 29v on its battery reading. (Due to an error in the SCCs battery v reading actually battery voltage would be around 29.5v)

Again the BMS shut down the system at 29.02v on its reading.

What should I try next?

 

[time2roll]

What did the cell voltages look like from the BMS at the time of shut down?

 

[Johannlog]

What did the cell voltages look like from the BMS at the time of shut down?

3.651 for the high and
3.581 for the low cell

 

[time2roll]

That seems adequately balanced to me. The charging voltage at 29.02 is just too high.
If the renogy is set to 26.8 there is no reason you should see 29.02 except the renogy is off calibration or defective.

If you think it is calibration issue I would go down a full volt to 12.5 (25v) and see what it runs to. Need to double check renogy is not reverting to a preset voltage profile.

 

[MisterSandals]

I set it to "Li" since I'm using LFP batteries.

I have not seen a mention of changing battery type to “USER” which is required to change the charge profile.

<<<<<
To enter the programming interface simply press and hold the right arrow button. After entering this feature press the Enter/Right button to switch between parameters. To change the parameters, press the Up or Down button. To save the parameter press and hold the Enter/Right button.
The charging parameter setting (Equalizing voltage, Boost voltage, Floating charging voltage, over-discharge return voltage, Over-discharge voltage) are only available under the battery “USER” mode. Press and hold the right arrow to enter the programming settings and continue pressing the right arrow button until you see the desired voltage screen.