Cell Full JBD/Overkill

[Levo]

Something I am failing to understand? Tried over and over to limit voltage to 13.6 (3400mv) per cell. Even when I set "cell full" to 3400 the charging seems to continue until over 14v total is reached. What am I missing with the settings? (tried overkill and Xiaoxiang apps). This seems to happen whether charging with MPPT or DC-DC charger. Any help would be very welcome.

 

[Brett V]

The BMS doesn't limit charging, it only reports the voltages and provides protection. Your MPPT settings determine when charging stops.

 

[Levo]

Okay, but if not, what are the settable values for? I understand protection is the main purpose of the BMS. However, I doubt I can configure specific values in the SCC or DC-DC charger, just select LIFePO4 from the charging profiles offered. Still don't know haw to avoid taking cell to a higher voltage point.

 

[Brett V]

Those values give the state of charge reading a point of reference but only if the built in coulomb counter loses track. What sort of DC charger and SCC are you using?

 

[Levo]

Well, just El Cheapo Renogy (MPPT Li 60 amp) and dc-dc 40 amp, so no settings beyond choosing basic Li profiles. I have read many times about the benefits of keeping the voltage out of top and bottom ends.
I am sure all the tier 1 gear has ways to fine-tune all the limits, but many units out there only offer basic settings. What would most people do to limit voltage? Surely I don't have to watch like a hawk and switch on and off manually?

 

[Brett V]

Renogy Rover?

 

[Levo]

yes

 

[Brett V]

Looking at the manual for the charge controller, it will stop charging at 14.4 volts or 3.6 volts per cell. Ideally, you should switch to user mode and input the voltages you want. For an easy solution, you could try the GEL setting since that will lower the charge limit to 3.55 volts per cell.

 

[Levo]

Okay, I'll try user mode and see if I can set limit to 13.6v while still set for Lithium. I somehow thought setting the BMS would do what I needed more easily. Thanks for the suggestion - I'll go see what works best.

 

[Brett V]

I marked it up quickly...try these settings.

 

[Bob B]

The "cell full" setting is for SOC calculations.

When a cell reaches that voltage, the BMS will set the SOC to 100% and if it's not already ..... start coulomb tracking of SOC.

The protection voltages are the ones that will cause the BMS to stop charging.

 

[Levo]

The "cell full" setting is for SOC calculations.

When a cell reaches that voltage, the BMS will set the SOC to 100% and if it's not already ..... start coulomb tracking of SOC.

The protection voltages are the ones that will cause the BMS to stop charging.

Okay, did not realise cell full was about culomb counting or SoC gauging, not limiting charge. Shall go enter those values now and see what difference it makes. Many thanks

 

[Lt.Dan]

The "cell full" setting is for SOC calculations.

When a cell reaches that voltage, the BMS will set the SOC to 100% and if it's not already ..... start coulomb tracking of SOC.

The protection voltages are the ones that will cause the BMS to stop charging.

This ^

 

[Bob B]

Okay, did not realise cell full was about culomb counting or SoC gauging, not limiting charge. Shall go enter those values now and see what difference it makes. Many thanks

Once you write a setting change, the SOC will default back to a guestimated SOC based on voltage until it cycles and reaches the cell full voltage again.

 

[Levo]

Okay, after adjusting the settings in "user" rather than default Li mode, The voltage is staying around a steady 13.5v (on xiaoxiang app) with solar panels on. Seems to be accepting no more charge. Your suggested parameters seem to have really helped Brett. Thanks for the info gents.

Regarding the DC-DC charger, I see nothing settable other than dipswitches for choosing battery type. I expect I'll just have to monitor when charging then disconnect. I should probably not set the protections too low.

 

[Brett V]

Regarding the DC-DC charger, I see nothing settable other than dipswitches for choosing battery type. I expect I'll just have to monitor when charging then disconnect. I should probably not set the protections too low.

I was unable to find any documentation on line for the charger but there is probably a voltage adjustment pot inside the thing. Assuming Renogy is consistent with their equipment, a GEL battery setting if it has one will likely be more gentle with your battery. Taking the cells over 3.5 volts occasionally for a few hours is a good thing and helps the passive balancing do its thing.

 

[offgridliving456]

Okay, after adjusting the settings in "user" rather than default Li mode, The voltage is staying around a steady 13.5v (on xiaoxiang app) with solar panels on. Seems to be accepting no more charge. Your suggested parameters seem to have really helped Brett. Thanks for the info gents.

Regarding the DC-DC charger, I see nothing settable other than dipswitches for choosing battery type. I expect I'll just have to monitor when charging then disconnect. I should probably not set the protections too low.

Is this the Renogy DC-DC you have? If so, yep, only DIP switches to set for battery type and charge voltage. It will absorb for 'not more than 3 hours'.

https://www.renogy.com/content/RNG-DCC1212-20-BC/DCC1212-204060-Manual.pdf

See page 17:

To get started, make sure SW5 = OFF to gear the charger for lithium batteries. There will not
be a float voltage and instead users will select between Type 1 lithium voltages or switch into
Type 2 lithium voltages depending on your lithium battery specifications. You must select
lithium Type to when selecting your charge voltage. Type 1 voltages range from 12.6V ~ 13.0V
and Type 2 voltages range from 14.0V~14.6V.

 

[Dynoman]

Renogy (MPPT Li 60 amp)

For more information on how to setup the Renogy Rover and program the settings read this post on this forum.

Renogy 40a mppt Li settings

Thanks for the info, I get no heat from the 2 awg wire so that's good for me. Just ordered a 40a circuit breaker to go between the charge controller and batteries plus the Blue Sea 5191 terminal block and 200a fuse today. The 8 guage is less than 2 feet and I did find a little heat when the...

diysolarforum.com

Also the thread contains a number of posts with info for the Renogy Rover.

 

[Levo]

Is this the Renogy DC-DC you have? If so, yep, only DIP switches to set for battery type and charge voltage. It will absorb for 'not more than 3 hours'.

https://www.renogy.com/content/RNG-DCC1212-20-BC/DCC1212-204060-Manual.pdf

See page 17:

To get started, make sure SW5 = OFF to gear the charger for lithium batteries. There will not
be a float voltage and instead users will select between Type 1 lithium voltages or switch into
Type 2 lithium voltages depending on your lithium battery specifications. You must select
lithium Type to when selecting your charge voltage. Type 1 voltages range from 12.6V ~ 13.0V
and Type 2 voltages range from 14.0V~14.6V.

Yes, that is the unit. It is currently set for Lithium type 2. Did not catch that detail regarding 3 hour absorption. Thanks for that.

 

[Levo]

For more information on how to setup the Renogy Rover and program the settings read this post on this forum.

Renogy 40a mppt Li settings

Thanks for the info, I get no heat from the 2 awg wire so that's good for me. Just ordered a 40a circuit breaker to go between the charge controller and batteries plus the Blue Sea 5191 terminal block and 200a fuse today. The 8 guage is less than 2 feet and I did find a little heat when the...

diysolarforum.com

Also the thread contains a number of posts with info for the Renogy Rover.

Thanks for that. I was searching for relevant threads. I'll learn what I can from it.