Inconsistent behaviour from charge controller

[Chasba]

Hi, I'm a solar power newbie and I'm trying to set up a small system to power grow lamps in my greenhouse. The system is powered by a 12V 30Ah LifePo4 battery, charged by a Renogy 100W 12V solar panel, both connected by MCB's to an Easun MPPT 6048 60 amp solar charge controller. The load is a set of 4 LED grow lamps strips consuming in total 36W at 12V, and have an in-line hand controller for on/off, timer (3,6,12Hr), dimmer and on/off for each grow lamp strip.
When the system is set to run without activating the grow lamp timer, everything works perfectly. The same is the case if I activate the 3 hour setting, after which the lamps switch off correctly after 3 hours.
The problem arises when I set the system to run for 12 hours overnight. The following morning before the 12 hours have elapsed, I wake up to find the grow lamps are no longer lit and cannot tell when they went out. When I check the grow lamp controller, it is unresponsive. If I check the voltage across the charge controller load connections, little or no voltage is registered. Also the battery state of charge is still 75%+ and the battery voltage 12.5-13.0 volts. But if I then turn off the MCB linking the solar panel to the charge controller, everything springs to life, 12.5-13 volts are available at the charge controller load terminals and all the functions on the grow lamp controller work perfectly.
I don't have enough technical knowledge to work out what's causing this problem, but i can only guess it's either some issue with the charge controller or the grow lamps controller (it isn't an expensive piece of kit and again the manufacturer's instructions are no help). I entered the charge controller settings as I understood them from the manufacturer's (rather cryptic) instructions and it's not a cheap unit.
Can anyone please give me a clue about what I might be doing wrong or what may be causing this issue? I really don't want my first DIY solar project to be a failure ;-) Many thanks.

 

[mikefitz]

still 75%+ and the battery voltage 12.5-13.0 volts

You battery is going flat overnight. Its internal management is shutting down the battery, in turn this shutdown upsets the controller.
30 Ah battery , 370 watts if fully charged, will power a 36 watt 12v load for 10 hours.
The reading of battery state given by the controller is inaccurate and misleading.
You need a larger battery and more solar.
A 100 watt panel is not going to produce much yield in at this time of the year, perhaps 300 watts per day, on a good day.

 

[Chasba]

You battery is going flat overnight. Its internal management is shutting down the battery,
30 Ah battery , 370 watts if fully charged, will power a 36 watt 12v load for 10 hours.
The reading of battery state given by the controller is inaccurate and misleading.
You need a larger battery and more solar.
A 100 watt panel is not going to produce much yield in at this time of the year, perhaps 300 watts per day, on a good day.

Many thanks for very prompt reply. I understand that the load on the battery would drain it in 10 hours but what I don't understand is why the grow lamps come on at full power as soon as I isolate the PV panel in the morning after going off during the night. This surely indicates that the battery isn't drained but rather that the charge controller stopped providing power to the lights overnight for some reason? Or?

 

[mikefitz]

Charge controller stopped providing power to the lights overnight for some reason?

If you are connecting your system to the load output of the controller then it can disable this output if the battery voltage drops below a preset voltage. This voltage is set in the perameters settings of the controller.

 

[Chasba]

Ah, OK that makes sense. Can I change a preset voltage on the charge controller to stop this happening? I attach the voltage settings I have in the charge controller now (except that SYS Volt is 12 not 24). I don't know what the different voltage settings mean but I know they can be changed. Thanks

 

[mikefitz]

know what the different voltage settings mean

Not having used this controller my guess is,
Set 8 LRV is low voltage recovery voltage for load outputs , and, set 7 LDV is low voltage disable of load outputs.
For a lithium battery I would suggest recovery at 12.8 volts and disable at 12.0 volts.

You could bypass the controller load control and connect you lighting system and timer direct to the battery.
There may still be an issue with the battery running out of power and its management shutting down the discharge path.

Voltage alone is not a practical guide to lithium state of charge, but for a rested battery, no load or charge, these charts offer some guidance .

 

[Chasba]

Thanks for this info. It’s beginning to make sense to me now. My battery measured 13.3V when I got it but it may not have been fully charged. This morning after not charging or applying a load at all yesterday it measured 12.68V which would equate to an SoC of only about 15% based on your table. The charge controller showed 68% SoC so there is clearly a discrepancy. The only thing I now don’t understand is, as I explained in my original post, why the Charge controller suddenly measured enough voltage to light the grow lamps when I isolated the PV panel. Don’t know if you have any thoughts about this? Thanks again for your help.