Issues with Makeskyblue charge controller

[StartledP]

Hi All,

Im having an issue with my makeskyblue v118 40 amp charge controller connected to a 24v lifepo4 battery. I have 3x310w longi panels in parallel, voc 40.5v. Whenever I start the charge controller I get something like the expected production, around 700 watts in full sun. However, over a period of about a minute, that production drops slowly down to around 380 watts and stays there.

I'm within the correct voc range for the device (37-105), so Im wondering whats going on here.

 

[HighTechLab]

Is your battery full? What AWG wire are you using to connect the battery to the charger? What is the voltage at the terminals of the battery when the controller is at the lower-power state, and voltage at the terminals of the controller as well?

 

[StartledP]

Battery is around 40 % soc, voltage of the battery is at 26.9 at the terminals, voltage is 26.79 at the controller battery outputs.

Wire is 12AWG, length of wire is about 15 cm. Its cold to the touch.

Power output continues to drop, its now at 250w in full sun after an hour. A reset brought it right back up to 700 ish.

PV voltage is 34 by multimeter, 33.4 on the SCC.

Additionally at peak production the voltage drops to 28v, then rises to 33 as the production drops. Wonder if this an mppt error.

 

[StartledP]

If I add load (ie switching on the inverter and powering the hot water tank), the production goes right back up to the expected value

 

[efficientPV]

Charge controller is doing just what it is supposed to do. This is the reason I divert power right from the panels to heat water instead of going thru a charge controller. Most of the time a charge controller is twiddling its thumbs and wasting energy which could be used to heat water.

 

[StartledP]

Charge controller is doing just what it is supposed to do. This is the reason I divert power right from the panels to heat water instead of going thru a charge controller. Most of the time a charge controller is twiddling its thumbs and wasting energy which could be used to heat water.

Id hope the SCC would charge the mostly empty battery, I suspect its faulty though. Will swap it out tomorrow.

 

[efficientPV]

Is that right, you are using a voc 40.5v array to charge a 24V battery? I have a MSB controller and it gets lost all the time. But, your array has no place to go.

 

[StartledP]

Faulty SCC. Swapped out with the same model and the new unit is working perfectly. Very annoying, this makesyblue unit was hardly used before failing. Will replace with a renogy/epever.