MT50 LiFePO4 User temp cuttoff

[chadat23]

When using an MT50 to set up an Epever charge controller, when you set it to use a Li profile it defaults to using a low temp cuttoff, but seemingly when you use the User profile it doesn't and will charge at too low of a temp. That said, my BMS has low temp stuff so the cells should be safe, but when the bms turns off charging, that seems like it'd be the functional equivalent of disconnecting the charge controller which seems to be bad for the charge controller (and could maybe create voltage spikes that could be bad for other things on the system?). Is this something I need to be worried about?

 

[sunshine_eggo]

Yes and no.

It is my understanding, the low temp charge protection is tied to the LFP setting. All the others expect/enable the use of temperature compensation for lead acid.

The likelihood of cut-off is going to be first thing in the morning right before sunrise, so the BMS is already saying "NO!" when the charge controller starts up. It will likely send a very small amount of current and observe the voltage spike to boost, where it will taper current to 0A, hold for the boost period and then fall to float.

BMS over-voltage protection is far more common on imbalanced batteries, and it's very common to see MPPT voltage spikes when this happens.

So the bigger concern is actually BMS over-voltage protection during normal operation.