Can BMS damage MPPT Charger?

[Hedges]

PV --> capacitor --> transistor --> inductor --> battery(+).
Also diode from transistor side of inductor to battery(-).

Transistor switches PWM. When on, PV - Vbat is across inductor, and current ramps up (as it charges battery).
When off, inductor flies negative, is clipped to battery(-) by diode, and current ramps down (as it charges battery)
Sawtooth current.

If you disconnect battery from inductor with current flowing, that end of inductor flies positive, towards infinity.
Something connected may get blown.
A large enough capacitor, or zener/transistor/resistor snubber might protect it.

SCC could be designed to survive this, or not.

 

[time2roll]

Wow this is an old thread.

I just want to add this is good reason to keep the charging voltage on the lower side and to have at least two batteries in parallel.

 

[bigshotdadz]

TS-MPPT-60 should be able to handle 150VDC on the input though. Any controller has to be able to handle the full Voc of the array, since that's what it sees when charging stops and there are no loads on the charge controller.

The operative word being "should".

 

[SpongeboB Sinewave]

The problem happens when the PV input to the MPPT controller is higher than the battery voltage by quite a bit and lots of current is going out of the controller and all of a sudden the battery load goes away. The input side of the MPPT controller can go WAY up in voltage before it has time to turn the switching circuit off. The MPPT controller should be able to handle this situation without hurting anything. i.e. It should turn OFF as soon as its battery voltage terminals goes a few volts above the regulation set point voltage.

You can think of this kind of like a tug of war with two ends of a rope. While pulling hard, one group of people just let go of the rope and the people on the other end of the rope fall back and fall down.

boB

 

[DIYrich]

The plan was to power down all but one SCC and change the CELL OVP value in the BMS to 3.455V to prevent it from deactivating the CHARGE function given the 55.2V ABSORB voltage

BMS is the last line of defense. Set the ovp at 3.60v. Keep the cells balanced, and the inverter should stop at 55.2v well before a cell gets close to 3.60v. The inverter should be able to gently control the mppts.