Step Down (Buck) charge v3 o.i. does not work

[Romale]

I have always used boost mode to charge the battery from the mains via a diode bridge. this is a great thing!
but now I have a low-voltage battery and I wanted to use the down mode. however, after I supply +12 to the power supply of the inverter and turn it on both forward and backward at the same time, the charging mode does NOT start, and the controller considers the value of the direction of movement as neutral. if you return the boost mode programmatically, then the charging mode works freely.
What am I doing wrong?
I checked 5.27 and 5.25 both foc.

[Romale]

am I really the only one using the ability of the OI board v3 to charge batteries through an inverter-motor?

[johu]

Indeed I haven't used buck mode in a long time. What inverter are you running it on and have you wired it correctly? https://openinverter.org/wiki/Battery_Charging

[Romale]

Indeed I haven't used buck mode in a long time. What inverter are you running it on and have you wired it correctly? https://openinverter.org/wiki/Battery_Charging

I used boost mode on all my inverters (Honda IMA, Nissan leaf 2) and it works fine even at 75 amps input current!!! This time I have an inverter with a 600 volt power part and it seemed to me that it would be more universal to use the lowering mode (for example, a three-phase diode bridge from a type-2 charging station) to charge the battery at least 120 volts at least 360 without changing the settings. However, when the "downgrade" charging mode is turned on programmatically, it does NOT start when +12 is applied to forward and reverse. the "boost" mode works fine at the same time. Yes. I connected everything correctly

[Romale]

you can test it just on the table without connecting a real battery, motor and input high voltage. it is enough to take the v3 board, apply +12 to the main power supply, turn on the "downgrade" charging setting and simultaneously apply +12 to "forward" and "backward", instead of the "downgrade" status of the inverter, you will get "waiting for start" + "neutral" mode, although you have applied a high input for forward and backward.

[johu]

ah, there is a different precharge setting because the DC bus is run at a higher voltage than your low voltage battery. The parameter is called "udcswbuck"

[Romale]

ah, there is a different precharge setting because the DC bus is run at a higher voltage than your low voltage battery. The parameter is called "udcswbuck"

does this mean that an inverter that does not know how to measure the battery voltage will not be able to use the step-down mode? I use the Honda ima inverter without information about the battery voltage, this does not prevent me from riding it perfectly or using boost mode.
I will try to lower the parameter you specified to a value lower than the controller considers the battery voltage (about 120 volts).

thanks for the hint!

[johu]

In step down mode the inverter simply doesn't know the battery voltage because it can only measure rectified mains voltage on the DC bus. It means you need some external mechanism to stop charging when the battery is full.

[Romale]

In step down mode the inverter simply doesn't know the battery voltage because it can only measure rectified mains voltage on the DC bus. It means you need some external mechanism to stop charging when the battery is full.

this hint had its positive effect, thank you so much for your help!

now, if you implement a lowering charging system, then you can put the j1772 + type-2 port in the car and for each its own diode bridge will be given 310 or 520 volts of constant voltage.
universal for charging any batteries up to 300 volts!


as a protection system, I use bms, which controls the high voltage output for one small dc/dc, which in turn powers the automotive relay that controls the inverter power supply circuit. as soon as overcharging or discharge of any of the cells occurs, the entire chain of actions will remove the +12 bus power from the inverter and charging/discharging will stop.

[johu]

Sounds like a plan Is it working now? What charge current did you reach and what are the noise levels?

[Romale]

Sounds like a plan Is it working now? What charge current did you reach and what are the noise levels?

the efficiency of the system is 85% (2 kW from the mains = 1.7 kW to the battery) . 36c battery (151 volts fully charged) . the current sensors are calibrated at 90 amps and their gain is 4.31 (Honda ima inverter) probably there is a very large error at a small current, if I set the charging current to 2 amps in the settings, I get "overcurrent" after a minute of the system working with a real current from the 14 amp network. when the 1.5 amp charging current is set, then the real consumption over the AC network is 12 amperes and 10 amperes current into the battery. at the same time, the inverter itself believes that the DC current of the line is only 0.5 amperes. When I get an overcurrent, in fact, the current on the current sensors of the inverter will not exceed 25 amps. Maybe there is some parameter that can make the system more stable? (in boost charging mode, I could stably have 75 amps at the input to the inverter and nothing turned off)

DC side

AC side

[Romale]

at the expense of noise, a very quiet squeak. it is the same for any mode of charging with any inverter and motor. now I have a honda ima inverter + a nissan serena motor (small starter generator)

as a connection between the motor and the gearbox, I used gear parts and a rubber coupling from a gimbal from some kind of car.

[Romale]

[Renegate2020]

And if I change the single-phase diode bridge to a three-phase diode bridge (type MDS100A), will the circuit work? What mode should be used in this case with the 96S battery?

[Romale]

if 380 is connected to the three-phase diode bridge, then the rectified voltage will be about 530 volts. A downgrade scheme is needed. but it is very unstable and does not allow you to work with a large charge capacity. in addition, it does not respond to settings and charges with whatever current it pleases.