December 5, 20232 yr Hi everyone Does anyone know what part of an axpert board controls the charging voltage? I have one with an integrated MPPT, and what happens is that the charging voltage is going up to 62V even though it's set to 57V or thereabouts. That'll cook the batteries. 🤔 This happens with both the grid charger & the MPPT. It's NOT the control card as I tried another one, nor the voltage divider resistors as it picks up the correct voltage on the screen, or should I say that the voltage on the LCD equals the voltage on my tester - 62V. I'm not sure where to look on the board. It's a Mark IV 5.6KW board, but it should be the same for any of the 5KW boards. Any help would be appreciated.
December 6, 20232 yr 19 hours ago, NathanL said: Does anyone know what part of an axpert board controls the charging voltage? For your model, it's all controlled by the main DSP chip's firmware. It varies the PWM of the solar boost converter or arranges the phase of the main DC to AC converter to push power backwards into the battery. The parts that are common to solar and utility charging are the buck converter (fifth IGBT) and some current measurements that are used to guesstimate the battery current. Do the utility current and load current measurements appear to be correct? If so, the problem is likely with the buck converter. There is a difference between the DC bus voltage and the transformed battery voltage, so adjusting the PWM of the buck transistor regulates the battery charging current. My guess would be a shorted buck transistor, or faulty associated gate drive components.
December 6, 20232 yr Author As usual Coulomb, you rock. Thank you. I just understood the charging curcuit a bit better. I did replaced the output IGBT's & buck, so it might be the optocoupler connected, or components in between the IGBT & optocoupler. Will strip the unit again and check later. Thank you once again. If I manage to fix it I will definitely buy you some coffee. 😉
December 11, 20232 yr On 2023/12/06 at 4:29 PM, NathanL said: If I manage to fix it I will definitely buy you some coffee. I see you bought me 8 coffees; thanks! 👍🙏 Can we presume success, or are you just grateful for the clues so far? Edited December 11, 20232 yr by Coulomb
December 11, 20232 yr Author It's a pleasure. I made money out of it & you helped, so I don't see why you shouldn't share in the spoils 😀. Yes success. The buck was damaged. Replaced. Sorted. Thank you. 😉
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