Hi,

I have two identical MPPSolar U5648MS inverters, but one of them failed this March.

Link: www.mppsolar.com/v3/u-gk_ms/

I disassembled the failed inverter and replaced both the low-side MOSFETs and the high-side IGBTs.

Right now, the inverter is only partially working. :(

• Without a battery, it does not switch on; instead, it makes a high-pitched noise. (The other working inverter does switch on with solar-only, and it also switches on with utility-only.)

• When I switch it on using the battery, I can then connect the solar panels — it detects them and uses them (charging the battery, and the output also works).

• If I connect utility power as well, it shows the utility voltage on the screen and uses it. So, with a battery, everything seems to work.

• If I disconnect the battery in that state, the inverter continues to operate (output still works) and shows “battery disconnected.” Everything looks normal as long as the load does not exceed the available solar energy. If the load is higher, it instantly switches off.

• Also, if I switch off the output-enable toggle, the inverter shuts down and cannot be switched back on.

So, without a battery, it cannot use utility power to supplement the solar energy.

I would like to obtain a schematic to check what else may have failed.

I also have many internal photos from the disassembly, which I can share if anyone is interested.

The lowside mosfets:

High side igbts:

it have a fault in mppt board

16 hours ago, shakeel ahmad said:

it have a fault in mppt board

Well you need to provide a little bit more info than that:)

For start:

Does it switches on, does it have screen lighting up, do you see any warning or error code?

If it switches on, does it do with utility-only, solar-only, battery-only and any of these combinations?

IS there any recent events you can recall that may be responsible for the nonworking state?

If you have knowledge of working in electronics, I can help you.

On 2025/09/17 at 2:02 AM, Boognevatz said:

Everything looks normal as long as the load does not exceed the available solar energy. If the load is higher, it instantly switches off.

The instantly switching off suggests to me a power supply collapsing. Check or replace all the usual suspects in the power supplies. Most of the power supplies seem similar, so this post probably applies:

https://powerforum.co.za/topic/14666-repair-of-axpert-inverters-a-journey-started/page/4/#comment-150549

As for schematics, I'm not aware of one for your specific model. But others may be close enough, e.g.

https://forums.aeva.asn.au/viewtopic.php?p=88434#p88434