Hi,
I recently got a defective apc back ups es 550 inverter,
and try to bring it back to life.
The problem: I can start the inverter, voltages seems ok
to me. But, it completely stops when I connect a load. I
am trying with a simple 25W desktop light.
I thought the issue cam from the inverter internal battery,
an acid lead 12V 7.5AH. Thus, I tried with a 60W lab power
supply, but the problem remains.
I checked the inverter DC output without a battery, it is
13.7V.
I checked the AC output with a multimeter, it is around
165V (I live in France, 220v AC). With an oscillo, I saw
that it is a modified sine wave based inverter, so the
measured voltage seems ok.
Do you have any idea what to check? Any troubleshouting
advice is more than welcome!
Thanks for your help,
Fabien.