Hi all,

I have a Mecer 3KVA 24V Plus (Axpert clone) and noticed that even though we've had some very sunny weather in the last couple of months it seldom has been charging the batteries fully - which it used to almost always do this time of the year. From what I can tell it starts charging in the morning, but seems to slow down to a few amps just after midday even when in full sun and the battery is only at a 60-70% SOC. Only very occasionally does it get to 100% SOC. It feels like this behavior actually started in summer last year but wasn't nearly as bad as it has been in the last couple of months.

I started by checking the panels, but they are all still connected and the inverter does report around the maximum of 1600W coming in occasionally.

On the weekend it had gradually been getting lower over a few days and at 2pm it had only charged back up to about 50%. While I was trying to diagnose the issue, the fridge kicked in with 166W load and suddenly the inverter went from reporting the solar coming in as 250W to 1000W and the fans on the inverter kicked in and suddenly the batteries started charging, going from a few amps into the batteries to around 30 amps.

There are no errors showing on the inverter and bulk and floating voltages are set to 28.1V with no settings having changed recently.

Just wondering if anyone has seen this behavior before or if there is something wrong with my inverter or other settings I could try change? I have considered buying a new inverter, but was hoping to hold off and keep using this one longer.

Thanks in advance.

For anyone interested, I ended up changing the source priority from SOL to SbU after seeing a post somewhere on the forum here regarding this. Not sure why it would make a difference since this only changes when it uses utility/mains power due to no solar or low battery (and my inverter is not plugged into mains) but it seemed to help for the one day of sun we had after this. Unfortunately since then we've had cloud and now rain today, so I will have to see how it goes when there is more sun!

Does the displayed battery voltage, when the inverter is not charging and has light loads, agree withing 0.1 or perhaps 0.2 V of a trusted multimeter's reading at the battery terminals?

It may be that the inverter firmware is reading the battery voltage as higher than it actually is, and so thinks that the battery is already full when it isn't.

Calibrating the battery voltage readings may help if that is the case.