Hi all, 

I bought a Mecer 3kVA (24V - 1500W PV) off grid inverter last year and have noticed some odd behaviours.

I've currently got the inverter set to SENS(?) where it pulses every second or two and then seems to only switch on if a load of at least 100W is detected. However, I notice it turning itself on for a couple of minutes several times an hour, even with no load and then switching off again.

I've also noticed that during the day I'll sometimes hear the relays inside clicking and the battery voltage will start falling, even though the panels are still in full sun. Then after about a minute it clicks again and then starts charging the battery again. I'm not sure if it is just switching from absorb/bulk to float, but I don't think I have any major load kicking in at the time.

If I have switched the inverter on (so not in SENS) and I have a variable load on the inverter (like an appliance that switches on and off with temperature, for example an induction cooker) then the voltage jumps around and can briefly go over 30V sometimes before correcting itself back to 28.8 or 27.4V. It worries me that I have some 24V fridges and other 24V devices (DC-DC buck converters etc) that connect direct to the battery and now have to deal with the voltage spiking over 30V.

Are the behaviours above normal and has anyone else noticed these?
Also, are there firmware updates for these inverters and if so how do you update them?

Thanks all!

8 hours ago, Lindsay said:

I've also noticed that during the day I'll sometimes hear the relays inside clicking and the battery voltage will start falling, even though the panels are still in full sun. Then after about a minute it clicks again and then starts charging the battery again. I'm not sure if it is just switching from absorb/bulk to float, but I don't think I have any major load kicking in at the time.

Despite not noticing major load changes, that sounds like the "dips" others have been describing with various recently manufactured models. Was yours manufactured towards the end of last year? A small sticker on the side should indicate the manufacturing month and year.

8 hours ago, Lindsay said:

If I have switched the inverter on (so not in SENS) and I have a variable load on the inverter (like an appliance that switches on and off with temperature, for example an induction cooker) then the voltage jumps around and can briefly go over 30V sometimes before correcting itself back to 28.8 or 27.4V.

3 kW from a 24 V battery is a significant load. Is your battery perhaps old and/or tired? If it has significant internal resistance, that will exacerbate this problem.

However, Axperts are renowned for their poor overshoot / undershoot performance.

8 hours ago, Lindsay said:

Also, are there firmware updates for these inverters and if so how do you update them?

Firmware updates have been hard to come by for many years now. There are no recent ones available for 24 V models that I'm aware of. You have to obtain a firmware update file from your supplier, then run the Windows program contained therein to update the firmware. Depending on the model, you may or may not need a USB to serial adapter. Does your model have an RJ-45 connector marked COMMS or similar near your USB connector?

Thanks for the responses.

 

I've seen that sticker, but will have to look for it again. I know I bought mine in July or August last year, so I think it would have been manufactured closer to the beginning of last year. As I said, it does click back on and start charging again after about a minute, maybe a bit longer than that.

 

My induction cooker is only 600-800W in the low power mode that I use it in. But I've even noticed this issue with smaller 300W loads that click on and off (like a 3d printers heating element) that the voltage goes all over the place. My batteries are only between 2-3 years old.

 

My model is the one with only has the USB port, no RJ-45 or COMMS board.