As the title says I have a Mecer 3KVA 24V Plus which I believe is an Axpert clone.

I was looking through the manual and don't see it specifying anywhere the maximum panel current, only the maximum open circuit voltage of 145V and rated solar panel power of 1500W as well as the maximum charging current from the MPPT of 90amps (although I think I currently have this set to a maximum of 60amps).

Based on my panels and the maximum watts I get, which is sometimes a bit over 1500W, it looks like over 20amps is coming in from the panels at times.

My question is can I connect around 1800W of panels if the open circuit voltage is well under the 145V limit (I would have an open circuit of only 84V and the manual says the PV array MPPT voltage range is 30-115V). What if I extended it as far as 2400W?

I've heard the MPPT just won't make use the extra current above its limit. The open circuit of 84V is a bit higher than I have now and I'm hoping it will start charging a bit earlier in the day and stop charging a bit later, especially in winter where currently I have to disconnect some of my loads.

I know the open circuit voltage you should definitely not exceed, so I'm really just asking if there is a maximum for the current and the panel watts?

Thanks in advance!

4 hours ago, Lindsay said:

As the title says I have a Mecer 3KVA 24V Plus which I believe is an Axpert clone.

I was looking through the manual and don't see it specifying anywhere the maximum panel current, only the maximum open circuit voltage of 145V and rated solar panel power of 1500W as well as the maximum charging current from the MPPT of 90amps (although I think I currently have this set to a maximum of 60amps).

Based on my panels and the maximum watts I get, which is sometimes a bit over 1500W, it looks like over 20amps is coming in from the panels at times.

My question is can I connect around 1800W of panels if the open circuit voltage is well under the 145V limit (I would have an open circuit of only 84V and the manual says the PV array MPPT voltage range is 30-115V). What if I extended it as far as 2400W?

I've heard the MPPT just won't make use the extra current above its limit. The open circuit of 84V is a bit higher than I have now and I'm hoping it will start charging a bit earlier in the day and stop charging a bit later, especially in winter where currently I have to disconnect some of my loads.

I know the open circuit voltage you should definitely not exceed, so I'm really just asking if there is a maximum for the current and the panel watts?

Thanks in advance!

Are you 100% sure it is MPPT and not PWM? I ask only because I had a Fivestar inverter 2kW at one stage and it had the exact same specs as your PV state. It was also 1500W, 30 to 115V and 60A PV charger.

How are your panels connected at the moment? For you to see 20A to me implies it is a PWM solar charger, not MPPT. I am not aware of any MPPT charge controllers for 3kVA inverters with MPPT current higher than 18A.

Edited November 11, 2025Nov 11 by Denns

5 hours ago, Lindsay said:

I was looking through the manual and don't see it specifying anywhere the maximum panel current, only the maximum open circuit voltage of 145V and rated solar panel power of 1500W as well as the maximum charging current from the MPPT of 90amps (although I think I currently have this set to a maximum of 60amps).

My question is can I connect around 1800W of panels if the open circuit voltage is well under the 145V limit (I would have an open circuit of only 84V and the manual says the PV array MPPT voltage range is 30-115V). What if I extended it as far as 2400W?

I've heard the MPPT just won't make use the extra current above its limit. The open circuit of 84V is a bit higher than I have now and I'm hoping it will start charging a bit earlier in the day and stop charging a bit later, especially in winter where currently I have to disconnect some of my loads.

I know the open circuit voltage you should definitely not exceed, so I'm really just asking if there is a maximum for the current and the panel watts?

Thanks in advance!

I have an identical clone with MPPT and it is also rated at 20A on the sticker on the inverter. I would say up to 1800W seems OK for the reason you mentioned. I would however not try and break it by going as high as 2400W. I may be conservative but would not rely on the inverter clamping the current over the maximum rating. Doing it you take the risk of knowing you are exceeding the maximum values.

I am not aware of the Plus specification using PWM solar controllers.

@Denns , definitely MPPT, as it says in the spec of the manual and I specifically chose for this reason. I bought it over 5 years ago now, it's a 24v model which I was first using with deep cycle batteries although now LiFePO4.

It does seem that all the newer inverter/charger models, even the 24v have much higher supported PV voltages now and lower currents, usually 18amps. I've attached the sticker from the side of mine and it only says 60amp solar charging current, which I assume is on the battery side (in my original message I said 90amps which was wrong), but nothing saying 20amps or the maximum for the solar panel side on the sticker or in the manual.

But I take your point @Scorp007 , possibly going over 30amps would be bad for it.

8 hours ago, Lindsay said:

@Denns , definitely MPPT, as it says in the spec of the manual and I specifically chose for this reason. I bought it over 5 years ago now, it's a 24v model which I was first using with deep cycle batteries although now LiFePO4.

It does seem that all the newer inverter/charger models, even the 24v have much higher supported PV voltages now and lower currents, usually 18amps. I've attached the sticker from the side of mine and it only says 60amp solar charging current, which I assume is on the battery side (in my original message I said 90amps which was wrong), but nothing saying 20amps or the maximum for the solar panel side on the sticker or in the manual.

But I take your point @Scorp007 , possibly going over 30amps would be bad for it.

Up to some time ago it was common not to indicate the maximum PV current but one could work from the Watts and battery voltage and current side of the MPPT to find the maximum PV current.

I also used mine on lead acid before going the lithium route and then this year got die Deye 5kW. The Deye is just such a joy in operation.

10 hours ago, Lindsay said:

@Denns , definitely MPPT, as it says in the spec of the manual and I specifically chose for this reason. I bought it over 5 years ago now, it's a 24v model which I was first using with deep cycle batteries although now LiFePO4.

It does seem that all the newer inverter/charger models, even the 24v have much higher supported PV voltages now and lower currents, usually 18amps. I've attached the sticker from the side of mine and it only says 60amp solar charging current, which I assume is on the battery side (in my original message I said 90amps which was wrong), but nothing saying 20amps or the maximum for the solar panel side on the sticker or in the manual.

But I take your point @Scorp007 , possibly going over 30amps would be bad for it.

I would go with @Scorp007 advice then.

Mine didnt mention whether it was MPPT or PWM. The manual said (MPPT/PWM) which unfortunately didnt mean anything so I took a chance an hooked up 2 panels in parallel and saw the current going over 25A. I added another 2 panels the the current from the panels hit alost 50A. I left it at 4 because i didnt want to go over the 60A battery charging spec.

Its just odd that your PV specs match the fivestar one to the letter if I am not mistaken.

Edit: It was 1600W, 60A charger and up to 105VDC. So not the same as yours.

Edited November 12, 2025Nov 12 by Denns

@Scorp007 that's odd that they didn't note down the maximum PV current because, with the sticker saying the solar charger operating voltage range is 30-115V, couldn't you have sized the array to the lower voltage of 30V and then arranged in parallel up to 50 amps to get to 1500W? It's also odd that the sticker on the side does not note the Watts of the array and the manual only refers to the 1500W as the "rated power", not as an absolute maximum solar array.

The maximum I've logged coming in from solar in the last two weeks is 1546W when the array voltage was 70.7V:

And also based on my logging it looks like the maximum current I've seen on the solar side recently is actually 27.2 amps (calculated as 1358/49.9):

As far as I can tell the 51 amps shown above is on the battery/inverter side since there is no way my current panel configuration could get to that (and my calculated value is much lower).

At the moment going from my current ~1500W array to 1800W would actually only be an increase in the voltage (if I did go 2400W it would be current as well).

@Denns 50A on the solar side is a lot higher than I would consider, are you over your inverter specs for the current and Watts?

1 hour ago, Lindsay said:

1 hour ago, Lindsay said:

@Scorp007 that's odd that they didn't note down the maximum PV current because, with the sticker saying the solar charger operating voltage range is 30-115V, couldn't you have sized the array to the lower voltage of 30V and then arranged in parallel up to 50 amps to get to 1500W? It's also odd that the sticker on the side does not note the Watts of the array and the manual only refers to the 1500W as the "rated power", not as an absolute maximum solar array.

The maximum I've logged coming in from solar in the last two weeks is 1546W when the array voltage was 70.7V:

And also based on my logging it looks like the maximum current I've seen on the solar side recently is actually 27.2 amps (calculated as 1358/49.9):

As far as I can tell the 51 amps shown above is on the battery/inverter side since there is no way my current panel configuration could get to that (and my calculated value is much lower).

At the moment going from my current ~1500W array to 1800W would actually only be an increase in the voltage (if I did go 2400W it would be current as well).

@Denns 50A on the solar side is a lot higher than I would consider, are you over your inverter specs for the current and Watts?

I did go over my inverter specs. It was rated 1600W and I had 2600W of panels connected. My panels output 15.5A if I am not mistaken so I had 4 in parallel to give a max of 62A. Because of my panel orientation etc I never hit the 62A so the most was about 40 to 50A. 50A is a stretch but it was definitely around the high 30s and low 40s. All in parallel so the voltage was only 42V.

I was being a bit of a cowboy though but when I did my research the voltage mattered more than the current. PWM just pulls the voltage down to the battery voltage so the current on the input side of the PV is basically the same as what is on the battery side.

It ran perfectly fine for about 3 months and then I gave it to my Dad to install on a cottage he has at his house. I since moved to a MPPT inverter.

I am still suspicious of your inverter being a PWM. Mine also never stated the maximum PV current. I think they assume you infer it from the battery side amps for PWM inverters. 60A.

Edited November 12, 2025Nov 12 by Denns

2 minutes ago, Denns said:

I did go over my inverter specs. It was rated 1600W and I had 2600W of panels connected. My panels output 15.5A if I am not mistaken so I had 4 in parallel to give a max of 62A. Because of my panel orientation etc I never hit the 62A so the most was about 40 to 50A. 50A is a stretch but it was definitely around the high 30s and low 40s. All in parallel so the voltage was only 42V.

I was being a bit of a cowboy though but when I did my research the voltage mattered more than the current. PWM just pulls the voltage down to the battery voltage so the current on the input side of the PV is basically the same as what is on the battery side.

It ran perfectly fine for about 3 months and then I gave it to my Dad to install on a cottage he has at his house. I since moved to a MPPT inverter.

I am still suspicious of your inverter being a PWM. Mine also never stated the maximum PV current. I think they assume you infer it from the battery side amps for PWM inverters. 60A.

Btw if it really is PWM dont wire the panels in series. PWM just pulls the voltage down so you waste a lot of the power. For the cottage at my dads house I told him to get panels with higher current and less voltage. The best we found were 33Vmp and 13A. He has 5 of these and he is pulling more current than I did with my 4 higher wattage ones. I think his were 415W or something like that compared to my 650W panels.

@Denns it seems that when I bought this inverter, over 5 years ago, @Scorp007 says it was common to only show panel watts and the maximum voltage.

There were PWM options of this type of inverter at the time, but I specifically bought the MPPT version and the manual lists MPPT multiple times and never PWM. I have a cheap 10 amp PWM solar controller in my garage as well as one for camping so I am familiar with them and matching panel voltages to be the most efficient. So the configuration for your dads house makes sense to maximise efficiency with PWM.

The voltage from the Mecer inverter is definitely not just being pulled down, I have shunts installed and I see over 50 amps going into the battery at times even though the panels are capable of under 30 amps. If it were PWM in my current configuration I would be getting a maximum of 30 amps and wasting any array voltage above 27v, so probably not even getting in 900W (30 amps x 27v). In reality, as mentioned, I get around 1500W at times.

3 minutes ago, Lindsay said:

@Denns it seems that when I bought this inverter, over 5 years ago, @Scorp007 says it was common to only show panel watts and the maximum voltage.

There were PWM options of this type of inverter at the time, but I specifically bought the MPPT version and the manual lists MPPT multiple times and never PWM. I have a cheap 10 amp PWM solar controller in my garage as well as one for camping so I am familiar with them and matching panel voltages to be the most efficient. So the configuration for your dads house makes sense to maximise efficiency with PWM.

The voltage from the Mecer inverter is definitely not just being pulled down, I have shunts installed and I see over 50 amps going into the battery at times even though the panels are capable of under 30 amps. If it were PWM in my current configuration I would be getting a maximum of 30 amps and wasting any array voltage above 27v, so probably not even getting in 900W (30 amps x 27v). In reality, as mentioned, I get around 1500W at times.

Yeah, its just the 27A i dont get. Seems awfully high for a MPPT inverter. But its 5 years old so they did stuff differently.

51 minutes ago, Denns said:

Yeah, its just the 27A i dont get. Seems awfully high for a MPPT inverter. But its 5 years old so they did stuff differently.

Reason I started this thread is that I want to upgrade my system, so starting with adding some new panels and using as many as I can with my existing inverter. Then a bit later adding a new MPPT inverter that can handle up to 4000W solar and wiring all the panels up to this. I also noticed and was surprised, that all the newer MPPT inverters seem to only go as high as 18 amps for the solar which affects how I will configure the array, probably two strings in parallel unlike the three strings I currently have.

30 minutes ago, Lindsay said:

Reason I started this thread is that I want to upgrade my system, so starting with adding some new panels and using as many as I can with my existing inverter. Then a bit later adding a new MPPT inverter that can handle up to 4000W solar and wiring all the panels up to this. I also noticed and was surprised, that all the newer MPPT inverters seem to only go as high as 18 amps for the solar which affects how I will configure the array, probably two strings in parallel unlike the three strings I currently have.

Are you sticking to 24V? Can just replace the inverter with a MPPT one rather than constantly reconfiguring. If you want to stay on 24V for the next few years then a 24V MPPT inverter is 3.5k to 4k. Mine is a 3.6kW and I got it for 3.4k. The 4kW one is 4k at the moment. My inverter is rated for 4kW of panels but I have 4.55kW connected to it. The 4kW is also rated for 4kW of panels but you can do a bit over 5kW with it. Just stay within the voltage spec.

On days when the load is high enough I have seen 3.9kW from my panels. When my inverter packs up then its as easy as putting a 48V inverter and no changes needed on the PV side. Batteries will be reconfigured for 48V. Currently running my whole house off-grid with the 3.6kW.

Yes, my LiFePO4 batteries are configured for 24v and pulling the cells out and reconfiguring for 48v with new BMS would be too much right now, but maybe like you I will at some point do that in the future. For now 24v seems fine and in summer I can run most of the house (except the geyser and sometimes cooking appliances).

So to allow me to use the solar for cooking more often as well as improving usage in winter, I am going to eventually replace the MPPT inverter with one that can officially handle more panels and also higher loads on the AC side. I am looking at the "Must" brand 3.6KW or 4KW inverters that can take 4000W solar. Their price is around what you indicate above so seems well priced.

19 minutes ago, Lindsay said:

Yes, my LiFePO4 batteries are configured for 24v and pulling the cells out and reconfiguring for 48v with new BMS would be too much right now, but maybe like you I will at some point do that in the future. For now 24v seems fine and in summer I can run most of the house (except the geyser and sometimes cooking appliances).

So to allow me to use the solar for cooking more often as well as improving usage in winter, I am going to eventually replace the MPPT inverter with one that can officially handle more panels and also higher loads on the AC side. I am looking at the "Must" brand 3.6KW or 4KW inverters that can take 4000W solar. Their price is around what you indicate above so seems well priced.

I have the 3.6kW MUST one. If you do go that route, get the 4kW. The extra 400W and the fact that its MPPT voltage operating range rating is 360V rather than 320 on mine gives a little headroom for adding more panels.

2 hours ago, Denns said:

Yeah, its just the 27A i dont get. Seems awfully high for a MPPT inverter. But its 5 years old so they did stuff differently.

To clear up the 27A a bit on older MPPT on the 5kW Axpert inverters. Bear in mind the maximum voltage of 145V for Voc.

The example in the manual shows up to 6 strings in parallel using 8A panels of 250W. This is far over 40A on a single MPPT. See at the top and bottom of the picture. It was very common to use only 2 in series. We tend to think of the current MPPTs at high voltage and low current. Those with 5 Yr and older Axpert know very well about the high currents and low voltages.

If you are still suspicious about the PWM vs MPPT I can share my 24V 3kVA Axpert plus sticker on the side which also shows 20A for the MPPT.

Most if not all older Axpert had a MPPT. The PWM models were only introduced later and only on the smaller models. Voc of 145V is in any case far too high for PWM due to the pulling down of the voltage. This I guess was only done to lower the price.

Edited November 12, 2025Nov 12 by Scorp007

4 minutes ago, Denns said:

I have the 3.6kW MUST one. If you do go that route, get the 4kW. The extra 400W and the fact that its MPPT voltage operating range rating is 360V rather than 320 on mine gives a little headroom for adding more panels.

Thanks for the advice, yes I will probably go for the larger one as there isn't a big cost difference and the extra headroom is always good, glad to hear of someone else using this brand as I was not aware of it before!

Do you know where there is a manual online for these or a very thorough list of specs? I was hoping to find out how many watts these use with no load on the inverter (my current one is < 20W but I've seen a lot of newer ones have higher values).

@Scorp007 thanks for clearing that up, my manual doesn't show any suggested configurations for the panels other than highlighting the maximum open voltage. It's good to hear that the higher current is ok (I have been running this fine with the current panel configuration and probably close to 30 amps at times for a few years now). While I probably won't go as high as 2400W it seems safe to go to 1800W since the current will be the same and only the voltage will be more, but still well below the maximum.

7 minutes ago, Lindsay said:

Thanks for the advice, yes I will probably go for the larger one as there isn't a big cost difference and the extra headroom is always good, glad to hear of someone else using this brand as I was not aware of it before!

Do you know where there is a manual online for these or a very thorough list of specs? I was hoping to find out how many watts these use with no load on the inverter (my current one is < 20W but I've seen a lot of newer ones have higher values).

@Scorp007 thanks for clearing that up, my manual doesn't show any suggested configurations for the panels other than highlighting the maximum open voltage. It's good to hear that the higher current is ok (I have been running this fine with the current panel configuration and probably close to 30 amps at times for a few years now). While I probably won't go as high as 2400W it seems safe to go to 1800W since the current will be the same and only the voltage will be more, but still well below the maximum.

Just remember you can also add an external MPPT like the EPEVER which I like due to lower price than a Victron to add more panels and charge the batteries directly together with the MPPT of your current 24V inverter. A few of us on the forum have done so before we went to higher spec inverters.

I would rather go for a Luxpower if you want to upgrade due to the 2 x MPPTs.

8 minutes ago, Lindsay said:

Thanks for the advice, yes I will probably go for the larger one as there isn't a big cost difference and the extra headroom is always good, glad to hear of someone else using this brand as I was not aware of it before!

Do you know where there is a manual online for these or a very thorough list of specs? I was hoping to find out how many watts these use with no load on the inverter (my current one is < 20W but I've seen a lot of newer ones have higher values).

@Scorp007 thanks for clearing that up, my manual doesn't show any suggested configurations for the panels other than highlighting the maximum open voltage. It's good to hear that the higher current is ok (I have been running this fine with the current panel configuration and probably close to 30 amps at times for a few years now). While I probably won't go as high as 2400W it seems safe to go to 1800W since the current will be the same and only the voltage will be more, but still well below the maximum.

I have the manual, but unfortunately, it is over 15mb, so I can't attach here. You can also just go on the MUST site for software, manuals, etc. The standby power consumption according to the manual is 2W.

https://www.mustpower.com/product/pv1800-prem-series-1-6-5-5kw/

9 minutes ago, Scorp007 said:

Just remember you can also add an external MPPT like the EPEVER which I like due to lower price than a Victron to add more panels and charge the batteries directly together with the MPPT of your current 24V inverter. A few of us on the forum have done so before we went to higher spec inverters.

I would rather go for a Luxpower if you want to upgrade due to the 2 x MPPTs.

I thought about telling him that but he has to be constantly reconfiguring the panels. Unless he leaves the charge controller in and adds separate panels to the new inverter when hes ready to upgrade. One inverter and one array is simpler in my opinion coz he needs another db box for the charge controller and a separate PV cable to the batteries. Its a bit of work.

@Denns thanks for the specs, I have tried to download the manual from their website, but the link to their page with downloads doesn't seem to work, I will try again sometime.

@Scorp007 thanks for the suggested other charging options, I'll check them out, although as Denns says I am trying to keep things as simple as I can.

1 hour ago, Lindsay said:

@Denns thanks for the specs, I have tried to download the manual from their website, but the link to their page with downloads doesn't seem to work, I will try again sometime.

@Scorp007 thanks for the suggested other charging options, I'll check them out, although as Denns says I am trying to keep things as simple as I can.

You can dM me your email and I can send you the datasheet if you want.