Can a typical Axpert inverter be used for 230VAC and solar MPPT charging only, without the DC/AC inverter being active?

Say I have a 12/24/48VDC only load and do not want the expense and clutter of using a separate 230VAC battery charger and a solar MPPT charger, but I don't want the inverter running and gobble 30 - 60 Watts of power.

I doubt that it is possible but I don't yet know the Axpert inverters that well.

AC charging will likely not work.  How about only using the MPPT?

Edited April 6, 20232 yr by Modina

1 hour ago, Modina said:

Can a typical Axpert inverter be used for 230VAC and solar MPPT charging only, without the DC/AC inverter being active?

Say I have a 12/24/48VDC only load and do not want the expense and clutter of using a separate 230VAC battery charger and a solar MPPT charger, but I don't want the inverter running and gobble 30 - 60 Watts of power.

I doubt that it is possible but I don't yet know the Axpert inverters that well.

AC charging will likely not work.  How about only using the MPPT?

Low voltage Axpert needs a battery as how would the AC charger and MPPT know when to stop charging. 

While inverter is off both forms of charging is always on. You cannot get away from the self power use on most battery driven devices. 25W for a 24V Axpert. Here the separate MPPTs work better. Up to 97% efficient. 

2 hours ago, Modina said:

Can a typical Axpert inverter be used for 230VAC and solar MPPT charging only, without the DC/AC inverter being active?

If it is a 5kW King it certainly can.  The inverter can be switched off using the pushbutton on the removable display.  The charging still works when the inverter is off.

This may apply to other models as well - my knowledge is limited to the 5kW King.

Edited April 6, 20232 yr by Calvin

38 minutes ago, Calvin said:

If it is a 5kW King it certainly can.  The inverter can be switched off using the pushbutton on the removable display.  The charging still works when the inverter is off.

This may apply to other models as well - my knowledge is limited to the 5kW King.

Generally speaking all UPSes would use the inputs to charge even when off as I indicated in my previous reply. 

These units remain the best value for money to do battery charging. While using it as a battery charger one can just as well use the inverter too. 

Thanks guys for your feedback.

@Scorp007  Yes I would connect a battery and yes, using an Axpert would be the cheapest way of charging a battery.  That is why I am interested in this.  Lithium mains powered battery chargers are also very rare animals, if you require 15+ Amps.  Also, there is less clutter.  It is all integrated in a single box.

I disagree with your 25W for a 24V Axpert.  My own 24V Axpert quotes a power dissipation of <35W, but I have measured it at about 40W.  That is even without the fans in operation and the LED backlight switched off.

There is nothing wrong with using the inverter as well - during times one needs 230V, but not as a UPS that runs 24/7.  My personal ideal would still be to have a small hardware circuit that measures the line impedance on the 230V output bus and then wakes up the inverter when the impedance drops.  In other words, if you plug a mains consumer into a wall-plug and switch it on, the inverter would be woken by the circuit.  This would be specially useful for small places such as off-grid cottages, holiday homes, tiny houses, RVs and such.

I note that when the inverter is off, the majority of the self consumption is gone. But still quite a large chunk remains. For a 5 kVA model, self consumption is some 50 W when inverting, but still around 35 W (from poor memory) when not inverting, e.g. charging directly from solar. It still has to run all the electronics. But at night, the power consumption with no AC input would be near zero.

AC charging however is with the inverter and DC-DC converter running in reverse, so you would have the full 50 W penalty.

On 2023/04/06 at 7:14 PM, Modina said:

Thanks guys for your feedback.

@Scorp007  Yes I would connect a battery and yes, using an Axpert would be the cheapest way of charging a battery.  That is why I am interested in this.  Lithium mains powered battery chargers are also very rare animals, if you require 15+ Amps. 

I find it strange that you have not tried these power supplies at below R500 that can charge lithium up to 85% using a constant voltage in float level. 24V 20A and adjustable voltage up to around 28V. Make specific. These units were priced at about R3000 not long ago but now super cheap. 

Once again as with most things I comment on we are using a range of them and they work very well and not just a Google response. 

 

41 minutes ago, Scorp007 said:

I find it strange that you have not tried these power supplies at below R500 that can charge lithium up to 85% using a constant voltage in float level. 24V 20A and adjustable voltage up to around 28V. Make specific. These units were priced at about R3000 not long ago but now super cheap. 

Once again as with most things I comment on we are using a range of them and they work very well and not just a Google response. 

 

I am scratching my head  around this constant voltage PSU. How does it behave when the 24V battery  is flat and may demand more than 20A initially. Will it perform in constant current mode as expected from a charger, ie will it limit to 20A or will it cut off? 

55 minutes ago, Scorp007 said:

I find it strange that you have not tried these power supplies at below R500 that can charge lithium up to 85% using a constant voltage in float level. 24V 20A and adjustable voltage up to around 28V. Make specific. These units were priced at about R3000 not long ago but now super cheap. 

Once again as with most things I comment on we are using a range of them and they work very well and not just a Google response. 

 

I have used these SMPS's but the 12v versions setup to 14.2v. They work great but i have burnt out 2 off these units as they do not have current limiting curcuits. I used them on 100ah 12v CFE lfp drop in but if the lfp is discharged to 30% soc 70% dod the current goes up to 30-35 amps and they run very hot until the fets give up. I now use the smps in conjunction with a 40 amp pwm charge controller input to the solar panel side and the smps are now running for 6 months without problems. 

Edited April 8, 20232 yr by TaliaB

@Scorp007  Where should I start?  I looked at these type of supplies for months.  You get them for various output voltages and power ratings from about 15W to 600W and beyond.  You can buy MeanWell power supplies arny time.  They are reliable and well made.  They are also very expensive.  There are some cheap ones on Takealot and they just seem to suck big time.  I ordered a small 12V 50W from them and at first switch-on I was greeted with a loud bang.  I opened the thing up and found a number of devices where blown.  The PWM chip doesn't even have markings on it.

I also spend some time at ACDC opening their boxes and peered through the ventilation slots to look inside.  The ACDC units are NOT cheap.  Yet some of them don't even have an input filter.  I can accept it if a 30W doesn't have an filter, but I saw one of their higher powered units also without a filter.  Now that is unforgivable.  It is for that reason that I cannot trust their products.  If the manufacture skips on the filter, he will cut other corners as well.

All these supplies have a preset potentiometer to adjust the output voltage but the range is not far enough for 12V or 24V battery charging.  Ideally you want a 15V/30V supply, and these are available overseas but not from places like Takealot, ACDC or Communica.

The output voltage doesn't worry me too much.  Its a schlep, but one could remove the transformer and change the turns ratio on the secondary and then make it whatever you want.  One could also change the feedback resistor(s) to give wider output voltage adjustment, but one should not overdo so.

a few high quality supplies have a current limiting potentiometer as well.  @BritishRacingGreen concern is 100% valid.  The normal supplies will shut down at over-current.  However this is a safety feature and not something you should use on a regular basis.  Sooner or later you will blow up the supply.  You definitely need current limitation/regulation.  Again, this can be implemented with a small add-on circuit.  These sort of modifications are just a challenge to implement neatly.  I don't like a wire mess with little PCBs glued with hot glue or double sided tape.  🙄

The next step one could consider would be to add a small 8-bit micro to implement a proper Lithium charging algorithm with charging shutdown and automatic re-starting when the voltage drops below a set value.  I would keep the PWM chip to do its thing, and the micro would only close the low-bandwidth voltage/current control loop.

Another route to cheap hardware is to use a ATX power supply from an old PC.  These supplies have over-voltage monitor circuits and the like, but it would be more work to modify these.  ATX supplies are normally very reliable, but then again they are not run at high load for long stretches of time.  20A for 12V battery charging is no problem.  For 24V batteries one would need powerful ATX supplies such as used in gaming PCs.  Those are scarce and expensive.

@Scorp007 where do you source these Hytronic supplies?

I am considering designing a 230VAC + MPPT battery charger for a 12V system.  I would base the MPPT on this opensource design:
//www.youtube.com/embed/ShXNJM6uHLM?enablejsapi=1&origin=https://www.instructables.com

Design a single PCB to take everything and mount it in one of these alarm panel enclosures that are readily available.  But it's more of a dream at the moment.  My house renovations are far behind and I just don't have the time for such a project at the moment.

1 hour ago, Modina said:

@Scorp007  Where should I start?  I looked at these type of supplies for months.  You get them for various output voltages and power ratings from about 15W to 600W and beyond.  You can buy MeanWell power supplies arny time.  They are reliable and well made.  They are also very expensive.  There are some cheap ones on Takealot and they just seem to suck big time.  I ordered a small 12V 50W from them and at first switch-on I was greeted with a loud bang.  I opened the thing up and found a number of devices where blown.  The PWM chip doesn't even have markings on it.

I also spend some time at ACDC opening their boxes and peered through the ventilation slots to look inside.  The ACDC units are NOT cheap.  Yet some of them don't even have an input filter.  I can accept it if a 30W doesn't have an filter, but I saw one of their higher powered units also without a filter.  Now that is unforgivable.  It is for that reason that I cannot trust their products.  If the manufacture skips on the filter, he will cut other corners as well.

All these supplies have a preset potentiometer to adjust the output voltage but the range is not far enough for 12V or 24V battery charging.  Ideally you want a 15V/30V supply, and these are available overseas but not from places like Takealot, ACDC or Communica.

The output voltage doesn't worry me too much.  Its a schlep, but one could remove the transformer and change the turns ratio on the secondary and then make it whatever you want.  One could also change the feedback resistor(s) to give wider output voltage adjustment, but one should not overdo so.

a few high quality supplies have a current limiting potentiometer as well.  @BritishRacingGreen concern is 100% valid.  The normal supplies will shut down at over-current.  However this is a safety feature and not something you should use on a regular basis.  Sooner or later you will blow up the supply.  You definitely need current limitation/regulation.  Again, this can be implemented with a small add-on circuit.  These sort of modifications are just a challenge to implement neatly.  I don't like a wire mess with little PCBs glued with hot glue or double sided tape.  🙄

The next step one could consider would be to add a small 8-bit micro to implement a proper Lithium charging algorithm with charging shutdown and automatic re-starting when the voltage drops below a set value.  I would keep the PWM chip to do its thing, and the micro would only close the low-bandwidth voltage/current control loop.

Another route to cheap hardware is to use a ATX power supply from an old PC.  These supplies have over-voltage monitor circuits and the like, but it would be more work to modify these.  ATX supplies are normally very reliable, but then again they are not run at high load for long stretches of time.  20A for 12V battery charging is no problem.  For 24V batteries one would need powerful ATX supplies such as used in gaming PCs.  Those are scarce and expensive.

@Scorp007 where do you source these Hytronic supplies?

Interesting what you experience and what we found. Due to the limit on voltage that you can adjust I mentioned that lithium can get close to full. 

We have them in the workshop and they are on 24/7 keeping lead acids in float for all the gate motors we repair PCBs. Also have the 12V/20A and 12V/30A and 24V/20A in use as we do full load tests on the PCBs to ensure they can handle the current needed. Some are 3yrs old and still working spot on. Even if they pack up after this time we will just dump it and buy the same again. 

The type I placed a picture off is the same design that many places sell. Does not matter if it is bought from Takealot, Bidorbuy, Geewiz or Microrobotics which happens to be where we buy.

5 minutes ago, Modina said:

I am considering designing a 230VAC + MPPT battery charger for a 12V system.  I would base the MPPT on this opensource design:
//www.youtube.com/embed/ShXNJM6uHLM?enablejsapi=1&origin=https://www.instructables.com

Design a single PCB to take everything and mount it in one of these alarm panel enclosures that are readily available.  But it's more of a dream at the moment.  My house renovations are far behind and I just don't have the time for such a project at the moment.

My time is more valuable than to design these things that cost below R500 and DO work as a charger/PSU if you know what voltage to use for quick no nonsense charging. You can hardly buy the box for this price in ZA 

16 minutes ago, Scorp007 said:

The type I placed a picture off is the same design that many places sell. Does not matter if it is bought from Takealot, Bidorbuy, Geewiz or Microrobotics which happens to be where we buy.

@Scorp007  You can't judge them by their looks.  They all look very similar but made by different Chinese manufacturers. The bad ones will use underrated switching transistors, Schottky diodes, smaller magnetic cores with thinner enameled copper wire, etc. yet appear similar to the better quality units.

Ah, Microrobotics.  I need to have a look what they stock.  Thanks.

Edited April 8, 20232 yr by Modina

On 2023/04/08 at 1:41 AM, Coulomb said:

AC charging however is with the inverter and DC-DC converter running in reverse, so you would have the full 50 W penalty.

Hi Coulomb, I've been wondering lately if its possible to set a 5 Kv Axpert to AC charge but not activate inverter mode at power fail if house is unoccupied and no one using power in the day. IOW the house owner would have to activate the inverter if the power was out once arriving home, Its pointless for inverter to run if no one is home and needing power.. My fridge manages to keep cold fine during load shedding..

4 hours ago, AndrewF said:

Hi Coulomb, I've been wondering lately if its possible to set a 5 Kv Axpert to AC charge but not activate inverter mode at power fail if house is unoccupied and no one using power in the day. IOW the house owner would have to activate the inverter if the power was out once arriving home, Its pointless for inverter to run if no one is home and needing power.. My fridge manages to keep cold fine during load shedding..

If I may chip in. Your request is easy. AC and PV charging will always take place if the setting is to use AC only, PV only or both. The inverter power switch is left off when not at home as charging has priority. This saves discharging the battery during grid off and no power is needed. 

Just switch it on when needed. 

Edited February 18, 20241 yr by Scorp007

On 2024/02/18 at 5:44 AM, Scorp007 said:

If I may chip in. Your request is easy. AC and PV charging will always take place if the setting is to use AC only, PV only or both. The inverter power switch is left off when not at home as charging has priority. This saves discharging the battery during grid off and no power is needed. 

Just switch it on when needed. 

Thank you @Scorp007 you had the answer I needed.