Hi all,

If you have an existing all-in-one inverter where the existing panels connect to, can you add a second dedicated charge controller and panels connected directly to the battery bank via a DC busbar?

In the event that the batteries are fully charged woul the inverter draw power from these additional panels during the day?

What would the pro's and cons be of doing this?

Edited May 3, 20233 yr by Douw G. Gerber

21 hours ago, Douw G. Gerber said:

If you have an existing all-in-one inverter where the existing panels connect to, can you add a second dedicated charge controller and panels connected directly to the battery bank via a DC busbar?

Yes. I used to do this myself.

21 hours ago, Douw G. Gerber said:

In the event that the batteries are fully charged would the inverter draw power from these additional panels during the day?

Yes. It will draw power from the extra panels even when the battery isn't full, in preference to drawing the battery down.

21 hours ago, Douw G. Gerber said:

What would the pro's and cons be of doing this?

Well there is the cost and installation of the extra gear, of course. The niggle I found is that the inverter sometimes got a bit confused near the end of the absorb stage. But you can avoid that problem by setting the absorb voltage setting for the external MPPT just a little lower than the inverter's. Adjust a little if the calibrations aren't perfect. That way, the external MPPT helps most of the time, just not at the very end of the charge, but then the battery current is low anyway.

I even had my monitoring system (written 99% by a colleague) figure out what power must be coming from the external MPPT, and graph that separately from the inverter's charge power. It got that wrong when the loads changed sharply, but most of the time it worked really well.

I only changed the system when I found I needed more power, so I added another inverter in parallel, and that had another MPPT. So I just swapped the panels to the new inverter.

22 hours ago, Douw G. Gerber said:

Hi all,

If you have an existing all-in-one inverter where the existing panels connect to, can you add a second dedicated charge controller and panels connected directly to the battery bank via a DC busbar?

In the event that the batteries are fully charged woul the inverter draw power from these additional panels during the day?

What would the pro's and cons be of doing this?

If your inverter has a gen input you could also use a separate string inverter

3 hours ago, Chris_S said:

If your inverter has a gen input you could also use a separate string inverter

Unfortunately not but that is also an interesting tidbit to know 🙂

Can you guys perhaps suggest a decent MPPT charge controller (30A) that wont break the bank?

Would this one work as an example?

https://shop.thesunpays.co.za/products/epever-xtra-solar-charge-controller-30a-mppt?variant=39474339676231&currency=ZAR&utm_medium=product_sync&utm_source=google&utm_content=sag_organic&utm_campaign=sag_organic&gclid=Cj0KCQjwr82iBhCuARIsAO0EAZzOASkGUQ4AZg7PnQ5JDdUrRj7RjK8ivrfZ3gRRFyCZ4eWpeVhlV4kaAimqEALw_wcB

My household rarely goes over 50A at present - I assume the inverter will pull from wherever it can to deliver say 60A if required.  What happens when you draw more than the 30A the unit above can deliver - will magic smoke come out or dies it just throttle back?

Edited May 4, 20233 yr by Douw G. Gerber

8 minutes ago, Douw G. Gerber said:

Can you guys perhaps suggest a decent MPPT charge controller (30A) that wont break the bank?

Would this one work as an example?

https://shop.thesunpays.co.za/products/epever-xtra-solar-charge-controller-30a-mppt?variant=39474339676231&currency=ZAR&utm_medium=product_sync&utm_source=google&utm_content=sag_organic&utm_campaign=sag_organic&gclid=Cj0KCQjwr82iBhCuARIsAO0EAZzOASkGUQ4AZg7PnQ5JDdUrRj7RjK8ivrfZ3gRRFyCZ4eWpeVhlV4kaAimqEALw_wcB

My household rarely goes over 50A at present - I assume the inverter will pull from wherever it can to deliver say 60A if required.  What happens when you draw more than the 30A the unit above can deliver - will magic smoke come out or dies it just throttle back?

Decent would be victron

The Epever Mppt 30A is a good option. Currently run 2 in parallel with Axpert inverter. Buy the communication cable for programming mppt. Can be used with Lithuim batteries. Only had good feedback from Forum members using Epever Mppt. 

28 minutes ago, Chris Louw said:

Buy the communication cable for programming mppt. Can be used with Lithuim batteries. Only had good feedback 

@Chris Louwwhere did you buy the comms cable? I agree very capable Mppt's i also use the Epever Xtra 150v 40a works like a charm

19 minutes ago, TaliaB said:

@Chris Louwwhere did you buy the comms cable? I agree very capable Mppt's i also use the Epever Xtra 150v 40a works like a charm

Sunpays do sell them. They have no stock. WhatsApp them for more info. 

54 minutes ago, Chris Louw said:

The Epever Mppt 30A is a good option. Currently run 2 in parallel with Axpert inverter. Buy the communication cable for programming mppt. Can be used with Lithuim batteries. Only had good feedback from Forum members using Epever Mppt. 

This is a vital point for expansion that you can parallel the Epever after loading the same settings on both. 😀

3 hours ago, Douw G. Gerber said:

What happens when you draw more than the 30A the unit above can deliver - will magic smoke come out or dies it just throttle back?

It should just throttle back, and the  battery has to supply the shortfall. It decides how much to push into the battery, you don't "pull" from the solar charger.

4 hours ago, Douw G. Gerber said:

Can you guys perhaps suggest a decent MPPT charge controller (30A) that wont break the bank?

Would this one work as an example?

https://shop.thesunpays.co.za/products/epever-xtra-solar-charge-controller-30a-mppt?variant=39474339676231&currency=ZAR&utm_medium=product_sync&utm_source=google&utm_content=sag_organic&utm_campaign=sag_organic&gclid=Cj0KCQjwr82iBhCuARIsAO0EAZzOASkGUQ4AZg7PnQ5JDdUrRj7RjK8ivrfZ3gRRFyCZ4eWpeVhlV4kaAimqEALw_wcB

My household rarely goes over 50A at present - I assume the inverter will pull from wherever it can to deliver say 60A if required.  What happens when you draw more than the 30A the unit above can deliver - will magic smoke come out or dies it just throttle back?

Here is an example of my Epever. Mine does over read by 10%+. Single panel charging 24V battery. 

 

 

2620 Watt produce by  2 extra MPPT. SolarAssistant can not connect to Epever. Output limited to 100 Amps. Max battery charging 111Amps. Off grid installation. 

Good day,

 

So if I am understanding this thread correctly.

 

The Separate MPPT Controller and batteries get added to a DC busbar and not the inverter?

 

Which busbar is the right one to get? 

 

Also can anyone show a wiring diagram of this setup? 

Hello,

currently I am also doing experiments with additional MPPT charge controller parallel to an Axpert Max Duplex 11K.

Batterie is an LFP Pylontech Battery Stack (6xUS3000C).

My PV generator basically exists of 5x3kWp string.

MPPT1 of The Axpert max is connected with 3 strings in paralell (9kWp and MPPT2 is connected to 2 strings (6kWp).

As each MPPT can only manage 5.5 kWp, the System will waste probably some earnings in summer, but in winter overloading will give an improvement.

I have an additional PV Generator with different PV Modules (MPP Point around 25 V, 16 A each, 6 Modules, but five of them are oriented SW, one is oriented NW, and so does not get much sunlight, or at least less than the other five modules.

All modules are vertical 90 degrees.

O.c. Voltage of 5 Modules in a string is around 166 to 170 V in summer, plus 20 % if its really cold could be up to 204 V.

MPP Voltage of 5 modules will only be around 125 Volts.

That is too low for the Axpert Max, here MPP Range Minimum is 150 V.

Integrating 4 of the modules in two of the existing strings is OK frommax. Voltage and is working, but maybe not agood idea, as module orientation is completely different:

SW 90 degrees slope vs. SE 22 degres slope.

No idea how good Axpert Max can handle that. I think at least not if only the 2 Modules get sun light.

So currently I connected experimentally an additional EASun MPPT to the batterie stack, and connected 4 SW90 modules to it.

It worked and will work at least if the additional MPPT is configured the right way and battery is not too full.

(That will help a lot winter, even it will probably not work till battery is completely full.)

There is a difference in Coulombs Setup and mine:

He has Pb Batteries and no BKS Connected to his Axpert Max.

So the inverter and mppt is able to control charging by only measuring voltage and current.

In my case this is not possible, as my Pylontech Stack has and BMS and the Inverter communicates with the BMS.

Here it gets max. allowed charge current and SOC.

I wonder if the inverter can handle the situation that actual current to the battery is higher than the current coming out of the inverter.

It will depend on the regulator algorithm. A normal PI(D) regulator would work, but if there is implemented a plausibility check between outgoing and bms measure current, maybe there will be situations this will fail.

I will continue to do the final connections for only 4 Modules and the additional EASun MPPT.

Than observe the earnings this winter, and beeing a little bit unhappy not to use at least the 5th 450 Wp PV Module

Other possibilities would be:

1.) Connect all five 3 kWp strings to one MPPT of the Axper Max. (3 times overload, just limited by the firmware!)

Connect 5 or even 6 of the SW/NW Modules to second string, but still be under 150 V Voltage n MMPT.

2.) Buy an new extra MPPT that can handle higher Voltages. But Victron is quite expensive and other higher Voltage MPPTs are very rare.

There is one at Alibaba with 230 V max. DC Voltage.

Does anyone has experience with that device ?

Is there any experience in the forum with Axpert max, Li Ion Battery with BMS communication to the Axpert Max

and an additional connected MPPT charge controller

Gruß

Roland

I have some Epever XTRA 3415N 30A units that I have used with Pylontech batteries . They are 150v max units .Connected 2 of these to the battery busbar and 1 strind to a 145v Axpert. 4kW

These units have their own program and can be setup to run with your current system . Can be programed to LFP or user settings Programming can be done using a PC .My Axpert had no communication with the pylontechs.

This system was connected with Solar assistant so I could see some of the battery info .

I have upgrade to 6 kW inverter and dont use them .