Ye i have comms to the batteries, I dont have bus bars but that wont be a problem to install, I will just need to buy extra cable to connect the batteries seperately. Yes I am aware that the cables must be the same length, will the second inverter then also be charging the batteries?

1 hour ago, HennieL said:

@Elro You should also make sure that the battery connection cables going to the busbars are the same length and diameter (cross-sectional area, actually) for both sets of batteries. Even though cable resistance is normally very low, the high current flowing when charging and/or discharging the batteries can result in the set of batteries with the longest cables being charged slightly less, and thus develop an imbalance with respect to the other set. Over time this can get gradually worse, and could lead to damage to your batteries in the long run (especially if they are lithium ion batteries...).

He hopefully should have done that already even with current setup.

49 minutes ago, Elro said:

Ye i have comms to the batteries, I dont have bus bars but that wont be a problem to install, I will just need to buy extra cable to connect the batteries seperately. Yes I am aware that the cables must be the same length, will the second inverter then also be charging the batteries?

Maybe some of the forum members can explain if you can do comms with 2 inverters to the same battery bank. I am unsure as haven’t done that myself.

And yes, your second inverter would also charge the batteries. They will charge together.

Can only one inverter have comms and charge the batteries and the other not have comms and do the same? I don’t know.

Can you run both with comms to the battery. Also don’t know.

Can you charge the battery bank with both inverters in voltage mode? Yes definitely that will work.

18 minutes ago, Denns said:

Maybe some of the forum members can explain if you can do comms with 2 inverters to the same battery bank. I am unsure as haven’t done that myself.

Typically inverters that are paralleled manage operation and charging with communication between the inverters. The battery comms goes to the master inverter, the slave inverters get instructions from the master.

9 minutes ago, frivan said:

Typically inverters that are paralleled manage operation and charging with communication between the inverters. The battery comms goes to the master inverter, the slave inverters get instructions from the master.

Yes but he is not paralleling the inverters. The only thing they will share is the battery bank.

I would not recommend using two different inverters to charge the 4 batteries because

A] If you are using comms which inverter would communicate with the batteries because both cannot communicate with the inverters at the same time - it is like working for two bosses one says go there and to that and the other one the exact opposite instruction.

B] If voltage settings are used there is also the danger that the batteries can be over charged or that one of the inverters shuts down because the other one is charging the batteries to a too high voltage, LiFePO4 batteries has a very flat voltage curve and on the cheaper inverters using voltage settings is risky - See the attached illustration as an example of the flat voltage vs SOC%.

I would recommend that the batteries are split between the inverters.

If the 24V batteries looks like the 48V battery with bolt battery terminal connections then do what I did with the Greenrich batteries that I have used in my installation, I used stainless steel grub screws with nuts, washers and lock washers to fasten the lugs to the battery terminal contact and between every lug there is also a washer so looking from the battery terminal it would be lug, washer, lug, washer and between the final washer and nut a lock washer and I used cables linking the batteries to each other instead of cables running from the batteries to bus-bars and from the bus-bars to the inverters. Measure the depth from the battery terminal to see if there are any obstructions inside the battery to make sure that the grub screws do not protrude to deep inside the battery, if memory serves me correct the Greenrich battery has a clearance of about 33mm until an obstruction is met inside the battery so I used 25mm or 30mm long grub screws to fasten all the lugs to the battery terminal connections, your batteries should be more or less the same internal clearance. The lugs of cables which are linking the batteries are rotated 180 deg so that the lugs going to the inverters fits properly without interference.

1 hour ago, Denns said:

not paralleling the inverters

Then don't parallel the batteries. Manage batteries and solar panels according to the connected loads.

36 minutes ago, GerhardK83 said:

I would not recommend using two different inverters to charge the 4 batteries because

A] If you are using comms which inverter would communicate with the batteries because both cannot communicate with the inverters at the same time - it is like working for two bosses one says go there and to that and the other one the exact opposite instruction.

B] If voltage settings are used there is also the danger that the batteries can be over charged or that one of the inverters shuts down because the other one is charging the batteries to a too high voltage, LiFePO4 batteries has a very flat voltage curve and on the cheaper inverters using voltage settings is risky - See the attached illustration as an example of the flat voltage vs SOC%.

I would recommend that the batteries are split between the inverters.

If the 24V batteries looks like the 48V battery with bolt battery terminal connections then do what I did with the Greenrich batteries that I have used in my installation, I used stainless steel grub screws with nuts, washers and lock washers to fasten the lugs to the battery terminal contact and between every lug there is also a washer so looking from the battery terminal it would be lug, washer, lug, washer and between the final washer and nut a lock washer and I used cables linking the batteries to each other instead of cables running from the batteries to bus-bars and from the bus-bars to the inverters. Measure the depth from the battery terminal to see if there are any obstructions inside the battery to make sure that the grub screws do not protrude to deep inside the battery, if memory serves me correct the Greenrich battery has a clearance of about 33mm until an obstruction is met inside the battery so I used 25mm or 30mm long grub screws to fasten all the lugs to the battery terminal connections, your batteries should be more or less the same internal clearance. The lugs of cables which are linking the batteries are rotated 180 deg so that the lugs going to the inverters fits properly without interference.

I disagree on the second point. I have used 2 devices (MPPT and inverter) to simultaneously charge the same bank for a time now.

The only way you will overcharge is if your charging current is set higher than what the batteries can handle.

set both so that the sum of both don’t exceed the max charging current of the entire bank. No competition will occur. You can have a 100 charge controllers on a bank and as long as the current total is within the battery spec it is perfectly fine.

38 minutes ago, frivan said:

Then don't parallel the batteries. Manage batteries and solar panels according to the connected loads.

His batteries are in parallel already.

If he runs the comms from one inverter to the batteries I just don’t know if it will cause issues having another inverter connected to the same bank without comms.

If he removes the comms between inverter and batter and lets both not have communications to the battery bank that definitely works.

If he wants to keep comms. Then yeah, split the battery bank in 2

1 hour ago, Denns said:

If he runs the comms from one inverter to the batteries I just don’t know if it will cause issues having another inverter connected to the same bank without comms.

If you held at wrench to my head, I would set the inverter not communicating with the batteries to only charge to about 90% of SOC based on voltage.

8 hours ago, frivan said:

If you held at wrench to my head, I would set the inverter not communicating with the batteries to only charge to about 90% of SOC based on voltage.

Not a bad idea at all!