I have 3 Axpert ( Mecer) 5kva inverters. I want to know if it is possible to connrct each inverter to its own battery pack while the inverters are connected in parallel?  My reason for asking, i have 8x 180ah batteries and 4x 200ah batteries. So if possible, i would want to use 4 batteries per inverter in stead of mixing batteries. I have got 20x 150watt panels available for the 3 inverters. Currently the inverters are used as 3 different setups. But i want to combine the 3 in parallel. Thanks. George

Edited March 5, 20197 yr by George
Posted before i completed typing

2 hours ago, George said:

to its own battery pack

No, must be connected to the same battery bank (I don't know these inverters at all, but I know this from hearing it too often 😉 ).

3 hours ago, George said:

I want to know if it is possible to connect each inverter to its own battery pack while the inverters are connected in parallel?

The manufacturer says don't do it, so that's really the end of the story.

Having said that, with some careful firmware, I imagine it could be done (without having thought it through in detail; dreaming is easier than designing 😴). One problem is that the batteries could all be at different states of charge. So one might have its low battery warning showing, so it can't contribute to the loads. Another might be just over the low battery warning level, but the Axperts don't have a good estimation of battery SOC, so you can't say OK this one has a power limit of 2 kW and that one has a limit of 4 kW, so a 3 kW load should be shared as 1 kW and 2 kW respectively. It would be a nightmare to test; so many corner cases.

Plus, it's entirely possible that there good reasons I simply haven't thought of. 🤔

TLDR: don't do it 😶

Thanks

One of the reasons, behind the rule that parallel Axperts have to share a common battery bank is, that manufacturer assumed that each unit will have it's solar panels oriented a bit differently. So, MPPT of 1st unit may receive 3000W, while the MPPT on the other unit might receive 1000W, or maybe just 200W. In such a case, Axperts are using a shared battery busbar as a freeway to exchange PV energy between the units. It's a very usefull feature if you have one string facing North, while some other is pointing to the East for example.

With separate battery banks, that energy flow would not be possible, so one unit would run completely from solar (and even not utilizing full PV power) while the other unit would drain the batteries at the same time.

So, it's a good thing

 

I don't think there is any particular reason for doing it this way, rather there are likely many reasons for not dealing with the complexities of multiple voltages, state-of-charge values and low-battery conditions. In the end it becomes  simple question: How much work is this vs how many more units will we sell if we do this. Quite likely, the cabbage just isn't worth the sauce (that's a direct translation of an Afrikaans idiom... in case it looks funny).