Connect two different hybrid inverters to the same battery bank?

[Wond3rboy]

Hi guys.

I have a 3.25KW solar-powered system using a hybrid inverter (grid + solar + battery pack) running some loads in the house.

I now want to add another hybrid inverter for a different set of loads, however, I want to try and use the same battery pack if possible to save on cost. The new loads would be completely "separate" from the first set of loads and will move to the grid whenever there isn't enough solar available.

I wanted to know if this is possible, and if so, what mods would you guys suggest. From a noob sense of solar system design/working, I was concerned with both inverters trying to charge the battery bank at the same time and perhaps damaging each other or going over the rate of charge of the battery. If its relevant, the battery pack consists of four tubular batteries.

Thanks,
Abbas

 

[Diver300]

If two chargers are charging the same battery, they will charge the battery faster. The batteries you linked to are 110 Ah, 12 V, so nominally 1.3 kWh each. Four of those is around 5.2 kWh so a single 3.25 kWh solar system will charge that in about an hour and a half.

I don't know what loads you are using so I don't know that fits in with your plans but 1.5 hours seems to short already.

 

[Wond3rboy]

Hi Diver300

Thank you for the answer to the question. That is a relief to know that my earlier concerns of damage to the inverter aren't justified.

The load I intend to connect is an air conditioner. The inverter I intend to add on has two load options, a normal load which is backed up by a battery (similar to a UPS), and a "smart load" which isn't completely backed up by the battery (for e.g. it will be run only when there is enough power from solar/grid and if the grid goes off and there isn't enough solar power, the smart load turns off. The catch is that the smart load is not shut off immediately when the grid turns off, but has a timer/delay set for its shutting off in consideration of any irregular variance in the generated solar power (cloud cover, etc)). I want to connect the air conditioner to the smart load option of the new inverter. Therefore the battery bank will just momentarily be used.

Regarding the details in terms of connections, I also wanted to know if it would be fine to connect both inverters at the same location to the battery bank?

Thanks!

 

[Diver300]

You should draw out what you are intending to do, as well as what you have now.

If the load is only for a few minutes, those batteries will be fine.

 

[Nigel Goodwin]

My concern is the air-conditioner load - don't they have high switch-on surges?, and will the inverters cope with it?.

 

[Wond3rboy]

Hi Diver and Nigel,

Thank you for the replies

Kindly find attached the proposed connection diagram for the solar system. Note that the intention is to connect the battery terminals of both inverters to the batteries at the same point.

The air conditioner is one of those DC inverter ACs. The inverter I hope to add already works with a similar AC at a friend's place. The starting current for the AC is just above 9 amperes which I feel should be alright for the inverter to handle. Correct me if I am wrong though. Also, there are separate sets of solar panels supplying solar power to each inverter.

Thanks again!

View attachment solarpowerconnection diagram.png

 

[rjenkinsgb]

You need to ask the inverter manufacturer.

If they use any kind of battery capacity metering internally, that cannot work with two units connected to the same battery bank.

 

[Wond3rboy]

Hello Rjenkinsgb

Thanks so much for the tip, I will check with the manufacturer/specs for this.