Parallel Charge Controllers Limiting Each Other

[Usangira]

Dear Members,
I am kinda frustrated with my two Chinese solar charge controllers which I have connected to charge same single battery bank of 400Ah

Array 1 is 5kwp and Array 2 is 5.6kwp both are on the same roof similar direction and tilt.

The problem is...When Array 1 charges at 40A Array 2 will charge at 12A and vice - versa

If I switch off any of the array, the remaining active will produce aroung the 50A+

The two controllers have same charging profile boost =float at 57.2v

This stresses me as total production capacity seems to be less compared to if these charge controllers would be charging two different battery banks.

Any idea ?
Thanks , Innocent

 

[mikefitz]

Perhaps your battery bank is limiting the charge current due to battery type or SOC. What happens if you load the system with a high current load?

 

[efficientPV]

At least in my experience I've never seen two charge controllers work well together unless they are in a deep bulk charge mode. They need to talk to each other otherwise one fools the other into thinking the battery is at a different state. Everyone says they do work well together, but I think they are just regurgitating what someone else says or they have never watched their system.

 

[Mattb4]

I run with two and it works good. I have one set for lower voltage than the other. It reaches full and shut downs first and the other carries on at full array power until battery is charged. No need for them to communicate. If the load draws more than the one array can keep up with and thus the battery drops in voltage than both kick back in at recovery voltage.

It comes down to loads. Without loads no PV array (non grid tie) will produce anything.

 

[efficientPV]

That is exactly what we said. Only one fully works at a time unless the battery is nearly dead. Think about that, it's insane. Solar people are the biggest energy wasters on the planet. That is why I divert energy directly from the panels. And charge controllers don't really know what they are doing unless they have two current sensors to know what is actually going into the battery. Many heavily used systems rarely get out of bulk charging. The battery is never really properly charged except when you go on vacation.

 

[timselectric]

You have more charging capacity available than battery capacity. One charger is more than enough to raise the surface charge voltage. Which is lowering the other chargers output.

 

[MisterSandals]

he problem is...When Array 1 charges at 40A Array 2 will charge at 12A and vice - versa

Can you post a pic that shows how your SCCs and battery are wired? I dunno, just grasping...

 

[Mattb4]

That is exactly what we said. Only one fully works at a time unless the battery is nearly dead. Think about that, it's insane. Solar people are the biggest energy wasters on the planet. That is why I divert energy directly from the panels. And charge controllers don't really know what they are doing unless they have two current sensors to know what is actually going into the battery. Many heavily used systems rarely get out of bulk charging. The battery is never really properly charged except when you go on vacation.

Uh, they do not need to work if there is no load. Both work full out if they are operating in bulk battery charge range. You are not wasting power just potential. Nor does the battery need to be nearly dead. All it has to be is at Bulk charge stage.

I don't know what your setup is but I achieve full charge on my batteries most sunny days. Often before 1pm.

I guess if you need to max out your PV production you should be grid tied. No batteries or SCC required.

 

[SolarForU2]

I have a similar setup, two 60A charge controllers each with a PV array connected to a 12v 400AH Lifepo4 battery.
Each controller output has its own 100A 2 pole cct breaker wired direct to the battery terminals; this minimizes voltage drops in the cabling of each controller affecting the other. However invariably one controller will go to float before the other and is somewhat dependant on the loading at the time. They do however both end up in float mode eventually; under heavy loads both controllers contribute almost the same output to the battery. As they dont talk to each other this situation will always occur, but doesn't really matter.... So nothing to worry about.

 

[efficientPV]

Get a bigger battery.......... Then you are back to the same problem once it is charged.

We all get panel mania. More panels, bigger battery always solve a problem or at least mask it. I have three charge controllers on my wall on three strings. It was disconcerting to see only one providing power on a rainy day. Just one controller is used now. I have eliminated over 1KW of panels. These panels had to be removed each winter and m too old for that. And the system now works better than ever by making it smarter.

As all arguments go, every side has a little truth. Did anyone watch the debate, What Uses More Power: Refrigerator Or Electric Vehicle? It is sad to see how everyday folk view technology, let alone make it political.

 

[timselectric]

Size matters lol

 

[Usangira]

I have tried to overload the inverter .....I can now see the variance between two arrays is ≈5A .....So may be my problem is storage......which means more dollars....


......sick n tired of lithium battery prices

 

[Tomthumb62]

I have one set for lower voltage than the other. It reaches full and shut downs first and the other carries on at full array power until battery is charged.

That’s freaking brilliant. I’m not an electrician but somehow this makes a lot of common sense.