Charging a battery pack linked to an inverter or charge controller

[Isetech]

All this talk about C ratings and warranty claims etc, what about charging the batteries.

Suddenly an interesting question popped up while chatting to someone yesterday, what if I have 6 x 5 kwh batteries in parallel, a 5 kva inverter and 16 panels on the roof.

That means you have 600 amp/hr of battery power, how are you going to charge it after day 3 of stage 6 load shedding?

You down to 20% DOD, you have 6 x 1C batteries, 11amps per mppt (22 amps) and 125 amps max charging capacity on the inverter.

8 hours per day the power is off, leaving you with 8 hours to fully charge the batteries.

Imagine if you are off grid and dont have a generator and you load shedding between 10 and 2 pm.

Even worse you have lead/gel or AGM batteries, you down to 50%, were does that leave you.

Do you think this Eskom power problem is all part of a bigger scheme to bring this country to its knees. I am not into conspiracy theories and stuff I dont have the expertise in that field nor understand the politics of it. But you have to ask yourself, what happened to all the manufacturing in SA and why is all the land being taken up by massive storage facilities to a point that they are now spreading like a wild fire over the empty land and the sound of the trucks running 24/7 is getting so loud and roads are impossible to travel on due to trucks jams waiting to load/unload.

We all going to say we didn't see that coming, as it unfolds right in front of us.

I saw this same thing happen when load shedding started back in 2008, suddenly everyone went into panic mode and rushed out and purchased large generators, we climbed on the band wagon and just installed generators for months. Then suddenly the panic stopped and investors who got conned and invested, lost millions. Lots of the generators eventually got sold as the load shedding stopped and started.

[Isetech]

Why dont we have more renewable product manufacturing lines in SA, we build cars, some of the best in the world.

People say the batteries are manufactured in SA, then why are the companies taking back orders while they wait for container load batteries to arrive?

What if China went to war and suddenly production lines stop, will the rest of the world collapse because everyone relies on China for everything?

[GCE]

All this talk about C ratings and warranty claims etc, what about charging the batteries.

Suddenly an interesting question popped up while chatting to someone yesterday, what if I have 6 x 5 kwh batteries in parallel, a 5 kva inverter and 16 panels on the roof.

That means you have 600 amp/hr of battery power, how are you going to charge it after day 3 of stage 6 load shedding?

You down to 20% DOD, you have 6 x 1C batteries, 11amps per mppt (22 amps) and 125 amps max charging capacity on the inverter.

8 hours per day the power is off, leaving you with 8 hours to fully charge the batteries.

Imagine if you are off grid and dont have a generator and you load shedding between 10 and 2 pm.

.

It all has to do with what does the client wants to achieve.

Once you know what they expect, after you have installed, then the design needs to accommodate the various factors like recharging capacity , panel capacity/sizing , inverter sizing.

Most clients start with - " I want off grid" - You put a number of 600K to them as a start figure then the expectation change generally to , " be comfortable during load shedding and save on electricity bill "

To be comfortable in my opinion is top have lights or some lights depending on size of house , TV , Router , alarm ,CCTV - I generally try to size that backup load at around 500watts and maybe a push to 1Kw .

Now you only need 2Kw of battery storage - Panels to suit budget and can be expanded later - 5KwH battery so that 3 to 4 KW can be used for storage and supplement electricity usage at night.

PV is easy to sell , it pays for itself , batteries are a grudge buy but you can use them to save electricity and the extra capacity can be used to extend your backup capacity if needed.

With PV installed the client needs to understand that he has to manage usage to obtain max from the system.

[Isetech]

The question amongst all the jiba jaba, got a little ahead of myself as always.

The question: What happens when a company installs a 5 kva unit with a ton panels and 6 x 5 kwh lithium batteries in parallel, how do you charge the batteries, if you only have a 125 amp charger in the inverter.

Panic buying is due to stage 4-6 load shedding, designing a system for this type of massive power outage would be like being off grid but instead of using a generator you do have a couple hours of grid power.

The design factor would be max charge capacity when the power is on or the sun is at its peak.

This is where C ratings of a battery might not be a big issue, the charge capacity of the inverter is a bigger consideration. If you start adding batteries in parallel, you need the charge capacity, 125 amps sounds great until you fit the 3rd 4 th 5 th and 6 th battery 100 amp/hr battery. You drop to 80% DoD how are you going to get the batteries recharged ?

Add more charge controllers or inverters and panels?

If I understand this, once you add the second battery, having a 1C battery means nothing, now understanding the cell and BMS warranty conditions become the important factor.

[Isetech]

As with everything that isnt planned right, we start with the problems related to these bad designs, shody workmanship and illegal connections.

You rush and panic buy, you are going to suffer the consequences of your actions.

Social media and the internet is full of experts, just make sure your expert has been doing it for a little longer than 6 weeks, has at least done some electrical and can sign off the electrical installation

As indicated in the past a 3 day course, a green card and 6 weeks electrical experience doesn't make an installer and expert in any field.

Think a little before you go out and blow R150 000.00 plus on a system.

Companies will start today and be gone by the end of the year if they are lucky. This shortage of batteries and inverters is going close many doors before they even get started.

Batteries have not been around long enough to really find out what they can do.

There are other things going on behind the scenes that most people aren't even aware of.

Solar is still to new with many wrinkles that need to be ironed out, which is going to result in a lot of new rules and regulations. Councils are still trying to figure out how they are to regulate and ease the massive feedback into a failing old grid.

You might think you have a good 10 year investment, which is going to pay off in a couple years, lets hope you are right.

[Justloadit]

Even a battery charge of 125Amps through your inverter is a problem, 6Kw - that is approximately 27Amps from your mains only to charge your battery, what about your essential loads running through the inverter, all of a sudden you pulling 35 to 40 amps through the source cables to your inverter.
Are the cables and circuit breaker sized correctly for this scenario?
Can the inverter actually handle this amount of energy through the incoming side inverter?
I have not had anyone who can explain this event to me.