Solar charge controller connected to solar charge controllers

[bugzbuks]

Hi peeps

I'm busy designing a battery charging station (BCS) for rural electrification in Africa. Basically the solar panels charge batteries that the community take home to power small appliances.

So the question is how should I setup the charge controllers (CC).

This diagram give a quick overview. This system can charge 20X 40Ah batteries per day. Though this array manages fine for most of the year, there are about 53 days a year (SolarGiS data) where the BCS doesn't meet its target of 20 batteries. So I've added a extra battery bank to charge the other batteries during bad weather. I understand that the Victron CC can handle a bidirectional input/output. So if the solar panels can handle the load the battery is dormant, but once the panels start struggling the battery bank picks up the difference. Is this correct?

BCS (20 slots - with battery).jpg

Also, I've heard that charging batteries from a battery is not a good idea. I've considered just adding a diesel generator instead but I don't want fossil fuels in rural Africa. It's hard to come by...

Any comments? Advice?

Thanks!
James

[thastinger]

Are wind tables published for your location? Is wind not an option?

[bugzbuks]

Are wind tables published for your location? Is wind not an option?

Africa's wind resource is not that great when compared to solar. My site is in South Africa where the sun is particularly good.

Ultimately it come down to cost of energy. These are micro-utilities (smaller than 1 MW) and small wind cannot compete with solar PV.

[SunEagle]

What about a water driven turbine? There are any number of ways to generate electricity. You just have to find a way to turn the generator.

Since it is only for specific times and not all the time this can be done manually (like one of them bicycle pedaled generator) or animal powered. Try thinking out of the box.

I like your plan. I hope you find a way to do it.

[russ]

I expect he is trying to start a business.

[bugzbuks]

I expect he is trying to start a business.

Correct, this is a small business run by the local community that sells electricity. I have considered all the renewable energy option and solar is simply the easiest to work with. No moving parts, little technical skills required and it work anywhere. So for now I'll stick to solar. Once the community starts scaling up I'll consider other options too, with hydro being the first on my list.

Here's a presentation I made that explains it in more detail.

Anyway, I need to figure out this battery charge controller issue first. Else I'll just scrap the idea of batteries charging batteries and just add a back generator. :P

[bugzbuks]

Any ideas?

So any ideas on connecting solar charge controllers to other solar charge controllers?

[bugzbuks]

Answer

Okay, I've talked to Stecca in Germany and you cannot have multiple solar chargers connected to a single power source. It's 1x panel -> 1x charger

So to make this setup work I had to add an inverter in between so I can get standard AC battery chargers.
BCS (20 slots - with inverter).jpg

[Tesla]

To keep it simple how long will it take to charge one battery ? and how long will that battery last for basic appliances plugged in ?

[SOLAR_FL]

Okay, I've talked to Stecca in Germany and you cannot have multiple solar chargers connected to a single power source. It's 1x panel -> 1x charger

So to make this setup work I had to add an inverter in between so I can get standard AC battery chargers.
[ATTACH=CONFIG]2949[/ATTACH]

I think your main issue is Time. Time is the constant which you cannot change. To charge the batteries in the least amount of time requires knowing the maximum charge rate, and being sure you can maintain that maximum rate. This brings you to how many batteries you can charge in one day.
The charge controllers will be needed for each bank of solar panels that supply the maximum level for a bank of batteries. You would start a new bank for the next bank of batteries. The only requirement is that each bank supply the maximum acceptable charge rate for its bank of batteries.

I may be far off on this, so feel free to tell me I'm wrong, and explain why.

You wanted to put more charge controllers on a great number of panels all working together. If you break them apart so you can use the charge controllers for each bank of panels for each bank of batteries you can bypass the lose you will have in using AC chargers. That requires an inverter which has your first lose of power, then the battery charger which brings in your second lose of power. Put all that you generate into the batteries, and you won't be fighting an up hill battle.

"Time" is what you left out, how long do you get to keep the batteries you charge? Do the customers leave with the same battery they brought, or only with another battery that is charged. Having them leave with any battery that is charged is good, and that brings you to the buffer. The buffer is to have more batteries than you need, so there are always charged batteries waiting for your customers, and you get as much time as you need to keep them coming. So think about the buffer, think about breaking the panels up into banks, and tell me what you think of my thoughts.

Best regards, and I wish you great success in the wonderful work you are doing.

Joe

[thastinger]

I believe we said you would have to do that in the beginning because of the low capacity and varying state of charge for the customer batteries, no way would I try to hook those to my system anyway, never know what is being returned to you.

To charge a 12V 12Ah battery with a 10A "smart" charger is going to take 10-60 min depending on the SOC it is returned to you. Those power my kids toys and when they are dead enough that they won't move the ride-on ATV at 1/4 speed, it takes about 40 minutes to fully charge them back up on the 10A setting of the black&decker charger...

[thastinger]

didn't mean to double post

[SOLAR_FL]

I think your main issue is Time. Time is the constant which you cannot change. To charge the batteries in the least amount of time requires knowing the maximum charge rate, and being sure you can maintain that maximum rate. This brings you to how many batteries you can charge in one day.
The charge controllers will be needed for each bank of solar panels that supply the maximum level for a bank of batteries. You would start a new bank for the next bank of batteries. The only requirement is that each bank supply the maximum acceptable charge rate for its bank of batteries.

I may be far off on this, so feel free to tell me I'm wrong, and explain why.

You wanted to put more charge controllers on a great number of panels all working together. If you break them apart so you can use the charge controllers for each bank of panels for each bank of batteries you can bypass the lose you will have in using AC chargers. That requires an inverter which has your first lose of power, then the battery charger which brings in your second lose of power. Put all that you generate into the batteries, and you won't be fighting an up hill battle.

"Time" is what you left out, how long do you get to keep the batteries you charge? Do the customers leave with the same battery they brought, or only with another battery that is charged. Having them leave with any battery that is charged is good, and that brings you to the buffer. The buffer is to have more batteries than you need, so there are always charged batteries waiting for your customers, and you get as much time as you need to keep them coming. So think about the buffer, think about breaking the panels up into banks, and tell me what you think of my thoughts.

Best regards, and I wish you great success in the wonderful work you are doing.

Joe

I was reading the post on using alternative modes of generation and it occurred to me that you could put a lot of people to work. Build a peddling station with 10 seats, maybe more, Buy some high output alternators which are normally powered by wind, and connect a pulley system so that the combined energy from the peddlers would drive the alternators. The alternators produce a great deal of power. The people who peddle would be supplied with clean water, food, and a certain amount of money for what they generate. You may be able to meter the revolutions of the peddles to use as a multiplier for the pay. The peddling station would produce power in any kind of weather, or time of day. Your biggest problem at that point will be to find enough customers for your charged batteries. Take a look at what the alternators can generate on WindyNation's web site.

[russ]

Build a peddling station with 10 seats, maybe more, Buy some high output alternators which are normally powered by wind, and connect a pulley system so that the combined energy from the peddlers would drive the alternators. T

That qualifies as the dumb idea of the month! Check into the math a little bit and you will find it is comic book standard.

[SOLAR_FL]

That qualifies as the dumb idea of the month! Check into the math a little bit and you will find it is comic book standard.

So it did make you laugh.