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Is My Solar Panel Design ok to achieve 60A charge rate for 1000AH 24V battery bank? Answered

Please I need your advice on a propose project in my office. we have an Inverter (Xantrex TR2424- 24V 2.5KVA) which charge rate capability of 70A. The Inverter battery bank is rated 1000AH 24V total ( 2V 1000AH x 12 in series).

I am sure of 5Hrs sunlight a day. and I want my project to charge the battery at 60A rate per hour. Our DC-current consumed when on Inverting mode is 26A DC (Approx 3A-4A AC inverter output). Our ac load on the inverter output is around 540W.

In my design as attached, each group of PV (4pcs in parallel) should produce around 30A). total amperage should be around 90A. since during the day (sunny) we will be draining 26A continously from the battery, deducting that from the total pv current, we should have around 64A left to charge the battery bank.

My request: kindly look into my propose design and advice where am wrong or need correction/adjustment and recommend with your experience.

I assumed a DOD of 60% on the battery hoping to charge the battery to full capacity within 5 hours of sunlight daily. we have standby generator which we can power on to charge the battery in situation where it is cloudy.

Thanks for your anticipated recommendation & advice

Discussions

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Josehf Murchison

3 years ago

If I get your design right you have 3 separate solar arrays, powering 3 separate charge controllers, then the 3 charge controllers outputs come together to charge 2 batteries.

I can see a serious problem with that, one charge controller will be working and the other two charge controllers will think the batteries are charged and stop charging.

You need to isolate the outputs of 3 charge controllers or use one charge controller.

Are you just in the design stage or have you bought the parts yet.

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jisaac6Josehf Murchison

Answer 3 years ago

also sir, I wish to use 1 charge controller but Magnum, midnight are 100A. That's why I use 3pcs of 60A mppt morning star controller in the design. Should I reduce the charge rate going to the Battery so that the design will use 1 charge controller perhaps Magnum PT-100A or Midnite Classic150A controller- to handle same design? Am scared if 1 controller fails d whole system is then until replaced unlike 2 controller.

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Josehf Murchisonjisaac6

Answer 3 years ago

The 100A charger should be perfect for a charge rate of C/10 on the 1000 Ah batteries.

The solar panels should have isolating diodes in them, but if they don't you will need to put diodes on the outputs to prevent one solar panel from bleeding back through the other when connected in parallel.

See step 9 of this Instructable:

https://www.instructables.com/id/Making-a-1-Watt-So...

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jisaac6Josehf Murchison

Answer 3 years ago

i just went through Midnite classic 150, the max DC voltage ( bulk and equalize) is 28.6v. I guess the controller might not supply beyond 30vdc to the Inverter . Though am jus assuming it operates as it is written. Pls any could help find out about this controller (Midnite classic 150.) Pls

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Josehf Murchisonjisaac6

Answer 3 years ago

The charge controller should have a voltage regulator in it and an automatic shut off so when the batteries are charged it won't over charge the batteries. That is why 3 charge controllers need to be isolated from each other and one charge controller is a better system.

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jisaac6Josehf Murchison

Answer 3 years ago

attached is the snap shot of the manual written 28.6v for bulk and float charge respectively as set on the charge controller

Screenshot_2016-07-23-23-49-02.pngScreenshot_2016-07-23-22-14-04.png
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jisaac6Josehf Murchison

Answer 3 years ago

thanks sir. The Pv has inbuilt diode to block feedback from other Pv in parallel with it. But am now concerned, I checked xantrex tr2424 ops manual, the DC max input is 22-30vdc. Hope the controller won't supply beyond 30vdc?

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jisaac6Josehf Murchison

Answer 3 years ago

Thanks Murchison.

Yes they are 3 arrays to its own charge controller. The output of the 3 controller via its own circuit breakers are all connected to the same battery bank. The battery bank is made of 2v 1000AH Gaston batteries connected in series to give 24v to the xantrex Inverter.

I have not bought the items for the solar design yet. What is existing already is the Inverter and battery. We use generator 5.5kva as a source to power the Inverter input thereby charging the battery.

What can I do to make the parallel charge controller to charge at same rate or what to do so one charge controller won't charge while the other not charging? I read if charge controller settings are same and network de can charge and operate evenly. Pls advice me, it's jus on design stage I have not bought any items.

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iceng

3 years ago

A lot depends on the PV voltage ?

540W Load = 120V x 4.5A the inverter has a top voltage of 24VDC , so if your PV peaks out at 20VDC that gives a safety factor of 4V BUT your battery bank is 24VDC.

That means the PV needs to deliver a minimum of 28V to charge your batteries BUT then the inverter would need to be able to handle a higher voltage

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jisaac6iceng

Answer 3 years ago

thanks iceng,

The max DC disconnect voltage is 32v DC.

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icengjisaac6

Answer 3 years ago

Then the inverter MUST have a minimum DC input capability of 36 VDC...

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Downunder35m

3 years ago

Apart from the other comment you need to consider the max charge rate for your batteries as well!
Makes no sense to kill the batteries by giving them a too high charge rate.

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jisaac6Downunder35m

Answer 3 years ago

dear Downunder35m,

For 1000ah Gaston battery our Inverter was set to max and it charges at 64A and it takes about 9hrs to fully charge the batteries. That's why I wanted the intending solar design to be able to charge at 50-60A so before sunset the batteries could b fully charged .