Need Help, I am a little confused.

[Mike90250]

Being able to fully recharge batteries at least 1x a week, is mandatory. What sort of battery charger do they have? You need to get a generator that is well matched to the draw of the charger, and able to supply the PF (power factor) the charger needs. Choose a winter angle, and don't have the panels be too flat, or the dirt will never be washed off them.

[Soho]

Hi Mike, They do not have a generator at the time, so on cloudy days they disconnect refrigerator and limit their tv time. They had a small generator, but it stopped working right after I installed the solar system. Requirements for angle, hmm Puerto Rico is sunny all year round. So not sure what would be best, in that case, I guess something that is a happy medium but allows them to generate more power in winter since the sun is not as high or as warm?

I am planning on getting them another generator so that they can at least once a week run it to keep the batteries topped off.

[Mike90250]

Before we can tell you the angle, we need to know the seasonal requirements. I have my arrays set for optimum winter angle, summers, I have long days, lots of sun, I don't care about the angle being off, winter - I need most efficient harvest on the days sun comes out.
If you add more batteries, you need to add more solar..

What is PPT controller - a typo of MPPT, or something different.

What do they have for a generator, do they run it on cloudy days to recharge the batteries ? I run mine every cloudy opportunity, so that if i'm trapped by heavy storm, I don't HAVE to go out and start the generator, I can choose to do it between cloudbursts.

[Soho]

I want to do a full update; I went to my parents as you all know in December. Installed the LP instant water heater for them, I also installed the 10 panels in pairs. I am happy to report that the system is working great for them, they are still without grid power. Since I installed it, they only drained the system to the halfway point twice "no power" I set the system to shut down the inverter if power got too low. They use the refrigerator 80 percent of the time and only disconnect it on cloudy days. I think someone either on this post or another was questioning the 100 watts usage of the refrigerator, I am happy to report that took along a load meter I measured the consumption and it was using 106 watts when it was running. So the refrigerator is using less than the 100 watts per hour I anticipated. The only challenge is the washing machine; it uses 800 watts. But I told my mother to do laundry on sunny days anywhere from 10 am to 3 pm. I left my parents a list to more or less tell them how much power they had left based on the voltage. They use the list a lot and can plan tv time "average 5 hours per day" without draining batteries to the point the switch shuts off. I also gave my neighbor an extension so that he could have one or two lamps "LED's" on his house and watch one hour per day on the tv after dark and as much as he wants during the day on sunny days. Thanks to the set up my mom is able to make ice and share with the neighbors that have no generator.

That has been working great for her. Thank you all for the help and advise.

I was considering going back soon and make the following adjustments, would appreciate the feedback. Currently, the system is as follows;

4- 210 amp hour 6v batteries wired in series for 24-volt output.

1- 40 amp MPPT controller "corrected typo thanks"

1- 2000 watt 24v Aims inverter/ battery charger/ transfer switch

10- 100w mono solar panels wired in pairs.

I am considering adding four more batteries, that way they do not have to be afraid of running out of power. I was also considering changing the inverter to a 48 volt inverter and changing the charger to a 60 or 80 amp Midnite solar or outback charge controller. I still have another 8 100watt panels there, I was considering adding 6 more panels for a total of 16 and wire them 48volts "groups of four" or should I wire them 60 volts "groups of 5" instead and use 15 instead of 16?

The extra batteries and panels will help on the cloudy days. Last but not least, can someone tell me the correct angle to put the panels on the zipcode 00637. I just want to confirm the angle as different apps appear to give a different answer.

Thanks much again, because of this community my parents are living a semi-normal life again. Only took me one cold shower to want to install the heater. Every time I talk to my mother that is the one thing she thanks me for the most. She suffers from arthritis and the hot water makes her feel better.

[Soho]

I want to thank everyone for the help. I just got back from installing the system for my parents. Works great, they now have enough power to run their home. I told them that there would have to be some adjustments, such as running the heavy loads during the day on sunny days. Thanks for the suggestions and the assistance.

[Mike90250]

Generally, MPPT controllers work well with PV array voltage twice that of the battery voltage. For a 24V bank, you want the array wired for 48V. That lets the MPPT down-convert the power most efficiently (around 95-99%) Higher voltages work, but become less efficient, so you need to do a trade off study between wire run gauge and length, vs conversion loss. Generally not more than a couple %, but you can save a bundle on wire cost for long lengths of copper wire..

[Soho]

Thank you all for the sound advice, I understand that with solar there is always more than one way to skin a cat. I for one appreciate different approaches, it gives me more options, and that is always good.

Thanks

[littleharbor]

I'm stepping out of this conversation due to conflicting suggestions on inputting power into a MPPT controller. Only other comment is watch out for the wattage limit for your 40 amp controller.

[sensij]

Yes, mppt controllers very efficiently (>90%) convert the higher PV voltage to the battery voltage.

Overcurrent protection is usually fuses or circuit breakers, either can be appropriate for PV.

[Soho]

Thanks again for the prompt responses.

Littleharbor,
if I was to wire three cables in series would that then make the power sent to to the controller far higher than the 24 volts needed by the battery bank? I think the controller will step down the current to the correct charging power, however, does that mean that if I send 36volts and the ban4 is a 24v bank the extra power is wasted by the controller? I am certain that is not the case, I would just appreciate a response to understand what happens to the extra energy in the case of 3 panels wired together.

Sensij,
Overcurrent protection, are you referring to fuses?


Thanks all

[sensij]

10 panels would be properly wired as you've suggested... put two in series, and then each of those 5 pairs in parallel. I think you will be happier using all 10 than dropping down to 9 panels. The next increment you could consider would be 12 panels, 4 strings in parallel each with 3 panels in series.

For any of these options, you will have more than two strings, so each string needs overcurrent protection. You will need to think about where to combine them in a way that balances wire costs with transmission loss.

[littleharbor]

Yes this will give you 24 volt nominal voltage, BUT,
If you're running a 24 volt system then you would want to wire your panels either 3, or 4 in series with a MPPT controller. Your best bet with that controller would be 3s3p. 9 panels will be right about the comfortable limit for that controller @ 24 volts.

[Soho]

They are 60 cell grid tie panels. A single panel, by itself doesn't have high enough voltage for 24 volt battery charging. These are considered 20 volt nominal panels. A 72 cell panel is considered a 24 volt nominal panel. Two or more series wired 60 cell panels and a MPPT charge controller will allow you to charge a 24 volt bank.

Thanks for the reply, the 100-watt panels I have are made by renogy. Again price of getting them to Puerto Rico was the main contributing factor in the purchase. the specs are as follows.

• Maximum Power: 100W
• Maximum System Voltage: 600V DC (UL)
• Optimum Operating Voltage (Vmp): 18.9V
• Optimum Operating Current (Imp): 5.29A
• Open-Circuit Voltage (Voc): 22.5V
• Short-Circuit Current (Isc): 5.75A
• Output Cables: 4.0 mm2 (0.006 in2), 800mm (31.5 in)
• Connectors: MC4 Connectors
• Dimensions: 47 X 21.3 X 1.4 In
• Weight: 16.5lbs

I am planning on wiring 5 pairs. in Serial to make them 24 volts. Then I was going to use a combiner box. Does that sound about right? Just want to ensure that this panels wired in pairs will deliver enough power to charge the bank.


Thanks

[littleharbor]

Bonus question The 30-volt panels are they intended for 24 volt battery systems?

They are 60 cell grid tie panels. A single panel, by itself doesn't have high enough voltage for 24 volt battery charging. These are considered 20 volt nominal panels. A 72 cell panel is considered a 24 volt nominal panel. Two or more series wired 60 cell panels and a MPPT charge controller will allow you to charge a 24 volt bank.

[Soho]

Thanks for the advice guys, truly appreciate it. I live in Florida, but the reason I did not buy from a local supplier is that they the few I contacted wanted 700 plus dollar to ship to Puerto Rico. I am installing this system for my mother, she is without power and expects to be for another six months due to the hurricane. I will give them a call tomorrow, to see if they ship to PR. I remember a while back they had opened an office in Puerto Rico, but I think that is no longer open. I am flying at the end of the week to do the install, I will take pictures, just waiting for some parts as I plan on installing internet while I am there to my mother's house via wifi, that will be an excellent experiment as I must shoot the signal 8 kilometers to a mountain and then shoot it down to her lol

So I am going to shoot for 10 panels to have a little extra juice for unexpected stuff.

Bonus question The 30-volt panels are they intended for 24 volt battery systems?