How to totally secure an off-grid PV system with fuses ?

[Hava'i]

Hi everybody,

We're in a south pacific island and have been living the last 19 years off-grid, just with oil lamps. We've been happy enough like this, but for the kids we think it's time to improve our lives a bit and we're planning to install a PV system. This is a very big investment for us and being new to this, I would really appreciate any advice or help to prevent me from making expensive mistakes.

I've already purchased 6 x 250 W poly Solarworld panels and a 24 V battery bank composed of 12 x 2 V 1220 Ah (I haven't fill them with acid yet).
For the CC, I'd have loved a Morningstar MPPT (the epoxy coating of its electronic would have been a major plus windward and 500 m from the sea...) but they don't have the Amps I need.
So I'm hesitating between the Midnite Solar 200 and the Outback Flexmax. The price is going to be a decisive factor as both have good reputation.
For the inverter I'm thinking about the Outback GFX 1024 E. I'm sure it will look undersized for most of you but we don't have big needs and won't have much to run at the same time.

Do you think these are good choices ?

For the wiring, I will overdo it and won't have far to go anyway. The panels are going to be on my garage's roof and the rest just under.

My main question is about the fuses and breakers and combiner boxes. There I'm totally dazed (and confused and would really appreciate if one of you could tell me :

Is there a way to do with a minimum of fuses and breakers without sacrificing security ?

Is there any link to a site with complete and clear drawings that could help me to this the best way ?

If not, could one of you teach me how to ? (I put this one in last position as I'm not sure to be the cleverest student when it comes to maths...

Thanks in advance for your answers.

[Mike90250]

Morningstar makes a wonderful 60A MPPT controller with 150V max DC input. I own 2 of them.

Depending on the size of the panels and their voltage, you may be able to have 2 strings of 3 series panels.

Midnight Solar stocks some good DC circuit breakers, which are more forgiving and useful than fuses.

Just about every install is unique, and there are "generic" layouts around.

do you have plans for a generator ?

[Hava'i]

Thank you a lot Mike for answering me. It's strange exchanging words directly with you cause almost all I know about PV (which isn't much cause I'm a bit dense) comes from this forum, so mostly from you and other major moderators and senior members like Sunking, sensij, Naptown. Thank you to all of you.
First of all I want to apologize for my imperfect English and if I don't always answer right away. The first is because we're french speaking on my island and the last because not having AC at home, I only have access to Internet through cybercafé or comprehensive friends

I don't have plans for a generator cause everything is horribly expensive on my island. To give you an idea, gas is almost 8 $ for a gallon and a 2 KW Honda is close to 6000 $. Taxes on everything electric are between 100 and 150 %, depending where it comes from. It's killing us but I'm not complaining too much as it's up to us to find happiness in what we have. Peace and mainly good weather all year long are good enough reasons but health is definitely the winner. Having a 20 years old daughter in chemotherapy and recovering myself from a stroke, I've learned to redefine priorities in my life...

The reason I've been able to buy everything I mentioned is because I bought it second hand but brand new from a rich man who changed his plans and sold it to me for half the price it's in the U.S. I've been incredibly lucky to meet him at the good time.

Not willing to play with fire, I wanted to keep everything as simple as possible : all in 24 V, like the panels and the battery bank voltage. But I'm not sure of anything and have no definite plan yet.

Morningstar would have been my first choice if I could use it but it seemed to me the Tristar 60 amps wasn't enough for the 62,2 Amps I'll have (1500W/24V).

I've been thinking about what you suggest just to be able to use the MS MPPT 60 A.

Correct me please if I'm wrong but the 6 panels being 250 W and 24 V each, that would be 3 parallel connections of pairs in series (3 x 500 w, 48 v), giving 1500 W in 48 V and 31,25 Amps. Theoretically making it possible to rely on the MS MPPT45 A to change it back to 24 V to charge the batteries ?

It's sure tempting in writing (if I'm not wrong...) but I confess I'm afraid playing with different tensions could be a factor of troubles for a newbie like me. It almost seems like magic...
Is it really possible ? Or is there another simpler way to achieve that ?

Like I wrote before, the fuse and breakers part is a main concern cause I understand how important it is but that's about all...
To be on the safe side, I'm planning 2/0 wire between batteries and inverter, and, if it's possible, 10 or 8 AWG everywhere else.
Everything is gonna be close enough together (furthest panel at 6 meters from CC and the rest in a 4 m2 room) so I hope loss shouldn't be a problem.

I'd gladly have a look at anything "generic" you think is worth pointing me to, even if it's just to have a better grasp of that part.

I'm anyway open to anything you'd suggest. I have time to think things trough. There's still a long way to go as panels and batteries are still in the main island Tahiti and I'm in Raiatea. Meanwhile, I'll have to build something secure and sturdy to keep everything protected from sea mist, lizards and bugs... But I can't wait for the day the system will be working...
Thanks a lot in advance for your answer.

[paulcheung]

You don't have enough panels to charge 1220 amp hour battery bank at 24 volts. you need 3000 watts panels power to charge the battery bank minimum at C/12 rate. you either have to get 6 more panels or a large enough generator to stir the Electrolyte in the battery before you kill them prematurely. Fuses and breakers are the least of your problem right now. for being on an island maybe you can check for a wind turbine to assist.

[Hava'i]

Thank you for your answer and your advice Paulcheung but I'm not too sure about that.
A friend in another island has a 1200 W panels array charging a 1320 Ah battery bank and his system has been working perfectly for 12 years now.

I would just have duplicated his system but the combiner boxes and CC box are impossible to open without him loosing his guaranty.

Like almost all the ones around here, his system has been installed and loaned to him by BP Solar(now Apex energy) and they're the ones doing the maintenance, with the keys to the boxes.
If it sounds like it makes no sense it's normal : don't forget we're French...

The good thing is he has at least access to the inverter and to a lever that turns the whole thing off in case of problem. It happened once cause a lizard entered the inverter which isn't even bug-proof. It made some nice sparks but except for that it's been working really good without generator.

Maybe because we have a lot of sun here but I'm sure Jamaica has about the same.

It's not even worth talking about the prices of wind mill here, you'd think they're solid gold...

Thank you again.

[paulcheung]

Your friend system is 24 volts or 12 volts? that is a lot of difference. Also is his batteries Lead acid batteries? Does he has generator? May be he just use the top 10 percent of the battery bank each day.

[Sunking]

I've already purchased 6 x 250 W poly Solarworld panels and a 24 V battery bank composed of 12 x 2 V 1220 Ah (I haven't fill them with acid yet).

Don't fill those batteries yet because you have some issues to work out first before you go live. One issue is you do not have enough panel wattage to support your batteries. Either you are going to have to obtain another 6 panels for a total of 2500 watts and use two charge controllers, or exchange/return the batteries for 600 AH batteries.

Another option which is going to be required is a 6 KW generator with a 24 volt 150 amp charging rectifier.

For the CC, I'd have loved a Morningstar MPPT (the epoxy coating of its electronic would have been a major plus windward and 500 m from the sea...) but they don't have the Amps I need.
So I'm hesitating between the Midnite Solar 200 and the Outback Flexmax. The price is going to be a decisive factor as both have good reputation.

Don't paint yourself into another corner like your panel wattage battery issue. Don't worry about that until you resolve what you are going to do about the panel wattage/battery/generator issue.

I know you said in a later post you were not going to use a generator because fuel and generator are expensive. Unfortunately a generator is required. Even though they are expensive, so is replacing dead batteries if you do not have a generator. Kind of like saying we want another baby and wife is pregnant, but we cannot afford another kid so we just will not feed the baby. Either way slow cruel death sentence.

[Hava'i]

Thanks to both of you for your answers.

Paul, my friend's system is 1200 W and 24 V (panels and batteries) and he never had a generator. I know his batteries were guaranty for 8 years but the BP Solar guy came to check after 10 years and the acid testing still gave 1.23 (1.26 the first year) it's been 2 years now and they were at 1.21 at the last maintenance so they're gonna change them soon. I know he's very conservative with energy but I'll have no problem being the same.

Thank you for the advice Sunking. I knew I had issues to fix but never thought the batteries capacity would be one of them... More the opposite.
I know that I know nothing but I can't help seeing all the BP Solar system (like my friend's) around the island working fine.

It's just too bad we can't have a look inside. One thing is for sure, they've been around since 2002, the year they sold the system + maintenance deal. I know 10 people who have the same and not only one has a generator... What's more, the efficiency of their BP panels is 13.8% and mine should be 15% minimum. I don't know what to say.

They don't even sale this kind of batteries here. The guy I bought them from imported them from Germany.
Looks like I'm not about to fill them soon...

Thank you again.

[Sunking]

Paul, my friend's system is 12200 W and 24 V (panels and batteries) and he never had a generator.

What AH capacity are the batteries?

[Hava'i]

Sunking,

His batteries are 1320 Ah. That's why I thought it wouldn't be a problem at all as I would have had more W and less Ah...

I didn't want to go too much into that but the real issue here is, like most of the time, money.

A good 6 KW generator here would cost more than our yearly income.

The deal for batteries and panels was so good that we took a loan for it and for what I was planning to buy to complete the system.
And we have 2 kids in college in France...

I'll think about it.

Thank you.

[Sunking]

Paul,

His batteries are 1320 Ah. That's why I thought it wouldn't be a problem at all as I would have had more W and less Ah...

I am not Paul

But you are really way off on your numbers. You state your friends panel wattage is:

Paul, my friend's system is 12200 W

You said your system is 1500 watts. 12,200 watts is over 8 times more power than 1500 watts.

[Hava'i]

I'm sorry Sunking, my mistake. Makes me feel even dumber than I am...

His system is 1200 W (8 x 150 w). I hadn't seen I had typed twice the 2.

His batteries are flooded lead batteries 12 x 2 V units 1320 Ah each, made by Exide

If other solar systems on the island were not working so fine I'd have suggested to their owners that we buy a generator together.

If I never go under 80%, how often should it be run to preserve the batteries ?

There's a guy who rent a 4 kW 50 $ for 2 hours....

The worse part is that using your thread about how to size an off-grid installation (thank you a lot for it, it's really useful and clearly explained), I estimated a 600 Ah battery bank in 24 V would be enough for my needs but I thought it would be even better to have a reserve for cloudy days.Talk about cleverness...

[Hava'i]

I want to say I'm very grateful to all of you for sharing your knowledge with me so please don't think I don't believe what you tell me about the need for a generator.

It sure came as a shock as it was totally unexpected. Like I said before, not one owner of BP Solar systems here has ever used a generator on his battery pack.

I did some checking today. There's been 108 BP Solar system sold in the entire French Polynesia. Some owners have had to change the pack before others because they were using too much current but none before 8 years. Some have small generators to run the washing machine but they've been forbidden to use it on the batteries.

The Apex maintenance guy told my friend he was using his system the best way possible, and that the batteries were often in floating mode in which 4 of the 8 panels are turned off. Could it be that engineers at BP found a special way to set their CC...

I'm just giving these info so you have more elements to ponder. The sun sure can't be stronger here than in the U.S.

In Tahiti, there's another company named Sunzil selling quite the same system. They have the same battery bank but 1500 w of panels array and they say like BP Solar not to use a generator on it. If you think of something you'd like to know I'd be glad to look or ask for it.

Thank you.

[Hava'i]

Hi guys,

The news of inadequacy between my battery bank and panels put such a gloom on me that I phoned the German company that makes them (Hoppecke).

I told them about what I've witnessed here in French Polynesia and what I've read and been told on forums.

Knowing you're real experts in these things I couldn't understand how badly maintained batteries (BP/apex maintenance job is terrible...) could last so long here.

They said you guys were absolutely right for all regular batteries and most deep cycle batteries but that a few brands like Exide and Hoppecke make stationary batteries that don't need to be regularly "boiled" to keep electrolytes active. That kind of solved the mystery and somewhat calmed me down...

http://www.hoppecke.com/energy-storage/lead-acid/opzs-solarpower.html

They also said the same things I've learned from your forum, that's what proved to me they really knew something about batteries
Just in case someone's interested, there's apparently also a way to stir electrolytes by injecting air in batteries.

[Sunking]

The issue with generators is not to stir electrolyte up as that is the panels daily job. Generator is used for:

• Monthly Equalization preventative maintenance routine. Not sure what your minimum Sun Hours are where you are at, but it could be possible enough.
• After a couple of cloudy days you have to run on a generator to get the batteries charged back up, or else go dark.