Advice on upgrading aging system on newly purchased off-grid property

[off.the.grid]

Ive just purchased an off the grid property with an old solar system that is pretty much at the end of its life.
There is alot to discuss, but I think its probably best to just provide the system specs and my observations on how its currently running.

I can provide photos if necessary.

Battery bank, 4x 6V Exide 6RP830 energy store batteries (830Ah each) configured as 24V theoretically is about 20KW.
Also a bunch of forklift batteries of unknown capacity have been added at some point in parallel to the existing bank, there are 12x 2V cells providing 24V although one cell is completley dead and the electrolyte has gone grey. This must cause some issues.

Now I have absolutely no way to tell what charge these batteries actually hold, other than going by the hydrometer that points to fair, somewhere in the middle. The forklift batteries are actually reading better.
The whole voltage readout on the bank reads about 25V or so with the charger and load disconnected. It was dropping off to around 23V if we were using alot of power during the day such as a pool pump and then the inverter would cut off and the alram sound.

The seller of the property told us if we wanted to run a toaster to turn on the generator. But with the battery capacity, we should not have had any issues. I have not as of yet performed any such load tests to see how it holds up, but we did have the system shut down once when running the pool pump and other water pumps one day, probably hit 700W or more at its peak i assume if our refrigerators were running.

Now on to the panels, at this time, I had not discovered there was a fault on the charging system and that only 2 panels were charging the whole system!
There is only 5 panels on this installation which would not be much to charge batteries of this capacity in a timely fashion.
There are 2x mitsubishi pv-AD180mf5 panels in parallel feeding a morningstar SS-MPPT-15L controller. Specs say these are rated at 180W each.
I was getting about 15-16A (according to the panel on the wall) output alone from this on a sunny day. Voltage output was reading about 49-50V
Now on to the other set of panels, there are 3 schott ASE-165-GT-FT/MC panels in parallel, this was not even working when I arrived.
After inspecting the switchboard, I found that a wire had corroded away and melted that lead to the solar controller, after repairing, its all working fine.
It looks like a bird or rodent had pooped on the wiring and caused some damage.
The controller is a morningstar TS-45 and when this was running, I got about 6A according to a digital readout on the panel.

Now the interesting bit is that the output from the other charge controller drops a bit when this one is running (all the charge controllers are in parallel)
So I dont really get that much overall gains from all the panels combined.
Is this possible that this is because it is detecting that the battery bank is almost full perhaps? I suspect its the case since the meter reads zero when the generator is charging.
What is the maximum charge current such a configuration of flooded wet cells can handle?

Now the inverter is a beefy unit and looks like its rated at 4400KW from what i can take. It also appears late model and recently installed.
This charges the battery bank when the generator is running.

It is a Steca HP-Compact 4400-24
Charge voltages with generator running is around 28.4V-28.9V
Voltage with panels charging is about 27.5V
Im not sure if these voltages are typical for flooded wet cell batteries or not.

Anyway, I have bought some golf cart batteries that are a modest 220Ah each, I have got 8 of them, so with 4 in series, then 2 strings in parallel should give me 440Ah which is almost 10KWh capacity which should be more than enough for my setup to tie me over for a few more years when I will be ready to upgrade to something far more substantial.
I am also considering adding more panels, not too sure how many more I need, but realistically im probably only getting 500-600W at best on a sunny day.
Ive been taking note of panel voltages to try and work out what im really getting.
They are obviously old panels with less efficiency than modern ones, but I dont see any harm in using them in addition to some new ones to bump up capacity.
I was looking at some Suntech STP 410W-24 panels, probably another pair would be enough?

Open to any other suggestions.

TIA

 

[Steve_S]

To be perfectly clear... ANY lead Battery can only be discharged to 50% DOD so the 800AH batteries at BEST will give you 400AH (when new). Grey or Muddy battery acid = Very Bad and crossing the line of useability most often. As the system had been handicapped with bad connections etc, it is Highly Unlikely that any of those batteries have been Equalized / DeSulphated in a very long time (that kills lead BTW).

WARNING:
If the Acid is Grey or Muddy White (not easy to tell) that is lead particulate floating in it and that will be causing internal issues within the cells. IF the previous owner ever used Regular Water (supposed to use only Distilled DeIonized water) there could be mineralization which is Battery Killing.

The worst part, is the Single Lowest/Weakest Battery in the whole assembly will RULE THE ROOST as it will be the limiter. This is WHY when commissioning a Lead Bank for Solar you have a very small window to add batteries. You just can plop 4 Fresh New in with 4 Old & Tired and expect much, the old & tired will immediately draw down the new ones.

The FACT that the guy told you that you have to run the genset to use a Toaster... Seriously ? That means the bank is DONE. My old Lead Bank (24V - 8 Rolls Surette S-550 Heavy Leads) can still run my house for 2 days from full and I am about to send it to recycle as I've converted to 1190AH of LFP. Lead was such a PITA.

SORRY TO SAY but from your description, this was not well maintained and bodged together with assorted material, I would hold little to no hope for those batteries (if he ignored shorted wires, what else will you find). I think you need to do a Full Reassessment of what is there, what is salvageable & what isn't and be prepared.

 

[Rednecktek]

Here's the shorter answer:

Step 1: Check you solar panels and connections all the way to the SCC. Make sure every panel is putting out somewhere near its rated voltage all the way past every joint and fuse and breaker. Disconnect them all wherever the panels come together for the SCC so you don't get false readings from string 1 while measuring string 2.

Step 2: Dump those batteries into the sun and start over with a fresh set. Even if you can only afford Wally World deep cycles, get a matching set of those and a jug of distilled water. If you can get AGM's, get those. If you can afford to jump to the rackmount LiFePo4's those are the best bang for the buck. Either way, walk away from any kind of used battery and don't even think of re-using those old boat anchors you have now.

Step 3: Check the performance on your charge controllers one at a time and independent from each other. If one is having issues it's probably playing havoc with the others.

Step 4: Fire up the BBQ and pull a cold beer out of your solar powered fridge running on your newly fully armed and operational solar power system.

 

[MichaelK]

Looks to me that the only thing worth saving is the inverter. Everything else is either trashed or obsolete. The charge controllers are older PWM, so I would replace those with a more modern MPPT controller. The panels can be disconnected and checked one by one for voltage and amperage. The batteries should go to the salvage yard. What are you getting in your area per pound for scrap batteries?

Here's what I would do. The golf-carts would not be my first choice, but they are workable. With 440Ah of storage, you really want to maximize charging so you can prolong their life. The primary reason why the original battery bank died is because of inadequate charging from the very start.

Those GC will want charging at up to 1/8 of C, which for two parallel strings would be (220Ah X 2 strings)/8= 55A

To get an honest 55A you'll need 55A X 25V charging X 1.175fudgefactor = 1615W of panels. Don't shop for panels online. Shop locally on your local site, for example Craigslist. Buy grid-tie panels with local pickup. What I'm seeing right now on Craigslist in my local area is 30V-250W panels for about 75$ each. I'm also seeing 290-300W panels in the 90-110$ range. Just select whatever's convienent and buy 1500-1600W of those panels.

You will need a charge controller that can handle 55+amps of current. You might look at Epever's 6415AN Tracer model. That has a 150Voc max limit. For a bit more money, you can get the 200V model.

https://www.ebay.com/itm/352895621778?hash=item522a37da92:g:pTYAAOSwQLZd9zji

I use Midnight200 controllers myself.

Let's say you are able to buy six 270W panels. Maybe they are 9A at 30Vmp . You could wire three of them in series to get 90Vmp. Their Voc might be somewhere around 120Voc? Wire the six panels 3S2P. You could mount your panels on rotating array frames, like what I have pictured below.

You might still be able to use your old panels. What I would do is disconnect each and individually test one by one and see what voltage they are putting out. You might be able to make a string of those, but wire them in only if you can match the voltage strings within 5% of each other.

With 220Ah of USEABLE storage, that's ~5.3kWh of power, so that's enough to keep the lights on and the refrigerator running

 

[Rednecktek]

What I'm seeing right now on Craigslist in my local area is 30V-250W panels for about 75$ each. I'm also seeing 290-300W panels in the 90-110$

You lucky bastard! Out here an old 75w panel is $120. The shipping for a pallet of used panels that I bought from Watts247 was totally worth it when compared to trying to buy anything locally in Western WA.

OK, as for the batteries you've got pretty much 3 options, and 1 of those is weather dependent.

1: LiFePo4 batteries, preferably the rackmount style are the best bang for the buck, especially when factoring the 20 years of lifespan. The only caveats are 1: they need to stay above freezing or you're gonna destroy them charging below that and 2: finding them in stock. If you can't get the rackmount style then there are LOTS of decently affordable (as in on par with AGM Golf Cart batteries, $400-ish) options, but pretty much none of them will protect the battery from freezing temps.

2: AGM Golf Cart or Deep Cycle batteries are good no maintenance all weather decent lifespan option if you don't have to tow them around anywhere. The biggest issue is that you can only get about 50% DoD out of them so your 220Ah battery is only good for 110Ah. That means you need to buy and house twice the physical batteries for the same run time. If you've got a bigger utility room then that's no problem.

3: Flooded Lead Acid Marine Deep Cycle batteries, Ala WallyWorld $100 120Ah bargain batteries. These are my first choice for ultra-low budget or Gotta-Have-It-Now systems because they're cheap and there is a WalMart around every corner. Yes, there is maintenance that needs to happen and you'll get really good at topping off with distilled water, and yes they're only good to 50% DoD like the GC batts, but they're only $100 and you can get 4 of those at 240Ah for the same cost as a 100Ah LiFe battery, and they don't care about the cold.

Just things to consider.

 

[MichaelK]

You lucky bastard! Out here an old 75w panel is $120. The shipping for a pallet of used panels that I bought from Watts247 was totally worth it when compared to trying to buy anything locally in Western WA.

I'm pissed right now because the good deals I was getting last year are gone! I was getting 250W panels for 55$ and 260W panels for 62$ Paying 75$ now is robbery!!!

The good news though is that I still have 1000W of those panels left that I haven't installed yet, so that's going to be a 2022 project. BTW, testing output, those cheap panels are the best performing panels I have. They outperform all the panels I paid retail for! I also tried to buy as many of those for the neighbors as I could carry. So, I got two other neighbors up and running with 500-1000W each of those panels.

 

[Jack Rabbit Off Grid]

good Info! Makes me feel better about my purchase.

I did a similar as the O/P. Bought an old off grid property with a failing solar system. Bulging L16’s that don’t hold a charge and only 738w of panels for 740ah bank.

 

[MichaelK]

Now I have absolutely no way to tell what charge these batteries actually hold, other than going by the hydrometer that points to fair, somewhere in the middle. The forklift batteries are actually reading better.

I may have been a bit hasty recommending you just scrap all your batteries. I should say that using a hydrometer to check the state of charge of lead acid batteries is the gold standard for ACCURATE state of charge determinations with lead-acid. A temperature-correcting hydrometer is the best choice.

It sounds like the forklift batteries could potentially might still be worth keeping. But, it will be important to determine their Ah rating, and their current state of charge. Most likely they will need a far heftier charge then the parallel strings of GC batteries.

What you might want to try before scrapping them is to at least get them charging on your new-and-improved system and see what happens? Perhaps getting an initial charge via the generator in the very early morning hours, then finish up with the solar followed by equilization towards the end the afternoon.

No promises, but you might just get lucky.

BTW, those Suntech might be a good choice, though I would not pay more than 1$/watt for new panels I would get four of them and wire them in 2S2P with a 150V controller, or 4S1P with the 200V controller to charge the GC. I'd guestimate you'd need at least double that to keep the forklifts properly charged if they are worth saving.

 

[off.the.grid]

To be perfectly clear... ANY lead Battery can only be discharged to 50% DOD so the 800AH batteries at BEST will give you 400AH (when new). Grey or Muddy battery acid = Very Bad and crossing the line of useability most often. As the system had been handicapped with bad connections etc, it is Highly Unlikely that any of those batteries have been Equalized / DeSulphated in a very long time (that kills lead BTW).

WARNING:
If the Acid is Grey or Muddy White (not easy to tell) that is lead particulate floating in it and that will be causing internal issues within the cells. IF the previous owner ever used Regular Water (supposed to use only Distilled DeIonized water) there could be mineralization which is Battery Killing.

The worst part, is the Single Lowest/Weakest Battery in the whole assembly will RULE THE ROOST as it will be the limiter. This is WHY when commissioning a Lead Bank for Solar you have a very small window to add batteries. You just can plop 4 Fresh New in with 4 Old & Tired and expect much, the old & tired will immediately draw down the new ones.

The FACT that the guy told you that you have to run the genset to use a Toaster... Seriously ? That means the bank is DONE. My old Lead Bank (24V - 8 Rolls Surette S-550 Heavy Leads) can still run my house for 2 days from full and I am about to send it to recycle as I've converted to 1190AH of LFP. Lead was such a PITA.

SORRY TO SAY but from your description, this was not well maintained and bodged together with assorted material, I would hold little to no hope for those batteries (if he ignored shorted wires, what else will you find). I think you need to do a Full Reassessment of what is there, what is salvageable & what isn't and be prepared.

You are confirming what I already suspected.

Im forgetting about the drain capacity of the batteries, didnt realise its only 50%. I can tell that with the few panels installed, that it wouldnt have been much power to charge all this!

I definitely think that replacing the batteries is the first step.

The owner did tell me to use distilled water and left me a container full of it and told me where to buy it from, but i get the feeling that these forklift batteries were just some old ones added to beef it up, which shouldnt have even been necessary, if those large 800Ah batteries were not working, then they must be pretty weak. It would have been better to have just swapped out the bank for the forklift batteries.

Looks to me that the only thing worth saving is the inverter. Everything else is either trashed or obsolete. The charge controllers are older PWM, so I would replace those with a more modern MPPT controller. The panels can be disconnected and checked one by one for voltage and amperage. The batteries should go to the salvage yard. What are you getting in your area per pound for scrap batteries?

Here's what I would do. The golf-carts would not be my first choice, but they are workable. With 440Ah of storage, you really want to maximize charging so you can prolong their life. The primary reason why the original battery bank died is because of inadequate charging from the very start.

Those GC will want charging at up to 1/8 of C, which for two parallel strings would be (220Ah X 2 strings)/8= 55A

To get an honest 55A you'll need 55A X 25V charging X 1.175fudgefactor = 1615W of panels. Don't shop for panels online. Shop locally on your local site, for example Craigslist. Buy grid-tie panels with local pickup. What I'm seeing right now on Craigslist in my local area is 30V-250W panels for about 75$ each. I'm also seeing 290-300W panels in the 90-110$ range. Just select whatever's convienent and buy 1500-1600W of those panels.

You will need a charge controller that can handle 55+amps of current. You might look at Epever's 6415AN Tracer model. That has a 150Voc max limit. For a bit more money, you can get the 200V model.

https://www.ebay.com/itm/352895621778?hash=item522a37da92:g:pTYAAOSwQLZd9zji

I use Midnight200 controllers myself.

Let's say you are able to buy six 270W panels. Maybe they are 9A at 30Vmp . You could wire three of them in series to get 90Vmp. Their Voc might be somewhere around 120Voc? Wire the six panels 3S2P. You could mount your panels on rotating array frames, like what I have pictured below.

You might still be able to use your old panels. What I would do is disconnect each and individually test one by one and see what voltage they are putting out. You might be able to make a string of those, but wire them in only if you can match the voltage strings within 5% of each other.

With 220Ah of USEABLE storage, that's ~5.3kWh of power, so that's enough to keep the lights on and the refrigerator running

One set of panels appears to be using an MPPT controller, the other set appears not, now ive measured the voltage of the panels and getting reasonable voltage up to 50V depending on how much sun and clouds with the first pair and about 28.8V with the other set of 3, but I need to take more measurements with these, as we didnt have full sun.

Going by the specs, the current is not matching what the meter is reading, but I currently dont trust the accuracy of this gear thats installed.
Im trusting my multimeter more.
Im wondering if the first pair of panels is actually wired in series if im getting 50V, because those modules are 24V each, either way, the panel meter reading about 16A and the voltage seems about right for these specs, the other set of 3 panels, the voltage was just shy of 30V, and the meter saying about 6-7A, but we had a little cloud.

Either way, they are putting out power, I think its probably best to replace the controllers on those panels if I keep them.
As you say, I will need to get up on the roof and test them individually.
Makes me wonder if I need to add more capacity to this battery bank, I want to run a pool pump (summer only) that uses a 190W motor, they say you need 8 hours a day which would equate to about 1.5KWh. I can cut this back to 6 hours if necessary

You lucky bastard! Out here an old 75w panel is $120. The shipping for a pallet of used panels that I bought from Watts247 was totally worth it when compared to trying to buy anything locally in Western WA.

OK, as for the batteries you've got pretty much 3 options, and 1 of those is weather dependent.

1: LiFePo4 batteries, preferably the rackmount style are the best bang for the buck, especially when factoring the 20 years of lifespan. The only caveats are 1: they need to stay above freezing or you're gonna destroy them charging below that and 2: finding them in stock. If you can't get the rackmount style then there are LOTS of decently affordable (as in on par with AGM Golf Cart batteries, $400-ish) options, but pretty much none of them will protect the battery from freezing temps.

2: AGM Golf Cart or Deep Cycle batteries are good no maintenance all weather decent lifespan option if you don't have to tow them around anywhere. The biggest issue is that you can only get about 50% DoD out of them so your 220Ah battery is only good for 110Ah. That means you need to buy and house twice the physical batteries for the same run time. If you've got a bigger utility room then that's no problem.

3: Flooded Lead Acid Marine Deep Cycle batteries, Ala WallyWorld $100 120Ah bargain batteries. These are my first choice for ultra-low budget or Gotta-Have-It-Now systems because they're cheap and there is a WalMart around every corner. Yes, there is maintenance that needs to happen and you'll get really good at topping off with distilled water, and yes they're only good to 50% DoD like the GC batts, but they're only $100 and you can get 4 of those at 240Ah for the same cost as a 100Ah LiFe battery, and they don't care about the cold.

Just things to consider.

OK, i was looking at all these battery options too and long term I will likely go with lithium when I intend to upgrade to a full 10KW system when i renovate the house, currently I am only needing to keep a fridge and pool pump running in summer.
I also am not occupying the place every day of the week which helps keep the battery topped up when im away,

I ended up settling on the golf cart flooded cells because they were easy to get and available at the time and they were cheap.
I can tolerate topping up the batteries with water every week for the time being.
I only am trying to get this to tie me over for the next 2 years or so for the cheapest dollars until im ready to upgrade the whole system.

 

[off.the.grid]

Now I have absolutely no way to tell what charge these batteries actually hold, other than going by the hydrometer that points to fair, somewhere in the middle. The forklift batteries are actually reading better.

I may have been a bit hasty recommending you just scrap all your batteries. I should say that using a hydrometer to check the state of charge of lead acid batteries is the gold standard for ACCURATE state of charge determinations with lead-acid. A temperature-correcting hydrometer is the best choice.

It sounds like the forklift batteries could potentially might still be worth keeping. But, it will be important to determine their Ah rating, and their current state of charge. Most likely they will need a far heftier charge then the parallel strings of GC batteries.

What you might want to try before scrapping them is to at least get them charging on your new-and-improved system and see what happens? Perhaps getting an initial charge via the generator in the very early morning hours, then finish up with the solar followed by equilization towards the end the afternoon.

No promises, but you might just get lucky.

BTW, those Suntech might be a good choice, though I would not pay more than 1$/watt for new panels I would get four of them and wire them in 2S2P with a 150V controller, or 4S1P with the 200V controller to charge the GC. I'd guestimate you'd need at least double that to keep the forklifts properly charged if they are worth saving.

OK, so those hydrometers are fairly accurate? Its only a cheap one from the auto store, but I can test it on my new batteries as a reference I guess?

I dont think the forklift batteries are worth keeping since one is dead and I need to locate an identical spec cell of similar age.
These panels are well under a dollar per watt, and are very tempting to purchase.
Here is the link to them. I might just grab four of them, and then I could just scrap the rest of my old panels?

HIGH EFFICIENCY A-GRADE 460W MONO PERC 10BB SOLAR PANEL NZ$469.00 - NZ Solar Energy Solutions

www.sunnytech.co.nz

The question is should I grab a third set of these GC batteries to give me another 2KW of capacity?


EDIT:
Ive also forgotten to add that there was a wind turbine connected, it must have a charge controller hooked up at the other end, because it is going straight to the battery, however it only seems to be reading around 11-12V, so ive disconnected it in case its causing battery drain

 

[MichaelK]

These panels are well under a dollar per watt, and are very tempting to purchase.
Here is the link to them. I might just grab four of them, and then I could just scrap the rest of my old panels?

HIGH EFFICIENCY A-GRADE 460W MONO PERC 10BB SOLAR PANEL NZ$469.00 - NZ Solar Energy Solutions

www.sunnytech.co.nz

Oh, are you in New Zealand? Wonderful! I only get to see your country in the movies! Those panels look like a good choice. Buy four of them to get the 1600W of power you need. Because they have a relatively high Voc of 50.1V you should wire them 2S2P. With a 200V controller though you could wire three in series.

Ive also forgotten to add that there was a wind turbine connected, it must have a charge controller hooked up at the other end, because it is going straight to the battery, however it only seems to be reading around 11-12V, so ive disconnected it in case its causing battery drain

I don't have any experience with wind turbines, though what I understand is that you'll need a controller especially designed for one. You might want to look at the Midnight Classic series. I believe that they are designed to incorporate turbines.

I dont think the forklift batteries are worth keeping since one is dead and I need to locate an identical spec cell of similar age.

If one of the forklifts is dead, then don't bother.

The question is should I grab a third set of these GC batteries to give me another 2KW of capacity?

Before adding more batteries, I'd focus first on getting the new system up and running. I'm not a big fan of parallel strings of batteries. I consider two to be acceptable if you really have to, but three is likely to easily get unbalanced. I'd recommend working with the batteries you already have right now, but upgrade to larger off-gird batteries a few years down the road. Don't worry about adding water weekly. Check once a month, and maybe top off every other month.

 

[off.the.grid]

Oh, are you in New Zealand? Wonderful! I only get to see your country in the movies! Those panels look like a good choice. Buy four of them to get the 1600W of power you need. Because they have a relatively high Voc of 50.1V you should wire them 2S2P. With a 200V controller though you could wire three in series.

I don't have any experience with wind turbines, though what I understand is that you'll need a controller especially designed for one. You might want to look at the Midnight Classic series. I believe that they are designed to incorporate turbines.

If one of the forklifts is dead, then don't bother.

Before adding more batteries, I'd focus first on getting the new system up and running. I'm not a big fan of parallel strings of batteries. I consider two to be acceptable if you really have to, but three is likely to easily get unbalanced. I'd recommend working with the batteries you already have right now, but upgrade to larger off-gird batteries a few years down the road. Don't worry about adding water weekly. Check once a month, and maybe top off every other month.

Sure am from New Zealand!
Doing the maths, it looks like 1600W will be enough for what im using.
Yes I expect it may have a 12V controller installed, Im keeping it disconnected until I can get a better look at how its configured.

OK, about putting batteries in parallel, ive read a few things about this that its a bad idea, but unless you have a real high capacity battery, you dont have much option. It seems alot of systems are going for much higher voltages like 48V. Im not sure if my inverter can be used as 48V, but im assuming that may be a better option if it can?
How does it work with lithium banks where many hundreds or thousands of batteries are in parallel strings?

I have also read that to balance batteries in parallel that you put schotty diodes across each battery. Do you know much about this?

Thats good to know that the batteries should not require topping up too often, from what i understand, they will bubble lots of gas when being charged or discharged heavily.
My battery bank is currently bubbling away really hard when the sun is up.
It also will bubble away when in use which i guess is expected. The old owner said 20 litres of water was lasting him about 3 months.
I have no idea if this is too much or not, but I wonder if the system is overcharging?
Either way, I will have new panels and controller, so should not be an issue going forward.

Is 28.5V too high to charge flooded wet cells? Thats what I get if the generator charges them.

 

[Rednecktek]

OK, about putting batteries in parallel, ive read a few things about this that its a bad idea, but unless you have a real high capacity battery, you don't have much option.

The biggest issue is how you've got your connections wired up. Hopefully someone will throw a link to that article about how to wire them up for best lifespan and performance.

What I would recommend is getting a couple beefy bus bars involved. Wire up each battery bank to the bus bar so all the cables are the same length. Wire the SCC's to the bus bar. Wire the inverter to the bus bar. By making everything central to one point of contact you really cut down on the issues of drawing from one battery more than the others which helps your lifespan a LOT.

As for bubbling off your water, if 20l was only lasting a month that's a LOT of batteries or a LOT of hard charging, another sign the batteries are pretty shot. I add about 2L per year between my 4x 120Ah FLA's although they have much less cycle time than yours do.

 

[off.the.grid]

OK, thats helpful, looks like I have something to work with now anyway.
Is there any advantage in running solar cells in series vs Parallel?
100VDC is quite a high voltage I would have thought.

 

[Wibla]

Pictures are worth a thousand words, would be lovely to see some photos documenting this install, easier to give advice that way.

 

[Rednecktek]

Is there any advantage in running solar cells in series vs Parallel?

Mostly in voltage drop between the panels and the SCC is where you see the difference. Putting a lot of panels in parallel adds up the amperage from each panel, so by the time you've got a few panels out there you've got to have thick expensive wire between the two to avoid too much voltage loss from the length of wire. When you run in series you're only putting through the amperage of a single panel but you're doing it at a much higher voltage. Since wire diameter is based on amperage, the wire is MUCH thinner and cheaper to pump 5a across than 50a across.

For example, using 10 bog standard 100w panels at 20VoC and 5a each the math looks something like this:

10 in series is 200v at 5a. If you run a 14AWG wire you might see 3% loss. 3% of 200 is squat.

10 in parallel would be 20v at 50a which is a FAT expensive wire. Now you're 3% loss is from 20v which is much more significant.

10 in Series/Parallel in a 5s2p system would get you 100v at 10a which would save you a good chunk of money still and allow you to aim your strings in different directions if you want and that voltage drop is still well under control.

As long as the SCC can handle the higher voltage, you'll net more power running in series with a lower voltage drop over distance and not have to re-mortgage the house to afford the copper. The biggest key here is the math for your panels. Use the VoC number when calculating how many you could put in series and give yourself some wiggle room because panel voltage increases a bit when the panels get really cold.

The major down side to running in series is that if you have a string of panels and a shadow from a tree branch or dark cloud or sleeping cat or leprechaun butt or something covers even 1 panel in the string, that whole string takes a MAJOR hit in performance. That's one of the reasons a lot of people prefer to do multiple strings in parallel. If one string gets shaded, the other strings can still be working fine. You get the advantages of higher voltages to save on wire AND the redundancy to help with any shading issues.

 

[MichaelK]

Yes I expect it may have a 12V controller installed, Im keeping it disconnected until I can get a better look at how its configured.

Throw the 12V controller away. Get yourself a good MPPT controller. Pay attention to both the maximal voltage and maximal amperage while shopping.

OK, about putting batteries in parallel, ive read a few things about this that its a bad idea, but unless you have a real high capacity battery, you dont have much option. It seems alot of systems are going for much higher voltages like 48V. Im not sure if my inverter can be used as 48V, but im assuming that may be a better option if it can?

NO, you have a 24v inverter, so you need a 24V battery bank. But, there are many, many high capacity battery options. That being said, I'm in the US, and the shipping options all the way across the Pacific may be more limited. I myself have 568Ah Canadian batteries, delivered right to my driveway. I'm guessing that's not likely to happen in NZ?

How does it work with lithium banks where many hundreds or thousands of batteries are in parallel strings?

Li ,batteries typically have a built-in battery management system, or BMS, which controls battery performance. Plain old lead-acid batteries just get wired in series and you're done.

I have also read that to balance batteries in parallel that you put schotty diodes across each battery. Do you know much about this?I
I would skip the gimmicky strategies completely. I think RNT gave a very good explaination of both why series panels are good and also how a battery should be wired.

Thats good to know that the batteries should not require topping up too often, from what i understand, they will bubble lots of gas when being charged or discharged heavily. My battery bank is currently bubbling away really hard when the sun is up.

Rapid bubbling is a good thing. It keeps the battery acid mixed and prevents statification. The big enemy of lead-acid batteries is chronic undercharging. Get them fully charged each and every day, and you will have many years of service. I upgraded my own GC batteries after 5 years of service. I gave them to a neighbor instead of recycling them because they still had lots of life in them. Remember, under-charged lead batteries die a quick death.

It also will bubble away when in use which i guess is expected. The old owner said 20 litres of water was lasting him about 3 months.
I have no idea if this is too much or not, but I wonder if the system is overcharging? Either way, I will have new panels and controller, so should not be an issue going forward.

Well, no. Even with the newest, most sophisticated electronics, you still have to watch the water levels. But, I check maybe once a month, and then add water maybe every two to three months. I'd say watch your system closely for the first couple of months till you are comfortable your rate of water loss. Just leave a jug of distilled water handy at all times. Remember, distilled water ONLY.

Is 28.5V too high to charge flooded wet cells? Thats what I get if the generator charges them.

This should be determined by the battery manufacturer. Look up your battery on their spec sheet/webpage and see what charging parameters they specify. My manufacturer is Rolls/Surrette and they recommend a range of 2.45-2.50V per cell. With 12 cells per 24V battery that range works out to be 29.4V to 30.0V. Right now I've got my charge controller set to 29.6V, which seems to balance getting the batteries fully charged, without consuming too much water.

I believe your generator power is being passed through your inverter, so most likely, there's a menu item you can go to to adjust charging voltage. A new MPPT charge controller will definately be voltage adjustable. Look up the charging rate for YOUR battery and set the voltage charging parameter to that. Remember, there may be different voltages for bulk charging, vs absorb, vs floating.

 

[off.the.grid]

Pictures are worth a thousand words, would be lovely to see some photos documenting this install, easier to give advice that way.

Hope this is some help! It's a bit of a sight for sore eyes!

 

[MisterSandals]

EDIT: correction, i have the MPPT version.

I have that same Morningstar Tristar 45. If its as old as mine (2009 i think), it needs to have the firmware upgraded so that it will accept a charge profile for lithium batteries (like LiFePO4). Its fairly easy except for getting the correct DB-9 connecting cable and the Windoze machine to run MSView software. I can forward the docs that i got from Morningstar on how to do this if you proceed.

That charge controller is a true workhorse.

 

[MichaelK]

Well, save those battery cables! So sad to see those previously fantastic batteries abused the way they have been. Will your local recycling center accept old batteries? I'm guessing you have hundreds of dollars of lead sitting there.

In terms of making changes to the inverter, is there some kind of plug-in computer port on it? Without even an LCD screen, I'm at a loss to tell you how to change charging parameters?

What kind of time frame are you now looking at for getting your new system up and running?