So did you get all that wiring you installed after the inspection re-inspected?
pdc1,
Aug 14, 6:18am
Hey muzz, any news on the batteries? Don’t get too bothered by all the crap that one or two people are generating! They can’t even comprehend that this is just a little added luxury to a weekend hideaway and not a full on residence!
The biggest elephant in the room at the moment appears to be the question of what voltage that you are running? Panels specs could allow for 24 volt battery system. Can you confirm that the two batteries are in parallel and everything gets drawn off them at 12 volts, or do you have the two batteries in series and charge as 24 volts?
If they are wired in series to get 24 volts, what voltage are you lights and inverter? I hope you aren’t going to say that they are 12 volts, or that you have items that are 12 volts taken from one battery
aredwood,
Aug 17, 11:22pm
No wonder your batteries are stuffed. As the solar controller should not be letting them get anywhere near 35V.
Also using a PWM controller on your panels drasticly lowers the amount of power that they will provide. Assuming the panels have been wired in parallel, they will be providing max of around 245W. And in series - 122W. This is because solar panels behave as a constant current power source.
Your panels are the type that is actually designed for use with grid tie systems. This is because they have a high output voltage and low current. You HAVE to use an MPPT controller with these type panels, to make them work fully on battery systems.
Also, typical output on cloudy days is only around 10-15% of whatever the rated output is. So during cloudy weather, you would only be getting max 78W output, instead of 520W. If it is cloudy all day, then your panels won't output anywhere near enough to fully recharge your batteries. Even if you do have the correct controller.
Can you confirm if your batteries are wired in series (24V system), or parallel (12V system). And are your solar panels wired in series or parallel? If you are unsure about the panels, temporally disconnect the solar panels from the charge controller and measure how much voltage you get from the panels (during the day). 35V = parallel, 70V = series.As this affects what MPPT controller you should buy.
fungles,
Aug 18, 10:19am
We are still waiting to discover if the system is 12 or 24 volt. Lets straighten out even more misinformation. Panel wattage remains the same whether in parallel or in series, the voltage/current changes only. Parallel 12 volts at 520 watts = 48.3 amps,series 24 volts at 520 watts = 22 amps. Thats why higher voltages use less current to supply the same power,.this increases efficiency. Your open circuit voltages are wrong too, a 12 volt panel will peak at around 20 volts, a 24 volt panel, or two 12 volt in series will peak at around 37. God give me strength.
muzz67,
Aug 20, 7:28am
UPDATE! Been away last week for work. Tested deep cycle batteries by fully charging and putting 4headlights on. One batt died in minutes, other one lasted 30minutes. Rooted I think is the technical term. Aredwood is correct,, panels are far too high voltage for controller. I disconnected one panel and voltage stayed high at 31v, amperage halved so parallel. So going to need 2 batteries and a much better controller. Expensive lesson.
intrade,
Aug 20, 8:58am
yea well if you dont listen and think cheap crap works You find out the hard way. i live rural here i had no power from 1990s till 2002 from 1998 onwards i had a 110 meter long 3 joined power cords from the naigbour. Because solar dont works and especially not in that time where i paid 450$ for a 5 year old bp solar cell . and used 2 year old deep cicle battery from a jacht . it just dont works there was not eaven led lights back then. So the drain was emense . had a generator then the extension cords lol. While today you could make it work if you use the right stuff and only do minimal loads -efficient charge i still have the solar charger from back then sunpower-plus i think it is. of no much use i would say today might test it if i ever learn it all and have expensive test gear. maybe my automotive scope could test it also if i find time i keep it seems to still work .
pdc1,
Aug 20, 9:20am
sounds like you are well on the way for stuffing the next batteries. one poster has managed to solve the problem even though the controller specs allowed the voltage of the panels. I think you have more fundamental problems that caused two rooted batteries in such a short time, but it is hard to help without even basic knowledge of supply voltage to your equipment. Could well be a controller fault, but could be other factors - Good luck
fungles,
Aug 20, 11:27am
Im picking the panels are wired as a 24 volt system, the batteries connected as 12 volts, and the poor old controller has suffered as a result. That is the only way 35 volts can appear across these batteries. You are correct though, we are short of facts to support any theory.
intrade,
Aug 20, 12:16pm
solarex sc-18 is my solar controller that i still have from the 90s i go look i doubt my one is chinesium as alibaba sells exactly the one i have . as i doubt a chinesium crap would last more then a year with circuit boards not flux cleaned as they do and use the cheapest of the cheapest onhanglow things inside and cut corners where ever possible. You be amazed how chinese manage to make stuff work with cutting every last corner. of course savety and longifity is completly gone like that also.
fungles,
Aug 20, 12:58pm
Intrade, i design, manufacture, and repair electronic devices for a living. The Chinese produce some dodgy stuff, as do the British, the Americans, and even the Germans, either by design or accident, I can even give examples. It is unfair to make these sweeping generalisations based on what you see on the internet, a medium primarily focused on views, thumbs ups and subs. The Chinese are world leaders in electronic design and manufacture, electric cars and solar energy, they got that way because they are good at it. They also lead in battery technology, and manufacture. They are also the largest user of solar and green technology, much of this information is not found on a US based youtube or google search engine.
aredwood,
Aug 21, 1:59am
I am using the panel specifications that the OP posted. They said that the open circuit voltage for 1 panel is 35V. If the panels are wired in series, then 35V + 35V = 70V. It is just simple maths.
Also compare the working current and the short circuit current. Note that those numbers are close together. Try connecting such a panel direct to a 12V deep cycle battery. In full sun, the panel will still only put out around 8A. Even though the battery terminal voltage won't go over 14V or so. This means that the panel output would only be 112W or so under that situation. To get the full 260W, the panel would have to output 18.5A. But even in a short circuit, the panel specifications say that it will only output 8.92A. So there is no way that you would magically get 18.5A without the correct controller.
A PWM controller simply connects the panel directly to the battery when the battery voltage is less than the set point. So the panel voltage will fall to closely match the battery voltage. And the controller will then pulse the panel on and off to regulate battery voltage when the set point is reached. Which is why most of the panel output is wasted with such a controller.
A MPPT regulator maintains a relatively constant panel voltage.And it constantly varies the panel current, to keep the panel operating at its max power point. While the output current of the MPPT regulator will vary based on how much sun the panel is getting. The panel voltage doesn't vary much.
The OP will have a similar panel to the Simax 270W panel from AA solar.
Also look at the power Vs current graphs on that page. You will see that they don't follow Ohms law. And instead they behave as a constant current source.
aredwood,
Aug 21, 2:05am
Edit, I realize that the 35V should actually be 38.08V Meaning X2 would be 76.16V But I'm sure that you can still see my point. As it is only to figure out if the panels have been wired in series or parallel.
fungles,
Aug 21, 1:18pm
The information we have is sketchy. One panel pushing out 35/38 volts is a "24" volt panel. If we assume the panels are in parallel, and the batteries in series, we have a nominal 24 volt system. this is yet to be established. If then, the batteries were sitting at 35 volts, this could indicate the controller has had its float voltage set too high, perhaps set to equalising mode, and there is no fault per se, the batteries have simply been overcharged for a long period, or, it may indicate the controller has shorted its Mosfets. applying the full panel output voltage to the bank Yes, a 24 volt panel will put out a fraction of its current when mismatched into a 12 volt battery bank, but over time, and remember, this system is used/loaded infrequently, even with that inefficiency, the batteries will eventually be trickle charged to whatever the controller will allow, in this case, 35 volts. We could successfully solve this riddle by taking comsolve's approach, when after declaring the problem is obvious, then sets about blaming the batteries are too small, the panels are inadequate, the electrician is to blame, the controller looks like junk, and of course, the lack of "paperwork", or compliance or something. Seems he has all bases covered. I think he even questioned the sunlight. We need more info here to confidentally solve this.
muzz67,
Aug 21, 5:40pm
Hang on guys,, I've put up wrong info. surprise surprise. these are the details of the panels we ENDED UP with
STC Power Rating 260W Imp 8.5A Vmp 30.7V Isc 9.01A Voc 37.8V Maximum System Voltage 600V
All in all, it's a bloody shambles. Sparky (mate) had worked on several grid-tied systems and had organised with local supplier for suitable panels for off grid, but I've picked up the wrong ones and not noticed. Too late to bitch about it now.
johotech,
Aug 21, 7:01pm
It shouldn't matter as long as you have a good solar controller. A good controller can work on solar Voc up to over 100V, with between 12 to 48V on the battery side.
aredwood,
Aug 22, 9:45pm
Just buy a proper MPPT controller. With MPPT, you no longer have to match your panel voltage to your battery voltage. (although panel voltage still has to be higher than battery voltage). With the right MPPT controller, you can have 120V coming from the panels, charging a 12V battery. You also get a big cost saving If there is a long cable run between the panels and batteries. As you can use a smaller size cable due to higher voltage and lower current.
comsolve,
Oct 19, 6:02am
Just remember with MPPT the input Voltage is Volts Open Circuit (Voc) NOT nominal Voltage (ie: "24V" panel) and it's at 25C.
So for a 150V controller, you can run 3x of your 37.8Voc panels per series string.
There is also a issue of temp adjustment but considering 3x 37.8 = 113.4V you have more than ample room so that won't be an issue.
But if your panels are around 45Voc as mine are, then you are getting close to the wind and should also consider what the Voc is at the lowest temp for your area.
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