Solar systen needs help

mpk · Jun 22, 2024

Hi,

I have a greenhouse with a small solar system set up to run a small hydroponics system and I need help with it. I have 4 100 watt solar panels wired in series going to an MPPT charge controller to 5 100ah AGM batteries wired in parallel. I also have a 2000 watt inverter. The problem is I can only run 12v accessories on the system. Every time I try to plug something into the inverter it sets off an alarm. I know I probably overloaded it when I tried plugging in the pump and fans all at once so I tried everything one at a time. I could only guess that the box fan was about 200 watts on high and the pump only uses 7 watts of power. It seems like the inverter should be strong enough to power the pump at least. Is the problem my batteries? Should I have them wired in series instead of parallel ? I've tried doing this on my own with YouTube for help but I'm getting tired of things not working. I think I need real help.

Thanks,
Maria

Mattb4 · Jun 22, 2024

Some pictures of your setup would help. I will mention that 5-100ah batteries will be very difficult to charge and maintain properly off of only 400w of PV.

Supervstech · Jun 22, 2024

You need to show us what you are working with.
400Ah of batteries connected to 2000W inverter should have ZERO difficulties with 207Watts of load...

Unless the batteries are damaged, miswired, undercharged...

Post lots of pictures of everything you have wired up, and take voltage readings at the cc, and at each battery.

mikefitz · Jun 22, 2024

mpk said:
I think I need real help.

You may have the inverter connected to the controller output. The inverter should be connected direct to the battery via a fuse at the battery end of the positive cable.
If its a 12v inverter then keep the batteries connected in parallel.

mpk · Saturday at 11:14 AM

Sorry it took so long to reply. I expected to get an email notification and then I forgot about it. The smaller 50 watt panels are a different set up just powering 4 12v fans as an experiment

Thanks
Maria

Mattb4 · Saturday at 11:29 AM

The wires to your inverter are inadequate and unless I miss what I am seeing they are being fed by the load terminals from your SCC instead of directly from the batteries. SCC load terminals are only good for a few amps. (edit: your SCC shows 20a, or 240w worth).

Depending on inverter ratings you will need to install proper size cable and fuse protection from battery.

I expect if you have much inverter loads your solar panels are inadequate to keep your batteries charged.

mpk · Saturday at 2:53 PM

I have the inverter connected directly to the battery. I have a 12v timer connected to the scc that’s probably what you saw. What size wire do I need?

Thanks

Mattb4 · Saturday at 4:46 PM

For full loading of a 2000w inverter at 12vDC the draw can be 167a up to 200a. Cable to handle that load would be best at 1/0. Fusing would be 200a.

Your 5 AGM 100ah batteries, in parallel, if you only discharge to 50% would need 250ah X 12vDC = 3000Wh from solar In an average of 5 hours that would mean 600 watts worth of panels if nothing other than the batteries was being recharged in a day.

mpk · Saturday at 7:27 PM

Mattb4 said:
For full loading of a 2000w inverter at 12vDC the draw can be 167a up to 200a. Cable to handle that load would be best at 1/0. Fusing would be 200a.

Your 5 AGM 100ah batteries, in parallel, if you only discharge to 50% would need 250ah X 12vDC = 3000Wh from solar In an average of 5 hours that would mean 600 watts worth of panels if nothing other than the batteries was being recharged in a day.

Thank you. Just one mor question. When I connect the new cables can I connect them both to the same batter or does one have to be on the first battery and one on the last battery?

Thanks

42OhmsPA · Saturday at 10:54 PM

mpk said:
When I connect the new cables can I connect them both to the same batter or does one have to be on the first battery and one on the last battery?

Ideally you'd use bus bars instead of connecting multiple cables to the same lug.

littleharbor2 · Sunday at 3:17 AM

As mentioned by 420, bus bars are the proper way to go. For now though I would connect the charging and inverter to opposite sides of the #2 and #4 batteries.

mpk · Sunday at 6:07 AM

Thanks

outboard1196 · Sunday at 6:18 AM

mpk said:
Thanks

What are the specs for the panels ? The charger can only handle 100v I suspect you are very close to that and should re configure to 2s 2p

aliarifat794 · Sunday at 9:08 AM

Check for voltage drops when the inverter tries to start a load. If the voltage drops significantly, it may point to issues with battery capacity or connections. All connections should be secure and free of corrosion. Poor connections can cause significant voltage drops. If your inverter cannot handle the startup surge of your devices, consider upgrading to one with a higher surge capacity. Use a power management system to monitor and control the loads on your inverter and batteries. This can help prevent overload and extend the lifespan of your components. If you are eager to do DIY, you can try this solar panel monitoring system by yourself: https://www.pcbway.com/project/shareproject/DIY_Solar_Panel_Monitoring_System_V2_0_08c396e5.html

mpk · Sunday at 9:56 AM

outboard1196 said:
What are the specs for the panels ? The charger can only handle 100v I suspect you are very close to that and should re configure to 2s 2p

The panels are 4 100w 18.6v panels wired in series.

Thanks

mpk · Sunday at 10:14 AM

outboard1196 said:
What are the specs for the panels ? The charger can only handle 100v I suspect you are very close to that and should re configure to 2s 2p

The panels are 100w 18.6v wired in series. These panels are about 5yrs old would it be better for me to invest in a couple of 200w panels wired in parallel instead of the 100w wired in series?
Thanks

Mattb4 · Sunday at 10:33 AM

Since you are in Florida chances are you can get a better deal on larger wattage panels. For your 5 batteries I would suggest coming in at least 600w worth, preferably more, to keep the batteries charged adequately. You need to use Voc of the panels specs to properly decide if parallel or series connection is best. From that you need to size your PV wire for the amount of current (Imp) Series is easiest.

BTW: Reading back through your first post it is possible that your inverter is damaged. For small loads it should not alarm if you have adequate battery power even though your wiring to it is inadequate. Just guessing from the photo the wire size looks to be 10awg and that would be 30a at12vDC or 360w approximately it could carry. Pumps have startup surge but plugging in a simple light should give you indication if the inverter is able to work at all.

outboard1196 · Sunday at 11:37 AM

mpk said:
The panels are 100w 18.6v wired in series. These panels are about 5yrs old would it be better for me to invest in a couple of 200w panels wired in parallel instead of the 100w wired in series?
Thanks

Is 18.6 v the VOC or what you measured ?
Thats around 75v and should be ok
But do the calculation here to be sure .

Maximum open circuit voltage calculator

I'm posting this in a thread here since it might be useful for people. Please keep in mind that the below calculator contains bugs and doesn't do error checking - it's literally been 5 minutes to put together. Ok, so what does it do? It calculates the maximum open circuit voltage you would see...

diysolarforum.com

You will need more panel watts to keep the battery's healthy 600w is your max , I'd look into a bigger charger and more panels . or downsize your battery bank in the short term .

mpk · Sunday at 12:12 PM

outboard1196 said:
Is 18.6 v the VOC or what you measured ?
Thats around 75v and should be ok
But do the calculation here to be sure .

Maximum open circuit voltage calculator

I'm posting this in a thread here since it might be useful for people. Please keep in mind that the below calculator contains bugs and doesn't do error checking - it's literally been 5 minutes to put together. Ok, so what does it do? It calculates the maximum open circuit voltage you would see...

diysolarforum.com

You will need more panel watts to keep the battery's healthy 600w is your max , I'd look into a bigger charger and more panels . or downsize your battery bank in the short term .

18.6 is the VOC

littleharbor2 · Sunday at 12:46 PM

mpk said:
18.6 is the VOC

Is that measured or off the data label?

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