Power for two 50w LED 240v lights

[8626michael]

Hi
I want to power two 50w led 240v lights in a barn for around 5 hours per day.

I have two 250w panels, a 90ah 12v battery, a 100ah controller.

Is two panels this size enough (if they get the requisite light per day)? Would I need more than one battery? Is the controller big enough? What inverter would I need or would I be better sticking with 12v lights?

I’m in the uk, sorry for so many questions ?
Thanks

 

[rmaddy]

The first thing that will help tremendously is to replace the 240VAC LEDs with 12VDC LEDs. You can avoid a lot of expense by avoiding an inverter just for a couple of LED lights.

What do you mean by "100Ah controller"? Do you mean a 100A controller? That's seriously oversized for 500W of solar at 12V. You only need a 40A controller. Of course the bigger controller would allow you to add more solar.

Let's assume you get 12V LEDs that are 50W total (they would be big and bright at that wattage). 50W for 5 hours is 250Wh/day. Being in the UK you probably need to account for some days of little sun. So plan on the battery lasting 3 days. That's now 750Wh of battery for 3 days. You have a 90Ah 12V battery. Assuming it is AGM or LA you can use 50%. That's 90Ah x 12V x 50% = 540Wh. So it turns out that your battery can only power the lights for a little under 11 hours. Find 25W LEDs and you can double that to about 21 hours - or about 4 days without recharge if used for 5 hours per day.

If you use 50W of LEDs for 5 hours you use 250Wh/day. 500W of solar could, in theory, recharge that in 0.5 hours. Figure more like 45 minutes in real life depending on how the panels are mounted. Of course it would take longer in lower sun conditions.

Your battery and solar should be plenty if you can switch to 12VDC LEDs and keep the total wattage down at 25W total. If you really need 2 50W LEDs (even at 12VDC) then you will need more battery and probably more solar.

 

[8626michael]

The first thing that will help tremendously is to replace the 240VAC LEDs with 12VDC LEDs. You can avoid a lot of expense by avoiding an inverter just for a couple of LED lights.

What do you mean by "100Ah controller"? Do you mean a 100A controller? That's seriously oversized for 500W of solar at 12V. You only need a 40A controller. Of course the bigger controller would allow you to add more solar.

Let's assume you get 12V LEDs that are 50W total (they would be big and bright at that wattage). 50W for 5 hours is 250Wh/day. Being in the UK you probably need to account for some days of little sun. So plan on the battery lasting 3 days. That's now 750Wh of battery for 3 days. You have a 90Ah 12V battery. Assuming it is AGM or LA you can use 50%. That's 90Ah x 12V x 50% = 540Wh. So it turns out that your battery can only power the lights for a little under 11 hours. Find 25W LEDs and you can double that to about 21 hours - or about 4 days without recharge if used for 5 hours per day.

If you use 50W of LEDs for 5 hours you use 250Wh/day. 500W of solar could, in theory, recharge that in 0.5 hours. Figure more like 45 minutes in real life depending on how the panels are mounted. Of course it would take longer in lower sun conditions.

Your battery and solar should be plenty if you can switch to 12VDC LEDs and keep the total wattage down at 25W total. If you really need 2 50W LEDs (even at 12VDC) then you will need more battery and probably more solar.

Thanks for the reply, yes sorry it’s a 100a controller, it was only a cheap one from Amazon.

This might be a silly question, are 50w or 25w 12volt led lamps the same brightness/lumens as 240v equivalents?

How do you connect multiple panels are they just tee’ed into a two linear lines that go into the controller? Also if I added another battery are they just linked together in-line, pos to pos, neg to neg? I hope this makes sense!

 

[rmaddy]

Post a link to the charge controller and a link to your solar panels. Based on the specs of both you can determine whether the panels can be connected in serial or parallel.

Not sure about the brightness of LEDs. I would look at the specs and compare the rated lumens values.

Two connect two batteries in parallel you need a pair of wires. Connect the two positive posts together and connect the two negative posts together. Connect your loads to the positive of one battery and the negative of the other battery. You do not want the loads all connected to one battery. If you do then the two batteries will not remain balanced very long.

You should put together a schematic showing how everything will be wired up, including wire lengths and wire gauges, fuses, etc. Post it for review.

 

[8626michael]

This is the link to the controller - I know it’s only cheap and I may have to upgrade it if it’s not suitable. What do I need to look for on the panel spec to see if they can be connected in series?

Tbkoly 100A MPPT Solar Panel Regulator Charge Controller Auto Focus Tracking 12V/24V https://www.amazon.co.uk/dp/B09B9WX...abc_QB44KYAMAET0Y6R6EN5B?_encoding=UTF8&psc=1

 

[rmaddy]

You need to know the max input voltage of the charge controller. Then you need to make sure the Voc of the solar panels, adjusted for your coldest possible temperatures, can't exceed that input voltage. Remember that two panels in series will have twice the voltage of a single panel.

 

[Bud Martin]

This is the link to the controller - I know it’s only cheap and I may have to upgrade it if it’s not suitable. What do I need to look for on the panel spec to see if they can be connected in series?

Tbkoly 100A MPPT Solar Panel Regulator Charge Controller Auto Focus Tracking 12V/24V https://www.amazon.co.uk/dp/B09B9WX33H/ref=cm_sw_r_cp_api_glt_fabc_QB44KYAMAET0Y6R6EN5B?_encoding=UTF8&

From the link:
'Tbkoly 100A MPPT Solar Panel Regulator Charge Controller Auto Focus Tracking 12V/24V'
£11.90 for 100A SCC! How do they get away with these kind of craps? It is just as bad as EBAY.
That is faked MPPT SCC, it is PWM and I doubt that it can actually do 100A of charging current, just look at the size the terminals, no way it can handle 100A.

 

[8626michael]

That is faked MPPT SCC, it is PWM and I doubt that it can actually do 100A of charging current, just look at the size the terminals, no way it can handle 100A.

I did think it was too good to be true ?

I have it at present on one 250w panel, an 80ah 12v battery, 12v time and 6w 12v bulb. I presume it’s ok for that? What is Pwm?

 

[8626michael]

Hi

I now have 8 solar panels, please see rating image attached, do these need linking in parallel or series? Also can somebody please explain the difference in the two ways of connecting?

Sorry to be so dumb ????

Thanks

 

[rmaddy]

It all depends on the charge controller you get. Each panel has a Voc of 37.85V. You need to keep the combined Voc, adjusted for the coldest temperature you will encounter, below the max input voltage of your charge controller.

With 8 panels you can wire the panels in 8S, 4S2P, 2S4P, or 8P if you have an MPPT charge controller. 8S would require a controller with a max input voltage of 360V. That's a lot. At 4S you need one that can handle 180V. That's still a lot. At 2S you need 90V. That's easy. So 2S4P is likely your best option.

Remember that things in series add voltage. Things in parallel add amperage. Panels in series tend to provide a little more benefit in lower light conditions. Panels in parallel are better when there are shading issues.

 

[8626michael]

Thank you. Are there any books or resources you could recommend to me as a beginner, so I can learn the basics please and maybe view diagrams of wiring panels in parallel and series etc?
Thanks

 

[rmaddy]

Will's book is probably a good start:

Official Site of "Mobile Solar Power - Made Easy!"

Building a vehicle mounted solar power system? Let me help.

www.mobile-solarpower.com

 

[8626michael]

Thank you ?