Batteries to Panel Ratio

[Arizona1234!]

Hi, I recently purchased a cabin with an existing solar system. It definitely needs revamped and maintained but when I spoke to a local solar tech he said the amount of batteries to the amount of panels is not correct. He stated those panels can’t charge that amount of batteries? Does this make sense? I don’t know the watts of the panels. I believe the inverters are 3500w (one needs repaired) EA and 48v. Batteries lead acid 12v. There are 24 batteries. The cabin is 2800 sq feet, two people living there part time. Half the year. Appliances electric fridge, toaster, blender, microwave. Tv, star link router and general lights for the house. I don’t know the KWH.

Basically what I’m wondering is, do I really need new panels or is this guy trying to upsell me? He also recommends 10k of lithium batteries. Any advice would be appreciated! Thanks for your help!

 

[timselectric]

when I spoke to a local solar tech he said the amount of batteries to the amount of panels is not correct. He stated those panels can’t charge that amount of batteries? Does this make sense?

Not exactly.
There is no direct correlation between battery capacity and solar production.
They are both affected by your loads.
Basic system design is.
1. You need enough inverter to cover your largest instantaneous load.
2. You need enough battery capacity to cover your loads when there is no sun. For the desired length of time.
3. You need enough solar production to cover your loads and recharge the batteries.

 

[sunshine_eggo]

For lead acid, there is a range. It can be anywhere from 5-30% of capacity depending on type/brand of battery, i.e., if you had a 100Ah battery, you would only charge in the 5-30A range. If those are Trojans, you're likely limited to 13A. This value increases as you add additional strings of batteries in parallel.

Those look like 6V battery, 3 caps = 3 cells = 6V.
The tops are filthy and the terminals are corroded. It looks like there's staining around them from electrolyte or spillage. These batteries have been neglected and are not long for this world.

The array looks like 4 panels of one type and 2 of another. If the installer didn't match the panels properly, the array could underperform.

Based on their physical size, you likely have a lot of rated capacity. Visually, I would agree the array is undersized.

Remember the local solar tech wants to make money off you... We are a bunch of cheap bastids, so we want to save you money...

Big plus is Outback hardware - quality stuff.

What part of AZ?

 

[400bird]

I don’t know the watts of the panels.

They are all labeled on the back with a sticker. Get pics of both panel type of you can.

 

[Mattb4]

In the image of your panel backs there appears to be the specification label on several of them. You will want to know what that says. You will also want to know how much loads you intend to use on a daily basis with both the running and starting surge.

From a simple glance at your setup it is hard to say if the solar tech you talked to is giving good or bad advice. Age of the solar panels may be in play as well as that of the batteries. Without testing and a more thorough examination all I would say is your observation about "needing revamped and maintained" is spot on.

 

[sunshine_eggo]

If that's only a 1200W array, the local installer is right - that's likely too little charge current for that many batteries.

SWAG...

Just looking at the 12 batteries on the right... guessing about 350Ah, so it looks like you have 1000Ah @ 48V...

You need at least 50A of charging, 1200W/48V = 25A - way too little.

 

[Warpspeed]

Not exactly.
There is no direct correlation between battery capacity and solar production.
They are both affected by your loads.
Basic system design is.
1. You need enough inverter to cover your largest instantaneous load.
2. You need enough battery capacity to cover your loads when there is no sun. For the desired length of time.
3. You need enough solar production to cover your loads and recharge the batteries.

Tim has nailed it.

Only thing pretty much set in stone is choosing an inverter.
Hook it all up and see how it goes.
Actual results will depend on local climate and electrical usage patterns, both of which are difficult to anticipate.

Both batteries and solar panels can then be gradually upgraded over time, as funds and need dictate.
First get an inverter that is a fair bit larger than you think you need.
Load "creep" guarantees that over time your loads will tend to increase rather than decrease !

 

[sunshine_eggo]

@timselectric and @Warpspeed

I generally hate to disagree with you guys, but with lead acid batteries, you absolutely positively have to ensure your array size is appropriate for your battery capacity.

A 1200W array on what may be well over 1000Ah of 48V lead acid is going to encourage sulfation on every charge.

 

[timselectric]

@timselectric and @Warpspeed

I generally hate to disagree with you guys, but with lead acid batteries, you absolutely positively have to ensure your array size is appropriate for your battery capacity.

A 1200W array on what may be well over 1000Ah of 48V lead acid is going to encourage sulfation on every charge.

I don't disagree. My recommendations are more for a LFP chemistry.
But, that is a massively low amount of solar for a system.
When you can't charge the batteries. Without even having any loads connected. That's another downside to LA chemistry. The best way to make them last. Is to never use them.

 

[sunshine_eggo]

I don't disagree. My recommendations are more for a LFP chemistry.
But, that is a massively low amount of solar for a system.
When you can't charge the batteries. Without even having any loads connected. That's another downside to LA chemistry. The best way to make them last. Is to never use them.

That there's funny.

 

[Arizona1234!]

Thank you for everyone’s answers. In Flagstaff AZ. Looks like I need more panels and probably some Lithium batteries. My wallet isn’t excited ?

 

[Warpspeed]

Thank you for everyone’s answers. In Flagstaff AZ. Looks like I need more panels and probably some Lithium batteries. My wallet isn’t excited ?

Get yourself a decent inverter.
Extra panels and batteries can be added to a bit at a time.

 

[sunshine_eggo]

Get yourself a decent inverter.
Extra panels and batteries can be added to a bit at a time.

He has Outback inverter and charger. That not good 'nuff fer ya?!

 

[sunshine_eggo]

Thank you for everyone’s answers. In Flagstaff AZ. Looks like I need more panels and probably some Lithium batteries. My wallet isn’t excited ?

There's a chance what you have is usable, but it will require a lot of work on your part to sort through it. We can help, but you have to want to do it...

 

[seneysolar]

Based on the pictures, the panels look fairly new, but i see 2 different kinds and i only see one charge controller. I would start by getting rid of the 2 "add ons" that somebody did. The outback flexmax charge controller is good, should be able to keep it. Dont mix panels on a string or a charge controller. If you want to later you can wire those 2 on another separate charge controller.

Do i see 2 inverters but one is abandoned? If one 3500w inverter at 120v is enough, then you are in good shape there assuming it also works. Get rid of the other one and the duct tape cables, looks like it failed and someone took it out of the equation. Maybe talk to Outback about getting it repaired.

Now the batteries.... there is absolutely too many batteries there and by now they are likely sulfated and relatively useless. Youll get lots of opinions on batteries here, but if price is your driver than stick with lead acid. Max for that array is probably 1 string of 8 trojan L-16's. That will give you roughly 400amp hours @ 48v for maybe $3200. Given you are in sunny Arizona i doubt you will actually deep cycle those. Just keep them clean and full of water.

Once up and running, report back on what charge current youre getting from those panels.

 

[G00SE]

Thank you for everyone’s answers. In Flagstaff AZ. Looks like I need more panels and probably some Lithium batteries. My wallet isn’t excited ?

I would highly recommend northern Arizona wind and sun/solar-electric for a local business to inquire if that wasn’t who you already spoke with