Need help sizing a portable solar system - Page 2

Xringer · 07-19-16, 10:31 AM

My Deep Cycle batteries are 5.5 years old now.. At last check, they were still okay.
http://ecorenovator.org/forum/solar-...r-project.html

I check the water and add some if needed, at least once a year..

This system was built to run 120VAC pumps. In case of grid fail during a storm.
It works! It has stopped all grid fails during storms for 5.5 years!

I assumed the bank would last about 6 years.. So far, that goal seems possible.

creeky · 07-19-16, 02:14 PM

Your batteries "seem" okay. Try a discharge test.

The advantage to lifepo4 is that they will happily keep with no charging for a year. If you don't trickle charge your lead acid. What would you come back to after a year? And in the event of a grid shut down ...

The lifepo4 may cost 4 times as much. but you need 1/3 the capacity or less. and they should last twice as long, at least. of course they are also far more efficient when in use.

Now if you don't ever use the batteries. Hey you can put in whatever. I've seen a guy using lead acid for 17 years. His 12kw battery now keeps 3 led lights on and allows 4 hours of tv watching per weekend at his camp. Before they "flat." He calls that "working."

But if you're using the batteries lithium is proven and tested to offer the lowest cost per cycle that you can buy right now. And a 12kw lithium system would run a small house for that weekend with lights, tv, internet, dishwasher, fridge ...

which is what I call working.

Xringer · 07-19-16, 02:54 PM

Since I use an 800w space heater for my discharge testing, I normally do a test when it's cooler.
Around December. When the forecast for the next day is sunny..

If the voltage stays => 48 volts for an hour or two, I call it good.
Since the bank is getting older, The last December test was only for an hour..
I'm always amazed how cool the inverter stays..

I want to be able to run my pumps until the power comes back on..
It's normally back in less than an hour. If it's not back on,
and my basement is flooding, I'll get out the gas generator while
the bank still has some watt hours left..

oil pan 4 · 07-19-16, 10:29 PM

The last AGM battery (44ah) I used in my home made solar inverter generator lasted 3 years.
http://ecorenovator.org/forum/solar-...or-hybrid.html
Then I took that battery out because I needed a group 34/78 battery for my vehicle and wanted to upgrad to something bigger to power my inverter. So I went with a 100ah group 31 Marine deep cycle AGM.
I have been using the old 44ah in my vehicle for almost a year now.
The only batteries that last 2 years in a solar power systems are the solar power systems put together by the lowest bidder or by idiots.
If the same people used LiFePO4 in a solar power system I bet they wouldn't even last a year. If LiFePO4 batteries get ran down to the typical 10.5v inverter shut off a few times they will be ruined.

Assuming you want to use no more than 80% on a lithium and no more than 50% on a lead acid:
On batteryspace dot com right now you can get 60ah cells for $100 each (you need 4 to build a "12 battery") and you still need to build the rest of the battery. Or you could buy a 100ah AGM for $300 that is ready to go.

I would never use lithium in a stationary application. Its a waste of money.
Plus the lithium batteries not being recycled. They just get tossed, where lead acid are from what I have read "are the most recyclable consumer product on the planet".

In case anyone thinks I don't like lithium batteries or don't use them or don't know anything about them. I build and use them.
DIY: BYOB, for more power, a lot less weight - Diesel Place : Chevrolet and GMC Diesel Truck Forums
I use my 60ah LiFePO4 battery to power a samlex 2,000 watt inverter which I then use to power my Lincoln mig welder.
When the 60ah LiFePO4 polymer battery goes bad I am going to replace all the 20ah cells with 100ah prismatics.

Also if you run the LiFePO4 batteries dead or near dead one time you may totally kill them or seriously damage their capacity. Also charging them when the pack is colder than 20'F will damage their capacity, lose up to 20% in one charging. The good news is you only lose that 20% one time so after you damage it you might as well charge it whenever.
That's why my LiFePO4 batteries all have Anderson connectors so I can bring them in at night.

07-19-16, 10:31 AM	#11
Xringer Lex Parsimoniae Join Date: Feb 2009 Location: Woburn, MA Posts: 4,918 Thanks: 115 Thanked 250 Times in 230 Posts	My Deep Cycle batteries are 5.5 years old now.. At last check, they were still okay. http://ecorenovator.org/forum/solar-...r-project.html I check the water and add some if needed, at least once a year.. This system was built to run 120VAC pumps. In case of grid fail during a storm. It works! It has stopped all grid fails during storms for 5.5 years! I assumed the bank would last about 6 years.. So far, that goal seems possible. __________________ My hobby is installing & trying to repair mini-splits EPA 608 Type 1 Technician Certification ~ 5 lbs or less..

07-19-16, 02:14 PM	#12
creeky Journeyman EcoRenovator Join Date: Jun 2011 Location: a field somewhere Posts: 304 Thanks: 64 Thanked 44 Times in 31 Posts	Your batteries "seem" okay. Try a discharge test. The advantage to lifepo4 is that they will happily keep with no charging for a year. If you don't trickle charge your lead acid. What would you come back to after a year? And in the event of a grid shut down ... The lifepo4 may cost 4 times as much. but you need 1/3 the capacity or less. and they should last twice as long, at least. of course they are also far more efficient when in use. Now if you don't ever use the batteries. Hey you can put in whatever. I've seen a guy using lead acid for 17 years. His 12kw battery now keeps 3 led lights on and allows 4 hours of tv watching per weekend at his camp. Before they "flat." He calls that "working." But if you're using the batteries lithium is proven and tested to offer the lowest cost per cycle that you can buy right now. And a 12kw lithium system would run a small house for that weekend with lights, tv, internet, dishwasher, fridge ... which is what I call working. __________________ Current projects Chevy Volt battery pack conversion To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. Blog that is down right now but will return To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. Business where I sell solar stuff [url]https://www.bobolinksolar.com

07-19-16, 02:54 PM	#13
Xringer Lex Parsimoniae Join Date: Feb 2009 Location: Woburn, MA Posts: 4,918 Thanks: 115 Thanked 250 Times in 230 Posts	Since I use an 800w space heater for my discharge testing, I normally do a test when it's cooler. Around December. When the forecast for the next day is sunny.. If the voltage stays => 48 volts for an hour or two, I call it good. Since the bank is getting older, The last December test was only for an hour.. I'm always amazed how cool the inverter stays.. I want to be able to run my pumps until the power comes back on.. It's normally back in less than an hour. If it's not back on, and my basement is flooding, I'll get out the gas generator while the bank still has some watt hours left.. __________________ My hobby is installing & trying to repair mini-splits EPA 608 Type 1 Technician Certification ~ 5 lbs or less..

07-19-16, 10:29 PM	#14
oil pan 4 Land owner Join Date: Nov 2012 Location: NM Posts: 1,026 Thanks: 12 Thanked 127 Times in 107 Posts	The last AGM battery (44ah) I used in my home made solar inverter generator lasted 3 years. http://ecorenovator.org/forum/solar-...or-hybrid.html Then I took that battery out because I needed a group 34/78 battery for my vehicle and wanted to upgrad to something bigger to power my inverter. So I went with a 100ah group 31 Marine deep cycle AGM. I have been using the old 44ah in my vehicle for almost a year now. The only batteries that last 2 years in a solar power systems are the solar power systems put together by the lowest bidder or by idiots. If the same people used LiFePO4 in a solar power system I bet they wouldn't even last a year. If LiFePO4 batteries get ran down to the typical 10.5v inverter shut off a few times they will be ruined. Assuming you want to use no more than 80% on a lithium and no more than 50% on a lead acid: On batteryspace dot com right now you can get 60ah cells for $100 each (you need 4 to build a "12 battery") and you still need to build the rest of the battery. Or you could buy a 100ah AGM for $300 that is ready to go. I would never use lithium in a stationary application. Its a waste of money. Plus the lithium batteries not being recycled. They just get tossed, where lead acid are from what I have read "are the most recyclable consumer product on the planet". In case anyone thinks I don't like lithium batteries or don't use them or don't know anything about them. I build and use them. DIY: BYOB, for more power, a lot less weight - Diesel Place : Chevrolet and GMC Diesel Truck Forums I use my 60ah LiFePO4 battery to power a samlex 2,000 watt inverter which I then use to power my Lincoln mig welder. When the 60ah LiFePO4 polymer battery goes bad I am going to replace all the 20ah cells with 100ah prismatics. Also if you run the LiFePO4 batteries dead or near dead one time you may totally kill them or seriously damage their capacity. Also charging them when the pack is colder than 20'F will damage their capacity, lose up to 20% in one charging. The good news is you only lose that 20% one time so after you damage it you might as well charge it whenever. That's why my LiFePO4 batteries all have Anderson connectors so I can bring them in at night.