lithium batts. not recommended

hillside · July 17

My 2 small stand alone systems have been working great for some time now but I need to install 4 new batteries and the Rolls I bought last year for the other system are not available. I'm using Renogy cc's and they do not recommend using lithium batteries. They don't say why...finding batteries on the island is hard enough and the lithium's are more widely available. What's the risk?

manzanita2 · July 25

I'm no expert, but here are my thoughts:

How old are your charge controllers? Do they have the programming that would allow them to charge LiFePo4 batteries? Lithium batteries do not use the same charging routines as Lead Acid batteries.

Lithium batteries would not be ideal if your weather gets very hot. I don't remember the high temperature limit. Perhaps about 110 to 115 degrees F. If your temperatures get very cold the batteries often need to be heated before they can accept a charge without damaging them. One manufacturer heats their batteries to 41 degrees F before the system will allow the batteries to be charged.

So if your charge controllers can charge lithium, or be updated to charge them, and your temperatures are managable, then lithium might work for you.

A final thought:

Many charge controllers for lithium have communication cables that connect with the electronics in the lithium batteries which allows the electronics in the batteries to communicate the status of the battery. It is possible to charge lithium without the communication cable, but I don't know any details about that.

hillside · July 25

Thanks...the charge controllers are a couple years old and in the manual they show settings for Sealed Lead Acid, Gel, and Flooded batteries only.
As for weather, we're in the central Caribbean. It rarely gets much over 92* and below 65*F. Stays in the mid 80's most days.
It's interesting to see the effect that a slight bit of cloud cover produces more voltage than straight open blazing sun. Panels being black get freakin' hot!

Dave Angelini · July 25

I have customers with various mixes of batteries. They are all 16 cell lithium iron phosphate and as long as somebody is paying attention you are fine.

All in parallel, set 55.2v absorb set for six hours with zero end amps. You must see the battery state of charge for each bank. When the individual battery state of charge variation gets too large, run an equalize session getting the battery voltage up to 56 V.

This is not a set and forget! There must be an adult in the room. I do not use Renogy and so that is your job to make sure it is going to work.

This strategy is basically open loop charging. Closed loop would need matching the battery BMS to the the charge and discharge sources. The BMS in closed loop is networked to the other identical LFP batts internal bms. It is a superior way to use lithium and often very easy to implement. Good Luck !

Where in the central Caribbean? Sailed there alot on my Ketch and alot on Moorings charter boats.

hillside · July 26

Puerto Rico.
Thanks Dave. Just after I made the first post I was able to get new Rolls batteries and everything is back up and running well. Now if the hurricanes stay away...

manzanita2 · July 28

High winds and flying objects are not good for PV. Hope the weather is nice to you.

hillside · July 29

Thanks. The biggest array is 8 panels on posts about 5-6 ft off the ground and the other 4 are on the deck awning and they would be the ones I worry about the most. Hurricane Maria (2017) did very little damage to our place but I had less panels up back then. The National Hurricane Center is checked regularly and the only good thing about these is we get a week's notice ahead of time. Dec. 1 is the end of hurricane season.
Manzanita, Oregon?

manzanita2 · August 13

I'm not in Oregon. In California about 25 miles from the coast and halfway between Los Angeles and San Francisco , if that makes any sense. There are Manzanitas on the sheltered north facing parts of my property.

(And too close to the Gifford fire at the moment. Looks okay though.)

hemmjo · September 16

I found this thread searching for battery information for a mission I work with. We do not have unlimited funds so cost is a huge factor. I am aware that often, higher upfront cost saves money in the log run.

In 2014 I installed a system in the Dominican Republic. In 2015, installed a nearly identical system in a different building on the same property. The only difference is the 2014 system has some 12DC LED lighting, the 2016 system uses 120vac LED lighting. Location about 19.796189°, -70.893594°. The purpose of the systems is refrigeration, lighting, WiFi, and charging phones, computers, etc. When used PROPERLY, the systems can keep refrigeration going for 2 days with no sun, IF batteries are full when the sun goes down and people are prudent on the sunless days.

The components for each system are; Midnight Classic 150 charge controller with WBJR, KISAE SW1210 -12volt - 1000w inverter, IOTA DLS 55/IQ4 charger, 4-roof mounted Solar World 275w panels, 4-6v x 225ah Trace Batteries Flooded LA batteries. (we have also had Interstate and a couple of other brands that I am not aware of). We also had a Powermate 7000 generator and a Honda 2000i. The Honda grew legs and walked away. The Powermate is not functional at the moment.

Over the 10 years in operation, we have had to replace the batteries about every 2-3 years. Although we had one "caretaker" on the property that would not follow procedures which killed a new set of batteries in about 2 months.

We need to replace another set of batteries. I have been looking at LiFePo4 4 batteries. I am very excited at the prospects of something better than our previous Lead/Acid batteries. Over the course of the year, the typically varies from 68°F to 89°F and is rarely below 65°F or above 92°F.(from weatherspark.com)

The Classic 150 Charge controller is adjustable for various states of charge for volts and end amps, etc required for the LFP batteries

There is so much information, it is difficult to sift through it all. This is where I am at this point.

According to my calculations, our current batteries provide;

4 batteries x 6 volts x 235 AH = 5640WH,

5640 x 30% = 1692 usable WH.

If we switch to LFP. we might get 2, 12v -100AH batteries where 2 x 12 x 100 = 2400WH,

2400 x 80% = 1920 WH.

As I currently understand the on board BMS will shutdown the battery at preset limits of charge or discharge and current flow + or -.

I am NOT SURE yet what kind of batteries are available in the country. I have someone checking on that now.

(for now) Specific questions are;

1) Are LiFePo batteries really a bad idea?

2) Less battery can provide more usable power. Is this correct?

2) Do all LFP batteries have a BMS component inside or is an external one required for some?

3) Is a battery balancer required if connecting 2 batteries in parallel or does the BMS do that?

4) Dave wrote, "This is not a set and forget! There must be an adult in the room" What is required of this adult?

I may be be smart enough yet to ask more questions. Feel free to educate me. I am looking for some direction.

Thanks,

John

littleharbor2 · September 17

Something like this should fit the bill It is simple no multiple connections And enough power for your needs
https://www.eco-worthy.com/products/lifepo4-12v-280ah-lithium-iron-phosphate-battery-with-bluetooth

BB. · September 17

I have to go soon... A few quick answers.

1. There are a wide variety of LiFePO4 batteries available. From single cell to wire into a "Battery Bank". To complete "battery banks" with 12 or 24 of 48 volt output with integrated BMS (Battery Management System). To save money, many folks will purchase "bare cells", wire them into parallel banks, and add a BMS that meets their needs. With enough research, you could build your own bank... But this is not a "simple" task.

2. There are lots of different BMS options. Ideally, you should find one that can "integrate" with your Solar charge controller and give you the communications options you would need (WIFI, Bluetooth, etc.) and have the protection you need (over charge, over discharge, over/under temperature, over current, over/under voltage, etc.).

3. Note on your battery capacity numbers... Your 30% for lead acid does give you upwards of 3 days of "no sun" capacity and still have decent battery life (assuming you get them charging >75% by the 4th+ days).

Your 80% capacity for LiFePO4 calculations give you only 1 day of of storage capacity, then you need sun/Genset/turn off loads... You can certainly run 80% on Lithium, but this may not give you the system "resilience' you would need for a multi-day outage.

-Bill

lithium batts. not recommended

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