lithium battery question

[ganto]

quick question bout solar and lithium batteries. i am planning on using lithium batteries in my house bank setup vs the typical agm batteries. i am being told that if i use lithium batteries that i will need a different charge controller since lithium batteries are a different animal over the agm batteries

 

[tx2sturgis]

Yep. Although some lithium batteries have a built-in BCM. Many of those are compatible with more or less normal chargers and solar controllers.

 

[jonyjoe303]

The lifepo4 12.8 volt lithiums are drop-in replacement for lead acid. All the expensive lithiums got the BMS built-in and will prevent the battery from going out of balance/overcharge/discharge.
The lithium powerpacks which are usually cylindrical (laptop) cells are usually 3s 11.1 volt (12.6 fully charge) packs those also have built-in BMS, but have to be slow charge because of their circuitry.

The only true solar charger that is lithium capable is the "electrodacus" but for 300 dollars it's not even mppt, and it's designer says mppt is not required. This charger actually balance charges the battery, so it is extremely safe for charging lithiums.
All the other solar chargers that claim to be lithium capable are not, If the battery goes out of balance and the BMS fails they will overcharge the battery. 

As long as your lithium has a good BMS, you can charge it with any controller. I charge my 3s 11.1 volt 94ah pattery pack with my 100 dollar 20 amp ecoworthy mppt. But you have to adjust the absorb voltage manually. For fast charge I set the absorb to 14.4 volts, to slow charge I set it to 13 volts (as low as it would go). If the battery is at 60 or less percent I fast charge it (up to 15 amps from 240 watt panel), once it gets to 90 percent I slow charge it (about 4 to 5 amps). I do this otherwise the fast charge voltage will give a false surface voltage on the battery and it will trip the BMS and the battery will be at 12.1 volts, By slow charging it, it wont trip the BMS too early.

I've been doing it this way for the past year, my lithium is running like a champ.

 

[VanKitten]

I have been researching this issue for a while. Been in chat with several people doing this off grid.

The Morning Star TS is the one I choose, The reason being that it will support the charging requirements of LiFePo4. It has four charge phases...programmable. No float if you choose.
The noticed shorter than expected life of LiFePo4 is likely attributable to charge controllers not delivering what the BMS really needs. Sure the BMS will protect the cells...but without the correct charge, they will not perform at top. They need constant current followed by constant voltage.

So...the BMS to properly handle it was more of a challenge. I finally settled on Darcus.

 

[IGBT]

As long as your lithium has a good BMS, you can charge it with any controller. I charge my 3s 11.1 volt 94ah pattery pack with my 100 dollar 20 amp ecoworthy mppt. But you have to adjust the absorb voltage manually. For fast charge I set the absorb to 14.4 volts, to slow charge I set it to 13 volts (as low as it would go). If the battery is at 60 or less percent I fast charge it (up to 15 amps from 240 watt panel), once it gets to 90 percent I slow charge it (about 4 to 5 amps). I do this otherwise the fast charge voltage will give a false surface voltage on the battery and it will trip the BMS and the battery will be at 12.1 volts, By slow charging it, it wont trip the BMS too early.

I've been doing it this way for the past year, my lithium is running like a champ.

Yuck.  I have not even looked at my Lifeline AGM batteries in 2 years!   I drain them to 70% most days and they are automatically charged back to 100% by solar.  Sometimes I drain them to 50% but solar still charges them full during the day.   No measurable capacity loss yet.

 

[ganto]

i'll be asking the manufacture tomorrow and see what they recomend as i am going for an 800 watt solar setup

 

[ganto]

I have been researching this issue for a while.   Been in chat with several people doing this off grid.

The Morning Star TS is the one I choose,   The reason being that it will support the charging requirements of LiFePo4.   It has four charge phases...programmable.  No float if you choose.  
The noticed shorter than expected life of LiFePo4 is likely attributable to charge controllers not delivering what the BMS really needs.   Sure the BMS will protect the cells...but without the correct charge, they will not perform at top.   They need constant current followed by constant voltage.  

So...the BMS to properly handle it was more of a challenge.   I finally settled on Darcus.

what model darcus did you get.. after reading some reviews on amazon they didn't seem to positive :huh:

 

[VanKitten]

I have prepaid the sbms60.

His timeline isn't as good as I would like...delivery somewhere end of next month. Meanwhile, I have not done any work on the cells.

My entire attention has turned to the needs of my Mom. No progress in weeks.

 

[frater secessus]

There is some evidence that Fractional C charging/discharging (as in RV and van use patterns) may not warrant BMS. 

I am in the process of organizing my notes from the thousands-of-posts LiFePO4 thread on the sailing forum.  SternWake and Bardo have spoken highly about some of the participants in that thread.

The notes are messy but there are footnotes folks can follow to see the primary info.

 

[frater secessus]

i am being told that if i use lithium batteries that i will need a different charge controller since lithium batteries are a different animal over the agm batteries

If the controller is reasonably accurate and has adjustable setpoints you should be good.  Li chemistries like to be charged then full stop;  no real absorption or float stages in the usual sense in Fractional C use.  We can fake that with a normal CC:

Vabs == 13.8v, 0 absorb minutes or as little as you get set it for.
Vfloat == something less than Vabs.  13.2v (20%DoD)?  Basically the bank should be able to come down off the full charge. 

Here is a list of how notable folks set up their controllers for Li.  BTW, I typoed Bardo (?) for Blars earlier.  Sorry about that, technoviking!

 

[Lisa Truck Gypsy]

What is BMS? I just bought the Anker 400Watt Powerhouse. Do you know if it has one of those built in.

 

[KathyC]

Anker is a very reputable manufacturer. They state the following on the Powerhouse:

"Safety Guaranteed: Battery Management System (BMS) undertakes voltage control, temperature control and more advanced safety operations, ensuring complete protection for you and your devices"

I think you are fine!

 

[frater secessus]

The noticed shorter than expected life of LiFePo4 is likely attributable to charge controllers not delivering what the BMS really needs.  

My reading suggests LFP capacity degradation is caused by high ambient temperatures (cf. Technomadia), charging higher than full (13.8v), or keeping the bank full for long periods.

 

[VanKitten]

It was really only a guess.

They were going to experiment with different configurations to make a better determination. That seems to be where their saga with lithium ended.

by getting the cells encased in aluminum instead of plastic the cells can shed heat better...also..nothing says all the cells have to be right next to each other. Since the battery takes up so much less room...why not leave a gap between rows of cells? Then a 12v fan would do the job. (Like those little ones they sell for computer circuit boards).

Also..not being warm enough can contribute to a shortened life. A small heating pad on a switch can help to fix that if you get caught in a cold climate. Like the little 12v warming pads you see sold for seed starting kits.

Then, get a charge controller that is going to delivery constant current, then constant voltage for the BMS

For an excellent website...

http://www.electriccarpartscompany.com

 

[frater secessus]

It was really only a guess.

They were going to experiment with different configurations to make a better determination.   That seems to be where their saga with lithium ended.

This info from their vendor makes it seem like more than only a guess:

Elite let me know that in their experience heat has a huge impact – even within that operating range.
They have observed that a 10C (18F) temperature increase over a baseline room temperature of ~23C (74F) results in the number of lifetime cycles being cut in half.
This means at 33C (91F) usable battery life will be cut in half, and presumably to a quarter at 43C (109F). This is VERY substantial.

Scholarly articles like these seem to support the position:

18650-type lithium iron phosphate/graphite cells are cycled at 25 and 55 °C in order to investigate cycle performance and diagnostics for capacity fading. The cell losses more than 30 % of its initial capacity after 600 cycles when cycled at 55 °C compared to a 5 % loss for the cell cycled at 25 °C.

Some researchers purposefully increase temperature to accellerate capacity loss in their testing protocols.

 

[ganto]

after doing some research and talking with some people about the use of lithium batteries in an off grid setup. i can't justify the expense as well as all of the pains that go along with them. it seems like that lithium batts will freeze up before AGM batts will freeze as well as i was also told that i would have to charge each cell seperately WTH.

 

[frater secessus]

Over time lithium is cheaper than flooded lead acid, and much cheaper than AGM.  The main benefits from a solar campervan point of view are:

• no absorption or float in our usage;  in practical terms they take full current until full.  Charging takes much less time. 
• no need to fully charge
• because of underspecing and ability to cycle LFE quite low, the rule of thumb is it takes 1/2 the AH of lithium in a bank to deliver the performance of lead chemistries.  200AH LFE == 400AH lead acid.

For a couple different reasons my first bank will be flooded lead acid, but I am setting up the system with a 200AH LiFePO4 in mind.  


You don't have to charge each cell separately.  I have started to summarize 1000s of posts on the sailing forum thread.  My summaries may be inaccurate but they are footnoted so you can check my work.