Lithium charge controllers

[jaunty]

I have one of those cheapo solar charge controllers for my solar setup. I am looking to go lithium/lifepo4 for batteries soon and im wondering what is the fundamental difference between the charge controllers. If you have the ability to set the controller to a particular voltage, what is it about the "lithium" charge controller. Just marketing?

https://genasun.com/products-store/mppt-solar-charge-controllers/mppt-for-lithium-batteries/

http://www.aliexpress.com/item/30A-12V-24V-wincong-sl03-30a-solar-Charge-Controllers-USB-LCD-Li-Li-ion-lithium-LiFePO4/32347726129.html

 

[Nobuo]

If you can set voltage cuts and floating charge, of course there is nothing more that could make a solar controller special for lithium chemistry. The temperature compensation voltages should not be activated with lithium-ion batteries, that's a function only good for SLA chemistry.

I have the second one (60V, 78Vmax version), it works pretty good.

 

[HydroDan]

most likely it would work just fine if you can set the full/float charge voltages properly, but if using charge controllers designed only for lead-acid it may ruin the batteries over time since lithium based batteries dont like to be continually trickle/float charged after reaching 100% like lead-acids.

lithium based also cant handle small over-voltages like a lead-acid. so just half a volt over the 4.2v/cell can cause damage(lifepo4 specifically is much more susceptible to this tho, but not as much as lead-acid). im not sure, but a lead-acid charger may not be as accurate with the voltage it outputs(but i most likely it is just fine). so maybe it is better to set the charge controller to not give it a full charge voltage, but like 90-95%, and have the float voltage where itll only keep it charged when the battery is discharged a little, and not trickle in any current when the battery is sitting at full charge.

but even with a lithium-ion charger, why do we charge them to complete 100% every time? its that last like 5-10% that is where things get iffy and heat is produced. do we really need that last 10%? lol its a conspiracy man! ive always wondered. maybe its just something left over from the old battery technologies that would get sulfation issues when not charged to 100%? im not sure...

also, since the curves are different, if there is some type of capacity meter, it wont be accurate, but that doesnt really matter.

o and good note about the temperature compensations . tho with a cheapo charge controller, does yours even have temp sensor? on a more expensive charger/inverter i use i was actually able to adjust the temperature compensation(i just shut it off actually) when i used LifePo4 batteries, even tho its only setup default to handle lead-acid.


so pretty much id say yes, you can make it work charge them ok if you set the voltages.

 

[jaunty]

thanks guys for echoing my sentiments. I just wanted verify because I heard a guy saying not to use a particular controller with lithium, but if you know, and can set (program), the high voltage point for your batteries then you're good.

 

[Doomsdayprep]

Hello there again something that ive been researching, it would appear that you need a fully programmable charge controller something like the morning star tristar series, you would need to set the float voltage much lower then the charge voltage, i have been reading on the cruiser forums the with lifepo4 you need to ensure the batteries get a good charge so they must follow the charge profile and reach the 3.8 volt mark roughly, please dont quote me on this but again i say its a safe zone, unlike LFA the LFP range dont mind a 80% charge, the nice thing is they dont need a long float charge time, and effectively harness the power quicker at higher C rate of charge, you want to make sure the battery float is set more conservative, and ensure you have loads on the battery system essentially skimming the top of the power generation .
If you dont have loads, i would really ensure i have a bms system with a smart relay out put, set the bms so that the relay disconnects the PV array when the batteries reach the 90-100% SOC, reason is that once they are full and there are no loads, like the battery system is used at night i would ensure there isnt even a float charge, because the loads effectively wick the excess power generation, you want the loads to balance the scale of power produced vs power used, keeping the batteries in a semi active state, and effectively means that you would charge your float range at 3.50 v per cell or 13.95-14.20 volts for a 12v application and respectively for 25v and 50v applications .
Hence the tristar charge controller can be effectively setup to ensure the float is lower then the cells max voltage and it will have no detriment on the cell structure of heat, as alot of guys on off grid setups are currently running this and effeciently too .
How long it will last is the question, because the few that have been running this setup havent had more then 4 years on its hard to say but they havent lost much capacity and they havent killed a battery yet because its never close to the threshold, it also makes the battery think its never fully charged but also gives it more life cycles, just 20% or 30% less capacity .

again im not professional this is merely my observation .

 

[Doomsdayprep]

found another user with a similar situation have a look at this post .

https://forums.energymatters.com.au/solar-wind-gear/topic6186-80.html

 

[CrazyJerry]

Not an expert here but I've been solar charging my LiFePo4's since early 2012, and in multiple configurations (somewhat out of interest). Like others have said, if you have a charge controller that you can program the actual settings, then you should be ok.
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Some controllers may not react very quickly to certain scenarios like: during the height of a partly sunny day.
Clouds can block the sun and then turn it back on like a switch. If your batteries were approaching a high state of charge from earlier, that initial output of the now unclouded solar panels can potentially and quickly raise your battery pack voltage into an area where you do not wish to be. How close are you pushing the limits of what your battery really needs? How accurate is your controller in relation to actual battery voltage? And how fast will your controller react in this situation? In my case, I can use the controller's aux output to trigger a high-voltage-disconnect and immediately stop solar panel input. Solar can be unpredictable at times.
Something to think about.
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A pack that is nearing the charge settings may never get there if the clouds move in and stay. If those settings are in the upper realm of the batteries advertised limits, then you may just be creating heat at that point. Some controllers can be set to terminate charging based on an additional parameter called "end amps"... EX: When your battery bank is at "X" voltage it will remain there until the amps tapers down to "X-amount" then the charge terminates.
The more settings the controller has - the more you can zero in a specific charge profile.
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As said elsewhere, suggestions are to stay away from over charging (keep away from the last steep charge curve voltage) and keep away from over discharging. Amongst other things, these two areas can cause your cell voltages to drift apart and prompt for balancing cells more frequently.
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On a related note, the system here uses Surrette flooded lead acids and GBS Lithiums. Both use the same brand/model of now discontinued (but superseded) controller but obviously not with the same settings. In daily use, the Surrettes have passed the 10 year mark and the GBS have passed 3.5 years.. No faults noted other than the Surrettes are getting tired.
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Charging these different battery chemistries is very do-able if you have the means to reliably regulate your charging source(s)..
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~CrazyJerry