Charge settings and top charge questions

[Swampy222]

Hello all! Im new to lipo batteries and will be replacing my old lead acid bank of rolls surretes this weekend. Ive ordered 4 of the 48volt 100ah eco worthy batteries that seem so highly recommended here and hopefully will be delivered by Friday? My question is about the initial top balancing charge and if I should buy a seperate dc charger with adjustable voltage and current? Am I correct that I want only .5 amp to balance and to maybe cycle the battery a few times before I parallel the 4 and connect to my system?? I have a schneider xw6048 inverter with xantrex xw mppt 60 150 charge controller...any recommendations for settings? Bulk, absorption, float, and equalize settings and voltages (also low voltage cut out)? I also have an auto gen start and what low voltage should I have the generator set to? I believe as far as low voltage triggers I can set 15 second, 30 second, 2 minutes, and 2 hours low voltage triggers? and also what voltage to trigger generator off? Thanks for any guidance and suggestions!!

 

[sunshine_eggo]

LiPo is short for lithium polymer, and that's something you want to stay away from aggressively.

LiFePO4 or LFP if you're referring to lithium iron phosphate. Some also use lithium iron, but that's easily confused with lithium ion.

Best results may be obtained by individual top balancing via a separate charger or power supply, but given that these are going into an already operational system, it would probably be best to just paralel install and go.

They're going to be at about 30% SoC as received, or at least they can't be legally over that due to hazmat shipping requirements.

Recommend you sneak up on bulk/absorption in case they aren't balanced.

56.8V is about as high as you want to go, but imbalance may trigger charge protection at this level. This level needs only 15-30 minutes of absorption to get fully charged, and maybe not even that much if you're starting at a 0.1 - 0.2C rate, but you probably want to keep it to 30 minutes for balancing purposes. This is the voltage you want to target for generator charging, or simply cut off generator charging when absorption is reached.

55.2V is about the lowest you can go and still get fully charged. You'll need about 2 hours @55.2V to ensure you get fully charged. If you find this charge level gets you to near 100% SoC (batteries may never actually show 100%, but they will be), then this is workable on an ongoing basis. There is evidence to suggest that charging to lower voltages/currents optimizes cycle life.

Absorption time is primarily used to allow the BMS time to balance, so you want to disable tail current.

Float at 54V.

Disable temperature compensation on all chargers.

At 48V you're going to be at about 10% SoC. You may need to experiment with cut-offs and times based on how your system operates.

 

[Swampy222]

Thank you, perfect! So my older inverter and charge controller are perfectly suitable to these new batteries and no need to upgrade anything? Also do I disable my equalization schedule? I dont think Ive ran across any "tail voltage" settings but I will check the menus and ensure it is disabled...
Also I am unsure about communication with my inverter or if I even have that ability or if its needed. I have 2 temp sensors in the bank of my flooded lead acid batteries now but I think that is all. These will not be used, correct?

Thanks again all!

 

[sunshine_eggo]

Thank you, perfect! So my older inverter and charge controller are perfectly suitable to these new batteries and no need to upgrade anything?

Probably not. 51.2V LFP is "drop in" voltage compatible with 48V lead-acid. Just make sure you disable temperature compensation. LFP doesn't need or want it. Often disabling is accomplished by disconnecting the battery temp sensor.

Also do I disable my equalization schedule?

Yes, or set it to the aforementioned 56.8V for 2 hours every 2-4 weeks. It's a semi-common strategy to charge regularly to the lower voltage and then push to the higher voltage periodically to confirm balance and provide additional opportunity for cell balancing if needed.

I dont think Ive ran across any "tail voltage" settings but I will check the menus and ensure it is disabled...

Tail current. It's the current at which the battery is fully charged at the absorption voltage. Your Rolls batteries have a formula for absorption duration. They also indicate something on the order of 0.02-0.03C for tail current, i.e., 100Ah battery is fully charged when the current has dropped to 2-3A at the absorption voltage.

IIRC, the Outback FM-80 refers to it as "End amps" or something like that.

If your system has this feature, you want to disable it.

Also I am unsure about communication with my inverter or if I even have that ability or if its needed.

I would check your manual. The battery communication protocol used is typically "PYLON" or "PYLONTECH".

It is not needed, but it can be beneficial. It can also be a pain in the ass.

I have 2 temp sensors in the bank of my flooded lead acid batteries now but I think that is all. These will not be used, correct?

Typically, removal should should disable temp comp.

 

[Swampy222]

Mr Sunshine Eggo- Thank you so much for taking the time to answer all my questions! Ive been scouring the forums and kept some notes when applicable but is sure is nice to confirm Im on the right track. Thank you very much!