gobi said:
Storage Voltage:
Battery UNI and other places say 3.5v for li-ion cells for storage,
What is the consensus here? 3.5v?
My machines specify 3.875v/cell. Storage voltage,...
... and I always do a taper anyway to the charge termination voltage. I have been told here that CC/CV doesnt matter, taper wise, but I do it anyway. If the cell datasheet calls for a C/50 or a C/100 taper, I do it. Some say you are fine with a C/10 or C/20 taper . But I baseline discharge all cell groups int eh string and then meter wH going into them, until a V is met, CC, then the taper time, CV. Compliance is equalized and the cells all balance to the mV or better.
My hobby grade RC charger is one of the best, very good configuration. You can configure any type of charge/discharge, taper current, termination voltage... and has like 200 safety fail check codes that detect error on charge and relays a message. Stops charging. It is my most powerful charger, and can gang up for 32s no prob if you power the channels from 4 separate isolated fueling stacks of cells. It has a 48v input voltage. It is digital Buck/Boost converter, of some sort I have read ( analog hardware inside).
I made my own dumb charger from DIN relays and current shunt watchdogs, fuses, breakers, wifi data sent from eh garage to the computer in the house. ... no real education. Based on a big industrial HV DC plc drive. It works great, and can do a very high voltage should i want it to. Never had a problem. 3kW, 250V DC. If it sees an overcurrent on the input AC voltage, or, an overcurrent on the output DC voltage, it stops charge, along with everything fused and breaker. Taper is changed with the potential meter.
I have three Kingpans, 300w, 600w, and the 900w, I dont really trust them much. Never go in the house when they are on, outside. They dont have wifi data ad I do not trust the much...Taper is changed with a Pot there too: and a DeltaQuiQ 1500W, and a Elcon PFC 1000w. Both of those are much better built. I trust my homemade charger, and the DeltaQ, and am trying to learn about the programming for the Elcon. The DeltaQ is really complicated, has many many charge profiles avaible to install. Those are the chargers that never fail and you see on the post at the factory, never failing.
I do not use a BMS, now, ( have in the past, smaller packs). Battery murder system. If you use one, get the one with teh metal shunt, and relay, not the mosfet switch. A NO gas filled relay is very reliable. I think I might even feel safer now with my experiences with the big 200A-600A BMS with the metal shunt and contact relay. I may install one, some day, but I do not trust the plethora of the mosfet design we see.
I have left a charger on overnight once. It stopped the charge as expected, when I fell asleep inside, but still I do not like it and scorned myself for the action. Sure only happen once, but once is all it take for a bad day.