wb9k said:
FWIW, the discussions over on DIY EC are usually in the context of a car using large-format LFP cells like CALB, Sinopoly, etc.. You don't have to dig very far on that board to see Sunking saying that people like me are in on a conspiracy by cell makers to sell you BMS's you don't actually need.
Quit putting words in my mouth. You have no clue what my capabilities and experiences are. All you know is your so called authority is being challenged and you do not like it.
There is absolutely no chance any company or business would ever even remotely think of ever up selling a customer or product they do not necessarily need or want? No company would ever dare think about that. Wake up my friend and go to a Fast Food Restaurant. Maybe even buy a car and buy that extended warranty. How about a Bong, booze, cigarettes, or Whacky Tobacky? How about a Pet Rock while you are at it?
I use to be a [text deleted by moderator] Engineer like yourself. I use to be in the
Thou Shall Use a BMS Club, let me design one for you. You know that Smart Arse Engineer that cannot be taught anything and closed minded.. Heck I even have MSEE and PE after my Jerk of a name with 35 years experience working with batteries and power. I use to think just like your [text deleted by moderator] does today. As a [text deleted by moderator] like yourself I use to think there was an engineered solution to everything. Heck even have an Orion Jr in my current EV. I just do not use it as BMS and wish I had not wasted my money on it as a simple Cell Monitor would tell me what needs be done.
Simple Fact is BMS are for Morons, Lazy, and commercial products. They are not required. For people who know nothing other than stick the key in the ignition and drive off. Bottom Balance of LFP cells does two simple thing no BMS cannot possible do or compete with. Passively eliminates the risk of Over Discharge, and cost NOTHING to implement putting your Smart our Smart Arse's out of work.
I never said you should not use a BMS. All I said is you do not need a BMS if you know what you are doing. Here is how I work and have more protection than any BMS alone can provide.
1. Bottom Balanced my 16S 100 AH GBS 48 volt battery 8 months ago to 2.5 vpc. Still in Balance today and I will re balance when and if it becomes unbalanced.
2 Set my Motor Controller LVD to 47 volts which is well above 2.5 vpc at 40 volts pack voltage.
3. Have Orion Jr monitor cell levels and send a Disconnect Signal to Motor Controller is any one single cell reaches 2.5 volts or less for more than 15 seconds. I also use it to send a Signal to the Charger to turn off Charger as soon as any cell reaches 3.6 volts which is always cell #4 which is the weakest at 102 AH.
To charge I use an old Telecom 48 volt 50 amp battery rectifier. All Telecom Battery Rectifiers are industrial Grade CC/CV units. I charge at C/2 until one cell reaches about 3.6 volts. It is always cell 4 the weakest cell, and after experimenting a bit with Cut Off Voltages in my case 3.6 volts is the point so when rested is roughly 80 to 90% SOC. All other cells are just slightly lower or equal voltages.
So I have 3 lines of defense on the Discharge Side. First line of Defense as designed is a very Conservative Automated LVD setting in my Motor Controller to trip off when Pack Voltage reaches 48 volts or roughly 20% remaining capacity. Second Line of Defense is a Battery Monitor that will operate th eLVD in th eMotor Controller is any one cell sees 2.5 volts or less for more than 15 seconds.
Third line of defense is completely Passive and Cost NOTHING and all that is really needed. I Bottom Balanced the batteries. If by some chance 1st and 2nd line of Automated Defense fails, once pack voltage reaches 40 volts or 2.5 vpc, th system just comes to a HALT. No damage other than calling the Wife telling here to bring the truck and Tow Bar.
See I use to be a [text deleted by moderator] like yourself. Then I grew and wised up with age. That is why I am retired at 57, and living in paradise playing all day long doing whatever I want.