18650 battery's float voltage setting
DConlyGuy
Registered Users Posts: 80 ✭✭
i am making 2 4p4s 16 volt battery's using the 18650 cells they are the 3.7 volt variety. my charge controller will charge at 16 plus volts and
it can limit how much amps it can put out too. im know full charge on the battery would be 16.8, but thinking of making it 16.4 or maybe even 16 volts . i can set the bulk and absorb to those voltages, but i know these cells dont like floated or trickled charged, so i was wandering on the float voltage to set is low so it never comes on might work? another thing is amp setting, these cells are averaging 2k mah so what amps setting on controller should i use to safely charge them ?
it can limit how much amps it can put out too. im know full charge on the battery would be 16.8, but thinking of making it 16.4 or maybe even 16 volts . i can set the bulk and absorb to those voltages, but i know these cells dont like floated or trickled charged, so i was wandering on the float voltage to set is low so it never comes on might work? another thing is amp setting, these cells are averaging 2k mah so what amps setting on controller should i use to safely charge them ?
600 watts of solar panels,Epever 30 mppt , 2 PWHR12500W4FR battery's in 24 volt setup
Comments
The "Bulk Charge Amps" is usually between 0.5C to 1.0C.
Follow the mfr specs.
RE: Float
Correct, it is better to not float at 16.8v
Let the voltage drop and the trigger a recharge
RE: Max Voltage
Yes, lowering the max voltage will significantly increase total cycles, with slightly lower capacity ...
16.4 Volts vs 16.8 Volts could produce twice the cycles @ ~92% capacity
16.2 Volts vs 16.8 Volts could produce triple the cycles @ ~86% capacity
16.0 Volts vs 16.8 Volts could produce quadruple the cycles @ ~75% capacity
RE: Recharge Modes
Mode 1: Bulk Charge to 16.8v, then STOP. Wait for voltage to drop
Mode 2: Bulk Charge to 16.8v, then Absorb Charge until Amps < 3% then STOP. Wait for voltage to drop
http://http//batteryuniversity.com/learn/article/charging_lithium_ion_batteries
http://dolgin.net/Charging%20Lithium-Ion%20Batteries.html
Do not over-charge.
Do not under-charge
Follow mfr specs.
String a whole bunch of batteries together, no BMS, no Binning of Cells to match them up, you will have trouble.
|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A
solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-Lister ,
-Bill
The catch-22 about doing lithium based projects, is that if you have to ask, you are unsafe. And with the limited info provided, you definitely are already in unsafe territory by thinking you just have to tack these things together, and set your charge controller voltage and be done with it.
So here are some more questions you need to know before you get started:
1) How are you going to handle temperature-compensation? (trick question)
2) What is your method of proving the all the cells have nearly identical capacity and internal resistance before assembly? How good are you at spotting fakes, or do you have a known good supplier?
3) Are you aware that these cells only have 300-500 cycles, and that a far safer but mech less energy-dense chemistry, like lead-acid AGM has similar cycle life?
4) Does your application actually demand this kind of energy-density? What voltage is your application actually going to use?
5) How much current does your application pull? - are you going to use "protected" or UNprotected cells?
6) What are your plans for over-charge and over-discharge? Similarly, what are you going to be doing in regards to balance?
7) What is your method of paralleling these 2K cells together? Soldering iron? Tack welds? Loose-fitting holders?
8) Have you give thought to switching lithium chemistry to LiFeP04, which is 3.2v nominal, and cutting your cell count down by only using 4 or 5 cells, like Headway's? Easier to charge with solar too by switching to the lower-voltage LFP chemistry.
So what exactly is your application with these cells? Maybe we can dissuade you from becoming a danger to yourself and others.
================
RE: Charge Amps
The "Bulk Charge Amps" is usually between 0.5C to 1.0C.
Follow the mfr specs.
================
If you do not understand the Li-Ion Charging Profile or the math, then you should not be charging Li-Ion batteries.
You must follow the manufacturers charging specifications.
Please provide the URL to the manufacturers charging specifications.
If you don't even understand what that means, you should NOT be trying to charge li-ion batteries. If you want to learn there are plenty of courses out there. Batteryuniversity.com is a good place to start.
You'll get a similar grilling from them asking you to provide more details, such as what is your actual application, to be safe.
Lithium battery projects, from a single-cell flashlight, your own unknown 32-cell application, to that of a Tesla, requires a *SYSTEMS* approach, where more than just a single spec is involved to be safe and successful.
Answering any one of the questions I posed above (in case you missed it), will help identify if you are making an unsafe toy, or have a real interest in a working system.
I'm glad I don't live within your blast radius (when it goes up).
Just trying to get your attention that you are into dangerous stuff, and while you are asking some good questions, you have no concept of the other questions you need to be asking. And I can't ask them for you, because you don't give straight info about what you are doing or the source of the cells, but hey, go for it. Post your pics at the end.
|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A
solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-Lister ,