Charging Lithium Battery - Page 1
Forum section: electronics / repair

author: 2X
author_rank: Frequent Contributor
timestamp: December 12, 2024, 08:56:53 pm
content: Hello,I want to charge this battery with a universal charger. The original charger is missing and I can't find a used one. Can I charge this battery with a universal charger? I open the battery and inside there is a PCB (I beleive this PCB is for short circuit protection of the battery?)I don't know what is the purpose of the "D" and "C" pins; I made a schematic and these pins are connected to U1 (I didn't find any datasheet of this chip).The "TH" pin I is for thermal protection?Any advise?

author: indeterminate
author_rank: Regular Contributor
timestamp: December 12, 2024, 10:19:23 pm
content: No you cannot use a universal charger.Many fires are started by people using the wrong charger on Lithium batteries.The PCB is for battery protection and possibly cell balancing it will disconnect the battery in the event of under / over voltageyou should be able to find a charger for a 7.4v 1500mah battery but there is no guarantee that it will work or be safe.the IC on the battery PCB may need to communicate to the charger

author: 2X
author_rank: Frequent Contributor
timestamp: December 12, 2024, 11:07:16 pm
content: Quote from: indeterminate on December 12, 2024, 10:19:23 pmI found the below. Do you beleive it will be ok? It refers that it has "USB IN: Adaptive Input Current Limitation, Over Heat/Reverse Connection Protection"Manufacturer Product Number: DFR0564https://mm.digikey.com/Volume0/opasdata/d220001/medias/docus/720/DFR0564_Web.pdfFrom the manual above:WarningUsers can choose to use DFRobot 7.4V lithium battery, or buy a 2s 7.4V lithium battery with battery protectioncircuit. Lithium battery manufacturers usually pack two identical 3.7V lithium batteries (usually lithium polymerbatteries or 18650 lithium batteries) in series and a battery protection circuit. This module is unbalancecharging type. When the battery connector is a JST-XH2.54 3P, please use a dedicated balance charger. Thismodule fits to the batteries, which only have a 2P connector (such as JST-HX2.54 2P or DC2.1mm power jack).Itis not recommended to use 7.4V lithium batteries without battery protection circuits.Do not charge any two 3.7V lithium batteries in series by yourself. Otherwise, the batteries are probablyovercharged, causing it to be scrapped or even explode.Thanks for your useful reply.

author: garrettm
author_rank: Frequent Contributor
timestamp: December 13, 2024, 12:59:53 am
content: I would NOT use a "universal" charger for any lithium battery. The exact chemistry type of the cell changes the set point voltages and can't be known by the charger. Additives like cobalt can change the max cell voltage. So I'd look at the pouch label and see what it says. In your case, 4.35V per cell.If any lithium cell is below 2.5V just throw it away. Irreversible chemical reactions happen below 2.5V that damage the cell. If above this voltage, then the cell is likely recoverable.7.4V ==> 2x 3.7V cells. This is likely the average voltage of the discharge curve.I would not charge these cells in series.You can charge each cell individually using a variable DC power supply and monitor the current till it reaches the cut-off threshold.Below are some notes I have for my own Li-polymer cells. But generally, the information here is valid for most Li-Ion / Li-polymer cells, with the exception of LiFePo that have an entirely different charge algorithm.Code:Lithium Polymer (Lipo) / Lithium Ion (Li-ion)Standard Lipo Charge Algorithm:If V_cell <= 2.50 V, discard: cell is likely damaged / recovery is unlikelyIf 2.50 V < V_cell < 3.00 V, CC charge at 0.05 to 0.10 C (3.00 V compliance limit)If V_cell >= 3.00 V, CC charge at 0.20 to 1.00 C (4.20 V compliance limit)Once V_cell = 4.20 V, CV charge until current < 0.10 CLong-life Lipo Charge Algorithm (~4x cycle life):If V_cell < 2.50 V, discard: cell is likely damaged / recovery is unlikelyIf 2.50 V <= V_cell < 3.35 V, CC charge at 0.05 to 0.10 C (3.40 V compliance limit)If V_cell >= 3.35 V, CC charge at 0.20 to 1.00 C (4.00 V compliance limit)Once V_cell = 4.00 V, CV charge until current < 0.10 CUltra Long-life Lipo Charge Algorithm (~12x cycle life):If V_cell < 2.50 V, discard: cell is likely damaged / recovery is unlikelyIf 2.50 V <= V_cell < 3.35 V, CC charge at 0.05 to 0.10 C (3.40 V compliance limit)If V_cell >= 3.35 V, CC charge at 0.20 to 1.00 C (3.85 V compliance limit)Once V_cell = 3.85 V, CV charge until current < 0.10 CPrecharge | CC 0.05-0.10C, 3.0V compliance | 2.5V < Vcell < 3VBulk | CC 0.20-0.70C, 4.2V compliance | Vcell >= 3VTop Off | CV 4.2V | Icell > 0.10CTerminate | disconnect from charger | Icell <= 0.10CCHARGE (voltages WRT charger, not cell)No energy is stored in a Lipo cell when charged below 3.40 V.Roughly, charging at 3.40 V (min) provides 0-1% SoC and 4.20 (max) 100% SoC.Charging a cell when 2.50 V < V_cell < 3.40 volts is pre-charging.Bulk charging occurs when 3.40 V <= V_cell < 4.10 V (0 to 90%)3.4 1%3.5 3%3.6 5%3.7 9%3.8 36%3.9 62%4.0 73%4.1 89%4.2 100%STORAGE (votages WRT cell)Li-ion cells should be stored in a partially discharged state: keep cell voltagebetween 3.8 (max) to 3.4 (min) volts for long term storage. This corresponds toroughly 40% to 0% state of charge.If cell voltage drops below 2.5 volts, permanent damage will occur.DISCHARGE (votages WRT cell)Never discharge Li-ion cells below 2.5 V, as this can cause permanent damage tothe cell.Terminate discharge at >= 3.0 V for faster recharging.

author: garrettm
author_rank: Frequent Contributor
timestamp: December 13, 2024, 01:14:31 am
content: I'd unsolder the cells from the PCB before recharging them and once tested to be working okay, resolder them back and charge normally in the equipment it was made for.You may end up needing to buy new pouch cells to replace these if one of the cells is bad or has low capacity WRT to the other cell.

author: garrettm
author_rank: Frequent Contributor
timestamp: December 13, 2024, 01:17:57 am
content: Also, a little trick to these BMS PCBs, is that they shut off the battery output when low and only turn it back on when a charge voltage is supplied to the correct pins. So the battery may look "dead" at the terminals, but really the BMS has just disconnected the cells at the output.The three thick wires going to the cells is where you should measure the voltage from.

author: 2X
author_rank: Frequent Contributor
timestamp: December 13, 2024, 01:59:25 am
content: Quote from: garrettm on December 13, 2024, 01:17:57 amYes, this have happend to me.

author: 2X
author_rank: Frequent Contributor
timestamp: December 13, 2024, 02:02:08 am
content: Quote from: garrettm on December 13, 2024, 01:14:31 amThe battery that I want to charge is brand new (now I bought it), but as you wrote me there is any safe way to charge at once the battery with the two cells connected in series. If anyone have to suggest me a way to safely charge the battery or if I could design a circuit a battery managment chip or whatever, please tell me, because inevitably I will have to thrown this device.

author: garrettm
author_rank: Frequent Contributor
timestamp: December 13, 2024, 03:46:03 am
content: Quote from: 2X on December 13, 2024, 02:02:08 amIf you have a bench top power supply and a multimeter, charging these can be done easily and relatively safely. You just have to babysit it, which is a little bothersome, but doable.The IC on that circuit board should work, if you know the pin out and what voltage it expects for the input. But these ICs usually do not optimize for long life: They just charge the cells up to 100% (4.2V generally or maybe 4.35V in your case) and disconnect power when the voltage is low. And in general, that is good enough. But for special applications, where extra long cell life is needed, a custom charge circuit is more desirable. Really, the charge algorithm is quite specific to the application, like powering an outdoor sensor with a photovoltaic cell for charging during the day and so on. Or an always-on device--where the battery should be held at 80 to 60 % SoC to avoid damaging it. Lithium cells do not like to be kept at 100% SoC for years at a time. This is ironically how many end up failing. That, or too deep of discharge (going past 2.5V).

author: shabaz
author_rank: Frequent Contributor
timestamp: December 13, 2024, 03:49:36 am
content: Hi,Unless there's something I'm missing, I don't see why you can't just use a 2-cell LiPo charger board, connected to the two battery terminals.Example: MCP73213You can set the charge current on it to either 500 mA or 1 A.Nice board, I've used it to charge generic 2-cell LiPo batteries too. They were new, obviously (and from a reputable source - both for the charger board, and for the battery).Obviously, it is far cheaper to buy the IC and make a custom board if the Microchip eval board is more expensive than desired.