Renewable Energy Questions/Discussion > Renewable Energy Q&A
Charging and Using Lithium Ion 18650 Batteries
WooferHound:
For the last year I have been playing a Lot with some Lithium Ion 18650 batteries. Charging and then using them in some of my recent projects. Everytime I mention Lithium batteries, people instantly mention about how dangerous they are because the Electrolyte spontaneously catches fire when it comes in contact with moisture, including the small amount of water in the air. These concerns are important and I will try to summarize the key points here...
Do Not Exceed 4.2 Volts or there will be Fire
Do Not Discharge Below 2.5 Volts or you will damage the Cell
Do Not Charge or Discharge the battery faster than Half of it's capacity
Do Not Short-Curcuit or there Will be Fire
Use Balanced Charging. Lithium Batteries in Series do not remain Equally Charged and must be Maintained Individually to keep the Charge Equalized
Do Not Charge a cell that is below Freezing Temperature, Causes an Overcharge Condition
It is also good to keep them Cool as possible and Protect them from Physical Damage
So if you are only using a single 18650 battery, with low charge/discharge currents, and stay between 2.6 volts to 4.1 volts (hard limits), you will have a lovely experience.
It acts much like a large capacitor and as long as you watch the voltage limits it is a happy playground to play in.
Here is a Dual 18650 charger I made using a 6 volt center tapped transformer, very few parts and charges the batteries up between 4.0 & 4.1 volts over a 6 hour period. There are some Push Terminal strips on there for charging old Cell Phone batteries. I have been putting 1/8 inch jacks on these projects to charge them up with, not the best choice because the plug has exposed power but I have a lot of them.
Purchased twenty 18650 Holders to make stuff with, mostly lighting. The item at the bottom is a 12 volt battery pack using 3 battery holders glued together and a wire ending in a standard 12v connector.
There is solar lighting on my bicycle and there is an 18650 battery in the back of the solar panel there.
So far I have been charging the batteries independently and then replacing them into the devices that they are being used in. Now I want to go a step farther and make devices with internal batteries that can be charged, plus adding protection from over charge/discharge.
If you are only using one 18650 battery this is very easily done with a TP4056 Charger Module which allows you to charge an 18650 from any 5v USB source and provides over charge/discharge protection.
https://www.ebay.com/itm/5pcs-5V-1A-Micro-USB-18650-Lithium-Battery-TP4056-Charging-Board-Charger-Module/222579681057?hash=item33d2c86721:rk:1:pf:0
If you want to charge these batteries in series it gets a little more complicated because the battery voltage between cells must be kept balanced in addition to the over/under voltage protection. I have not made anything yet, but this seems to be the best solution for using and charging series lithium batteries in the device.
Use a MAX745 charger module to control the battery charging for up to 4 batteries in series. This will take up to 20vdc for charging and convert it to what the battery needs. It also allows you to control the max battery voltage and the charging current.
https://www.ebay.com/itm/MAX745-4-2-4-35V-1-4-Packs-Lithium-Battery-Charging-Board-Voltage-Current-adjust/111825916930?hash=item1a09581402:g:N2kAAOSwcdBWSogV:rk:2:pf:0
Then your battery pack needs a Protection/Balancing Board to keep the batteries healthy. This board needs to be made for the number of batteries that are in Series ( 2s , 3s or 4s ) and the amount of Current you expect to use from the batteries. This is called a Battery Management System or BMS.
Here are some examples ...
2s
https://www.ebay.com/itm/7-4V-8-4V-2S-PCB-Protection-Balance-Board-For-18650-Li-ion-Lithium-Battery-Cell/233006225988?hash=item364040da44:rk:1:pf:0
3s
https://www.ebay.com/itm/3S-25A-Protection-PCB-Board-w-Balance-BMS-for-18650-Li-ion-Lithium-Battery-Cell/173647618112?epid=2118855608&hash=item286e346040:g:~S4AAOSw6jJb8V2A:rk:2:pf:0
4s
https://www.ebay.com/itm/4S-14-8V-30A-PCB-BMS-Protection-Board-Charger-18650-Lithium-Battery-Cell-Balance/232966966020?epid=586125349&hash=item363de9cb04:g:~voAAOSwqLRcHEue:rk:3:pf:0
Here is some good healthy reading from the Battery University ...
Charging Lithium Ion Batteries
https://batteryuniversity.com/learn/article/charging_lithium_ion_batteries
Prolonging Lithium Battery Life
https://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries
ClockmanFrance:
Nicely written post 'WooferHound'.
I love real empirical evidence.
frackers:
For single cells I've found that a USB charger like these is ideal
https://www.aliexpress.com/item/Free-Shipping-10pcs-lot-5V-Micro-USB-1A-18650-Lithium-Battery-Charging-Board-With-Protection-Charger/32489196709.html
Its what I use between a 1w 6v solar cell something like this
ttps://www.aliexpress.com/item/ANBES-Solar-Panel-5V-6V-12V-Mini-Solar-System-DIY-For-Battery-Cell-Phone-Chargers-Portable/32848710253.html
and an 18650 cell on my weather station remote sender. It keeps an Arduino Nano clone alive 24/7 without any power save techniques etc.
For multiple cells, I use a bq76920 (for 3/4/5 cell setups) of up to 21 volts fully charged, but that requires a micro to run all the code, especially for charging and balancing. The code soon gets pretty hairy if you employ the correct value of paranoia :)
WooferHound:
--- Quote from: frackers on December 26, 2018, 07:47:08 pm ---For single cells I've found that a USB charger like these is ideal
https://www.aliexpress.com/item/Free-Shipping-10pcs-lot-5V-Micro-USB-1A-18650-Lithium-Battery-Charging-Board-With-Protection-Charger/32489196709.html
Its what I use between a 1w 6v solar cell something like this
ttps://www.aliexpress.com/item/ANBES-Solar-Panel-5V-6V-12V-Mini-Solar-System-DIY-For-Battery-Cell-Phone-Chargers-Portable/32848710253.html
and an 18650 cell on my weather station remote sender. It keeps an Arduino Nano clone alive 24/7 without any power save techniques etc.
For multiple cells, I use a bq76920 (for 3/4/5 cell setups) of up to 21 volts fully charged, but that requires a micro to run all the code, especially for charging and balancing. The code soon gets pretty hairy if you employ the correct value of paranoia :)
--- End quote ---
After posting yesterday I bounced across the internet and found better information about Lithium Ion Chargers
I think the TP4056 is a clone of the 03962A module that you linked above. These chargers have inefficient Linear regulators in them and better options are available. Found this video comparing 4 different charger modules in a shootout . They are talking highly of the TP5000 Switchmode single cell charger which has good charge curves and can be set to charge 2 different Lithium battery types.
//www.youtube.com/watch?v=u4CQ62PsLiI
A Review of the TP5000 with lots of graphs and information
https://lygte-info.dk/review/Review%20Charger%20TP5000%204.2-3.6V%20module%20UK.html
WooferHound:
I found this little Gem after looking around some more.
It is a 2s charger with a buck converter input. Voltage is 9.4 to 20 volts, perfect for 12 volt input.
Output is 2 cells in series with all the protections and balancing needed.
https://www.ebay.com/itm/Intelligent-Balance-Charging-Protection-Board-2S-Packs-18650-lithium-Satellite/311721987212?hash=item4894140c8c:g:J~kAAOSwCGVYBRVB:rk:14:pf:0
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