18650, 3.7V ( nominal ), Li Ion batteries may prove to be ideal to power guitar pedals, low power audio amplifiers, music players, cellular telephones, etcetera.
Presently, these batteries are available in different capacities. The maximum capacities is higher than 10A/h. Probably, in the future, higher capacities will become available.
These batteries are, usually, recharged by commercial battery chargers. These battery charges are, usually, made to be able to charge many different types of batteries. Usually, the charger will recognise the type of a given battery and will apply a certain algorithm to recharge the battery. Usually, the user can select the charge current between 0.5A and 1A with 0.5A recommended. The algorithm will, usually, charge the battery to around the nominal voltage of 3.7V with the selected current and, then, will continue to charge the battery to 4.2V at much lower currents.
However, there is a nasty problem : when the battery is still good, yet, either recharged to a very low voltage or overused and with many recharge cycles, the charger cannot recognise the battery.
Therefore, a simple, pure analogue charger has been designed and made.
1. This charger is only for 18650, 3.7V ( nominal ), Li Ion batteries and, therefore, the said batteries are always " recognised ".
2. The pure analogue way without spikes and switching noise may be safer for the battery.
3. The recommended charge algorithm is applied in an analogue way.
The design is standard as suggested in the datasheet of LM317. The document, which explains this design and gives and idea for another design with two LM317 per battery, the first, connected as a constant current source and the second as a constant voltage source ( as suggested online in many sites and videos ).
Here is the document :
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Scroll down for the schematics and pictures!
Presently, these batteries are available in different capacities. The maximum capacities is higher than 10A/h. Probably, in the future, higher capacities will become available.
These batteries are, usually, recharged by commercial battery chargers. These battery charges are, usually, made to be able to charge many different types of batteries. Usually, the charger will recognise the type of a given battery and will apply a certain algorithm to recharge the battery. Usually, the user can select the charge current between 0.5A and 1A with 0.5A recommended. The algorithm will, usually, charge the battery to around the nominal voltage of 3.7V with the selected current and, then, will continue to charge the battery to 4.2V at much lower currents.
However, there is a nasty problem : when the battery is still good, yet, either recharged to a very low voltage or overused and with many recharge cycles, the charger cannot recognise the battery.
Therefore, a simple, pure analogue charger has been designed and made.
1. This charger is only for 18650, 3.7V ( nominal ), Li Ion batteries and, therefore, the said batteries are always " recognised ".
2. The pure analogue way without spikes and switching noise may be safer for the battery.
3. The recommended charge algorithm is applied in an analogue way.
The design is standard as suggested in the datasheet of LM317. The document, which explains this design and gives and idea for another design with two LM317 per battery, the first, connected as a constant current source and the second as a constant voltage source ( as suggested online in many sites and videos ).
Here is the document :
Update your browser to use Google Drive, Docs, Sheets, Sites, Slides, and Forms - Google Drive Help
Scroll down for the schematics and pictures!
TP4056 1A Li-Ion Lithium Battery charging Module with Current Protection - Micro USB buy online at Low Price in India - ElectronicsComp.com
Why don't you check if it has been done before?
Why don't you check if it has been done before?
I have not looked at your suggestion, yet, I realise, this is a commercial charger. I, already, have two of these and am not interested in other, except, maybe, when they do not, automatically, check for a battery type, but, instead, have been made specifically, for 18650, 3.7V ( nominal ), Li Ion.
I certainly wasn't expecting a 48 page document when I clicked on your link. Impressive amount of research and documentation, even if TBH I didn't do more than skim it. I've been in Li-Ion batteries for 20+ years and it's rare to see this analysis done in DIY battery work.
I don't know what commercial chargers you are comparing to, but I would agree that a charger that is trying to charge multiple chemistries, different voltages, even capacities is never going to be ideal. Designing a charger for a single battery type and capacity allows you to make sure it's being charged in a manner that keeps it safe and gives it the best longevity.
However there are good reasons you don't want to just recognize and charge any battery you put in the charger. Especially if it's a commercial product that you have safety and liability to think about. Old, degraded, or cells that have been over discharged are better off being scrapped than recharged.
My 2 cents on other parts.
Quickly looking at commercially available linear charger ICs I'm not sure what the benefit of the design is other than being able to easily DIY it on a through hole board.
The switching noise from a well designed switching charger has no impact on longevity or safety of a battery. Unless the voltage is going way over the max charge voltage. But the battery should have some protection from that, right?
Does your design have a method to turn off charge once the charge is complete and the current drops below the cutoff current?
I don't know what commercial chargers you are comparing to, but I would agree that a charger that is trying to charge multiple chemistries, different voltages, even capacities is never going to be ideal. Designing a charger for a single battery type and capacity allows you to make sure it's being charged in a manner that keeps it safe and gives it the best longevity.
However there are good reasons you don't want to just recognize and charge any battery you put in the charger. Especially if it's a commercial product that you have safety and liability to think about. Old, degraded, or cells that have been over discharged are better off being scrapped than recharged.
My 2 cents on other parts.
Quickly looking at commercially available linear charger ICs I'm not sure what the benefit of the design is other than being able to easily DIY it on a through hole board.
The switching noise from a well designed switching charger has no impact on longevity or safety of a battery. Unless the voltage is going way over the max charge voltage. But the battery should have some protection from that, right?
Does your design have a method to turn off charge once the charge is complete and the current drops below the cutoff current?
My understanding is to charge a Li-ion battery or cell with constant current at 1C up to the rated voltage of 3.4Vdc or so. Then go into constant voltage mode. "C" refers to the mAh rating of the cell or battery.
Standard charging for most Li-Ion is 0.5-0.7C constant current up to the charge voltage (historically 4.2 but go higher than that now) then switch to constant voltage until the current decreases below 0.05C.
Because a Li-Ion cell accepts charge more rapidly at low states of charge you can sometimes charge at a higher C-rate to a lower voltage then switch to the standard 0.5 or 0.7 up to 4.2 . But unless you need that charging speed it's added complexity, and done wrong will adversely affect your cells longevity.
Because a Li-Ion cell accepts charge more rapidly at low states of charge you can sometimes charge at a higher C-rate to a lower voltage then switch to the standard 0.5 or 0.7 up to 4.2 . But unless you need that charging speed it's added complexity, and done wrong will adversely affect your cells longevity.
Generally : Switching noise is always present with any digital system or charger, regardless how expensive they are. Again, generally, any digital noise is always bad for everything else and, always, degrades or damages. Now, these are in general. Practically, expensive chargers do, also, have a strong digital noise, such as spikes, etcetera. Now, can they degrade the battery significantly? This I do not know. Most likely, no as mentioned in the document.
In regards for automatic shutdown, the answer is yes. The regulator can provide a maximum of 4.5V. Theoretically, in case the battery voltage is, say, 4.2V, the diode between the regulator and the battery is closed and no current flows through the battery. Practically, the battery will discharge through the light diode, until the voltage is around 4.8V, in which case, the regulator will supply the light diode and not the battery and all, possible, current will go through the light diode and none through the battery. The diode is like a throttle.