I'm implementing a project to turn on lights with battery feeded by solar panel.
I was reading that TP4056 has an under voltage protection at 2.5V which is too close to the "dangerous" limit for 18650 batteries so I decided to add a second protection with KA75330.
However I only saw this is used to control "EN/RST" pin of the microcontrollers to keep them off while the voltage regulator is working. So I'm not sure if it can be used to cut off the circuit as I pretend to do on my circuit.
Can you give me some advice about this schema. I'm interested to know if this will work/ is safe/ there is better way to handle this issue.
Each LED should have its own current-limiting resistor, they don't share current equally if directly in parallel, and indeed you might get thermal runaway with that circuit and start roasting them one by one.
You don't have a fuse in circuit - does the LiPo battery have over-current protection?
Simplest solution is get a LiPo with full protection circuit built in - then undervoltage isn't an issue, and if the wiring is able to take the max current you won't need a fuse either.
People forget that LiPo packs are easily able to set wiring on fire unless some sort of over-current protection is used.
I thougt the 11 smd leds 5730 couldd be too much at some point for the awg26 wires but the 1ohm resistor would act as fuse on the worst scenario but I didn't know that 2 meters awg26 wire resistance would be less so now I'm looking for a lipo with protection circuits (or maybe a LiFePo4 which I read are very safe to use).
Seems you have understood it wrong.
The TP4065 dose not have under voltage protection.
Only the slightly larger boards with three chips have a under voltage protection.
Provided by the DW01A (and a dual mosfet chip).
Protection is also set to 2.9volt, not 2.5volt.
When the chip turns off is irrelevant, when it turns on again is.
"Battery voltage" and "battery voltage under load" are two different things.
A flat battery has a high internal resistance.
Leo..
Does it means that when tp4056 chip is not loading the battery (getting external power) the battery protections provided by DW01A and dual mosfets are not working and the battery is unprotected until it is charging again?
On one hand It makes sense since this module is thinked to only charge the battery, on the other hand I can't imagine a situation where under voltage protection is useful while you are charging so I'm a little bit confuse now...
About 2.9V/2.5V limit confusion I think it could be a mistake on my side since I saw the battery at 2.5V using this module but I still don't know if it is due a defective chip, an error on my circuit or I missunderstood how this protection works.
I was researching more about what you said and realized about this weise words. I use to think that a load (led diodes in this case) would use only the current they needs but discovered this is not the case with leds (and probable other components).
Now I'm researching about current mirrors with transistors which seems the better solution to solve this problem.
The DW01A protect against battery over-voltage (4.3volt), under-voltage (2.9volt) and over-current.
Over-voltage is there in case the TP4065 fails (to stop charging).
Once a battery is almost flat, it's internal resistance increases (it can't provide current), and battery voltage much easier drops when you draw some current. A small current draw could already drop battery voltage below 2.5volt, even if the battery is still 3volt unloaded.
The DW01A does not re-connect the battery anymore if the battery does not recover above 2.9volt. So 2.9volt is the real protection threshold.
Leo..
I was researching about this, checking diferent current drivers (IC?) for Leds circuits and understood why I need a resistor per led. But after a lot of research on the forum and articles there is something unclear for me maybe you can help me to understand.
This are the leds specification I would use and what I'm trying to simulate on the next circuits:
I ask that because for me seems obvious the parallel is the right way to go with its won resistor (prefeveribly calculated per led due batch error tolerance).
However I'm reading a lot about currnet mirrors, led drivers, stpeers up for led in series and somewhere I read if a led string in parallel die the current is shared for the rest of the leds but on my circuit this is not happening or I'm not understanding:
I would appreciate if someone can answer the question: Would a simple led killed on the sample increase the current on the rest of the leds causing the rest die also?
With a constant voltage source the remaining LEDs are safe when one is disconnected. With a constant current source it increases the output voltage to pass the set current through the remaining LEDs.
Think about it for a minute: how likely would it be that it's a constant current source? I.e. how useful would that be and what would the implications be for output voltage? So which possibility does that leave?
I'm not kind and expert on electronic fields but I guess it would be very useful if I need some kind of protection where the device must have a constant current or not work at all, kind of protection for the device, i.e. a DC motor, I think dc motors overheats if the current is lower than requried until they breaks.
For the output voltage I don't know which implications would have, as far as I know V=I*R so if the resistance (leds+resistor) is fixed and the voltage depends mostly of the battery level (except when the solar panel is charging) the voltage should be constant also.
For some reason I thought the tp4056 could play with V and I as some steppers up/down does.
So I think we can conclude it is not constant voltage source (since voltage depends on the battery level) and is not constant current source (since current depends on the load).
Anyways this is not clear for me so I will try to use it tp4056+ led diodes + resistors in parallel. If it burns out then I will try to add a MCP1700-3302E to regulate the voltage, and if it burns out also I will keep researching for a solution.
Hi, I just want to inform everyone I could fianlly get my project working.
Finally I used 10ohm resistor in parallel for the leds. 11 leds + 11 resistors.
The lamp is working all night and still remains about 4 V on ther morning with a 18650 Battery. So I decided to don't use the [KA75330] IC regulator by now and trust on the tp4056 module under voltage cut off.
There is still some concepts I don't understand related to how is tp4056 + 18650 voltage / current. If the are constant / variable. Whatever they are the project is working as expected at least on the last 48 hours.
I just want to animate to everyone like me who could be afraid about burning circuits or blow batteries that sometimes is better the method "try and failure" with some cautions of course. i.e.: I keep my project on a field isolated for more than 3 meters radius so in case something went wrong anyone get damaged.
