Hi, I am really trying to start using rechargeable batteries with my project, and I learned from a bunch of sources, including GreatScott (DIY LiPo Charge/Protect/5V Boost Circuit - YouTube) that dw01 is a popular cell protection IC, so I bought a couple of those to replicate his circuit. But I then realized that this IC has a low voltage cutoff at 2.4 volts!! which is waaay too low for lipo cells. Is there something I am missing? Why is everyone using this IC if it is discharging lipo cells to a point where it becomes potentially dangerous?
I think I found a better suited IC, (https://www.ic-fortune.com/eng/new_product1_1_1.asp?pno=FS312F-G) The FS312F- which has a discharge release at 3v instead of 2.4 but its more expensive than DW01 on ebay. Is there another option? Am I right about the DW01 not being suited for lipo batteries? thanks!
I would not use a cut-off of 2.4V with any lipo and its overcharge voltage of 4.3V is too high. In fact it doesn't seem to offer anything that I would call real protection.
slipstick:
I would not use a cut-off of 2.4V with any lipo and its overcharge voltage of 4.3V is too high. In fact it doesn't seem to offer anything that I would call real protection.
Steve
Totally agreed! so why the hell are there influential makers like GreatScott using it?? and this circuit offered by EasyEDA is all crap then?? TP4056 DW01 WITH PROTECTION Resources - EasyEDA... they do brand it as a 3.7 4.2 V recharging circuit
And also, which alternatives could I use, apart from SF312, for circuit protection? I'd like a very cheap smd chip with free shipping on ebay like DW01 haha!
JCSB:
Totally agreed! so why the hell are there influential makers like GreatScott using it?? and this circuit offered by EasyEDA is all crap then?? TP4056 DW01 WITH PROTECTION Resources - EasyEDA... they do brand it as a 3.7 4.2 V recharging circuit
And also, which alternatives could I use, apart from SF312, for circuit protection? I'd like a very cheap smd chip with free shipping on ebay like DW01 haha!
I think there might be something Im missing with tp4056 that prevents overdischarge at a certain voltage? Id really like answers to the last post but they are hard to find!
The explanation that I've seen about the 2.4V is that that's the voltage under load. If you shut down at that point, the battery will soon recover to about 3V. So you are really shutting down at 3V. I don't know if that makes sense, but there are many millions of the DW01s out there, and I think they work pretty well.
JCSB:
Am I right about the DW01 not being suited for lipo batteries? thanks!
On its own, then yes, they are not suitable.
Most LiPos are used in devices that have 'proper' low voltage cutoffs, phones, tablets, cameras etc. These devices will, you mave have noticed, warn you that the battery is low and turn off the device in a graceful manner. They do this of course with their own cut-off circuits. A common safe cut-off would be 3.0V, no point in going lower anyway, there is virtually no capacity left in the battery at this voltage.
This leaves battery manufactures with an issue, its well known that LiPos can explode and cause fires, so what to do to protect themselves if an idiot designer produces a wizard device that does not have a 'proper' low voltage cutoff ? So the manufacturers fit last ditch protection devices internal to the batteries as a backstop. They have a very low level cutoff so that they dont interfere with a 'proper' low voltage cutoff and turn off a device before data can be saved. The devices used for these internal battery cut-outs are made in very large quantities and become very cheap.
So hobbyists, who are mainly concerned with doing stuff on the cheap, see these very low cost 'protection' devices coming out of China as all they need to make their own wizard device and battery safe.
Hobbyists are apparently re-assured by the fact that you would not be able to buy these low cost so called 'protection' devices if they were not safe ?
ShermanP:
The explanation that I've seen about the 2.4V is that that's the voltage under load.
Thats possibly true for batteries used in applications where the battery drain is in the 10s of Amps region, radio controlled aeroplanes for instance.
For the vast majority of LiPo applications, phones, tablets, cammeras etc, the on load and off load voltage will not vary much since LiPos have a very low internal impedance, which is one of the factors that makes them so dangerous.
Hey JCSB,
Did you find a solution?
FS312F seems to be 3-4 time more expensive than DW01. If that or anything else is the issue like you have loads of DW01 in stock, then can we do the following.
Use 2x DW01 instead of 1x. So that one can handle the overcharge control mosfet as usual but another one can drive the overdischarge control mosfet with a little trick. What if you could trick the discharge mosfet controller DW01 to think that the battety has 2.4 volt when it actually is at much high voltage like 3 to 3.3 volt. It can be done by a voltage divider before the IC's power supply pin. Hiwever, the overdischarge protection release trigger voltage will also increase.
mostafakhan1971:
Use 2x DW01 instead of 1x. So that one can handle the overcharge control mosfet as usual but another one can drive the overdischarge control mosfet with a little trick. What if you could trick the discharge mosfet controller DW01 to think that the battety has 2.4 volt when it actually is at much high voltage like 3 to 3.3 volt. It can be done by a voltage divider before the IC's power supply pin. Hiwever, the overdischarge protection release trigger voltage will also increase.
It's hard to tell like this without having a schematic in mind but if it works, could be a good idea? But what I do when using this chip is using a diode to drop Vin before the chip.
Do you plan on using those chips for your applications?
Yes, I am trying to use DW01. Its low power consumption is tempting. I am actually trying to order the chip but due to Corona, everything is in a standstill.
JCSB:
But what I do when using this chip is using a diode to drop Vin before the chip.
If you try to use a diode before the chip power supply pin(a not-so-good alternative to a more accurate resistor voltage divider), it will probably read 2.4 volt when the actual voltage is 3volts, considering the diode has 0.6v forward voltage drop. This is probably what you want BUT, what happens when the chip tries to cut-off during overvoltage situation? The chip will not cut-off even if the battery voltage is 4.8volts(4.2v+0.6v). A huge RISK. Also, regular diode voltage drop highly depends on temperature and the current you are drawing through them. So you will not be able to accurately determine what actually happens in what situation.
This is why I said you can probably try 2 DW01 chips. So that you can separately control the charge and discharge situation. If you are concerned about only 1S battery and you can charge with constant 4.2 volt and constant current, then you, probably, do not have to worry about the overcharge situation and you can only use 1x DW01 chip in the above mentioned circuit for over-discharge control only.