Hi, I have a DFR0969 2-Way 18650 Battery Holder which I can’t get to stay ‘on’ once the USB charging cable is removed. I have two good 18650 batteries installed (4.13v each), the board believes they are charged (all 4 red LEDs are on), but when I remove the micro-USB charge cable the holder will supply power (5v from the soldered output pads) to an Arduino Uno for 5 seconds and then turn off. It does the same from its 3.3v outputs.
I have tried both Mode switch settings with similar outcomes… about 5 seconds after pressing the ‘on’ switch, in ‘Normal’ mode the 5v drops quickly to about 0.6v and slowly discharges to near zero. In the ‘Hold’ mode you get 5v for 5 secs and then it drops to zero immediately.
I can’t find any reference to this issue elsewhere, or much data about the holder itself (for instance what load does it expect in ‘Normal’ mode to stay on). Anyone had any experience with these?
Hi Peter.
Welcome.
Did you not read the description re this device. The core description and DFRobot should be the same as I think one is a copy of the other.
This reads
The onboard DIP switch allows users to switch between HOLD and NORMAL modes. In Normal mode, it auto shutdown when the current is too low, while in HOLD mode, it keeps outputting and does not shut down until the over-discharge protection is triggered.
This shutdown with low load is normal for power banks designed for charging phones but this one at least gives you the option of keeping it on with a low output requirement. I think the Arduino UNOload would be pretty small.
Sorry I have just re read your post. You apparently have tried both switch settings so the device is not working as described.
Most power banks it would be about 100mA.
Don’t expect much of this sort of info from the manufacturers of this sort of thing as it is usually a bit thin.
I have not looked but there may be more info in a “product wiki” on the DFRobot web site.
Cheers Bob
Yep, thanks Bob, I tried the DFRobot site (product info, forum, wiki) but nothing. I’ll try applying a bigger load today to see if that makes a difference, but my reading of the description is that it should stay ‘on’ regardless of the load in the ‘Hold’ mode…its pretty useless for running micros in low power mode if it doesn’t.
Can you measure the voltage across the battery terminals immediately before it shuts down? That will tell you whether it is shutting down because of insufficient battery voltage, which could be caused by an internal short in the device.
Yes, that is what I would have thought also.
Jeff might have a point. The batteries are fully charged aren’t they but You mentioned 4.13V which would imply they are. Might be a dodgy device. Interested to see what happens with a bigger load.
Cheers Bob
Jeff, the batteries only show a 5 micro-volt drop when the unit is turned on, and it stays constant until it turns off.
Bob is right about needing a heavier load when running in ‘Normal’ mode…at 100mA it continues to run until it is unloaded, then stops after 4-5 secs. With the same load in ‘Hold’ mode it also runs fine until you remove the load and then it also turns off after a short but variable (5-10 secs) time.
After reconnecting to the Uno, about 30mA, in ‘Hold’ mode it also ran (not sure why, perhaps it is on the brink of sufficient load) but only while the load is on. Once you remove the load (or, for instance put the micro to sleep) the battery board turns off…which it shouldn’t. I also tried a lower load with a 680R resistor, 7mA, and it won’t stay on at all.
Seems to me that it is not functioning as designed, I’ll discuss it with Core team.
Just bringing the relevant parts of our email chain out into the open for the community to benefit from:
I’ve tested a unit from stock on an electronic load, and determined that it shuts down after a few seconds at 120mA in “Normal” mode, and 40mA in “Hold” mode. I can see that the switch seems to connect a 62 Ohm 1206 SMD resistor, this likely loads up the circuit, so if you had a lower resistance lying around, you could solder to this pad to trick the hold mode into operating at a lower current (though you’d be burning off more energy, not the best for a battery powered project).
This strikes me as inappropriate for low-power projects as you suggested, so I’ve made a note to update the product page
Hi James
What a cheap and cheerful way to fool the gullible public.
Particularly as there seems to be nothing published at all about the device not staying on when in hold mode. Shutting down under low voltage situations is fair enough and understood but Peter has purchased this thing believing it would hold the 5V under no load conditions.
I have said often I am reluctant to purchase anything without access to pertinent detail. Proves my point a bit doesn’t it.
Cheers Bob
PS: This is not a reflection on Core as I believe they reproduce the manufacturers text in good faith. It would not be a viable proposition to test every aspect of every product they re sell. There is just too much. It is the supplier that fails fairly miserably at times to provide the full story. OR the product is released too early but in this case just putting a resistor across the 5V to increase the load makes one suspect that this shutting down was a known thing. This is pretty much a universal way to detect end of charge and stops the process at this point. All good for charging your phone but not so for a power supply.
Good points here. I think James is suggesting at the end of the post that they’ll update the product page, but it’d be nice if suppliers did their due diligence.
My guess is that this board uses an off-the-shelf 2S-lipo-to-usb chip designed to go into a power bank, and that it doesn’t offer enough control to bypass the end-of-charge circuit. I’ve come across better ICs that allow you more control, perhaps I should start walking the walk and actually do up a design around one.
Old thread, but I bought one of these things a while ago and didn’t get around to using it until yesterday. The text in the ad does mention the 40mA cutoff “feature”. I don’t know if it was there when I bought mine, but like a lot of other people who bought one I just assumed I could use it to power my Pi Pico project. I can’t, it won’t work. My project draws way less than 40mA.
The spiel for this device specifically says it is suitable for powering microdevices. It isn’t, and the ad copy should say that it is NOT suitable for powering microdevices such as Arduinos and the like. It also says it is suitable for outdoor devices, whatever that means, and DIY smart vehicles, again, whatever that means. What it should say is that it is suitable as a backup power device for devices that constantly draw more than 40mA, or to charge a smaller battery. There may be other use cases I’m not aware of which could be mentioned. But certainly the current ad copy is misleading and needs to be changed.
I agree, this doesn’t seem suitable at all for powering microdevices. I’ve removed all reference to that.
If you were looking to power a Pico, keep in mind it has an internal regulator, so a charge board is all that’s needed to use a single cell to power one. You could solder a JST pigtail to an 18650 with solder tabs.
Thanks for the feedback. That charge board looks good. Just a small technical question, could it be used to charge two 18650s connected in parallel? Also, with a 215mA charging current it’s going to take a long time to charge one 2600mAh 18650, never mind two. The spec sheet says that the charge current can be set to a max 500mA, but is that available for this board?
Hey Ian,
I don’t see why it couldn’t charge two cells, of course this will take twice as long as you’ve described.
It looks like the 215mA is set on-board and so it won’t be able to supply the maximum for the chip (500mA)
You can charge two lithium batteries in parallel IF they each have charge/discharge protection built-in to the battery. Without charge protection or balancing any voltage difference between the batteries can result in a very high current flowing from one battery to the other and either damaging a battery or creating a fire risk.
Or, you can use the batteries in a dual battery pack that includes charge/discharge protection, in which case you don’t need an external charger, just a sufficient power supply.
Thanks for the replies and advice.
I’ve done a bit of research on the net, and basically @Jeff105671 is right.
I looked at BMSs on ebay and there are many balancers available for not much money, but they all, as far as I could see, work with the cells connected in series. I couldn’t find one that would would work with the batteries connected in parallel. There are single cell protection modules that look like they can be stuck on to the battery, and they are very cheap, so that could be an option for an unprotected battery.
So, next question. Do the cells sold by Core have charge/discharge protection? They have a ridge around the top, which may suggest they do, according to one website I found, but it isn’t definitive. I bought two of them when I bought the holder.
I don’t think you will find a 2P BMS module. You will find 2P battery packs. They may have a custom protection board, but are often just two cells in parallel with protection for each cell. Single cell protection is so inexpensive that there’s likely no point in making standalone 2P, 3P etc protection modules.
It is a good rule that flat-top and tab-top batteries are not protected, while button-top are. AFAICT both Core cells are not protected - protected cells are usually clearly advertised as such, in part because they can be sold at a higher price.
