*BLF LT1 Lantern Project) (updated Nov,17,2020)

Thanks for your feedback TomTom. My biggest concern about the TP4056, and most charger circuits, is the lack of reverse voltage protection.

DEL was doing the driver board for this project and had a powerbank board designed, but he has disappeared. And his powerbank design suffered from lack of reverse voltage protection as well. Adding a schottky diode is an option, but of course the battery charge goes down by the diode forward voltage. DELs design was quite nice, but also requires a 24 pin surface mount IC which I don’t have the ability to work with for prototyping.

I have considered that if one installs the batteries properly once, having USB charging will eliminate the need for removing and replacing the batteries for charging, which is a good thing.

Take a look at the Microchip MCP73861.

“6.1.1.4 Reverse-Blocking Protection
The MCP7386X provides protection from a faulted or
shorted input, or from a reversed-polarity input source.
Without the protection, a faulted or shorted input would
discharge the battery pack through the body diode of
the internal pass transistor.”

Edit: sorry, appears to be obsolete. I’ll do a little more digging.

Edit 2, see MCP73113 and MCP73871. Also protected from RP.

I daresay there are others.

Why was USB-C rejected? I think it should be the obvious choice. Everything has recently went to USB-C, so it already has wide spread adoption. Micro USB is on it way out, and in just a few years will not be as easily available. Whereas USB-C will be easily found for the next 5-10 years, maybe more. Not to mention that the USB-C cables tend to last much longer. I’ve been using the same two USB-C cables for two years (bedside and car charger). MicroSD would only last 3-9 months for good quality cables, and about 1-2 months for cheap cables.

As far as I remember we already discussed the charging solution a while ago (check page 64) and decided that we want to use USB c and a BQ25895 (datasheet ) charging chip.

I don’t know which planet you live on but here you can still easily get any USB cable, even the big fat type B. Micro USB cables will likely be around for decades.

Perhaps more relevant is that a few years from now, USB-C is more likely to mean one less cable to bring on a trip. But I don’t really care either way and I think either choice will be the wrong one for many people so we might as well just toss a coin.

I did state that there was a design completed by DEL that used the BQ25895. However, I do not have the equipment to solder this part to a PCB for testing purposes. I really like the part and the circuit DEL designed, but am unable to build a prototype. That was part of the reason I wrote this post to see if there were any forum members willing to assist in this part of the project.

If we receive offers for the ability to build prototypes using the BQ25895, then it is certainly still a possibility.

Thanks Tom Tom, I will take a look into those parts. Ok, I took a quick look and they quote reverse discharge protection. I think those are strange words to say the leakage back into the chip is “low” whatever that means. I did not look at those specifications. What I did look at was that if the voltage between the BATT output and the return are reversed, then you exceed the rating of the part, and it likely fails. It only takes once to kill the part.

You can protect against reverse polarity very simply with just a small inexpensive FET. No significant voltage drop (unlike a diode).

Edit: a PFet protection is pretty much universal for automotove electronics, together with a big Transzorb to protect against alternator load dump events (not a torch problem).

I think you mis-remember.

As for using the BQ25895 that’s a mad idea. to benefit from any of the features it has to have a microcontroller to set it up, and I think the firmware required would make the stuff to run the LEDs on the lantern seem trivial.

And it is an expensive part. Very expensive.

Study the datasheet.

This is just a torch/lantern, a simple USB micro to charge it up is all that it needs.

If you want it to be a powerbank, well, it’s possible, but take a look at how they are usually done, a USB micro to charge, and a big clunky (but so reliable) USB A for power output.

USBC is not necessarily the next big thing. And is expensive to implement. I have two devices that use it (a smartphone and a Samsung Galaxy TabPro S. Both of them now have dodgy connectors, only used with the OEM cables, a couple of insertions per day. If the connectors fail completely then I will have no way to get my data out, or even charge them. Not happy.

I also thought we had decided on Usb-C. I am 70 and my eyesight is failing. Up until recently I struggled with multiple different Usb cables trying to find the right one and especially the right orientation. Last year I got a Note8 which has ‘C’ and it has been SO MUCH easier …… I know we usually learn from our mistakes, and I think this would be one, but I am confident BLF L2 will have ‘C’…. if I am still around for it.

@ Tom Tom- Are you saying that the C is more prone to damage than the others? I would think it would be the other way around since usually if there is a problem with a damaged connection it is because users either try to force a wrong plug or try to connect with the plug upside down…… Are the C plugs inferior in quality? If it is a cost issue…… how much more would it be per lantern?

Am i the only one here who dont have any usb-c device? :zipper_mouth_face:

I don’t, not even sure what it looks like.

Thanks for the link Tom Tom. BlueSwordM described an identical circuit to me recently and for some reason I just did not get it. Seeing it in a different presentation made it click I guess. :student: I will be adding this to the driver for sure.

well said TomTom, that’s the reasons why i tested the 1 amp TP4056 to be perfectly suited for the lantern, as even with four 3600mah high capacity cells, the 1A TP4056 would charge them in less than a day (of which time the lantern is not used) and the lantern will run for a few nights on a charge at 5 to 6 hours per night on high. There is no need for “Fast charging” at 2+ amps what so ever for this application, which causes problems i tested when trying to charge from lower powered Solar panels, wall adapters, RV USB ports, etc. it will be likely limited to 1 amp charging for the production model for those reasons. Unlike phones & tablets where fast0charging ratea are a great idea, for the lantern purpose it really does not need it at all.

USB-C is the planned charging port interface for the production lantern (if it do not add to much more to the retail price of the lantern) if USB-C is to cost-prohibitive, then we will have to go with USB-Micro. we will know once Barry can determine the cost difference for us.

EDIT: - I been searching for USB-C type charger/USB power bank modules and have had no luck with finding anything at all that seems to use the USB-C port for both charging cells and use as a power bank output all in one port (as some people said it was capable of, but i have not found that option existing at this time)
it seems to have both the charging capability & USB power bank option there will be have to be two ports, and a separate female-USB-A socket for connecting devices like smart phones to charge them. (USB-C for the charging-in port, (or revert to USB-Micro if the manufacturer determines that USB-C is too cost prohibitive for the production lantern)

The next ‘new’ Usb device you get should have it……
it is symmetrical(there is no right/wrong way to plug it in)

Hahaha I was afraid to say that I don’t have any either. But it seems that I’m not the only one without one.

Baseus 2 in 1 Type C Micro USB Data Sync Charging 1.2M Cable for Samsung S8 Xiaomi 6 Letv
https://banggood.app.link/XtLGqYYiMO

To all those who doesn’t have USB type C yet, I suggest you get some of these. Great quality at an affordable price. I have one in my car, a couple in my house as well as in my camping box.

If not too late, PLEASE put me on the list!

Definitely do not want to miss this!

Thanks!