The making of the BLF UC4 charger: the start of a new venture, INTEREST LIST, UPDATE 7 (Well, ramping stopped :/ )

Hello again BLF. BlueSwordM here.
So, I’ve noticed something interesting here.

We’ve had BLF group buys, for flashlights, for individual flashlight components, and even battery GBs in some rare cases.

So, why not make a BLF charger, the ultimate charger from companies that we know, trust, and have confidence in their skills and experience?

It would be the best charger on the market, with amazing features such as these:



1. Adjustable charging current: (0.03A - 0.05A - 0.08A - 0.12A - 0.18A - 0.25A - 0.35A - 0.50A - 0.70A - 1.00A - 1.40A - 2.00A - 2.50A- 3.00).

  • Limited to 2,5A for NiMH cells.

2. Support for multiple chemistries (Lithium-ion 3,6V-4,2V/3,8V-4,35V, LiFePO4, NiMH, NiZn)

3. Temperature monitoring (45C below 2,5A, 60C below 3A).
For NiMH, if temperature excees 45C, drop charge current.

4. 4 cell channels, with support for 10180 cells all the way up to 78mm 21700s.

5. Active cooling if temperature exceeds 45C, or/and if all channels are active above 2,5A.

6. Full current cut-off according to charging current (8%).

7. (5-10V)–30V input voltage compatibility. Stops charging if voltage goes below 10V, but keeps charging settings. DOES NOT RESET ON CHARGING INTERRUPTION.

8. Nickel plated brass rails for accurate internal resistance measurements. Or nickel plated A3 steel just in case. I have a backup plan for that last one

9. Internal resistance measurements.

10. Manual low voltage recovery for lithium-ion cells. Numbers based on 18650 capacities

- Below 2,5V: maximum charge rate of 100mA

- Below 2,0V: maximum charge rate of 50mA

- Below 1,75V: has to be manually activated

  • Below 1,0V: maximum charge rate of 25mA

11. Adjustable max charging voltage for lithium-ion: 3,50V-(n1+0,1V)…(n6+0,1V)–4,2V-4,25V-4,30V-4,35V-4,40V

12. Storage charge/discharge mode: 3,6V

13. Individual channel selection

14. 8 button UI (4 for voltage control, 4 for current control and other functions)

15. 100-200-350-500-700-1000mA constant current discharging functionality for measuring capacity and internal resistance.

16. Automatic charging current adjustment available.


1. Factory voltage calibration.

2. Reverse polarity protection.

*3. Charging/discharging data to USB drive.

Wouldn’t that be great to have? Our own perfect little charger.


Instead of an interest list on the forum, here’s a spreadsheet where you can see how many of each you want.

SecondLifeStorage Interest List

  1. 1x BlueSwordM

Target price: 49$US


UI is in conception. With an 8x button UI, all functions should be easily attainable without going close to Anduril levels of customization.

Now that we are in the UI design stage, this shouldn’t take too long actually.

It’s the 2nd stage, being external charger design, which would be rather hard.

People that will be testing and reviewing the charger:

-HKJ (Waiting for response)
-Mooch (Confirmed)
-BlueSwordM (Confirmed)
-Maybe Lexel


UI is in progress. Waiting for feedback from DLYFull, and wondering if they could use Cheali as a base.


Physical design is currently in process.


Project has been put on hold.

1 Thank

Here are the manufacturers that I would like to be working with:

- Folomov

- MiBoxer

  • SkyRC.

However, the chosen manufacturer has been:



My friend Henry Xu of Opus is unfortunately MIA for a very long time I could easily propose the idea to him. :frowning:

Oh, I hadn’t thought of OPUS. I’ll try to contact them alongside the others.
I think we have the highest chance of success with Miboxer or SkyRC, since they already have a lot of experience in these fields.

What would the ideal target price be? 39$ for the charger with every non-USB feature and 49$ for the charger with USB features?

I am not a charger expert, but this looks impressive so far!

Can the charger automatically choose a suitable charging current based on which type of battery is inserted?

(That's the feature that I would be looking for.)

I’d love something like this. Has been much needed as most chargers on the market are severely lacking.

i’m in for this! :+1:

@raccoon city, that is an excellent idea. It would have to be rather conservative however, as to only allow currents based on previous charging measurements or set in by the user.

@Jtm94, yeah, same thing here.

Adjustable charging voltage and low capacity recovery are two things that no charger on the market currently have right now.

@DBSAR, excellent.

BTW, if you want to give suggestions, just do! I want as much community feedback as I can get, and note of course.

Miboxer’s C2-4000 can do ~1A*2 discharge with a noisy ass fan. Get a better fan and run it at half power and I would propose 1A discharge if possible.

It should be easy to use, like using a hobby charger (which has already the features this project aims) but this time having 4 individual bays.

Enable it to keep four cells in trickle charge indefinitely and put a floody LED with a smart (TK) user interface on it — so it becomes a grab-and-go item for those of us in earthquake territory.

@contactcr, no problem. Just upped the discharging current to 700mA. 1A could be possible, but you’d have to limit discharging current to 1A/2 bays to help with heat dissapation.
Also, putting a small aluminium heatsink on these resistors would help a lot.

@hank, that is easy peasy. Just set the charging voltage to 3,9V, and be off with it. Charge it normally up to 4,2V once you need it.

I love the idea of a perfect charger. I have to use a Folomov A1 to charge my Wuben 21700 that is 75.1mm. Could this project somehow ensure that the longest 21700s fit?

Yes, absolutely.

What is the absolute longest 21700 that exists?

Is it that 21700 from Acebeam that uses a buck-boost converter to charge USB devices and charge itself?

I was thinking of something plug-and-play.

The charger recognizes the chemistry and length of the cell being charged, and chooses a suitable charging current.

(I don't know if that's possible.)

That is possible, but is slightly harder and more error prone.

Chemistry is just based on the internal resistance analysis, but it has to be conservative. Currently, the C4-12 that I have likes to go at 3A on my 30Q during automatic charging, while I would prefer 1,5A at max.

Length would be slightly harder, but would require additional hardware.

would be cool if it did it based on length + resistance so high current 18350’s dont get overcharged but still allow like a VTC5A to be fast charged

How about a BLF firmware for the MC3000?

Wouldn’t that cover just about everything you’ve asked for?

Yes, but not in this case.

The MC3000 doesn’t have:

- Support for long 21700 cells.

- USB data out.

  • The higher conductivity brass contacts.

And other miscellaneous stuff that I haven’t included.

The design of the MC3000 isn’t also optimal. I prefer the C4-12’s design.

And it’s also rather expensive.

Okay, cell length might not need to play a factor if internal resistance is being analyzed.

I told you I'm not a charger expert.