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

BLF Special Edition Products
265

Just dropped by…

TL;DRed most.

Danger exists only in the eye of the moronholder beholder. ;-)

Cannot agree. There's people who may want to recover over-discharged cells while perfectly knowing what they're doing.

Place, for example, a li-ion cell on a crappy SK68 for amusement or testing. Or a couple cells on some crappy flashlight with lame buck driver. If I notice a cell just got over-discharged and my charger doesn't allows me to recover it, what do you think am I going to do?

Let people have options. This supposedly is an advanced custom charger. If pleasing the @#$% crowd is a priority, the potentially problematic advanced functions could be left accessible only after activating a special mode in some options menu or by pressing some specific key sequence. A warning message could then appear asking for activation consent.

The charger is going to have a dot matrix LCD screen, doesn't it? :-D

BlueSwordM, please fix this mess in the opening post.

266

Yes, can we please have the first post updated with the final set of specs, as it stands today?

Thanks.

267

Great project idea. Interested!

268

Interested as well…

269

@Barkuti, thanks.

500mA below 2,0V would be rather bad for safety, and longevity.

270

Final features that will probably be included:

1. Adjustable charging current (0,05-0,10A-…–3,0A) in 0,1A steps.

2. Support for multiple chemistries (NiMH, lithium-ion, lithium ion HV, LiFePO4).

3. Temperature monitoring (45C max below 2A, 60C max below 3A).

4. 4 cell channels, with support for AAA sized cells all the way to the largest 21700/26650/D cells up to 78mm length.

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

6. Full current cutoff according to charging current (10%).

7. 12V-20V input voltage compatibility.

8. Nickel coated phosphor bronze/brass rails for highest conductivity and accurate internal resistance measurement. Or just well plated nickel plated A3 steel if too expensive.

9. Internal resistance measurement.

10. Manual low voltage recovery for normal lithium-ion cells
Below 2,5V, maximum charge rate of 100mA.
Below 2,0V, maximum charge rate of 50mA.
Below 1,75V, it has to be manually activated.
Below 1,0V, maximum charge rate of at 25mA.

11. Adjustable max voltage for lithium ion charging: 3,65V-4,35V in 0,05V steps.

12. Storage charge mode: 3,6V. Lower would be better, but it is too low otherwise for most people.

13. Individual channel selection.

14. 4 button UI.

15. 100-200-350-500mA-1000mA discharging functionality.

16. Automatic charging current adjustment available.

Some extras that would be very nice, but not necessary if costs exceed 49$US with the below feature set.

  1. microSD card slot for graphs.
  2. Bluetooth functionality.
  3. Charging/discharging graphs to a USB drive.

Feature freeze will occur at 11:59PM EST.

271

Looks great.

Is there a price target for this? Or still too early to say?

272

39$US would be a superb price, but 49$US is more realistic.

273

That’s fairly reasonable.
I’d add reverse polarity protection, too, if not yet mentioned.

274

Yes of course.

It’s such a basic feature that I forgot to put it in.

275

How would it differentiate between NiMh and an over discharged 14500? Probably something simple that I’m overlooking otherwise the NiMh will be charging for a long time.

276

This is why I added manual to low voltage recovery.

Lexel and the other guy did have a point that even if my method is very safe, there is still a risk, even if it’s 0,00001%, so I decided to change it to a manual setting below 1,75V.

277

Dot matrix LCD screen? :-)

Now that I'm here I will say that for accurate internal resistance measurement cell voltage needs to be measured right at the battery terminals. I mean, a 4-wire setup like in battery testing holders (example). Give up on this @#$% being fully accurate otherwise.

278

Ok…so it will assume NiMh if below 1.5v or so? That would make sense.

279

For price see post #277

280

At BlueSwordM
I would extend the input Voltage up to ~30V. The most used PSUs have 12V and below. Above there is not much compatibility gain up to 20V. But like it was said before many Trucks use 24V and many industrial used PSUs are also 24V. Next step would be 48V but i think this will only add more costs and will not gain much options.
But to raise the possible input voltage above 24V (to be a bit more save from voltage spikes something arround 30V) would give the user much more options for PSUs and also the option to use the charger inside a Truck without any other converters.

281

I remember my Opus, when powered by my 12vdc cigarette lighter aux power, loses its screen data when the car is started, resetting the charger to its default ‘Charge’ mode due to the momentary loss or drop of voltage, going to as low as nine dc volts when starting, especially with diesel engines.

I wonder how much minimum voltage is required so as not to lose data and re-starting ?

282

Please forgive me for chiming in during the last day, but I would like to suggest a few more things.

This should be in 0.2A steps above 1.6A and in 0.05A steps below 0.3A (more convenience).

Lithium ion HV (4.35V) is fairly uncommon - there could be also NiZn included, as it is very easy to implement (charges almost like a Li ion, just the target is different).

For better NiMH termination, sometimes -dv/dt termination is too late, and cells are getting cooked extensively (lower currents need lower temperature limits). Will you include a method for both voltage and temperature based termination?

There could be one plastic adapter accessory included with additional springs to host some of the very small oddball li ion cells like 10180, 14230 etc.

Double d=5cm fans, and very good set of heatsinks could be necessary - (for discharging at ~16W power).

I think, these rates are only meaningful for bigger cells (21700, 26650), for smaller cells, these maybe would be too harsh.
I would suggest these:
Below 3.0V, maximum charge rate of 100mA. Below 2.5V, maximum charge rate of 40mA. Below 2.0V, maximum charge rate of 20mA.
Below 1.75V, it has to be manually activated. Below 1.5V, maximum charge rate of 10mA. Below 1.0V, maximum charge rate of 5mA.

I would also add, that for each charging bay, if a battery is inserted, but no program started, the charger is required to not drain the battery (even if it is just a few hundred microamps).

I would make this chemistry dependent.
lithium-ion: 4.05V - 4.20V
lithium ion HV: 4.15V - 4.35V
LiFePO4: 3.40V - 3.65V (I saw an article somewhere, which mentions, that at 3.4V, most of LiFePo cells are ~99% charged)

There could be more than one storage targets (different requirements). I would suggest to let the user set the target voltage in a range of 3.5 to 4.0 V (by 0.1V steps).
Storage mode could also include a discharge to the above mentioned target, if current cell voltage is above target.

I think, 4 buttons for channel quick selection (and program start/stop) + 4 more buttons could be better. Only 4 button in total could result in early button fatigue if they are used extensively.

I would add 50mA for very small cells, and 700mA is also missing.

283

The Incurable Gadget Freak within sez,

"gottahaveitgottahaveitgottahaveit".

The Hopeless Tool Junkie within sez,

"gottahaveitgottahaveitgottahaveit".

The tiny, oft-overridden percentage of Practical Thinker within asks,

"Will a 12v DC automotive adapter be included or available?

slmjim

284

Ok, I came back from SecondLifeStorage, and I have some new ideas. Last features to be implemented.

@TheOnlyDocc, you came before I did. You know about 7S lithium ion battery packs? Their max voltage is 29,4V, a (5V-10V)–30V compatibility would be excellent.

@adam7027, that would be insane below 0,3A, but I get your idea.

1. Here is how I would prefer doing it:
0,05A
0,10A
0,20A
0,30A
0,50A
0,70A
0,80A
1,00A
1,20A
1,40A
1,50A
1,70A
1,80A
2,00A
2,20A
2,50A
2,75A
3,00A

2. That includes NiZn.

3. NiMH charging will throttle below 2A if it gets too hot(above 45C), and if it exceeds 60C or 1,75V, it will completely stop charging.

4. 10180 support is planned.

5. Nooo. Only one 90/120mm fan would be best.

6. These maximum charge rates have only been tested for 18650 cells.
You can set them lower obviously. Your current targets are way too low.

7. No, not exactly.
It should be: 3,5V-4,35V in 0,05V steps for all chemistries.

8. Storage mode does exactly that.

9. 4 button UI.

10. Ok for discharge rates.

Sorry if it took some time. I’m writing this on a phone.