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 ?
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.
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
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.
Guys and gals, I want you to be realistic.
I want this to be the best BLF charger in terms of features, functionality, and bang for buck.
We have to be careful of feature creep.
Interested. But I think the price point should be no more than $35.
This is where I disagree.
If we want to make the ultimate BLF charger, then not only software features will have to be implemented, but also hardware features, like nickel plated brass holders, microSD slot.
We are making a no compromise BLF charger.
I’m very very interested in a no-compromise charger with a wide voltage input range. Cost is less of a consideration for me.
Amen. I think the target price should be no LOWER than $50, or major compromises will be certain. And, unless I am mistaken, the goal here is not a mass market product that will outsell Nitecore. I imagine any potential production partner understands that, just from the specs.
interested
^ This
We already have a number of cheap(er) chargers that only do some things right. If we can manage to build a charger that does everything right, to me that’s worth more. Alas, we all have different price tolerance.
Very low, really. Microcontroller(s) don't need high voltage. Down to ≈5-8V without reset is easily feasible.
Sorry but, how is the charger going to know what kind of cell is inserted?
@#$% no to those limited voltage range figures.
Going down to 3.4V for LiFePO4 is nice, as you say they get fully charged without need for any higher voltage.
Let me say I need no nanny in a charger. How about Let's make it with fully selectable charging voltage from 4.4V down to 3.4V. Certain functions “only for the experts” could be made accessible only after activating PRO mode by powering up the charger while keeping pressed the two main buttons. Or something sort of. 
Those of you who need a nanny charger could be happier by buying something else. Don't you?
Concerning the discharge feature, I agree with the big axial fan at the bottom idea. However, the charger chassis should or needs to be designed in a way that the fan's air intake may not be inadvertently interrupted. Making the charger a bit taller and setting dual air intakes each side or top and bottom definitively solves this if properly done. So be it imho. 
BluewordM, please edit the opening post and change the input voltage compatibility to something like 7V - 30V. Let me also say that this charger may require a very high amount of power when charging at 3A per slot, probably close to 60W. So, I believe it could be better served by a 19V - 24V power supply, similar to the ones bundled with laptops, mainly to alleviate current losses in the cable.
Sun, 08/25/2019 - 00:09
Of course. Never said that full power could be achieved with anything less than 12V.
(5-10V) is the range in which the charger will stop charging, but not completely turn off.
Looking forward to seeing this product come to market!
Will the requirements definitions (document) address accuracy tolerances, safety features, robustness/reliability, assembly quality, QC practices, etc.?
It’s often left to the manufacturer to do this but it can cripple a product if not done well enough, or to the level expected by the community. Defining it up front can also help with the cost analysis and any necessary adjustments to the feature set or MSRP.
No worries Mooch.
I’ll be starting serious discussion with manufacturers about manufacturing and the other stuff Monday.
Say, what made you come up in this forum?
Been a lurker at BLF for far too long!
My apologies for just diving in like that with concerns.
Barkuti posted about the charger over at ECF (electronic cigarette forums) and I was quite excited to see this project coming to light. I had to chime in to say I think it’s a fantastic idea. 
Nice to see you Mooch. Been in the e-cig forums for years. Always enjoyed your candidness with these battery manufacturers. How many years ago was the efest fiasco? lol
Agree. Many laptop power supplies use such standard plug, it could then be powered by a typical 19V 65W/90W brick. The charger could be sold with or without power supply at different price points. LiitoKala does this.
I for example have many “retired” quality laptop bricks which I could easily convert to ∅5.5 × 2.5mm plug if needed.
Of course what I'm trying to imply here is that, with such long list of charger features and a minimum of quality, what manufacturer is willing to make a device which such potential to cannibalize its own products? The ones who already have good chargers at beefy price points may not.
A quality charger with so many features and an expensive power brick at $49? Maybe a little more money would be more realistic. Or a tiny bit less without the brick.
LiitoKala may want to go with this. They do not have a high end charger, thus 0% chance of cannibalization. Careful negotiation may be due to make 'em understand the quality and feature requirements. Also, if they were to want to make a cut-down version later, I'd at least tell them to name it differently.
DLYFULL is also a good candidate. This would turn out to be their “flagship” charger or sort of. Careful negotiation is due too.
By the way, to ensure proper cooling of cells their slots may need some holes or slot gaps on the floor. 
Sun, 08/25/2019 - 05:31; Sun, 08/25/2019 - 05:34