beanflying "Partly because a lot of us will see little advantage in reinventing the wheel when you can buy a good one for around $30."
Again, beanflying, I am not interested in buying modules or even dedicated BM IC's if I can avoid it.
I am interested in furthering my experience in designing circuits, to learn how to design circuits.
I am not a newbie. I have been designing and successfully building my own CPU-based power supplies and Li-Ion chargers for projects for over 20-years.
I am therefore not trying to "start from scratch."
Nobody said you'd be
starting from scratch. I said you intend to
build it from scratch, which means "not relying on premade things", i.e. in this case, avoiding modules and ICs. I used "build from scratch" to avoid using "DIY", which has connotations that might not be applicable here.
Like, haven't you ever heard anyone say "I'm going to bake a cake from scratch"? That means starting with flour, sugar, eggs, milk, baking powder, and vanilla, as opposed to starting with a cake
mix that only needs eggs and milk. It doesn't mean that it's their first time baking!!
Tooki: So now suddenly you are willing to use dedicated ICs? That’s a very sensible approach. Later you can build your own truly from scratch.
I never said I was willing to use dedicated ICs. I don't understand how you misread what I posted to think this is true.
Easy, because your lousy punctuation and run-on sentences make it easy to misunderstand what you mean.
You wrote:
I would also say that I can circuit design as good as the best groups of engineers by learning their technology, their methods to solve this problem using up to date battery-charging/balancing IC's.
That sentence construction (Do X by doing Y) means that the Y is qualifying
how you will do X. Using italics to mark X, and bold for Y, your sentence parses as either:
I would also say that I can circuit design … by … using up to date battery-charging/balancing IC's.or I would also say that I can … solve this problem using up to date battery-charging/balancing IC's.
Either way, you end with the qualifier of
using modern ICs.
My goal is to try to achieve the smallest footprint without resorting to buying a dedicated chip and certainly not a pre-built module. I may not be able to closely achieve that goal but I will make that effort.
My solution may not even be as cheap, but it will be my design. It will by my design and undergo testing, so I am sure to say it is able to very closely work as well as the pre-built module or dedicated IC.
If I design a circuit to accomplish my goals, I will be able to completely control the circuit operation and size to fit my needs for performance, parts sourcing, cost and safety.
You say that now. But above, you stated repeatedly how your goals were to:
a) match or undercut the price of a low-cost product from a supermarket
andb) minimize space
Well the first one is practically impossible anyway, so let's ignore it. But if space savings matter, which they seem to be since you bring it up every time, then you'd want to go with a dedicated IC.
As I said in a prior reply: if your actual #1 goal is to avoid using anything premade, even ICs, then you should not have kept insisting on low cost and compact.
Finally, I can say (after quite a lot of Googling) that charge-balancing is not really complicated of something "taboo" to play with.
Charge balancing needn't be complicated nor unsafe to attempt.
Nobody said balancing was taboo. Without knowing your skill level (which you didn't share until your final tirade), the etiquette here is to err on the side of
safety, which is why you will see people express warnings about lithium charging.
I had hoped my topic posted would have been about sharing experience with charge-balancing instead of spending post after post attempting to convince others that I am not interested in modules.
The first person to mention a module to you, to which you immediately freaked out, said to look at a module
to see how they do it. They did not say to
buy the module!
The reason you're getting so much pushback, SuzyC, is your awful attitude. You've been on the defensive since the first reply was posted, a reply you didn't even read properly. You attack everyone, and then oscillate between acting like a newbie and claiming you're super-experienced, ultimately spending more time whining than anything else. Your sloppy use of terminology also makes me very skeptical of your claimed expertise.
Always in charging LI-Ion, current must throtle down once the 4.2V (or 4.15 or 4.1V) desired cutoff voltage limit is reached.
Proper charging always allows the constant-current to decrease during the voltage float phase of charging, once the target cutoff voltage is reached while charging.
You are always in
either constant-voltage (CV)
OR constant-current (CC) mode — you can't be in both at the same time. (Float charging is something else, btw.)
When the CC phase has finished by reaching the termination voltage, the charger switches to the CV phase, during which current (not "constant current") drops until reaching the termination current.
This is why voltage balancing seems enticing, because some cells could reach the cutoff voltage before others and equalizing prevents these cells from being damaged by over-voltage while allowing any lower-voltage cells to continue charging.
I think a better word than "enticing" is "necessary". But yes, that's exactly why you need balancing.
Charge-balancing is accomplished in two ways. The first is to switch on a shunt resistor across a cell that is too high in voltage (relative to other cells in the battery) to slow its charging.
The second way (and I am not sure if it is used in modern charging circuits) is to momentarily shunt a capacitor across th higher-voltage cell and then transfer this charged capacitor to shunt a lower-voltage cell to discharge the transfer-capacitor.
The second idea seems enticing because it does not waste charging current, but could be less safe and very complicated to achieve i a charging circuit without a very large number of extra parts.
Another way it's done is with inductors as energy store. See e.g. how the Analog Devices LT8584 does it. But it definitely adds lots of parts (even more so when rolling your own control circuit.)
There are also some systems that use an additional, dedicated cell as the energy store for balancing.