If your trying to find out the discharge capacity and have it graphed like HKJ does, I don’t see why you need to do more than one cell at a time. To me seeing what one cell can do at 3 amps is more important than what 4 cells can do at .5 amps.
Doing 4 cells at a time would require 4 data logging graphs going at once which I guess is possible but the first link I posted would handle one battery at 3 amps, so for 4, you’ll need 4 of those or one 4 times the size.
And how much power are they discharging and how big is the load discharger.
If its going to be all in one unit a middle ground has to be meet somewhere, if not then bulkier additional devices could be added I guess.
How about small cells like 10180?? Make it universal for evey battery out there. And make take protected and unprotected batteries with power bank functionality.
Opus and skyrc and maybe xtar is my choice for manufacturers
So I was went over to https://secondlifestorage.com before dropping a link in this thread, and it turns out BlueSwordM is an active member with a matching display pic. So I guess he’s more qualified to explain this use case. lol
Graphing can help track the full behavior of the battery, seek for spikes, patterns, etc and understand the real life of the cell.
Or put simply: graphs is what makes "lygte-info.dk" so understandable and relevant, it helps bring objectivism to battery tests. A killer feature to me, and probably #1 reason why a MC3000 is sitting a cable away from my computer.
I hope HKJ don’t mind me borrowing some of his pics. Credit goes to him for the testing.
This is the reason discharging a cell at a higher rate (3 to 5 amps) can determine how good a cell is in the real world flashlight use. This is a bad example because I have chosen probably one of the worst again’t one of the best but it helps to understand the differences.
If you were to only discharge these two cells at .2 amps this would be what you get and the cells would seem very similar in use.
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now try it at a 3 amp discharge.
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In a flashlight 3 amps of current draw is becoming some what low now days, imagine the difference using those two batteries. If you couldn’t run a 3 amp discharge test on some fake 30Q’s with the Ultrafire cell wrapped inside you wouldn’t know the difference unless you had a authentic 30Q to compare it to.
Most all the 4 bay discharge chargers (unless on a professional level) I have seen are limited to 500 ma discharge that requires 4.2v x .5a x 4 = 8.4 watts of power to dissipate.
One cell at 4.2v x 3 amps = 12.6 watts of power to dissipate, 4 at that current would take 50.4 watts of power to dissipate. The 15 watt discharge tester I linked above used a 30mm x 30mm fan and heatsink. To keep the size down it could have a function to discharge only one bay at 3 amps and 750 ma with all 4 bays running.
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All the hobby chargers I have owned used the case made out of finned aluminum and a small fan to dissipate the heat.
Logging is going to be harder than expected if it can do high discharge. The resistance of the wires will likely become significant.
Estimating the correction in software would be no fun, and having a separate set of wires for sensing would be no fun. I don’t have a fix, I just wanted to point out the hazard ahead.
I really like the idea!
At the moment i am building 2 charger adapter to connect my opus to 2 external battery holder (26650) because my 26650 shocklis are popping out of the charger bay way to often.
But untill i find a charger that suits me better i will use the opus. This charger could be the one that sends my opus in retierment.
It offset all these features that will add cost, I propose saving money by making this project just a module. Basically just the heart of the charger, no case. At least until version 1 units are sold to BLF fans. Iterating a full product would be much more expensive than just a module. And functionality is the same.
we can detect the protocol of the AC adapter we are using, if it’s low power( 5V2A or 12V1.5A) we can limit the maximum charging current, it’s easy to implement in software, no need to include 20V3A PD psu( 60w adapter is quite overkill IMO)
As a flashlight (not powerwall) user, I think this is important. 2C seems to be a pretty typical discharge rate for this purpose, and for today’s higher capacity batteries, even 3A is minimal. The ideal would be four cells at 3A, but the bare minimum should be at least one cell at 3A. As a side note, the MC3000 can discharge four cells at 2A, with a 60W (12-18V) power supply. The power supply is an in-line brick that seems fine to me, in terms of size.
I know there are compromises to be made here between use cases (flashlights, power walls), size, cost, etc., and I will support this project however those turn out.