GarageBoy
Flashlight Enthusiast
I noticed that many of them can do up to 6 cells in series, but no option to do it in parallel or individually? So I should just charge them 1 at a time?
Hobby charger- how to charge 2 cells indivudually?
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TranceAddict
Newly Enlightened
if it is li-ion then you can connect them in parallel, the cells voltage will be same and will trigger cut-off once it reach 4.2v
or you can connect them in series with balancing leads connect to each cells
but if it is nimh, some charger might or might not cut-off according to dV/dT, or some simply cut-off at max V.
or you can connect them in series with balancing leads connect to each cells
but if it is nimh, some charger might or might not cut-off according to dV/dT, or some simply cut-off at max V.
GarageBoy
Flashlight Enthusiast
Wait, but if they're both unequal to start with, when will it cut, if they're in parallel? I guess that's why I should use the balancing
kramer5150
Flashaholic
Doesn't the charger NEED to be a CV/CC as well? at least that is my (perhaps flawed) understanding.
TranceAddict
Newly Enlightened
the nature of parallel circuit is that all cells connected in parallel shall have same voltage, even cell A is low in voltage cell B is high it will balance themselves by cell B charging cell A to reach equilibrium.
in the scenario of different capacity, cell A high and cell B low, when the circuit voltage raise up, current supply by charger will go to the low capacity one because the low cell require less charging time, and its voltage build up faster, when cell voltage are high, charger need to output even higher voltage in order to "push" current in, so in nature current will go to the lower capacity cell until both cells reached same 4.2v
conclusion: in parallel, cells capacity, charge state, brands can be disregarded. only make sure all cells are same in chemistry.
The cells do balance themselves out, but you can have HUGE current spikes if you couple together a full and a depleted cell (almost like short circuiting in the first very short period). I think the rule of the thumb is to keep the voltage difference less than 0.5V apart if you do them in parallel.
rmteo
Flashlight Enthusiast
Have you actually done this (couple a fully charged cell with a depleted cell), particularly Lithium rechargeables? Were there any adverse effects?
No, not really. I think SilverFox did try something like that (fully charged and fully discharged liIon) and he got some 5-10A spike in the first second or so. While that shouln't be too much of a problem, i still wouldn't suggest paralleling cells that differ too much. Especially not a full kickass high C with a depleted cheap low capacity one :]
I'm not sure if that initial surge is actually that bad for the cells, but with all the li-ion safety concerns around here, i guess it doesn't hurt to try and keep the cells at least a bit alike.
OK, probably not that much of a problem with single cells. With packs things can get a bit worse tho. Especially NiXX ones.
I'm not sure if that initial surge is actually that bad for the cells, but with all the li-ion safety concerns around here, i guess it doesn't hurt to try and keep the cells at least a bit alike.
OK, probably not that much of a problem with single cells. With packs things can get a bit worse tho. Especially NiXX ones.
GarageBoy
Flashlight Enthusiast
I mean, I guess those NiMH chargers charge in parallel too? (the cheapie charge in pairs ones)
I think they charge in series. Because they won't charge one cell on its own.
Norm
SilverFox
Flashaholic
Hello GarageBoy,
Charging NiXX chemistry in parallel doesn't work. Parallel charging is reserved for Li-Ion and Lead Acid chemistries.
Tom
Charging NiXX chemistry in parallel doesn't work. Parallel charging is reserved for Li-Ion and Lead Acid chemistries.
Tom
kramer5150
Flashaholic
Heres how I charge my 26650 cells. I couldn't find the correct sized cell carrier so I made my own by cutting a C sized carrier in half. Epoxy the two halves onto .25" delrin stock. I haven't tried more than 2 cells in parallel. There is a wattage limit to the carrier contact springs, although i am not certain what it is. I have charged up to 2.5A (1.25A split into each cell) and not had any problems. Also, I only charge these cells in equally depleted pairs. If one cell were even slightly discharged more than the other I would just charge them one at a time.
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rmteo
Flashlight Enthusiast
The effect of connecting a completely discharged LiIon cell in parallel with a similar fully charged cell is a lot less dramatic than theory would suggest. In fact, I would say that their is no drama at all.
That said, if you have a need to charge more than some cell at a time, I assume that you have accumulated a quantity of cells that are discharged to one degree or another. Keep these discharged cells separate from your fully charged cells and you will be OK. Here is how I charge 1-8 unprotected 16340 cells in parallel:
