Hello,
Not too long ago i had a small conversation with another member here about Lithium Ion battery chargers and how a purchase of one of those chargers might result in a final cell voltage either too high or too low. That's why i preferred to build my own chargers even if it was using simpler technology like an LM317. But then it came time to buy a charger for someone else as a gift, and i cant build chargers for everyone
Ok, so i have the charger now. It's a fairly inexpensive charger that does two cells at the same time at a rate of about 650ma per cell. That's not too bad really, and the whole thing is only about 2 x 1.5 x 3.5 inches in size, so it is small and compact. No wire, just plugs into the 120vac outlet with a fold out plug.
The 18650 cells plug into the front in two battery holders.
The indicator is a dual color LED (red/green) that changes color for power, charging, almost done, done. It's a little strange because for almost done it looks half red and half green, but hey it works and you know what it is doing.
So all is well and good, except for the problem of low final cell voltage. It's not too bad, measuring 4.10 volts, but i prefer 4.15 volts and the cells are rated for 4.20 volts.
I always suspected this would happen with a charger that was purchased, and since i build my own this is the first one i ever had to purchase so i am finding out first hand now.
It would be interesting to hear comments about this and possible solutions. What i am afraid of is i dont think the plastic case will come apart too easy so i am not sure if it can be modified. There is also the chance that it uses a dedicated charging chip that does not have external resistors for voltage adjustment anyway.
It would be interesting if anyone has taken one of these apart, to see what is inside. If there are different connections for the battery charge lead and sense leads it may be possible to use a voltage divider to fool it into thinking that the cell voltage is 0.05v lower than it really is.
I know that 0.05v doesnt seem like much, but i may want to go up to 4.17 or 4.18 also which would mean almost 0.1v higher.
It's really a shame that these dont come with a small adjustment feature so you can set it to what you want, from say 4.100 to 4.200 volts. 4.100 volts is "livable" but if it could go higher that would be even nicer.
Not too long ago i had a small conversation with another member here about Lithium Ion battery chargers and how a purchase of one of those chargers might result in a final cell voltage either too high or too low. That's why i preferred to build my own chargers even if it was using simpler technology like an LM317. But then it came time to buy a charger for someone else as a gift, and i cant build chargers for everyone
Ok, so i have the charger now. It's a fairly inexpensive charger that does two cells at the same time at a rate of about 650ma per cell. That's not too bad really, and the whole thing is only about 2 x 1.5 x 3.5 inches in size, so it is small and compact. No wire, just plugs into the 120vac outlet with a fold out plug.
The 18650 cells plug into the front in two battery holders.
The indicator is a dual color LED (red/green) that changes color for power, charging, almost done, done. It's a little strange because for almost done it looks half red and half green, but hey it works and you know what it is doing.
So all is well and good, except for the problem of low final cell voltage. It's not too bad, measuring 4.10 volts, but i prefer 4.15 volts and the cells are rated for 4.20 volts.
I always suspected this would happen with a charger that was purchased, and since i build my own this is the first one i ever had to purchase so i am finding out first hand now.
It would be interesting to hear comments about this and possible solutions. What i am afraid of is i dont think the plastic case will come apart too easy so i am not sure if it can be modified. There is also the chance that it uses a dedicated charging chip that does not have external resistors for voltage adjustment anyway.
It would be interesting if anyone has taken one of these apart, to see what is inside. If there are different connections for the battery charge lead and sense leads it may be possible to use a voltage divider to fool it into thinking that the cell voltage is 0.05v lower than it really is.
I know that 0.05v doesnt seem like much, but i may want to go up to 4.17 or 4.18 also which would mean almost 0.1v higher.
It's really a shame that these dont come with a small adjustment feature so you can set it to what you want, from say 4.100 to 4.200 volts. 4.100 volts is "livable" but if it could go higher that would be even nicer.