2 charging questions

[rockz4532]

I'm kind of a noob when it comes to charging, but I know the basics.

I was charging eneloops on my eneloop smart charger, but without batteries inserted, the open circuit voltage on the charger is ~5v. Is this right? My other chargers have 1.4v output, but are trickle chargers.

Also I was charging my Ultrafire 2600 mah pink 18650's, and I noticed the light hadn't gone green for a while, so I checked the batteries voltages while still in the charger, and it shows 4.25v, so I immediately took the cells out, and rested them.
Later, I checked the voltage again, and it was 4.16v :thinking:, I didnt use the batts for anything. Whats going on here? The light goes green for my AW's at 4.21v, and after rested show 4.2v.

 

[clintb]

Open circuit voltage of a cell is almost always higher when coming hot off the charger. The cells will tend to normalize as time goes on.

As to the chargers; check voltage of your Eneloop charger as it's charging, not without a cell. What charger are you using for the UltraFire 18650's? If it's the WF-139, they have a long history of overcharging, just do some searches.

I got sick of the cheap chargers and combined my flashaholic tendencies with that of my love of radio controlled vehicles. Now, I use a hobby charger exclusively that allows me to set the cut-off *I* want, which is 4.18V. That said, I do like the DX charger here.

 

[Light Sabre]

NMH's are charged using constant current. Without a battery in the circuit there wasn't any charge current detected, so the chargers output voltage went to maximum voltage. 5V in your case. The voltage will be much lower with a battery in the circuit and charge current detected

 

[rockz4532]

Thanks. As for the 18650s, i use the digital li-ion charger, DX sku. 6105.
So should I just leave the batts on the charger at 4.25v?

 

[Light Sabre]

Can't help ya on the Li-Ion batteries, I refuse to use them for safety reasons except for the ones that came with my cell phones, my mp3 player, or my laptop computer.

 

[clintb]

Well, that's actually the charger I'm using; just didn't realize I had linked to the European version. I'll have to double-check the terminating voltage.

 

[rockz4532]

Actually I think I've been measuring the charger voltage, not the battery voltage. When the battery in the charger is measured, it is 4.25v, but when taken out of the charger it is 4.19v. I noticed there is a trickle charge if the batt is left in the charger, so its best to take the batt out immediately when the light is green. I left the batt 1 hour in the charger after the light went green, and the voltage was 4.22v, a bit overcharged.

 

[J_C]

0.02V is nothing to worry about.

 

[xeonsaga88]

0.02V is nothing to worry about.

however , total battery life cycle will be reduced.

 

[xeonsaga88]

"Charging to 4.1 volts gives you >2000 cycles.​

Charging to 4.2 volts gives you 500 cycles.
Charging to 4.3 volts gives you <100 cycles.
Charging to 4.4 volts gives you <5 cycles.''

Taken from silverfox's post. I prefer to charge to 4.15v , for me the increased life cycle is worth more than the little increase in capacity.