How to safely use this charger?

I purchased this charger from DX http://www.dealextreme.com/details.dx/sku.973

Does anyone have this or know how to use it safely. If you read the discussions you will see that someone from dx says that it does not have two separate charging channels. Does that mean that the charger will work better with one cell than 2? I have just been checking the batteries often when charging because I don't trust it. I only use it for 10440 cells.

I have one of these chargers. I haven't used it much. I only used it with 10440's also. I don't know why DX would say it doesn't have separate channels. It will charge a single battery as that's how I used it. In their comment, it kinda sounds like they're suggesting when 2 cells are charged at the same time, they're connected and charged as one. Don't know, I never tried it. I guess it could be designed that way. ? Anyway, the reason I stopped using it is because the 10440's (individually) would come off the charger at around 4.25+ volts. The + meaning it depended on how soon you got to it and removed the battery after the light turned green. With anything over 4.2v you're loosing cycle life unnecessarily.

So I got a Nano charger. I had a chance to play with one that I ordered for a friend and I liked it. It's small and handy. It's doesn't take up alot of room on the bench, just pick it up and plug it in. The best part though, is that the cells come off between 4.1 / 4.2v. The one I got for my friend read 4.17v. Mine come off at 4.15v tops. That's if I leave it on for around a 30min after it turns green. I'd say it takes around 90 - 120min. for a charge. Depending of course how far you've run it down. When charging, the cells only feel slightly warn to the touch. And they're not expensive. I've read nothing but positive comments about them.

I have this charger, and I agree, the first and only time I used it the cells came off the charger @ 4.3V, way too high. From now on, I'll have to "babysit" the cells with a DMM, and pull them when they hit 4.1V. I don't use these cells all that much, I got the charger back in Feb, charged the cells up once, put them in my MKII lights. I've used them for about 20 min each over the past 3.5 mo, and last night I decided to check their voltages. Both cells read 4.1V, so I may not have to charge them for quite some time.

But yes, pull the cells at 4.1-4.2V when using this charger, and you should get decent life out of your cells.

Thanks guys, I guess that I will just babysit the cells. I don't use them much. I will probably pick up a nano charger at some point.

Would you mind to open up the charger, show it to us, maybe there is somewhere to tweak and limit it's voltage to 4.1v or 4.2v?

I could, but I would rather not mess with it. I don't use the 10440 cells that much now. If I start using them more often I am going to buy a nano charger. The charger was inexspensive and I was already ordering some stuff from DX. I mainly purchased the charger and the 10440s to try in my LOD-CE. I do like the performance better of the 10440s, but the light (on medium) runs hotter than on NIMHs (on high). I do a lot of hiking when the light runs for several hours and I think for that application the NIMHs are fine.

Interesting.

I've got this charger, and as others have frequently charged a single cell in it. I just ordered some 10440s, so I've never charged them but haven't had any problems with my 14500s charging in it.

I've tried to keep an eye on it and not leave them in too long past "green light", but I don't have a means to measure voltage, so I don't know what they're coming off at. :green:

I know this has been covered over and over and I apologize.

What is the low number that you shouldn't discharge the unprotected cells under?? I read 3.0 to 3.5 volts resting (not under load) is low. So which is it - 3 or 3.5? If 3.5 then it is important to keep the cells between 3.5 and 4.1 which is a bit tight but can be done.

Is this correct?

Hello Martytoo,

This whole question revolves around acceptable cycle life.

In general, charging to 4.2 volts should give you around 300 - 500 cycles. Charging to 4.1 volts should give you around 1500 cycles, however at 4.1 volts you are only getting about 90% of the capacity.

The discharging side seems to depend on the brand of cells and the load during the discharge. A normal low voltage cut off is around 2.5 - 3.0 volts under load. The cell will rebound to over 3.5 volts resting if the load is in the 0.5C - 2C range. Under lower loads, the rebound will not be as much and the cycle life will drop off.

Unfortunately, the amount of cycle life loss through over discharge is dependent on the brand of cell. Name brand cells can go for 125 cycles, whereas other cells can drop off in as little as 10 cycles.

If you stay in the range of 3.5 - 4.1 volts, you should get the best cycle life from your cells.

Tom

I used this charger again yesterday/today with 10440 cells. Yesterday I kinda forgot about it - was supposed to be babysiting it. I checked it a while after I was supposed to. Light was green and no overcharging. Today I was topping off a cell - light was green - no overcharging. I didn't leave the cells for xtra hours so I am not sure how that would have turned out. So far it looks to be performing fine.

servents,
You say no overcharging but you didn't provide any specifics. Are you saying they terminated at or before 4.2v? I've used 2 of these chargers and with both of them 10440's would come off the charger at 4.25v, and I pulled the batteries out when the light was alternating between Red & Green, meaning, it wasn't quite finished. I didn't want to let it go any longer. The batteries read 4.25v when checked right after removal from the charger. When I check them later in the day, they would drop to around 4.17v. They then seem to hold this voltage for days, maybe weeks.

The way I understand it, this is overcharging. Even though the voltage drops to a 'safe' level, it was pushed beyond. Someone correct me if this is wrong.

When did you check your batteries, and what was the voltage?

Sorry. Yesterday I put a battery in to top it off and the starting voltage was 4.0. Todays starting voltage was 3.8. The light was red (or blinking). The light stayed on green when I removed both batteries. I never checked them in between. One came off at 4.14 and one at 4.17. I have a Cheap voltage meter, and never checked its accuracy, but thats what it read. I'll use the batteries up during the week and I'll see what happens next time I use it. I am going to keep a closer eye on it next time.

I charged another 10440 battery in this charger. The starting voltage was 3.77v. About 50 minutes later the green light kicked on. Battery read 4.17v. For the 2 10440 cells that I own everything is working good so far. I also had a 14450 cell in there and when I checked (light was red) the voltage was 4.19v (I don't know if it would have overcharged or not, and I don't know what cell it was so I cannot say what it comes off of the WF-139 at.). I am new to lion cells and currently own 2 chargers. This one and the WF-139. All the cells I own are unprotected. The thing is that I have noticed so far is that all of the cells are different. I have cells that come off the charger (WF-139) at 4.19 and others that come off at 4.17, etc., no matter what bay they are in. I also have some cells that come off at 4.2. I think that either I got a good charger (and some others got bad ones), the batteries that were overcharged in this charger were bad, or this charger cuts out a little bit after the WF-139 and those cells that would come off at 4.19v are overcharging. I do not trust either of my chargers based on reports of both chargers overcharging batteries. I think that if I purchase protected cells that will solve part of the problem. (Not with 10440s though)