# I am trying to charge my first set of Eneloop batteries. What am I doing wrong?



## someguy4747 (Jul 8, 2011)

So I recently decided to buy some Eneloops after realizing I was unhappy with the performance of my lights using the Duracell Procell Alkaline batteries I get from work. 

I bought a pack of Eneloops from Costco 10 AA's and 4 AAA's. It did not come with a charger. I bought this charger. I thought it was better than the newer Eneloop chargers that only charge in pairs. http://www.amazon.com/gp/product/B003GS6FIE/?tag=cpf0b6-20 I bought it because I was being cheap and thought it was good enough. (I am also a broke college student who just spent all my money on my girlfriends birthday present.) From what I understand each battery is charged and cut off from power individually. I also understood that each cell was charged at 360mah per hour. I thought this is what I wanted. As individual cells were fully charged I understood that the charger would stop supplying power to those cells and only charge the cells that were not fully charged. Only when all the cells were charged I thought the light would turn off to let me know they were charged. This is how I thought it would work. Is it naive to believe that the charger will not overcharge cells that are fully charged while the charger is charging the more depleted cells?

I guess my main problem is that I do not trust the charger yet and I am unsure of what the voltage of the Eneloops should be hot out off the charger. I keep pulling them to check where they are at. I have two cells at 1.45v, one at 1.47v and another at 1.48v. What is the recommended voltage that I should charge these Eneloops to?

Thank you for anyone who answers and I apologize if this is already in another thread as I searched before I started charging and before I post this now but I did not find any good info and do not want to risk my precious new batteries!


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## Mr Happy (Jul 8, 2011)

Perhaps you are being too paranoid?

As mentioned in NLee's Amazon review, this charger will take about 6 hours to charge Eneloops from empty. Of course it will take less if they are partially charged out of the package.

Fortunately, at 360 mA it is quite hard to overcharge Eneloops. What you should do is trust the charger. Put your Eneloops in it and wait until the light goes off. You can tell if an individual cell in one channel is being overcharged or not by feeling the temperature. A warm cell is being charged, a cool cell has stopped charging. If a cell remains warm for an hour and the charger doesn't stop, then pull the plug manually. Otherwise, just wait. Don't panic.

For info, the voltage immediately hot off the charger for a fully charged Eneloop will be around 1.5 V, give or take. But wait a few seconds and it will be down to 1.45 V.

I guess really I don't know what it is that is bothering you? You are correct that the light will stay on until the last cell finishes charging. Why do you think this is not happening?


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## Mr Happy (Jul 8, 2011)

Broken forum again. Duplicate post deleted.


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## samgab (Jul 8, 2011)

I agree with Mr Happy. Just put them on the charger and leave them till they are done. The charger treats each of the 4 batteries individually, and has protections in place to prevent overcharging. Don't over think it.


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## robostudent5000 (Jul 8, 2011)

i have two of those chargers and they work well. they cut off on fully charged AA's pretty quickly. they don't cut off on fully charged AAA's as fast, and the more batteries you have charging, the less sensitive the cut off seems to be on the third and fourth channels. i charge my AA's four at a time without problems. i charge my AAA's two at a time. i haven't had any problems with my batteries. they perform better than when they were new.

you'll probably have to charge/drain/charge your batteries a few times to get comfortable with how the chargers are handling your batteries. Eneloops take a few cycles to get up to speed anyway. but you really shouldn't worry. in the end, they are just batteries.


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## someguy4747 (Jul 9, 2011)

Thanks for the responses! 1.5v then cools to 1.45 got it! I think you people are right. I am just being too paranoid. I did read NLee's review in fact he was the main reason I bought the charger and the batteries were partially charged so I guess I was expecting them to charge a little quicker(3hours or less they took about 3 1/2) I also did not know what voltage they would or should charge to. I ended up just trusting the charger and let the batteries charge until the light turned off. Once they cooled down 3 read at 1.45 and one at 1.46. I imagine I will start to feel more comfortable with how the charger charges the batteries but I think because I started off using Lions and was told to be very cautious(especially since I use an Ultrafire 139) I carried that sentiment over to Nimh where it may not be as necessary?

One more question though if you guys will. Do I need to worry about over discharge and if so how much? I am super paranoid with my lions. I don't want to get hurt or even worst my girlfriend or my cats ha ha. I usually check them after a bit of use and charge them when they near 3.8 volts and maybe 3.75v at the lowest. So with the eneloops can I just run them till my light dies or will this shorten the life of the cell? will it never recover if I do this? Are there any protection circuits? Should I charge them at 1.0v or 0.9 or some other voltage? What do you guys suggest? Thanks for the help.


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## robostudent5000 (Jul 9, 2011)

over discharge risk is very low. in most cases, you can run your lights til they die without hurting your batteries. if you run a bunch of batteries in series and one cell is weak to begin with, that cell might get driven down and get damaged. but if you use batteries of similar charge and they're in reasonably good shape, you'll be fine.

fire risk is also very low. and since you're using a very slow charger and it has a voltage cut off, fire risk is almost non-existent.


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## someguy4747 (Jul 9, 2011)

Thanks. That is exactly what I wanted to know. Thanks everyone for your helpful responses.


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## Mr Happy (Jul 9, 2011)

someguy4747 said:


> So with the eneloops can I just run them till my light dies or will this shorten the life of the cell?


With a single cell light you can run until the light dies. With a two cell light (or more), you should run until the first sign of loss of output and then recharge. Running a two cell light until the light dies will potentially shorten the life of the weaker cell.


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## someguy4747 (Jul 9, 2011)

Alright good to know. I imagine I will switch them out as soon as I see any diminishing output as i like my lights to be as bright as they can be and with rechargables there is no reason to keep using depleted batteries! Thanks.


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## march.brown (Jul 10, 2011)

How much use will the batteries get ?

I charge or top-up my batteries about twice a year , even if they don't get used ... If they are in my EDC torches, the top-up can be every two or three months.

Even my 18650's are topped up every few months ... I tend to estimate (guess) how much discharge there has been and then top up when I think it is needed.

If you have several spare Eneloops, they won't mind being topped up a couple of times a year ... Just try to use them occasionally to run them down a bit ... My Eneloops are not treated well and they still give me good service.

As far as EDC torches, I have one on each of my two keyrings (iTP A3) and one in my pocket (iTP A2) ... The chances of all three batteries dying at the same time is very small ... There's also my two Car torches fitted with Lithium primaries along with several spare cells just in case ... There's safety in numbers.
.


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## someguy4747 (Jul 10, 2011)

march.brown said:


> How much use will the batteries get ?
> .


 
I will use them in my Bluetooth keyboard and mouse as well as my two aa and aaa lights. So I use the computer all the time but I expect those to last for a while. As far as my lights go I like to play with them a lot and have also been geocaching at night a lot which means they get run down pretty quickly. So I would say the batteries will get a moderate amount of use. 

I also tend to top off my batteries(previously only li-ion). If I think I will need the light I check the voltage. If it is a little low I grab a fresh cell and top the old one off and put it back in rotation. I do my best to cycle my batteries evenly and plan to treat the new eneloops the same. Although since there is a low risk of over discharge with the eneloops I may be more inclined to just use the batteries in the light and take spares with me just incase they die. Probably not though. I'd rather start with fresh batteries.


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## someguy4747 (Jul 12, 2011)

Ok. So one more question. I just looked at my eneloops that I charged Sunday. I checked the voltage just because and they were down to 1.36 from 1.45? What gives? Is there some sort of break in period. That seems like a lot of self discharge to me. A lot more than claimed.


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## march.brown (Jul 12, 2011)

someguy4747 said:


> Ok. So one more question. I just looked at my eneloops that I charged Sunday. I checked the voltage just because and they were down to 1.36 from 1.45? What gives? Is there some sort of break in period. That seems like a lot of self discharge to me. A lot more than claimed.


 Mine were last charged on 25 March 2011 and are all measuring 1.340 to 1.341 volts.
.


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## someguy4747 (Jul 12, 2011)

Yeah I just charged these batteries July 10th 2011. So I guess my batteries are definitely self discharging rather fast. How are you storing your batteries? Mine have been in my apartment which gets up to about 85 in the middle of the day(I only have evaporative cooling). Is that hot enough to cause the excessive self discharge? Should I store my batteries in the refrigerator? Is that safe?


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## march.brown (Jul 12, 2011)

someguy4747 said:


> Yeah I just charged these batteries July 10th 2011. So I guess my batteries are definitely self discharging rather fast. How are you storing your batteries? Mine have been in my apartment which gets up to about 85 in the middle of the day(I only have evaporative cooling). Is that hot enough to cause the excessive self discharge? Should I store my batteries in the refrigerator? Is that safe?


 My batteries are all kept in a desk drawer in my study ... Temperature about 70 ... Apparently the refrigerator is the best place to store batteries to minimise self-discharge ... I've never done that though ... They are kept at whatever temperature the room is at ... Never over 75.

Batteries are better if they are discharged every once in a while ... Unfortunately I don't do this either ... I top them up about twice a year whether they need it or not and have (so far) never been let down ... You will probably now find that your batteries won't drop much in voltage as the voltage drops most in the first day or so after they come off charge ... It isn't due to self-discharge ... All batteries do it. 
.


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## Mr Happy (Jul 12, 2011)

someguy4747 said:


> Ok. So one more question. I just looked at my eneloops that I charged Sunday. I checked the voltage just because and they were down to 1.36 from 1.45? What gives? Is there some sort of break in period. That seems like a lot of self discharge to me. A lot more than claimed.


That's not self discharge, that's entirely normal. An NiMH battery is like a wide jar with a tall thin neck. Just because the liquid level is at the top of the goose neck it doesn't mean there is much more liquid in the jar than if the level is at the bottom of the neck. The neck is so thin that it only takes a tiny amount of liquid to make the difference.

An Eneloop in resting storage will have a voltage eventually of about 1.33 V. This is essentially fully charged, while a voltage of 1.20 V is essentially empty. Also note that the "real" capacity of an Eneloop or other NiMH cell is about 90-95% of the "maximum" capacity. You should ignore that last 10% as it is not very useful and evaporates quickly.


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## someguy4747 (Jul 12, 2011)

Ahhh...ok then. Thank you march.brown and Mr Happy for your responses. I guess I am fine then. As you can tell I have issues with just "using" the batteries. I want to monitor them but I don't have any idea what they are supposed to be doing. I am glad to know that my batteries are working fine. I will try to just "use" them the best I can.


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## Mr Happy (Jul 12, 2011)

Monitoring your batteries to see what they do is a good way to understand them. That way you can quickly tell how healthy they are and find out if something isn't right. I measure the voltage of my batteries all the time. Otherwise it's like trying to work blindfolded.


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## 45/70 (Jul 12, 2011)

Just a comment I'd like to throw in here, I think there is way too much concern regarding the voltage of your cells, someguy. While it's true you can tell something about a particular group of NiMh cells such as your eneloops, in general NiMh cell voltage doesn't really tell you a whole lot. If you were checking the voltage of a different set of cells, LSD, traditional NiMh, or even another batch of eneloops purchased at another time, having a different date of manufacture, you would likely become very confused, as the "rules" would likely have to be changed to accommodate a different group of cells.

Unlike other types of rechargeable cells, such as lithium ions, simply measuring the voltage of NiMh cells alone, just doesn't really tell you very much. That said, I do as Mr H does, and am constantly measuring the voltage of all my various chemistry cells.

Dave


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## Bat (Jul 12, 2011)

anything over 1.4V is normal. your particular sony charger is a 4 channel smart charger with "voltage monitor".


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## samgab (Jul 12, 2011)

Also, I've noticed that the voltage of NiMH cells has a certain amount of "elasticity"... meaning when charged they go up to a certain voltage, then during the rest after charging they rubber band back to a resting voltage, and the same with discharging, they discharge down to a certain voltage, say 0.9 volts, and then when resting they will bounce back to a different resting voltage, like 1.18 volts.
So unlike li-ions, the voltage does change after charging, and moves around somewhat in what I've seen. Different battery chemistries act in different ways. If you were working with lead acid batteries, you'd have whole different set of behaviours again.


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## someguy4747 (Jul 13, 2011)

Ok, so NiMH cells have "elasticity" and the voltage is not representative of the remaining energy, is there a way to know how much energy the cells have left or the general health of the cell?


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## hellokitty[hk] (Jul 13, 2011)

Discharge them, and measure how much.


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## samgab (Jul 13, 2011)

someguy4747 said:


> Ok, so NiMH cells have "elasticity" and the voltage is not representative of the remaining energy, is there a way to know how much energy the cells have left or the general health of the cell?


 


hellokitty[hk] said:


> Discharge them, and measure how much.


 
Yup, hellokitty is right. That's the only way to do it. A clever charger/analyzer like the Maha MH-C9000 will enable you to do that, but it might be a bit more than what you're needing. Basically, eneloops are as close to fool-proof as rechargeable batteries can get. Little children manage them fine with their toys etc. You charge them in the charger. The charger finishes when they are charged. You use them, and when the device doesn't work anymore, you recharge them again. After several years, you'll find the device doesn't go for as long between charges, and it might be time for a new pack of eneloops, or whatever the equivalent is by then. Pretty simple stuff really. 
But if you want to learn all about them and get into it, do lots of reading. This forum is good and Google is your friend. I personally found the Panasonic_Ni-MH_Handbook pdf useful (Google) as well as the eneloop handbook pdf (Google). 
And a C9000 wouldn't go amiss if you're into this sort of thing, as I am.


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