Is it a problem that my Duracell charger charged 4 Eneloops to 1.51v?

The other night the weather experts were calling for Snow-pocalypse in our area, and to be prepared I began re-charging many 18650s that I had discharged to under 3.9v to store.

After I was done with that, I started topping off the many Eneloops I had in 2 larger lights. I only had 2 decent chargers and 14 batteries to charge, but then I found a Duracell charger that my mom must've given to me. So I tossed 4 Eneloops onto it. Later, the Xtar charger had finished charging its batteries, so I removed the 4 AA from the Duracell charger, which were still charging, and put them into the new Xtar charger. I was surprised to read that they were being measured at 1.51v on the Xtar, and I assumed it was wrong.

I removed all 4 and tested them on my DMM that I had been using throughout the recharge process, but it also read 1.51v on all 4 batteries. After about 20mins or so, they dropped to 1.46v, which made me feel better.

I've charged many Eneloops on my old I4 charger, but they usually come off of it at approx 1.44v as I recall. Another issue is that the Duracell charger appeared to still be charging them when I removed them at 1.51v. Now, maybe it was just seconds away from terminating their charge cycle, but who knows(?). Is it a problem?

Chargers differ in their termination points, so 1.51v isn't bad, or unheard of.

My LaCrosse BC-700 terminates at 1.51v, IIRC, but my Maha C9000 stops full charge at 1.47, but needs another 2 hours at 100mA to get the cells full, IIRC again.

I have the little Sanyo USB 'Eneloop' charger and it's somewhat scattered.

I wouldn't worry about it, as the voltages will settle down around the 1.4x volt range after a day and furthermore after a longer period.

Chris

1.51v is fine, I have seen 1.55v and no problems, one thing to check, The battery`s should never be to hot to hold(they will be their hottest just before they show as full), If they are to hot the battery`s are being damaged.

Old battery`s that have developed a high resistance can get hot, If to hot to hold then it`s time to recycle them, If new battery`s get to hot to hold on a regular basis you could have a problem with your charger, maybe a too high charge rate or missing the battery full/termination point.

John.

my ikea ladda charger stops at 1.51 as well...

Even at 1.6V is still within range, although it's the max (according to my iCharger)

guys, I don't think it is the charger that determines where the charge teminates, but the dv/dt, the cells suddently heating up when they are at charged capacity. IME, spanking new fresh out of the package AA Eneloops will charge to around 1.44V, but as they get used, they get better, and begin to terminate charging around 1.51V, and as they get worn in will start terminating around 1.54V, and I have seen them terminate as high as 1.57V.

TinderBox (UK) said:

1.51v is fine, I have seen 1.55v and no problems, one thing to check, The battery`s should never be to hot to hold(they will be their hottest just before they show as full), If they are to hot the battery`s are being damaged.

Old battery`s that have developed a high resistance can get hot, If to hot to hold then it`s time to recycle them, If new battery`s get to hot to hold on a regular basis you could have a problem with your charger, maybe a too high charge rate or missing the battery full/termination point.

John.

Click to expand...

None of the 14 Eneloops and Eneloop XX's that I charged were any more than warm when they came off the chargers. They were fairly warm, but certainly not uncomfortably hot to hold, nor were they remotely close to it.

HighlanderNorth said:

None of the 14 Eneloops and Eneloop XX's that I charged were any more than warm when they came off the chargers. They were fairly warm, but certainly not uncomfortably hot to hold, nor were they remotely close to it.

Click to expand...

When a NiMH charger terminated on -dv/dt the batteries will get warm at the end, in my reviews I avoid IR photos of that phase. Usual that phase takes between 10 minutes and half an hour (A few chargers are considerable slower).

Duracell made a lot of chargers, you could have a dumb timer based charger instead of a smart charger.

@chillinn

i always thought it was the charger thing to cut off at certain voltage?

Cekid said:

@chillinn

i always thought it was the charger thing to cut off at certain voltage?

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hmm... that is not my understanding. My understanding of charge termination, however, is not deep, and all I know I learned from HKJ's posts, who is the master, and he has already posted in this thread. By the power of Greyskull, HKJ, I summon you to help us all better understand how most chargers, dumb and smart, accomplish NiMH charge termination. And I thank you HKJ, for the generosity of your wisdom.

chillinn said:

hmm... that is not my understanding. My understanding of charge termination, however, is not deep, and all I know I learned from HKJ's posts, who is the master, and he has already posted in this thread. By the power of Greyskull, HKJ, I summon you to help us all better understand how most chargers, dumb and smart, accomplish NiMH charge termination. And I thank you HKJ, for the generosity of your wisdom.

Click to expand...

I have written about it before: http://lygte-info.dk/info/batteryChargingNiMH UK.html