Eneloop Battery / Charger Query

[cerbera147]

Hi,

I have received my Eneloop AAA batteries today  Now I had read that fast chargers are not ideal for these batteries, ok now and again but not ideal. Five seconds after I ordered I thought I'd check my trusty charger. It certainly did seem fast 

Then I read the name of the charger 'Fujifilm Ultra Fast Battery Charger' 

Do I need a new charger then?



No big problem if I do; I could always get one the deals with an Eneloop charger with batteries 

[Neil]

I've heard the the use of such a fast charger can significantly reduce the life expectancy of the cells.  That said, I've not personally seen any reliable data to back up the claim.

I wonder if any of our resident flashaholics can shed any light on the subject

[Blackbeard]

The eneloop charger takes 8-10 hours FWIW

[NutSAK]

Fast chargers are OK as long as there's a decent amount of breathing room around the cells so they won't overheat, and the charging current is 2A or less.  The recommended charge rate for Eneloops is .5C - 1C.  "C" is 2000mAh for Eneloops, so 1A - 2A is ideal.

Many folks want to charge at lower rates such as 200mA or 500mA, but the danger there is whether the charger can reliably terminate charge at those rates.  Higher rates terminate more reliably, so it's typically safer for the cells to charge at the higher rates (1-2A) than lower rates so that overcharging is avoided.

I would guess that the pictured charger has a 2A charge rate since the batteries are 2100mAh and it's a one-hour charger.  However, I wouldn't buy it unless I knew the exact rate.  The cells look very close together in the charger too, so I would be worried about overheating them.

[Sazabi]

Fast chargers are OK as long as there's a decent amount of breathing room around the cells so they won't overheat, and the charging current is 2A or less.  The recommended charge rate for Eneloops is .5C - 1C.  "C" is 2000mAh for Eneloops, so 1A - 2A is ideal.

Many folks want to charge at lower rates such as 200mA or 500mA, but the danger there is whether the charger can reliably terminate charge at those rates.  Higher rates terminate more reliably, so it's typically safer for the cells to charge at the higher rates (1-2A) than lower rates so that overcharging is avoided.

And you know, here I was thinking I'd never have to worry about what I was learning in physics currently... good thing I've been paying attention. 

[cerbera147]

Thanks for this info 

On the rear of the charger is the following:

• Input: DC12V 700mA
• Output: DC6V 1000mA Max

Charging Current:

• AA: 1000mA
• AAA: 400mA

Does this help in whether it is a no no or not?

[NutSAK]

And you know, here I was thinking I'd never have to worry about what I was learning in physics currently... good thing I've been paying attention. 

Physics is fun stuff!  I enjoyed physics courses more than any other.

In a nutshell, what you want to avoid with Eneloops (or any other NiMH cell for that matter), is overcharging and overheating.  The reason most people say to avoid fast chargers is that they heat they have a tendency to overheat the cells, but that's not always the case.  Some chargers can charge a depleted Eneloop in an hour without overheating them.

[Neil]

And you know, here I was thinking I'd never have to worry about what I was learning in physics currently... good thing I've been paying attention. 

  Can't recommend it.   Change course quick, choose the easy course that still leaves plenty of time for propping up bars. A few years down the line no one will care what subject you got your bits of paper doing 

Me, bitter?  Nah

[NutSAK]

Thanks for this info 

On the rear of the charger is the following:

• Input: DC12V 700mA
• Output: DC6V 1000mA Max

Charging Current:

• AA: 1000mA
• AAA: 400mA

Does this help in whether it is a no no or not?

Yes, that certainly helps.  I like those charge rates, and they should work well for Eneloops.  However, you should monitor the charger while it's operating to be sure the cells don't get too hot toward the end of the charge.  Warm is OK.

Does the charger have 4 independent circuits, or two?  Another way to ask that same question is; can you just charge one cell at a time in this charger, or do you have to charge two at a time?  If it has 4 independent circuits, I would suggest you charge only two cells at a time, but put the cells in slots #1 and #3 to give them more room to breathe.  You will not be able to do that if it has only 2 independent circuits.

I don't really recommend using a charger with only two circuits, that can only charge two cells at a time (rather than 1 cell at a time).  That is, unless you ALWAYS use your cells in pairs.  This is because you should NEVER charge two cells of different charge on the same circuit.  If you do, the one with the higher voltage will be overcharged (and probably overheat) in the charger.

[Sazabi]

And you know, here I was thinking I'd never have to worry about what I was learning in physics currently... good thing I've been paying attention. 

  Can't recommend it.   Change course quick, choose the easy course that still leaves plenty of time for propping up bars. A few years down the line no one will care what subject you got your bits of paper doing 

Me, bitter?  Nah

I'm actually a biological sciences major, but physics is required - and definitely stressed if I wish to do well on the PCAT for pharmacy school.  No worries about plenty of time for propping up bars - I don't drink. 

[NutSAK]

Ah.. waitaminute.  I see the charger has two slots for AAA and two for AA, right?  So, the only question to ask is; do you HAVE to charge two AA or two AAA cells at a time in this charger?

I also see that you're charging AAA Eneloops (I really should read better the first time).  400mA should also be OK for the 850mAh Eneloop AAA cells.  400mA falls into the .5C - 1C spec.

[cerbera147]

Does the charger have 4 independent circuits, or two?  Another way to ask that same question is; can you just charge one cell at a time in this charger, or do you have to charge two at a time?  If it has 4 independent circuits, I would suggest you charge only two cells at a time, but put the cells in slots #1 and #3 to give them more room to breathe.  You will not be able to do that if it has only 2 independent circuits.

Ah.. waitaminute.  I see the charger has two slots for AAA and two for AA, right?  So, the only question to ask is; do you HAVE to charge two AA or two AAA cells at a time in this charger?

Thanks for this great advice NutSAK 

This charger can charge either AA or AAA in pairs only.

So my charger should be ok for the AAA's provided I monitor the charge towards the end?

What about as and when I get some AA's?

[NutSAK]

Does the charger have 4 independent circuits, or two?  Another way to ask that same question is; can you just charge one cell at a time in this charger, or do you have to charge two at a time?  If it has 4 independent circuits, I would suggest you charge only two cells at a time, but put the cells in slots #1 and #3 to give them more room to breathe.  You will not be able to do that if it has only 2 independent circuits.

Ah.. waitaminute.  I see the charger has two slots for AAA and two for AA, right?  So, the only question to ask is; do you HAVE to charge two AA or two AAA cells at a time in this charger?

Thanks for this great advice NutSAK 

This charger can charge either AA or AAA in pairs only.

So my charger should be ok for the AAA's provided I monitor the charge towards the end?

What about as and when I get some AA's?

You should be fine with AAA or AAs in this charger.  Yes, just watch for heat toward the end of the charge, and be sure that both cells you're charging are at equal voltage/charge levels before recharging them.

[cerbera147]

Thanks for your help Terry 

'tis much appreciated