Eneloop Battery Question

[Flatshovel]

Hello all,
I am looking to purchase some Eneloop batterys for my scanners, radios, and flashlights. I currently have a BC-900 charger. Looking on the Sanyo website best that I can tell that the Eneloop batterys are 2000mah. Now my question is what is the correct charge rate to charge these batterys at? At 0.5c for a 2000mah battery would be 1000mah correct? Would charging at 500mah be better on the battery and prolong the life of it? Just wondering on this. I currently have some Lacrosse 2650mah nimh batts that seem to always be dead when I use them, I let them sit overnight as well and according to my tester the next morning they only have 20% charge in them for some reason. I also charge them at 500mah rate and do not let them die completely before charging them. Looking for comments or suggestions.

Thanks,
Joey

 

[Mr Happy]

Somewhere in the 500 - 1000 mA range should be OK. The thing to do is watch the batteries charging a few times to get familiar with their behavior. Look at the charge supplied at the end of charge and make sure it is no higher than say 2100 - 2200 mAh, so you know the charger terminated correctly. Also feel the temperature and make sure the charger cuts off before the batteries start feeling too hot to hold.

If it passes both those tests then your selected charge rate should be fine.

 

[Marduke]

1) 500mA is too low, which may be part of the reason your current cells are lackluster

2) Most likely your battery tester is horribly inaccurate for NiMH cells, so I would not put stock in that 20% estimation unless you have ran a discharge test

3) 1A charge rate would be better than 500mA.

 

[tbenedict]

Just to share my experience since I use my rechargeables for the same purposes.....

Eneloops seem best in items you do not use frequently (charge every few months). I use PowerEx (by Maha) 2700ma batteries for my scanners since they benefit from the extra current. In other words if you charge your scanner batteries every few days like me, you will probably be better off with the PowerEx or Sanyo's version of the non LSD batteries.

I use a Maha charger (401) on slow that takes about 8 hours to charge the 2700ma.

 

[Flatshovel]

Thanks for all the responses to my question. So basically is it better to fast charge Nimh battery rather than slow charge? I have read that nimh prefers be charged faster and that slow charging them is not so good for them? What is the best answer on this and I will kick up the charge on the laCrosse NIMH 2650mah batteries and see how they do. Matter of fact I use my scanner on a daily basis as well.

Thanks,
Joey

 

[Marduke]

Just to share my experience since I use my rechargeables for the same purposes.....

Eneloops seem best in items you do not use frequently (charge every few months). I use PowerEx (by Maha) 2700ma batteries for my scanners since they benefit from the extra current. In other words if you charge your scanner batteries every few days like me, you will probably be better off with the PowerEx or Sanyo's version of the non LSD batteries.

I use a Maha charger (401) on slow that takes about 8 hours to charge the 2700ma.

Unless your electronic device is voltage sensitive, in which case the higher voltage of Eneloops would be a substantial benefit. They will also last many more cycles.

 

[TakeTheActive]

...I am looking to purchase some Eneloop batterys... ...I currently have a BC-900 charger... ...the Eneloop batterys are 2000mah. Now my question is what is the correct charge rate to charge these batterys at? At 0.5c for a 2000mah battery would be 1000mah correct? Would charging at 500mah be better on the battery and prolong the life of it?

You asked about 'Charge Rate' just a few weeks ago in: BC-900 Charger Question.

Did you try "The Experiment" (Post #8)? What did you learn?

Did you read the STICKYs?

 

[TakeTheActive]

1) 500mA is too low, which may be part of the reason your current cells are lackluster...

I thought so too [with my Rayovac PS1 (@200mA) & PS3 (@500mA) and La Crosse BC-900 (@200mA) COOKING cells!].

But, if the charger is TERMINATING PROPERLY (i.e. Sanyo MQN05/MQN06 @ 300mA, Duracell CEF23 @ 550mA), low current appears viable. :thinking:

 

[brted]

But, if the charger is TERMINATING PROPERLY (i.e. Sanyo MQN05/MQN06 @ 300mA, Duracell CEF23 @ 550mA), low current appears viable.

I agree with that. I've been noticing that when I am playing around with cells that the capacity goes down fairly quickly if I do repeated Refresh/Analyze cycles charging at 1000mA and discharging at 500mA. I ran some Rayovac 4.0 cells this week and after an initial RA cycle I discharged them and lost 50-80 mAh capacity. But then I did an RA at 600mA/300mA and they show 115-125 mAh additional capacity.

It probably depends on the cell and Eneloops probably don't mind higher currents, but other cells might rather be babied. Maybe not all the time, but most of the time.

 

[Mr Happy]

I agree with that. I've been noticing that when I am playing around with cells that the capacity goes down fairly quickly if I do repeated Refresh/Analyze cycles charging at 1000mA and discharging at 500mA. I ran some Rayovac 4.0 cells this week and after an initial RA cycle I discharged them and lost 50-80 mAh capacity. But then I did an RA at 600mA/300mA and they show 115-125 mAh additional capacity.

It probably depends on the cell and Eneloops probably don't mind higher currents, but other cells might rather be babied. Maybe not all the time, but most of the time.

This is partly because using higher charge currents tends to lead to a less complete charge. The higher charge currents will lead to higher voltages at the end of charge point and a more pronounced -dV signal, causing the charger to terminate sooner. However, when a cell is almost fully charged the charge acceptance is quite low. Much of the current being fed into the cell is wasted as heat, and only a little of it is stored as increased charge. To get the charge up to 100% you have to go more slowly, for longer, which lower charge rates tend to do.

Also, contrary to popular imaginings, NiMH cells do not get damaged the moment you overcharge them. They can take a fair bit of excess charge before bad things happen. That's why all those cheap timed chargers out there actually work well enough to be sold.

So don't get too paranoid about charging at 0.5C rates. This is not a hard equation; there is a lot of leeway in the rules and failing to stick rigidly to them will not lead to instant disaster.

 

[TakeTheActive]

This is partly because using higher charge currents tends to lead to a less complete charge. The higher charge currents will lead to higher voltages at the end of charge point and a more pronounced -dV signal, causing the charger to terminate sooner. However, when a cell is almost fully charged the charge acceptance is quite low. Much of the current being fed into the cell is wasted as heat, and only a little of it is stored as increased charge. To get the charge up to 100% you have to go more slowly, for longer, which lower charge rates tend to do...

brted,

jtr1962 explained this rather well back in 2004 in Theory: Nickel-Based Rechargeables from my Sig Line LINKs.