How to charge Eneloops in La Crosse BC-700?

[ChrisGarrett]

I have the same charger, charge gen2/3 aaa eneloops at 500mah and have noticed from time to time that the bc700's readout says one (or more) has taken way over 800mah, like 895mah the last time I saw this. does that mean it's being overcharged?

they're all newish batts, 2013 date stamp, have run them down and recharged a number of times, etc. the recharge voltage was in the 1.5x range but took it out of the charger instead of waiting for "full" because I was afraid it was being damaged.

also given the battery is considered dead when voltage gets down around 1v, there must still be mah left in it at that point correct? so the battery 800 mah rating in effect means "800 mah above and beyond what's in it when considered 'dead'" so maybe seeing ~900 mah going into it isn't anything to worry about?

I was fiddling with some AccuPower 1200 AAAs in my BC-700 the other day, that are two years old and not doing so well. I.R. in the 1.80v range on my Maha C-9000 and some of them missed termination and seemed to keep charging for 20 extra minutes, before I terminated them.

I like my BC-700, but you need to watch it with batteries that might be 'hitting the wall.'

I remember early on, with some older batteries, I would miss a termination, here and there, but I was ignorant at the time and didn't put two and two together.

Chris

 

[Dimt]

I'm lazy so I usually charge my Eneloop's at the default 200ma. Most of the time they are FULL within 24 hours. If I'm in a hurry I will pump it up to 700ma.
I have been using the same batteries for at least four years without a problem.

 

[LAM09]

I know this is might be a stupid question, but is their any difference in charging batteries on different currents on a BC-700 other than the time it takes to charge the batteries?

 

[ChrisGarrett]

I know this is might be a stupid question, but is their any difference in charging batteries on different currents on a BC-700 other than the time it takes to charge the batteries?

You'll get heat build up charging at the higher rate, which can momentarily stop the charger from charging for a bit, until the temps come down. I think that bays 1&3 and 2&4 (don't quote me on the exact pairings) are connected, so when things shut down due to temps (140*F?) those two bays affected, will stop charging.

This is generally an issue with older batteries, with higher internal resistances and not new ones, but the BC-700 is a smaller charger and the batteries are crammed in there, close to each other, unlike the Maha C-9000, which offers some 'breathing room' around the bays.

Chris

 

[SilverFox]

Hello LAM90,

Welcome to CPF.

In addition to the heat issue that Chris mentioned you also need to be aware of how the charger terminates the charge.

Many chargers terminate on a change in voltage (-dV). As the cell reaches full charge and goes into overcharging the voltage of the cell will drop a little. Studies have shown that the -dV signal is stronger when the charge rate is such that the cell is fully charged in about 1 - 2 hours. This is also called charging at 0.5 - 1.0C. To determine the charge rate you look at the capacity of the cell. A cell with 2000 mAh would have a 0.5C charge rate of 1000 mA and a 1.0C charge rate of 2000 mA.

Charging at lower rates can still produce a end of charge termination signal with newer cells, but as a cell ages the signal becomes weaker and weaker. This results in a missed termination and that results in overcharging damage to the cell. Most chargers have a maximum charge amount termination as a back up so you may not notice that the termination signal has been missed.

If you need to charge at a lower charge rate do your best to estimate that amount of time a charge should take and set a timer. When the timer goes off check to see if the charge has terminated. If it hasn't give it a little while longer then if it still hasn't terminated take the cells out and manually terminate the charge.

Tom

 

[markr6]

That's good info. Charging my 2500mAh Eneloops is a problem even at 700mA. They get up to about 1.44v and sit there getting pretty hot. Regular Eneloops get into 1.45-1.50, then very quickly hit 1.52v or so then terminate.

If I had more than just a few Eneloop XX, I would get a better charger just for them.

 

[LAM09]

Thanks Silver Fox and Chris for the info. I am going to check how long they charge for in the future, and keep an eye on the batteries whilst charging.

 

[LAM09]

One other thing guys, what is the best charged on the market ATM?

I currently have a BC-700 ATM as mentioned previously.

 

[ChrisGarrett]

One other thing guys, what is the best charged on the market ATM?

I currently have a BC-700 ATM as mentioned previously.

The BC-700 is a very good charger and if you travel a lot, it's small enough and sophisticated enough, to be quite useful on the road. Plus, it does 12v, even though it doesn't have a true 12v input.

It has quirks, like any other man made device and if you learn and watch out for those quirks, you'll be well served.

I bought both the BC-700 and Maha C-9000 because I figured that I'd try a few different batteries and a couple of chargers, for sense of variety. I was already committed to spending some money, so the $40 BC-700 wasn't breaking the bank.

That being said and repeating myself once again, if I could go back and do it all over again, I would buy another Maha C-9000 in lieu of the BC-700 and then pick up something like the Sanyo Eneloop NC MQR-06 for traveling. Also, I won't be buying any AccuPower 2900/1200s, nor the PowerEx Imedion AA LSD batteries, going forward.

Live and learn.

Chris

 

[LAM09]

The BC-700 is a very good charger and if you travel a lot, it's small enough and sophisticated enough, to be quite useful on the road. Plus, it does 12v, even though it doesn't have a true 12v input.

It has quirks, like any other man made device and if you learn and watch out for those quirks, you'll be well served.

I bought both the BC-700 and Maha C-9000 because I figured that I'd try a few different batteries and a couple of chargers, for sense of variety. I was already committed to spending some money, so the $40 BC-700 wasn't breaking the bank.

That being said and repeating myself once again, if I could go back and do it all over again, I would buy another Maha C-9000 in lieu of the BC-700 and then pick up something like the Sanyo Eneloop NC MQR-06 for traveling. Also, I won't be buying any AccuPower 2900/1200s, nor the PowerEx Imedion AA LSD batteries, going forward.

Live and learn.

Chris

Cheers for the reply mate. Thanks for giving me an insight as to what I should look out for in general.

 

[LAM09]

Has anyone tried Varta rechargeable batteries, and if so; what are they like?

 

[markr6]

That being said and repeating myself once again, if I could go back and do it all over again, I would buy another Maha C-9000 in lieu of the BC-700...

I'd jump in that time machine with you there Chris!

 

[pinoy]

Thanks Silver Fox and Chris for the info. I am going to check how long they charge for in the future, and keep an eye on the batteries whilst charging.

Keep in mind. If a battery has significant internal resistance that will cause the charging time to increase.

 

[Cekid]

Has anyone tried Varta rechargeable batteries, and if so; what are they like?

not happy at all...avoid if you can...they are not reliable, have short shelf life, and gone for good after not so much use...i throw already i think 12 of them AA 2100 while i still have eneloops older than them...varta was big name back in the day here in europe, but now it's only a name...