Charging Eneloop batteries

[offroad]

BC-700 and Eneloop Questions

I have a LaCrosse BC-700 and some AA/AAA Eneloops on order from Amazon. I've read many threads here on chargers and cells but I'm still a bit confused.

The eneloops are:
AA - 2000mah
AAA - 800mah

The BC-700 offers charge rates of: 200, 500 & 700ma
For normal charging, which of these is the best for the AA and AAA eneloops?
Is this a trade off between lowering the risk of missed termination (charge rate to low) and battery life (charge rate to high)?

What should I put these cells through the first time out of the box? Charge, Discharge/Charge, Capacity Test or a Refresh and at what rate?

Thanks.

 

[Hondo]

Re: BC-700 and Eneloop Questions

Hi offroad, you have a good setup coming.

You are correct, the trade-off is risk of missed termination if charging too slow vs reduced cycle life of cells if charging too fast.

If you are in no hurry, you can try charging at 200 mA, and just monitor the cells fairly often. If they terminate fairly soon after they begin to feel warm, the charger is detecting their peak fine. If they sit for hours warm, you need to charge faster. Before nearing full charge, the cells should stay pretty much room temp at 200 mA, and probably at 500 and 700 as well. Hot cells during the bulk of the charge usually comes from under 1 hour charging, which is not something the BC700 does. Because of this, you really don't have to worry much about excess wear and tear on your cells at the higher charge rates on that charger, especially for the AA's. I don't use 700 mA for AAA's, but there is nothing wrong with it, and I do use 500 mA for them often. So, it is hard to go far wrong with your set up.

As to "break-in" charging, Eneloops don't really need anything, but it won't hurt to put one cycle on them, and you can check their capacity that way. Using the Refresh feature will take them up and down at least twice looking for minimal gain, I would just use the Test feature which will top them up and discharge/charge and show their capacity. At 200 mA, this is simillar to the "Break In" feature of the C-9000 for AA's, but stopping on peak detection rather than 160% of cell capacity. The BC700 won't charge slow enough to match what the C-9000 does for the AAA's. If you would like to know how full they were out of the package, you can do a discharge first, but if memory serves, and it may not, the BC700 will recharge at the end of the discharge and not retain the discharge capacity, so you would have to keep an eye on it to get the capacity close to end of discharge. That is one thing I always use the C-9000 for.

 

[brh]

Re: BC-700 and Eneloop Questions

I use the same setup, works pretty well, and the cost is low. Even 700ma is a fairly low charge rate, .37C assuming the min capacity of an AA Eneloop at 1900mAh. I have charged them at the 200ma many a time, simply out of forgetfulness (200 being the default), and have never had them miss termination. YMMV of course, but I think the Eneloops are pretty well behaved, as opposed to some cells…

 

[offroad]

Re: BC-700 and Eneloop Questions

You really don't have to worry much about excess wear and tear on your cells at the higher charge rates on that charger, especially for the AA's. I don't use 700 mA for AAA's, but there is nothing wrong with it, and I do use 500 mA for them often.

If you would like to know how full they were out of the package, you can do a discharge first, but if memory serves, the BC700 will recharge at the end of the discharge and not retain the discharge capacity.

So, 700ma for AA and 500ma for AAA would probably reduce cell life little if any over the lower rates, and have less chances of missing a termination? I was hoping it would tell me remaining capacity (storage testing) without intervention, but at least it will test a cells capacity when full.

Edit: Looks like you can using Discharge/Refresh as long as you catch it before it finishes charging: http://www.candlepowerforums.com/vb/showpost.php?p=2722811&postcount=2

 

[Turbo DV8]

Re: BC-700 and Eneloop Questions

... but if memory serves, and it may not, the BC700 will recharge at the end of the discharge and not retain the discharge capacity, so you would have to keep an eye on it to get the capacity close to end of discharge.

If you use the discharge portion of the refresh function for the discharge, when it begins to charge at the end of discharge, the discharge capacity will be displayed in the display for the entire duration of the charge, until it begins another discharge. So you don't have to be there right when it switches over. You just need to be there to read the discharge capacity during recharge, and after doing so, halt the refresh cycle and restart it as a straight charge.

With Eneloops, here is what I do with my BC-900's. I charge AAA Eneloops at 200 mA, and AA Eneloops at 500 mA. As was mentioned, theya re very well behaved, and unless the cells are near the end of their life, they will terminate fine at these rates. ROV Hybrids, and similar, OTOH, I charge at 500 mA for AAA and 700 mA for AA, because I've had plenty of ROV Hybrid AAA's fail to terminate on the BC-900 at 200 mA.

 

[shadowjk]

Re: BC-700 and Eneloop Questions

Heh, I charge eneloop AA at 1000mA in BC-900 precisely because they're so well behaved and don't heat up like my aging regular nimh...

 

[Hondo]

Re: BC-700 and Eneloop Questions

If you use the discharge portion of the refresh function for the discharge, when it begins to charge at the end of discharge, the discharge capacity will be displayed in the display for the entire duration of the charge, until it begins another discharge. So you don't have to be there right when it switches over. You just need to be there to read the discharge capacity during recharge, and after doing so, halt the refresh cycle and restart it as a straight charge.

Looks like I was right about the discharge function not holding the capacity number, which makes it almost useless for determining remaining capacity, but as Turbo DV8 says, you can still get it done reasonably well on the BC700 using refresh. I had remembered that the refresh cycle started with charge, which would not allow you to measure the remaining charge, but it is the "test" cycle that does that. I just checked, and it is the C-9000 that starts "refresh & analyze" with a charge cycle. But it also stops after a discharge and holds the capacity until you come and set the charge program you want.

 

[DisrupTer911]

Re: BC-700 and Eneloop Questions

On the BC700 how can you half the refresh cycle and go straight into charging after 1 discharge cycle?

I had to let my batteries sit for nearly 2 days before they went Full.

 

[MarioJP]

Re: BC-700 and Eneloop Questions

If you use the discharge portion of the refresh function for the discharge, when it begins to charge at the end of discharge, the discharge capacity will be displayed in the display for the entire duration of the charge, until it begins another discharge. So you don't have to be there right when it switches over. You just need to be there to read the discharge capacity during recharge, and after doing so, halt the refresh cycle and restart it as a straight charge.

With Eneloops, here is what I do with my BC-900's. I charge AAA Eneloops at 200 mA, and AA Eneloops at 500 mA. As was mentioned, theya re very well behaved, and unless the cells are near the end of their life, they will terminate fine at these rates. ROV Hybrids, and similar, OTOH, I charge at 500 mA for AAA and 700 mA for AA, because I've had plenty of ROV Hybrid AAA's fail to terminate on the BC-900 at 200 mA.

I used to charge the eneloops at a higher rate until one day I started hearing hissing and popping sounds coming from the cells. Since then I been very wary of charging any NiMh cell past 500mA. Have any of you guys had this happen while charging at 1000mA?? I feel that 500 is the true sweet spot to ensure the cells are not being cooked. There's been debates previously, that charging at 500 increase the chance of miss termination. As far as i can tell it barely misses the termination, however at 200 could result of missing the termination, and when it does, overcharges the cell by 50-70% if you don't keep an eye on it.

The good news though at 200mA. It is too slow, and you have plenty of time to react before real damage occurs. I've now considered 200mA as a "maintenance charge".

 

[illumiGeek]

Re: BC-700 and Eneloop Questions

If you read Sanyo's white paper on the Eneloop, they recommend charging at 0.5C, which would be 1000mAh for AA, and 400mAh for AAA. That's pretty much what I've been doing for years, and I've not had any problem with cell damage or life. I have some very old Eneloops that are still going strong.

I used to charge the eneloops at a higher rate until one day I started hearing hissing and popping sounds coming from the cells. Since then I been very wary of charging any NiMh cell past 500mA. Have any of you guys had this happen while charging at 1000mA?? I feel that 500 is the true sweet spot to ensure the cells are not being cooked...

That sounds more like a problem with your charger. It definitely should not happen. I've been charging AA Eneloops at 1000mAh for years with no problems whatsoever. If you were using a LaCrosse charger, there is a thermal runaway problem that happens with LaCrosse BC series chargers. Mostly the 9009, but it also happens with other models as well. Just google LaCrosse charger melt down and you will find lots of info.

 

[MarioJP]

Re: BC-700 and Eneloop Questions

If you read Sanyo's white paper on the Eneloop, they recommend charging at 0.5C, which would be 1000mAh for AA, and 400mAh for AAA. That's pretty much what I've been doing for years, and I've not had any problem with cell damage or life. I have some very old Eneloops that are still going strong.


That sounds more like a problem with your charger. It definitely should not happen. I've been charging AA Eneloops at 1000mAh for years with no problems whatsoever. If you were using a LaCrosse charger, there is a thermal runaway problem that happens with LaCrosse BC series chargers. Mostly the 9009, but it also happens with other models as well. Just google LaCrosse charger melt down and you will find lots of info.

Granted I only had this happen twice and this was a long ago.the first time was with the energizer brand, even after I took the cell off the charger it was still hissing. Not so much with the eneloops. Has not happened since then, but still just have that feeling if I charge at 0.5. This could happen.

 

[Lite_me]

Re: BC-700 and Eneloop Questions

As far as i can tell it barely misses the termination,

This is like being, 'a little bit pregnant'. :huh:

 

[MarioJP]

Re: BC-700 and Eneloop Questions

This is like being, 'a little bit pregnant'. :huh:

I was referring at 500ma not 200. From what I witness at 500 good cells terminates as the charge being put in ranging from 2.1-2.2Ah for cells like the eneloops. I can't say for sure If that's good or not but, definitely beats charging cells at 200mA. I suppose I can try again charging at 0.5C and see what happens. Maybe the cells that were causing the pops, and hiss was probably defective.

 

[shadowjk]

Re: BC-700 and Eneloop Questions

I've had BC-900 charge batteries into a hissing a popping state too.

 

[illumiGeek]

Re: BC-700 and Eneloop Questions

...but still just have that feeling if I charge at 0.5. This could happen.
...Maybe the cells that were causing the pops, and hiss was probably defective.

As I said, that should not happen, EVER! If it does, then it's the charger's fault and you should get a better charger. I usually use 0.5C but have often used 1C when I need my Eneloops more quickly. Zero problems with my Maha chargers.

When I had the BC9009 I had a thermal runaway incident @ .5C and the batteries got very hot. Fortunately I was home at the time and smelled that infamous "melting plastic" odor. Followed my nose to the charger and found one of the LCD displays dark, and one of the buttons sinking into the unit (melting). I unplugged it and removed the batteries, and they were burning hot (literally painful to handle)! It seemed like the charger did, eventually get control, because when I found it the displays all read 0.00, indicating that the charge cycle had paused, but clearly it was too late. After everything had cooled down I plugged the charger back in and ran a quick test. The charger was still functional, so it wasn't a complete melt down, but it wasn't something I would ever trust again, so I returned it to Amazon and got a Maha C9000 instead. It seems to me like you have had some partial thermal runaway issues with your charger as well.

Even though I've had the BC900 for many years, and it has never given my any trouble, after the incident with the 9009, and reports I have read about other LaCrosse BC series chargers having similar issues, I am cautious about using the BC900. I rely mainly on my Maha chargers now. My "go to" charger is the Maha MH-C801D, which is an 8-cell charger with 1C and 0.5C charge rates. I use the C9000 for analysis, and when I need to charge more than 8 batteries at once, and I only use the BC900 when I need to charge more than 12 batteries (and only when I'm home).

I have complete faith in my Maha chargers, but I'm quite skeptical of all things LaCrosse. The included LaCrosse batteries were certainly crap, and the charger is suspect at best. That's my opinion, take it for what you feel it's worth.


EDIT:

I've had BC-900 charge batteries into a hissing a popping state too.

I rest my case... :(

 

[MarioJP]

Re: BC-700 and Eneloop Questions

That was true about the thermal runaway incident but i had the charger long before this started and still works fine till this day no meltdown here. As for the cells... They never got too hot to the point where i could not hold them. If i recall correctly the Maha terminates the charge early or when the voltage reaches 1.48 and then goes into a 2 hour top off charge. This charger trips when it senses the minor voltage drop. This is why you can charge faster with no issue as the 1.48v is the cutoff point regardless if there was voltage drop or not.

So in the end. Does not matter how fast the charge. You still have to wait 2 hours to top it off, although I am sure that part is optional if you're in a hurry though.

 

[illumiGeek]

Re: BC-700 and Eneloop Questions

That was true about the thermal runaway incident but i had the charger long before this started and still works fine...

That reminds me of what my father used to say. "I've been smoking for 40 years and I don't have cancer!" Want to guess what killed him, and my mother as well (secondary smoke)...

You asked if anyone else had problems charging @ 0.5C, and I told you the problem was your charger, not the batteries or the charge rate, but for some reason you seem intent on not believing me. The LaCrosse chargers are flawed, period! But you can go on living in your fantasy world where thermal runaway is caused by defective batteries or cosmic rays or whatever. It's your batteries (and possibly your home) at risk, not mine. What I don't understand is why you come to a forum to ask questions when you don't have any intention of accepting the answers?

FYI: both the Maha and LaCrosse chargers use negative delta V to sense full charge. I have not noticed any difference in the charged capacity between the brands, if there is it must be pretty small. An extra 100mA or so of fresh off the charger capacity is less important to me than safety. How much extra charge did you get out of those popping, hissing batteries?

Anyway, enjoy using your LaCrosse time bomb. I hope it never goes nuclear on you, but based on the fact that your charger has already demonstrated the common failure mode on at least 2 occasions, I suspect your history with that charger will not end well.

 

[illumiGeek]

Re: BC-700 and Eneloop Questions

Here's something that may help with LaCrosse overheating. Ever wonder what to do with all those Eneloop battery adapters you've accumulated? Well, here's a tip for using those "D" adapters. Place them under your LaCrosse BCxxx charger for better air circulation and cooler temps. When I use my BC900, this is how I do it.


The little nub feet on the charger fit nicely into the tips of the battery adapters.


Click the pics for larger images.

 

[MarioJP]

Re: BC-700 and Eneloop Questions

I guess I never experienced the meltdown But I've seen reports that even brand new eneloops off the package caused a meltdown of matter hours and images were shown that the wrapper melted away. I agree something is not right and its a faulty charger. I suspect the La-Crosse screwed up with those particular units, but you insist that my charger is one of those defective units.

If it was I would of have a meltdown already and its been 3-4 years with it. No need to put it on spacers or anything as i am not having any overheating issue with the charger in the first place. I said that the popping and hissing happened twice and it was a while back, but has yet to happen again since I replaced the cells.

I am not disagreeing with you about the meltdowns that happened while back. I am trying to find the right balance between shorter charging times/longer lifespan.

Cheers.

 

[lwien]

Re: BC-700 and Eneloop Questions

What I find kind of funny about this is that the title of this thread is, "BC-700 and Eneloop Questions", yet all of the negative discussions regarding LaCross have been about the BC900 and 9009 and those that are bashing Lacross are making the assumption that the same problems exist with the BC700, which is NOT the case.[h=2][/h][h=2][/h]