New La Crosse BC700 termination questions.

I just bought a new BC700 and it has missed termination twice while charging AAA's at 200mah. One set was brand new, the other was new, but partially drained. I bought this as a companion to a new Maha C9000, mainly as something I could use as a back up, or at work or when traveling. Should I use the 500mah setting for the AAA'? Or is there more likely a problem with the charger it's self? I wasn't in a hurry so I figured I'd charge them slower, now I'm hesitant at charging at the lower 200mah setting. The C9000 was busy refreshing some batteries for my brother in law or I'd been using it. Makes me think I should've got two C9000's. Any suggestions or help would be appreciated, thanks in advance.

If the charger uses -dv/dt termination (The recommended termination for NiMH), the charge current must not be to low. The recommended current is between 0.5C and 1C.
The C9000 uses voltage termination, this is a more reliable termination method, but will usual stop before the batteries are filled. The C9000 get around this by charger for two extra hours after it has reported done.

HKJ said:

If the charger uses -dv/dt termination (The recommended termination for NiMH), the charge current must not be to low. The recommended current is between 0.5C and 1C.
The C9000 uses voltage termination, this is a more reliable termination method, but will usual stop before the batteries are filled. The C9000 get around this by charger for two extra hours after it has reported done.

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Thanks for the reply HKJ. I've read many of the product reviews you've done...great work!

I have to ask, how would you know whether the charger missed the termination? Also what batteries are you charging?

MidnightDistortions said:

I have to ask, how would you know whether the charger missed the termination? Also what batteries are you charging?

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The batteries I was charging and topping off are new Duracell Ion Core AAA's, made in Japan. The first set were never used, I wanted to top them off before using them for the coming work week. The second set have been in a couple flashlight's my kids have been playing with for a day or so. I was charging the unused set, I thought they were accepting more mah than they should, so I pulled one out of the bay, reinstalled it and it read full. I pulled the remaining cells with the same result. The second set held around 1000mah, I pulled them and they all read full as well. When the C9000 finished I put them in it to use as a reference check, the first set said "Done" as soon as it cycled though the four cells. The second set of batteries did take from 7 to 16mah and they read Done. So I know the second set were NOT overcharging. I'm now concerned the first set may have been though.

jwag73 said:

The batteries I was charging and topping off are new Duracell Ion Core AAA's, made in Japan. The first set were never used, I wanted to top them off before using them for the coming work week. The second set have been in a couple flashlight's my kids have been playing with for a day or so. I was charging the unused set, I thought they were accepting more mah than they should, so I pulled one out of the bay, reinstalled it and it read full. I pulled the remaining cells with the same result. The second set held around 1000mah, I pulled them and they all read full as well. When the C9000 finished I put them in it to use as a reference check, the first set said "Done" as soon as it cycled though the four cells. The second set of batteries did take from 7 to 16mah and they read Done. So I know the second set were NOT overcharging. I'm now concerned the first set may have been though.

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Often times new LSD batteries are not entirely full, as i have read they do a mass rapid charge to new batteries from the factory and often times will only be charged up to around 70%. Often times you'll only get half charge time as even LSD batteries will self discharge, depending on when the batteries are manufactured they might take longer to charge than normally. Normally if you are looking to top off LSD cells charging them at a higher charge rate will help out the -dV termination but since these are new cells a little overcharge doesn't hurt. You could always discharge the battery fully for slightly overcharged batteries. I've tried refreshing some badly overcharged batteries that has permanently lost capacity as a result but you should be fine. The reason the charger reads full when you took out the batteries and put them back in is because you interrupted the charge so the charger thinks the batteries are full. That's a good sign though that your batteries are in good condition. Older batteries that has permanently lost capacity, voltage depression and overdischarged won't do that. Some might but i have encountered crap cells won't even properly give off -dV so sometimes they'll say they are full but still have room for more charge.

Voltage depression and lost capacity are general signs of overcharging so next time you get a chance, run those batteries through a discharge/refresh cycle and see whether they were overcharged. Most of the discharge cycle should be 1.2-1.3 volts so if you're seeing 1.1 volts mostly throughout the discharge cycle that means the battery was overcharged. It could also mean that they were overdischarged but with my experience with the Eneloop technology it's difficult to drive them into cell reversal. Not sure if the Duracell AAA's are capable of doing the same so i wouldn't try to drain your batteries fully in the device you are using. I'd use the discharge function on the La Crosse charger to safely discharge the battery.

Hope that helps

MidnightDistortions said:

Hope that helps

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Thanks, I appreciate all the help I can get. I'm pretty familiar charging the 18350/18490/18650's, I've not had a charger that does what the Maha C9000 or BC700 does. I've been using an Xtar VP2 and a Nitecore D2, and i2. They obviously have nowhere the capability of my new chargers. Thanks again for all the help.

MidnightDistortions said:

I have to ask, how would you know whether the charger missed the termination? Also what batteries are you charging?

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My BC-700 has missed termination on batteries in the past. You know it when three of the four batteries are finished and the fourth one keeps charging and charging and charging.

My Maha has never missed a termination.

Chris

ChrisGarrett said:

My BC-700 has missed termination on batteries in the past. You know it when three of the four batteries are finished and the fourth one keeps charging and charging and charging.

My Maha has never missed a termination.

Chris

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Hmm.. is it always just one battery or is it the charging terminal slot? At the most i had one battery will charge an extra hour over the others. If it ran over an hour i would just pull it out and mark it to see if it's the battery or the charger that is causing the problem. In most cases though it's the battery because it's not giving off a -dV signal for the charger to recognize. But you are right, the Maha charger at least a few of them terminate early to avoid the overcharging, i believe they set a limit of 1.47 (or 1.46) volts which is why they never overcharge .

MidnightDistortions said:

Hmm.. is it always just one battery or is it the charging terminal slot? At the most i had one battery will charge an extra hour over the others. If it ran over an hour i would just pull it out and mark it to see if it's the battery or the charger that is causing the problem. In most cases though it's the battery because it's not giving off a -dV signal for the charger to recognize. But you are right, the Maha charger at least a few of them terminate early to avoid the overcharging, i believe they set a limit of 1.47 (or 1.46) volts which is why they never overcharge .

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Well, to be honest, I'm going back almost 3 years, when I bought both the Maha and the LC chargers. I had some older batteries and I had a bunch of new AccuPowers, Sanyo 2700s and Eneloops.

IIRC, it was usually one battery that wouldn't stop, but I seem to recall that a batch of batteries failed to terminate together. Now whether those were some older ones, or some of my newer ones, I can't exactly say, but maybe three times in almost 3 years, so not a lot. Finally, I could have been charging some hi-cap cells at the lowest rate and maybe they just didn't hit the proper temperature?

I like my LaCrosse BC-700 and although I say that I probably should have just bought two Mahas, I'm happy with the smaller size BC-700 and when I travel back home to California, I take that with me if I'm not carrying li-ion lights and my Xtar chargers.

That issue along with the temperature protection kicking in are really the only two nits that I have with it.

Chris

As of last night, as well as today I've been charging some old 1800mAh Duracell's we have at work. The charger seems to working fine, but at 700mAh I notice it runs a little warm. It's not hot, just warmer than I thought it might be.

ChrisGarrett said:

Well, to be honest, I'm going back almost 3 years, when I bought both the Maha and the LC chargers. I had some older batteries and I had a bunch of new AccuPowers, Sanyo 2700s and Eneloops.

IIRC, it was usually one battery that wouldn't stop, but I seem to recall that a batch of batteries failed to terminate together. Now whether those were some older ones, or some of my newer ones, I can't exactly say, but maybe three times in almost 3 years, so not a lot. Finally, I could have been charging some hi-cap cells at the lowest rate and maybe they just didn't hit the proper temperature?

I like my LaCrosse BC-700 and although I say that I probably should have just bought two Mahas, I'm happy with the smaller size BC-700 and when I travel back home to California, I take that with me if I'm not carrying li-ion lights and my Xtar chargers.

That issue along with the temperature protection kicking in are really the only two nits that I have with it.

Chris

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Yeah using the lowest rate on high capacity batteries might have caused that. I also noticed that already charged cells (about a month in storage) take an hour or two to charge. The charger could be overcharging them, but i was refreshing the batteries anyway and i usually like to top them off before putting them through a few cycles. I'd like to get a couple of Maha chargers as well, their break in feature is pretty awesome and probably would be useful in older cells that work but are a bit weak, i got some Duracells that are pretty weak, they work but they lack both in capacity and suffering from some voltage depression (probably from overcharging or overdischarging) but they still hold their charge for several months like they did when they were new.

jwag73 said:

As of last night, as well as today I've been charging some old 1800mAh Duracell's we have at work. The charger seems to working fine, but at 700mAh I notice it runs a little warm. It's not hot, just warmer than I thought it might be.

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Yep that's perfectly normal. If they were getting too hot the charger would stop charging the batteries until temps return to normal, i have an inferred thermometer so i can check the temps and switch to a lower charge rate to avoid having to wait for the batteries/charger to cool off.

I might have the same model Duracells that you got that only get warm even at 1000mA. New LSD cells, La Crosse batteries and my Energizer AAA's are the only ones that heat up pretty fast, i don't know why most of my older batteries don't heat up that much. These Rayovac batteries that won't sustain much mAh capacity barely heat up at 1800mA.

When charging cells in my BC700, I always change the display to volts. The cells usually rise to about 1.52volts before showing that they are done. Next time, try switching the display and see. The charger does get a little warm, but nothing more than that. It is pretty normal.

RI Chevy said:

When charging cells in my BC700, I always change the display to volts. The cells usually rise to about 1.52volts before showing that they are done. Next time, try switching the display and see. The charger does get a little warm, but nothing more than that. It is pretty normal.

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Thanks for the tip! I'll try that on the batteries I'm currently charging.

jwag73 said:

............. I was charging the unused set, I thought they were accepting more mah than they should, so I pulled one out of the bay, reinstalled it and it read full. I pulled the remaining cells with the same result.

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That sounds normal. If the voltage is above a certain point (not sure what that value is.......maybe 1.40v or higher), then the charger will just say they are full and you can't top it off anymore.

jwag73 said:

The second set held around 1000mah, I pulled them and they all read full as well. When the C9000 finished I put them in it to use as a reference check, the first set said "Done" as soon as it cycled though the four cells. The second set of batteries did take from 7 to 16mah and they read Done. So I know the second set were NOT overcharging. I'm now concerned the first set may have been though.

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I'd be curious as to why you think the batteries didn't terminate?

Here's what I'd do. Discharge a battery(s) all the say down in a flashlight such that the voltage is around 1.00v. That way you know they are fully discharged. I always use 200mA on the BC-700 for AAA's and haven't had any problems. Seems they terminate around 1.52v. So after the batteries have started charging, select the voltage display on the BC-700 while the batteries are charging and when you get up to 1.50v start watching them more closely. I have found mine terminate after sitting on 1.52v for a short amount of time. Tell me what you find. If they sit on 1.52v for a long time or the voltage climbs a bit higher or they start to get too warm, then I'd say that termination was missed. Switch the display over to the capacity reading (mAh) to see how much charge they have taken. Between voltage, temperature, & capacity.........this might help in determining if they really are getting over charged.

Good description. Mine stop charging right after they hit 1.52 as well. Reads full shortly after.

I can confirm that on a couple of other chargers I have, they tend to terminate Eneloops around 1.52v as well. That's apparently what a lot of NiMH cells charge to, if you terminate on the -dV signal.

Thanks for all the replies, you've all been extremely helpful. RI Chevy pointed out the voltage reading last night. I observed the batteries when they were close to the 1.50v mark, and they did all terminate right after reaching 1.52v. What a relief, now I know what to look for as the charge gets close to completion. I'm still in the infancy stage in regards to AAA/AA batteries, that goes for the C9000 and BC-700 as well. These are the first chargers I've had with the capability to do more than simply charge. I've been using a Nitecore i2, D2, and recently picked up a Xtar VP2 for my 18350-650 series batteries. They pale in comparison to what these chargers can do.

I'm excited about finally using rechargeable AA / AAA type batteries, and even more excited to keep learning how to use my new chargers to maintain and hopefully prolong the life of my new batteries. Thanks again to all of you who shared some knowledge with a new guy that's happy to be here!

jwag73 said:

Thanks for all the replies, you've all been extremely helpful. RI Chevy pointed out the voltage reading last night. I observed the batteries when they were close to the 1.50v mark, and they did all terminate right after reaching 1.52v. What a relief, now I know what to look for as the charge gets close to completion. I'm still in the infancy stage in regards to AAA/AA batteries, that goes for the C9000 and BC-700 as well. These are the first chargers I've had with the capability to do more than simply charge. I've been using a Nitecore i2, D2, and recently picked up a Xtar VP2 for my 18350-650 series batteries. They pale in comparison to what these chargers can do.

I'm excited about finally using rechargeable AA / AAA type batteries, and even more excited to keep learning how to use my new chargers to maintain and hopefully prolong the life of my new batteries. Thanks again to all of you who shared some knowledge with a new guy that's happy to be here!

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Glad to hear your excited in using rechargeables They should last if you take good care of them. Cycle the AA / AAA batteries every so often, shouldn't need to be much though if you take the batteries out of the charger once they read full. I refresh them once a year at least and check the voltage on them and usually will recharge them around 1.23 volts or less. Older cells i usually will wait until they are near death (below 1.1volts) since they wouldn't handle refreshing as much as newer cells but i usually will attempt to do them regardless if they function well or not. If you don't have a multimeter, i suggest to get one . I currently have the Innova 3320. It doesn't prevent overdischarged batteries but usually when i pull out batteries from a light that is dim, it lets me know whether the batteries need charging and it helps to avoid cell reversal which i haven't tested the Duracells but the basic 2000mAh Eneloops i tried to test but they would only go to 0 volts which is a bit better than cell reversal but it probably eats up recharge cycles. Anyway have fun with your new charger and batteries .