BC-900 Charger Question

[Flatshovel]

I have a question.
I have a BC-900 charger that I use to charge up AA batteries with. The capacity of the batts are 2600mah, If I charge them at 500mah will this hurt them? I tired charging at 700mah but the batts got rather hot I think. What is the safe charge rate to charge NIMH batts 1600mah up to 2900mah?

Also I have a Tokina 2 hr battery charger I am using that came with 4 2000mah AA cells. It says that the charge rate is 700mah when charging 4 batts, the charger cuts off in 2 hrs. If it charges at 700mah thats only 1400mah that is put into the batts so is the battery getting overcharged? Also It safe to use the Tokina 2hr charger? I have read that it is better to fast charge than slow-charge. Need some numbers on how fast I can charge without doing damage to the batteries. What is safe and what is not. I assume anything over 1000mah charge would be bad and 200 mah is too slow correct? Any ideas?

Thanks,
Joey

 

[Metatron]

I have a question.
I have a BC-900 charger that I use to charge up AA batteries with. The capacity of the batts are 2600mah, If I charge them at 500mah will this hurt them? I tired charging at 700mah but the batts got rather hot I think. What is the safe charge rate to charge NIMH batts 1600mah up to 2900mah?

Also I have a Tokina 2 hr battery charger I am using that came with 4 2000mah AA cells. It says that the charge rate is 700mah when charging 4 batts, the charger cuts off in 2 hrs. If it charges at 700mah thats only 1400mah that is put into the batts so is the battery getting overcharged? Also It safe to use the Tokina 2hr charger? I have read that it is better to fast charge than slow-charge. Need some numbers on how fast I can charge without doing damage to the batteries. What is safe and what is not. I assume anything over 1000mah charge would be bad and 200 mah is too slow correct? Any ideas?

Thanks,
Joey

@ 500 u are fine, the slower the better mate, even @ 1600 u will be fine , charging wont be more than an hour there, but if u go at 1amp will be also ok.

 

[Mr Happy]

I have a question.
I have a BC-900 charger that I use to charge up AA batteries with. The capacity of the batts are 2600mah, If I charge them at 500mah will this hurt them? I tired charging at 700mah but the batts got rather hot I think. What is the safe charge rate to charge NIMH batts 1600mah up to 2900mah?

Also I have a Tokina 2 hr battery charger I am using that came with 4 2000mah AA cells. It says that the charge rate is 700mah when charging 4 batts, the charger cuts off in 2 hrs. If it charges at 700mah thats only 1400mah that is put into the batts so is the battery getting overcharged? Also It safe to use the Tokina 2hr charger? I have read that it is better to fast charge than slow-charge. Need some numbers on how fast I can charge without doing damage to the batteries. What is safe and what is not. I assume anything over 1000mah charge would be bad and 200 mah is too slow correct? Any ideas?

Thanks,
Joey

This is a difficult question to answer. But first, one note of clarification. You are not charging the batteries at 500 mAh, you are charging them at 500 mA. You multiply current (mA) by time (hours) to get accumulated charge (mAh). So, 500 mA x 4 hours = 2000 mAh.

Now in answer to your question, I would charge them at 500 mA.

It is difficult to choose a good charging current. If too high, the batteries may get too hot. If too low, the charger may not stop when it is supposed to and may overcharge the batteries.

I have some batteries that test with a known capacity of 1900 mAh on the Maha C9000. When I charged them at 1000 mA they reached a temperature of 55°C and a supplied charge of about 2200 mAh before the charger terminated. When I charged them at 1600 mA they reached a temperature as high as 63°C and still a supplied charge of about 2200 mAh. So in this case a lower charge rate was better since the batteries stayed cooler.

 

[Metatron]

++++ always use ur temp sensor, it may just save ur batts and ur house

 

[TakeTheActive]

...I have a BC-900 charger that I use to charge up AA batteries with. The capacity of the batts are 2600mah, If I charge them at 500mah will this hurt them?

Eventually.

...I tired charging at 700mah but the batts got rather hot I think. What is the safe charge rate to charge NIMH batts 1600mah up to 2900mah?

The proper CHARGE RATE for healthy, vibrant cells is 0.5-1.0C (where 'C' is the cell's Capacity in mAh). Thus for:

• 1600mAh: 800-1600mA
• 2900mAh: 1450-2900mA (where'd you find 2900mAh cells? :thinking: )

...Also I have a Tokina 2 hr battery charger I am using that came with 4 2000mah AA cells. It says that the charge rate is 700mah when charging 4 batts, the charger cuts off in 2 hrs. If it charges at 700mah thats only 1400mah that is put into the batts so is the battery getting overcharged?

How?

700mA x 2 hours = 1400mAh into 2000mAh cell... :thinking:

...Also It safe to use the Tokina 2hr charger? I have read that it is better to fast charge than slow-charge. Need some numbers on how fast I can charge without doing damage to the batteries. What is safe and what is not. I assume anything over 1000mah charge would be bad and 200 mah is too slow correct? Any ideas?:

No, Yes, No, Yes... :sick2:

[PODIUM MODE ON]

Too many Newbies come here looking for RULES! Instead, you should be looking / SEARCHing for KNOWLEDGE.

If someone WITH KNOWLEDGE answered EACH AND EVERY "Newbie Reluctant / Refusing to Invest His/Her Personal Time SEARCHing", this forum would be CHOCK FULL of RE-POSTS! :sigh:

When I arrived here, I also knew very little. But, instead of posting questions, I invested *MY* PERSONAL TIME and READ THE ARCHIVES - for Hours / Days / Weeks / Months. And, when I found something INTERESTING, I BOOKMARKED it. And, when my BOOKMARKs starting mounting up, I created a "CPF - Batteries Included FAQ" to share with other Newbies.

CLICK on my Sig Line LINK and spend some of *YOUR* PERSONAL TIME reading. If you DON'T find your answer after reading *ALL* of my LINKs, *PLEASE* send me a PM explaining your question IN DETAIL.

[PODIUM MODE OFF]

 

[Metatron]

also, ur BC 900 booklet will have all ur answers for u mate:thumbsup:

 

[Mr Happy]

The proper CHARGE RATE for healthy, vibrant cells is 0.5-1.0C (where 'C' is the cell's Capacity in mAh). Thus for:

• 1600mAh: 800-1600mA
• 2900mAh: 1450-2900mA (where'd you find 2900mAh cells? :thinking: )

But knowledge changes and we have to adapt to survive. Knowing what I know now, I would be very cautious about blindly adopting that 0.5-1.0C guideline. The batteries might not like it and might get cooked. 'Proper', maybe; appropriate in all cases, not so sure.

And it also depends on the charger. The BC900 is a known "hot" charger, so lower charge rates are appropriate.

 

[TakeTheActive]

...I have a BC-900 charger that I use to charge up AA batteries with. The capacity of the batts are 2600mah, If I charge them at 500mah will this hurt them? I tired charging at 700mah but the batts got rather hot I think...

This is a difficult question to answer...

Either I'm missing something VERY OBVIOUS or the OP has *CRAP* cells.

...Now in answer to your question, I would charge them at 500 mA.

It is difficult to choose a good charging current. If too high, the batteries may get too hot. If too low, the charger may not stop when it is supposed to and may overcharge the batteries.

I have some batteries that test with a known capacity of 1900 mAh on the Maha C9000. When I charged them at 1000 mA they reached a temperature of 55°C and a supplied charge of about 2200 mAh before the charger terminated. When I charged them at 1600 mA they reached a temperature as high as 63°C and still a supplied charge of about 2200 mAh. So in this case a lower charge rate was better since the batteries stayed cooler.

I'm puzzled / confused!

While your reply is indeed ACCURATE (i.e. if they get too hot @ XXXmA, try something lower ), it is also, IMHO, INCOMPLETE. I don't understand why you didn't point out that "when XXXXmAh cells charged at 0.5-1.0C get *HOT*, their Internal Resistance has increased and thus, they are now *CRAP* CELLS!"

...Any ideas?

Try this experiment, ESPECIALLY on older non-LSD cells (skip Step #4 on AAA cells). Instead of REFRESH, or TEST (which only display Discharge capacity):

1. Do a DISCHARGE @ 200/100 and note the final 'Accumulated Capacity'.
2. Do a DISCHARGE @ 500/250 and note the final 'Accumulated Capacity'.
3. Do a DISCHARGE @ 700/350 and note the final 'Accumulated Capacity'.
4. Do a DISCHARGE @ 1000/500 and note the final 'Accumulated Capacity' (watch for overheating).

Compare the results. If the result from #1/2/3 is way higher than the other(s), it missed the -DeltaV termination and overcharged.

 

[TakeTheActive]

also, ur BC 900 booklet will have all ur answers for u mate:thumbsup:

Does your ISP determine your monthly bill based on 'Total BYTES Sent'? :sigh: :tinfoil:

 

[TakeTheActive]

But knowledge changes and we have to adapt to survive. Knowing what I know now, I would be very cautious about blindly adopting that 0.5-1.0C guideline. The batteries might not like it and might get cooked. 'Proper', maybe; appropriate in all cases, not so sure...

I agree with your statement "...The batteries might not like it and might get cooked. 'Proper', maybe; appropriate in all cases, not so sure...

BUT you also need to include the (possible / probable) REASON (i.e. High Internal Resistance - Definition: Internal Resistance)

...And it also depends on the charger. The BC900 is a known "hot" charger, so lower charge rates are appropriate.

I disagree with you here.

Yes, the BC-900 runs HOTTER (than the Maha MH-C9000 for example) because, for ONE reason, the cells are spaced too tightly together. That inherent DEFICIT is, IMHO, no reason to deviate from the recommended "0.5-1.0C Rule". Charge only TWO cells, in the OUTER slots and see if there's a difference.

BOTTOM LINE: Before you advise users to lower their Charge Current, also inform them of the POSSIBILITY of having *CRAP* cells with HIGH INTERNAL RESISTANCE. You could also point them to methods to MEASURE their cell's Internal Resistance *AND*, if high, procedures to possibly REDUCE their cell's Internal Resistance. (CLICK on my Sig Line LINK for LINKs)

CLOSING THOUGHTS: While I do appreciate the participation of *MANY* ">1000+ Posts" Members on *MANY* different forums (not just CPF), I also note the 'INCOMPLETENESS' of *MANY* of their posts. Personally, I strive to make my posts 'Standalone' (i.e. sometimes VERY LONG!), such that if a GOOGLE SEARCH found one, the reader would receive a COMPLETE answer to his/her question.

 

[Mr Happy]

Even "good" cells can get hot when charged at high rates. My cells that reached 63°C were good cells with low resistance.

So everything is not always black and white. There are many shades of grey.

 

[45/70]

......The BC900 is a known "hot" charger, so lower charge rates are appropriate.

I agree. Especially with four cells, I use mine at no more than 700mA in the summer. In the winter 1000mA works OK, as it's usually in the 60's (F) here.

There are many shades of grey.

Ain't that the truth! Sometimes it's advantageous to be colorblind!

Dave

 

[Mr Happy]

Just to add to the story of post #3, I charged the very same cells at a rate of 600 mA. This time they reached a maximum temperature of only 45°C, which is barely warm to the touch, and the charge supplied at termination was lower on average than with the higher currents.

So clearly you don't have to charge at rates higher than 0.5C unless your cells are not terminating well at lower currents.

 

[Bones]

...

Ain't that the truth! Sometimes it's advantageous to be colorblind!

Dave

+1...