Author Topic: Lithium Battery Charging help needed  (Read 3068 times)

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Offline peps1

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Lithium Battery Charging help needed
« on: January 16, 2015, 07:05:14 pm »

I just got some Lithium Battery Charging PCBs in the post, and being totally new to the world of lithium battery charging was wondering if the mAH of the batteries I want to charge with this matters, or if I can use for example anything like a 8650 3.7V 5000mAH or small 250mAH through to say, 1100mAH 3.7v Li-ion polymer?
 

Offline Maxlor

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Re: Lithium Battery Charging help needed
« Reply #1 on: January 16, 2015, 10:04:10 pm »
yes, it matters. Most batteries specify a maximum charge current of 0.5C to 2C, with 1C being the most common. The C means the battery's capacity. So, if you have a 250mAh battery and the max charge current is specified as 1C, the charge current should be 250mA max, whereas with a 3000mAh battery, it should be 3000mA max.

If nothing is specified, assume 1C max current for both charging and discharging. If you have the time though, a lower max current will reduce the battery's aging.
« Last Edit: January 16, 2015, 10:06:05 pm by Maxlor »
 

Offline peps1

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Re: Lithium Battery Charging help needed
« Reply #2 on: January 16, 2015, 10:28:50 pm »
How would I adjust the charge current?  :-//
 

Offline ion

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Re: Lithium Battery Charging help needed
« Reply #3 on: January 16, 2015, 10:30:14 pm »
I believe with lithium, standard charging currents are more like 0.7C.

Personally, with an unknown battery I'd stick to 0.5C for safety.
 

Offline sleemanj

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Re: Lithium Battery Charging help needed
« Reply #4 on: January 17, 2015, 12:00:26 am »
How would I adjust the charge current?  :-//

Look at the datasheet for the charge management IC on that board you have purchased.  You will almost certainly find that the current is set by way of a resistor value. 

Locate the resistor on the PCB, take it off, replace it with one that gives the current you want.

For example, for the common TP4056, these are suitable values as taken from datasheets, I'd hazard a guess on your board that it will be R3 (see if it's 1.2k or thereabouts), and probably the same values will work.

Code: [Select]
30k = 50mA
20k = 70mA
10k = 130mA
5k = 250mA
4k = 300mA
3k = 400mA
2k = 580mA
1.66k = 690mA
1.5k = 780mA
1.33k = 900mA
1.2k = 1000mA  (default)

This looks close enough (but not exact) to R = 1000 * (1.2/A)
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Offline eas

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Re: Lithium Battery Charging help needed
« Reply #5 on: January 17, 2015, 09:04:38 am »

I just got some Lithium Battery Charging PCBs 8650 3.7V 5000mAH?

I assume you mean 18650, and if you do, you should know that you do not have an 5000mAh 18650. They don't exist, though that doesn't stop people from lying about it. The largest capacity 18650 right now is 3,400 mAh, but you can be pretty sure that you aren't getting one of those when you buy one that claims a capacity of 5,000mAh. My guess is that you'll be lucky if it has 2000mAh capacity.   
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Offline peps1

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Re: Lithium Battery Charging help needed
« Reply #6 on: January 17, 2015, 03:28:43 pm »
For example, for the common TP4056, these are suitable values as taken from datasheets, I'd hazard a guess on your board that it will be R3 (see if it's 1.2k or thereabouts), and probably the same values will work.

Code: [Select]
30k = 50mA
20k = 70mA
10k = 130mA
5k = 250mA
4k = 300mA
3k = 400mA
2k = 580mA
1.66k = 690mA
1.5k = 780mA
1.33k = 900mA
1.2k = 1000mA  (default)

This looks close enough (but not exact) to R = 1000 * (1.2/A)

Thanks sleemanj, you are 100% correct, it is a TP4056  :-+
 

Offline IanB

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Re: Lithium Battery Charging help needed
« Reply #7 on: January 17, 2015, 03:53:14 pm »

I just got some Lithium Battery Charging PCBs in the post, and being totally new to the world of lithium battery charging was wondering if the mAH of the batteries I want to charge with this matters, or if I can use for example anything like a 8650 3.7V 5000mAH or small 250mAH through to say, 1100mAH 3.7v Li-ion polymer?

You posted this question with a link to what you bought. Here is what it says in the description when following that link:

Quote
Specification:

100% brand new and high quality
Charge module- Linear charging.
Current- 1 A adjustable.
Charge precision- 1.5%.
Input voltage- 4.5 V - 5.5 V.
Full charge voltage- 4.2 V.
Led indicator- red is charging Green is full charged.
Input interface- micro USB.
Work temperature- -10? to +85?.
Reverse polarity- NO.
Size- small to 25 x 19 x 10 mm.
NOTE:
1. Ampere meter can only be connected to 5 V input end of the module.
2. It is better that the charging current is 37% of the battery capacity. If you charge to the battery of 1000 mAh, current of 400 is enough.
3. The connection wire should not be too thick.
4. Make sure the connect point is good.
5. If the input voltage is too high, like 5.2 V, the current will be less than 1000 mA, it is normal. It is protection function, auto-subtract the charging current to avoid burn damage to chip.
6. NO Reverse polarity.

It seems to answer some of your questions.
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Offline peps1

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Re: Lithium Battery Charging help needed
« Reply #8 on: January 17, 2015, 04:00:48 pm »
Obviously I disagree that the listing answered my questions, or I would not have made this post.  :-+
 

Offline IanB

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Re: Lithium Battery Charging help needed
« Reply #9 on: January 17, 2015, 04:05:39 pm »
So, you asked this question:

I was wondering if the mAH of the batteries I want to charge with this matters, or if I can use for example anything like a 8650 3.7V 5000mAH or small 250mAH through to say, 1100mAH 3.7v Li-ion polymer?

And yet the information in the listing says this:

Quote
It is better that the charging current is 37% of the battery capacity. If you charge to the battery of 1000 mAh, current of 400 is enough.

Call me crazy, but it looks like this answers your question.
I'm not an EE--what am I doing here?
 

Offline peps1

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Re: Lithium Battery Charging help needed
« Reply #10 on: January 17, 2015, 04:25:25 pm »
Again, obviously not, or I would not have made the post. I think my questions have been far better answered by the helpful members here who grasp the concept of a "Beginners section" than that single line in the item listing.

But, thanks for popping by and contributing  :-+
 


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