Re: [funwithtransistors] Li-ion battery?


Jan 25, 2014

 


----------------------------

#1577 Jan 25, 2014

My last post talked about battery power. .I must admit I'm still in the stone age. .I'm using AA size rechargeable and I take them out and place them in a charger.

But I have a few cell phone batteries with really good specs. .One reads "3.7V 1800mAh" and it is literally the size of a credit card. . .To get the same from my AA cels I'd need three AA cells with is about 3 or 4 times the bulk and weight.

Has anyone here used these? .They all seem to be about the same in that there are three electrical terminals and only two are marked. .There are "+", "-" and "no mark". .The first two I can figure out. .The third blank one is not obvious. . .But I'm guessing it is needed or it would not be one every li-ion battery.

I need to learn how to use these

--

Chris AlbertsonRedondo Beach, California



----------------------------

#1579 Jan 25, 2014

The third terminal usually goes to a thermister for temperature sensing. This

is more of a safety feature than something which is needed for normal charging.



Charging a lithium cell is not all that difficult but care must be taken to

limit the charging current and voltage. They are very intolerant of overcharge

and cell life is severely degraded at higher voltages which is why long life

applications use a lower peak charging voltage and sacrifice the top 20% of the

capacity.

On Sat, 25 Jan 2014 10:59:22 -0800, you wrote:



>My last post talked about battery power. I must admit I'm still in the

>stone age. I'm using AA size rechargeable and I take them out and place

>them in a charger.

>

>But I have a few cell phone batteries with really good specs. One reads

>"3.7V 1800mAh" and it is literally the size of a credit card. To get the

>same from my AA cels I'd need three AA cells with is about 3 or 4 times the

>bulk and weight.

>

>Has anyone here used these? They all seem to be about the same in that

>there are three electrical terminals and only two are marked. There are

>"+", "-" and "no mark". The first two I can figure out. The third blank

>one is not obvious. But I'm guessing it is needed or it would not be one

>every li-ion battery.

>

>I need to learn how to use these



----------------------------

#1580 Jan 25, 2014

Chris:

������ The third terminal is used only for charging........... It hassomething to do with temperature control.���� The individual cellsdon't have it.



������ ������ ������ ������ ������ ������ ������ ������ ������ ������ ������ ������ ������ ������ ������ ������������ ������ ������ ������ Howard



On 01/25/2014 11:59 AM, Chris Albertson wrote:





My last post talked about batterypower. ��I must admit I'm still in the stone age. ��I'm using AAsize rechargeable and I take them out and place them in acharger.



But I have a few cell phone batterieswith really good specs. ��One reads "3.7V 1800mAh" and it isliterally the size of a credit card. �� ��To get the same frommy AA cels I'd need three AA cells with is about 3 or 4 timesthe bulk and weight.

Has anyone here used these? ��They allseem to be about the same in that there are three electricalterminals and only two are marked. ��There are "+", "-" and "nomark". ��The first two I can figure out. ��The third blank oneis not obvious. �� ��But I'm guessing it is needed or it wouldnot be one every li-ion battery.

I need to learn how to use these



--



Chris Albertson

Redondo Beach, California



----------------------------

#1581 Jan 25, 2014

albertson.chris@... writes:Has anyone here used these?



I have not, but I understand that some of these batteries contain "smarts" and will only work with that manufacturers product.��



Regards,

Mark KB9VKE



----------------------------

#1582 Jan 25, 2014

Thanks, .I've been putting off using the batteries because the third terminal. .Seems I can ignore temperature if I'm willing to charge way-slow.

Let's say it is a 3.7 volt battery rated at 1000mAh. .I just put it on a power supply that is limited to say 50mA and wait until it gets to about 3.7volts? . .Worst case, it takes 24 hours



I have two of these one measures 4.0 volts, the other 3.8 volts. .Both are rated at 3.7V 1800mA. .I use an otherwise non-functional cell phone as a charger. .So it looks like the phone will slightly over charge the cells, likely looking for more air-time. .I can stop right before 3.7V.



----------------------------

#1583 Jan 25, 2014

That will certainly work.



I am a little fuzzy on the charge voltages and currents for the various lithium

chemistries but it looks like lithium polymer cells should be charged to 4.2

volts and should never be discharged below 3.0 volts. If multiple cells are

used in series, each cells needs to stay within those limits to avoid damage.



The current limit is between about 0.2C and 0.8C depending on the manufacturer.

At low charge currents, by the time the cell reaches 4.2 volts it will be almost

completely charged. At high currents, the cell will not be fully charged once

it reached 4.2 volts and some additional time will be necessary with the voltage

held at that level while the charging current tapers off.



If a lower voltage is used, then total cell capacity can be traded off for

service life. The batteries wear out just sitting there. Oddly enough

ultracapacitors have the same trade off; for every rise in their charging

voltage of 0.2 volts, their service life drops to 1/10th.



I would not say they are any more difficult to use than sealed lead acid

batteries except that they extremely intolerant of overcharging which makes cell

balancing more complicated. On a lead acid battery you can use an equalization

charge to balance the cells but that would damage a lithium battery.



The lithium phosphate iron rechargeable cells are tougher and operate between

2.0 and 3.65 volts but have a lower capacity.

On Sat, 25 Jan 2014 12:05:30 -0800, you wrote:



>Thanks, I've been putting off using the batteries because the third

>terminal. Seems I can ignore temperature if I'm willing to charge way-slow.

>

>Let's say it is a 3.7 volt battery rated at 1000mAh. I just put it on a

>power supply that is limited to say 50mA and wait until it gets to about

>3.7volts? Worst case, it takes 24 hours

>

>I have two of these one measures 4.0 volts, the other 3.8 volts. Both are

>rated at 3.7V 1800mA. I use an otherwise non-functional cell phone as a

>charger. So it looks like the phone will slightly over charge the cells,

>likely looking for more air-time. I can stop right before 3.7V.

>

>On Sat, Jan 25, 2014 at 11:23 AM, David davidwhess@...> wrote:

>

>> The third terminal usually goes to a thermister for temperature sensing.

>> This

>> is more of a safety feature than something which is needed for normal

>> charging.

>>

>> Charging a lithium cell is not all that difficult but care must be taken to

>> limit the charging current and voltage. They are very intolerant of

>> overcharge

>> and cell life is severely degraded at higher voltages which is why long

>> life

>> applications use a lower peak charging voltage and sacrifice the top 20%

>> of the

>> capacity.

>>

>> On Sat, 25 Jan 2014 10:59:22 -0800, you wrote:

>>

>> >My last post talked about battery power. I must admit I'm still in the

>> >stone age. I'm using AA size rechargeable and I take them out and place

>> >them in a charger.

>> >

>> >But I have a few cell phone batteries with really good specs. One reads

>> >"3.7V 1800mAh" and it is literally the size of a credit card. To get the

>> >same from my AA cels I'd need three AA cells with is about 3 or 4 times

>> the

>> >bulk and weight.

>> >

>> >Has anyone here used these? They all seem to be about the same in that

>> >there are three electrical terminals and only two are marked. There are

>> >"+", "-" and "no mark". The first two I can figure out. The third blank

>> >one is not obvious. But I'm guessing it is needed or it would not be one

>> >every li-ion battery.

>> >

>> >I need to learn how to use these







----------------------------

#1584 Jan 26, 2014

I found a good reference.batteryuniversity.com/learn/article/charging_lithium_ion_batteries



Then I found that these batteries are very popular is the hobby .model car, airplane and helicopter industry and there are many suppliers. .I can buy a charger on a bare 2" square PCB for $1.78 or small retail charger for under $10. .Also in the hobby industry they have standardized on connectors for discharge and for charging (they use different connections for each.) .

The charge connecter brings out leads for each cell so they can be charged independently. .The discharge connector (called a T6) has the cells in series and the connector is rated at 60A. . .

It looks like these have completely replaced the need to ever again buy a lead acid gell cell..



----------------------------

#1585 Jan 26, 2014

The logical solution to the problem is to use the intelligent charger

that is designed for the battery. As an example, you can buy a tracphone

with a lithium battery for about $20 at Wallmart. In that case the

cheap phone is the charger for the lithium battery... or multiple

copies. I own a Samsung camera....... an inexpensive pistol grip unit

with an excellent lithium battery pack that has an external

charger...... A battery an charger like this is probably available

separate from the camera if you know what to order. There must be

dozens of products out there with externally charged LION batteries...

And of course there is Ebay....



Howard

On 01/25/2014 01:41 PM, David wrote:

> That will certainly work.

>

> I am a little fuzzy on the charge voltages and currents for the various lithium

> chemistries but it looks like lithium polymer cells should be charged to 4.2

> volts and should never be discharged below 3.0 volts. If multiple cells are

> used in series, each cells needs to stay within those limits to avoid damage.

>

> The current limit is between about 0.2C and 0.8C depending on the manufacturer.

> At low charge currents, by the time the cell reaches 4.2 volts it will be almost

> completely charged. At high currents, the cell will not be fully charged once

> it reached 4.2 volts and some additional time will be necessary with the voltage

> held at that level while the charging current tapers off.

>

> If a lower voltage is used, then total cell capacity can be traded off for

> service life. The batteries wear out just sitting there. Oddly enough

> ultracapacitors have the same trade off; for every rise in their charging

> voltage of 0.2 volts, their service life drops to 1/10th.

>

> I would not say they are any more difficult to use than sealed lead acid

> batteries except that they extremely intolerant of overcharging which makes cell

> balancing more complicated. On a lead acid battery you can use an equalization

> charge to balance the cells but that would damage a lithium battery.

>

> The lithium phosphate iron rechargeable cells are tougher and operate between

> 2.0 and 3.65 volts but have a lower capacity.

>

> On Sat, 25 Jan 2014 12:05:30 -0800, you wrote:

>

>> Thanks, I've been putting off using the batteries because the third

>> terminal. Seems I can ignore temperature if I'm willing to charge way-slow.

>>

>> Let's say it is a 3.7 volt battery rated at 1000mAh. I just put it on a

>> power supply that is limited to say 50mA and wait until it gets to about

>> 3.7volts? Worst case, it takes 24 hours

>>

>> I have two of these one measures 4.0 volts, the other 3.8 volts. Both are

>> rated at 3.7V 1800mA. I use an otherwise non-functional cell phone as a

>> charger. So it looks like the phone will slightly over charge the cells,

>> likely looking for more air-time. I can stop right before 3.7V.

>>

>> On Sat, Jan 25, 2014 at 11:23 AM, David davidwhess@...> wrote:

>>

>>> The third terminal usually goes to a thermister for temperature sensing.

>>> This

>>> is more of a safety feature than something which is needed for normal

>>> charging.

>>>

>>> Charging a lithium cell is not all that difficult but care must be taken to

>>> limit the charging current and voltage. They are very intolerant of

>>> overcharge

>>> and cell life is severely degraded at higher voltages which is why long

>>> life

>>> applications use a lower peak charging voltage and sacrifice the top 20%

>>> of the

>>> capacity.

>>>

>>> On Sat, 25 Jan 2014 10:59:22 -0800, you wrote:

>>>

>>>> My last post talked about battery power. I must admit I'm still in the

>>>> stone age. I'm using AA size rechargeable and I take them out and place

>>>> them in a charger.

>>>>

>>>> But I have a few cell phone batteries with really good specs. One reads

>>>> "3.7V 1800mAh" and it is literally the size of a credit card. To get the

>>>> same from my AA cels I'd need three AA cells with is about 3 or 4 times

>>> the

>>>> bulk and weight.

>>>>

>>>> Has anyone here used these? They all seem to be about the same in that

>>>> there are three electrical terminals and only two are marked. There are

>>>> "+", "-" and "no mark". The first two I can figure out. The third blank

>>>> one is not obvious. But I'm guessing it is needed or it would not be one

>>>> every li-ion battery.

>>>>

>>>> I need to learn how to use these

>

---------------

>

> Always keep electrons and holes flowing in opposite directions.Yahoo Groups Links

>

>

>

>







----------------------------

#1586 Jan 26, 2014

Actually that is what I was going to do. . You don't have to spend even $20 as junk phones with smashed screens and whatever are free. .I've collected a half dozen of them. .

The trouble is if I solder a cable to the battery then it will not fit back into the phone and I have to solder a matching connector into the phone. .That works. . I was worried about that center contact that is for temperature. . .Maybe I can ignore it as this junk is all free. .But what if the phone things the battery is not getting warm and ups the current? . If phones had standard batteries I'd make a battery holder. .But every one is different. .so I have to solder directly to the phone battery.

Then I found out about the hobby aircraft market. .They have mostly standardized batteries and chargers across the industry and across brands. . The chargers start as very low prices, under $2 if you can use a bare PCB. $10 for a small retail unit. . .These batteries get .big. .A small quadcopter can pull 60A continually from the battery.



----------------------------

#1587 Jan 26, 2014

Chris:

... I'm thinking that the center terminal is probably used aseither the positive or negative terminal for charging..........The idea being that the thermister regulates the current based ontemp.. That would suggest that if you know the charging voltagefor the battery, you should be able to make a simple charger thatcharges through this terminal, and you will have the regulationyou need.. It should not be difficult to test this............



... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ...... ... ... ... ... Howard

On 01/26/2014 12:35 AM, Chris Albertson wrote:



Actually that is what I was going to do. . Youdon't have to spend even $20 as junk phones with smashed screensand whatever are free. .I've collected a half dozen of them. .

The trouble is if I solder a cable to the battery then itwill not fit back into the phone and I have to solder amatching connector into the phone. .That works. . I wasworried about that center contact that is for temperature. ..Maybe I can ignore it as this junk is all free. .But what ifthe phone things the battery is not getting warm and ups thecurrent? . If phones had standard batteries I'd make a batteryholder. .But every one is different. .so I have to solderdirectly to the phone battery.

Then I found out about the hobby aircraft market. .Theyhave mostly standardized batteries and chargers across theindustry and across brands. . The chargers start as very lowprices, under $2 if you can use a bare PCB. $10 for a smallretail unit. . .These batteries get .big. .A small quadcoptercan pull 60A continually from the battery.



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