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Charge time for lithium batteries

Gary4242

Dec 11, 2018
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Hi all,
You will tell from this post that I do not have a clue about electronics.
I have a bank of 3 lithium ion rechargeable batteries that are total 10.8V/12.6 V, with energy/capacity 14Wh/1.3Ah.
The supplied charger is 25 V 130mah.
How long should it take to charge these fully drained batteries.
If my charger is rated 25 Volts, should it actually put out more? say 28-30Volts

Thanks in advance......... Gary
 

Bluejets

Oct 5, 2014
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1300mAh /130 mA= ???

Are you sure that is an input of 25v?
Seems an abnormally high value which would only have to be reduced internally.
 

Gary4242

Dec 11, 2018
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The wall charger label is 25 volts...confirmed with voltmeter. Label also has -------- 130 Ah
Batteries are 3 18650 handed together
Application is a bath lift for elderly.
Thx.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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Using the correct charger, the batteries are charged when the charger indicates they are.

The time depends on the amount of charge remaining before you start to charge them, the capacity of the batteries, the charging efficiency, and the power the charger can put back into the battery (i.e. the rate at which energy is transferred).

There is no simple answer unless all these factors are known.

An easy method is to put it on charge and time it.
 

Gary4242

Dec 11, 2018
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Using the correct charger, the batteries are charged when the charger indicates they are.

The time depends on the amount of charge remaining before you start to charge them, the capacity of the batteries, the charging efficiency, and the power the charger can put back into the battery (i.e. the rate at which energy is transferred).

There is no simple answer unless all these factors are known.

An easy method is to put it on charge and time it.
Thanks...I really am just looking for rough idea...ie...3 hrs... 10 hours....24 hours.... 48 hour? Based on the numbers provided in these posts. There is a red light that comes on when charged.... but have been on charge for about 10 hours now... i believe the batteries may be toast. Just want sure how long to wait.
 

Bluejets

Oct 5, 2014
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The battery says max charge rate is 0.1A or 100mA.
Previously you asked how long to charge from "fully drained" and with the info previously supplied the answer was given with the numbers you supplied back then..
If you say the charger has been on for 10 hours then in my calculations that's just about right, give or take a bit.
I would imagine this "charger" is not top shelf stuff.
 

BobK

Jan 5, 2010
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Your battery pack shows 1300 mAh capacity and a charge rate of 100 mA. If charging was 100% efficient it would take 13 hours. So, probably about 15 hours.

Bob
 

Gary4242

Dec 11, 2018
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Thank you Bob. That is exactly the type of answer I was looking for.
Hi Bob,
How does the 25V charger fit into the picture when the battery pack is 10.8V/12.6. Any significance that they did not use 12V charger and went with the 25V
Thanks, Gary
 

BobK

Jan 5, 2010
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No idea why they would use such a high voltage. The max voltage that it can put on the battery is 12.4V.

Lithium batteries are charged in two or more stages. First, a contant current phase , where the voltage is adjusted as it charges to maintain the current. Then, when the charging voltage reaches 4.2V per cell, it stays at that voltage and the current reduces to a preset level at which it is cut off.

Bob
 

WHONOES

May 20, 2017
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Bob K is correct regarding the process.
Simplistically,if your Batts are really 18650mAH capacity and the charger output is a max of 130mA then a fully discharged battery will take 18650 / 130 hours to charge assuming 100% charge efficiency which is not realistic. That translates to an absolute minimum of 143 hours but probably more like 180 hours.
 

Audioguru

Sep 24, 2016
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Simplistically,if your Batts are really 18650mAH capacity and the charger output is a max of 130mA then a fully discharged battery will take 18650 / 130 hours to charge assuming 100% charge efficiency which is not realistic. That translates to an absolute minimum of 143 hours but probably more like 180 hours.
Look at the numbers 18650. Each cell is 18mm in diameter and is 65mm long. The mAh is from 55mAh for a Chinese cheap fake one (many use the word "Fire" in their name) to about 3300mAh for a good name-brand one.
 

WHONOES

May 20, 2017
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Look at the numbers 18650. Each cell is 18mm in diameter and is 65mm long. The mAh is from 55mAh for a Chinese cheap fake one (many use the word "Fire" in their name) to about 3300mAh for a good name-brand one.
Was just pointing out how long it would take to charge the batteries if they really were 18650 mAH capacity.
 

Audioguru

Sep 24, 2016
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A kid on my street has a skateboard that powers him up the hill. Its lithium battery and motor are very small and can barely be seen.
He charges it each night and rides it to school every day. Other kids carry their unpowered skateboard up the hill.
 
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