How many ma to charge a lithium polymer power bank?

I just bought a 2600mah lithium polymer battery power bank.
Its specs say 5V-800 ma input
and 5V 1000 ma output.

That seems strange to me, I would think that input and out put should be at least the same, and that it should be able to take much more input, at 1c.
3.7v/5v*2.6amp= 1.924 amp or 1924 ma.

I charged it with a 1 amp wall wart, and it didn't even get warm.

I have two USB ports in my car, one is 1 amp, the other 2.1 amps.
Thoughts?

I bought this one:

http://lygte-info.dk/review/Review USB battery box 4x18650 Ruinovo UK.html

It has a 1A output and a 2.1A output and it can accept a 1A input and a 2A input with the barrel connector USB cable.

My 2A input seems to have stopped charging at 2A and I'm only getting 200mA on that connector, but it did work for a while.

I would think that 1A would be typical for this type of device.

Chris

1 amp should be enough to charge and the charging current usually drops has the battery becomes charged. Charging at 1 amp usually has charging input at about 200mAh during the last hour and will drop even more near full charge.

Poppy said:

I would think that input and out put should be at least the same

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Why do you think that the power used to charge the powerbank should be the same as the max power the bank can output?

The USB 2.0 sped specifies 1000 mA as the maximum current load on a single USB port for general use.

I predict that with the advent of the universal C connector, power banks will start to appear that can take more than 1 A as input, but, as always, the power bank and the USB port will negotiate as to what the port can provide and what the power bank can take.

Timothybil said:

The USB 2.0 sped specifies 1000 mA as the maximum current load on a single USB port for general use.

I predict that with the advent of the universal C connector, power banks will start to appear that can take more than 1 A as input, but, as always, the power bank and the USB port will negotiate as to what the port can provide and what the power bank can take.

Click to expand...

I take this to mean that the limit has more to do with the port than with the battery's ability to take a charge at a higher rate. Correct?

I think that the Apple Tablet takes a 2.1 amp charge.
Have the USB ports been upgraded to allow a higher amperage flow?

Poppy said:

I take this to mean that the limit has more to do with the port than with the battery's ability to take a charge at a higher rate. Correct?

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No, even if it could accept more power it would not be fast charging at 1C since this would cause much faster degradation (vs. standard rates like C/4 or C/5), e.g. compare the green C/5 charge vs aqua C charge curves below (from here). To fast charge without degradaton one needs to replace the ancient CC-CV algorithm by more modern multistage fast-charging algorithms such as those by Telsa or Philips that I discuss in this thread. But it will be some time before they percolate down to powerbanks.

Gauss163 said:

No, even if it could accept more power it would not be fast charging at 1C since this would cause much faster degradation (vs. standard rates like C/4 or C/5).

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Could you please explain in greater detail? What you wrote, or the way you wrote it doesn't make sense to me.
THanks

Poppy said:

Could you please explain in greater detail? What you wrote, or the way you wrote it doesn't make sense to me.
THanks

Click to expand...

The higher charging current will shorten the lifespan of the cell(s).

I'm assuming that your LiFeP04 is a single 2600mAh cell.

C would be a charging rate of 2.6A.

.5C would be 1.3A.

Given two identical cells, the one being charged at 2.6A, or C, will lose more of its capacity over its life, than the cell being charged up at 1.3A.

The same can be said about 'discharging' current. The higher the drain, the more damage the cell suffers.

Chris

Poppy said:

Could you please explain in greater detail? What you wrote, or the way you wrote it doesn't make sense to me.
THanks

Click to expand...

Sure, but I don't know where to start since you don't say what is not clear to you.

ChrisGarrett said:

The same can be said about 'discharging' current. The higher the drain, the more damage the cell suffers.

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But to a much lesser extent. Fast charging causes much more severe degradation than does fast discharging at the same rates. See the NASA study I linked in my penultimate post with the excerpted graph.

Gauss163 said:

But to a much lesser extent. Fast charging causes much more severe degradation than does fast discharging at the same rates. See the NASA study I linked in my penultimate post with the excerpted graph.

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They used the older 2900mAh NCR18650 and that test is from 2009. I think those are the last of the pure li-cos, IIRC? I wonder if the newer chemistries and hybrids fare better?

Those plots seem pretty pessimistic to me, but I'm no rocket scientist and they are.

Chris

ChrisGarrett said:

Those plots seem pretty pessimistic to me, but I'm no rocket scientist and they are.

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I'm not aware of any evidence refuting that study. NASA studies are generally quite reliable in my experience. You don't want failures in outer space.

Gauss163 said:

I'm not aware of any evidence refuting that study. NASA studies are generally quite reliable in my experience. You don't want failures in outer space.

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It's dated.

New chemistries are out with their own behavioral characteristics.

Chris

ChrisGarrett said:

It's dated. New chemistries are out with their own behavioral characteristics.

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Hardly. If you have scientific evidence refuting the study then post it. Otherwise please stop posting non-scientific guesses.

Gauss163 said:

Hardly. If you have scientific evidence refuting the study then post it. Otherwise please stop posting non-scientific guesses.

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Don't be so touchy! Yes, NASA is very meticulous, with reason. Knowing government procurement like I do, I would guess that in the absence of any updated studies, NASA is still buying cells made with the formulation of 2009. Gotta love government contracts. What Chris is saying is that the 2009 study was of the common cell chemistry of that time. Since then there have been modifications to that chemistry in an effort to increase the power density of a cell (and I am not talking about ICR vs IMR vs INR, either. Just ICR to ICR). Have any studies been done to see if those changes have affected the results of the 2009 study?

Gauss163 said:

Hardly. If you have scientific evidence refuting the study then post it. Otherwise please stop posting non-scientific guesses.

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New chemistries are out and that's hardly a guess.

Please post something a bit more timely and relevant to the current chemistries.

That NASA study was done in 2009 and studied a Panasonic cell that's about 4 generations in the past.

I'm sure that the oxygen generators found in the Mercury program are vastly inferior to the current generation of O.G.s.

Oh and NASA is hardly beyond reproach in their testing and implementation protocols.

Chris

I bought an 8x18650 diy power bank with an lcd display, really cheap for £4-5 , strange thing is it has two micro usb charging sockets, can you charge the battery bank with two micro usb chargers at the same time to get a full charge faster.

John.

Gauss163 said:

Sure, but I don't know where to start since you don't say what is not clear to you.

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Gauss,
The graph you added to post #7 made what you were trying to say more clear. Thanks.

I thought that I had read that LiIon batteries could take a 1C charge, and some could be charged at a much higher rate than that. The batteries for my Ryobi 18V tools charge in an hour. Many LiPo batteries for R/C toys may have a 3-4 C discharge rate.

I went to battery university for additional information and found this...

The maximum charge current a Li-ion can accept is governed by cell design, and not the cathode material as is commonly assumed. The goal is to avoid lithium-plating on the anode and to keep the temperature under control. A thin anode with high porosity and small graphite particles enables ultra-fast-charging because of the large surface area. These so-called Power Cells can be charged and discharged at high currents, but the energy density is low. The Energy Cell, in comparison, has a thicker anode and lower porosity but this battery should be charged at 1C or less. Some hybrid Cells in NCA (nickel-cobalt-aluminum) can be charged at 4C with moderate stress.
Apply the ultra-fast charge only when necessary. A well-designed ultra-fast charger should have charge-time selection to give the user the option to choose the least stressful charge for the time allotted. Figure 3 compares the cycle life of a typical lithium-ion battery when charged and discharged at 1C, 2C and 3C rates. The longevity can further be prolonged by charging and discharging bellow 1C; 0.8C is the recommended rate.

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They say 0.8C is the recommended rate of charge and discharge.

So now I have a new question.

What amperage from a 5V source would give me a 0.8C rate of charge for a presumably 3.7 V LiPO battery encased in that power bank?

ChrisGarrett said:

Please post something a bit more timely and relevant to the current chemistries.

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Please post logically sound arguments. Your reasoning (those results "seem pretty pessimistic to me", or they are too old, or maybe they don't apply to different cells) is neither logical nor scientific. Neither opinions nor time changes facts. Nor have you given even a single shred of evidence of any advances that would affect said results. Rather, you made some wild guesses.

Exactly the same faulty reasoning could be applied to every known defect of Li-ion batteries, including all of the known degradation and safety mechanisms (the safety studies are even older). Do you similarly ignore all safety matters because they "seem pretty pessimistic" to you? You won't win many arguments with that logic, but you might win a Darwin award. Best of luck with that.