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Long story short, I have a Toshiba laptop. Its adapter outputs 19.05 volt and 3A.

I wanted to build a powerbank for my laptop. I have built one using Li-ion cells. 5 cells in series with each cell as 3.7 volts and it works just fine but the cells take a lot of space and still have a capacity just around 6000 mAh...

So I was thinking of using mobile powerbanks with capacity as high as 15000 mAh are easily available and I have also found a DC boost converter that can boost from 5V upto 45V.

Do you think if I connect the powerbank's 5V port to the boost converter and set it to 19.1V. Will it be able to run the laptop?

Neil_UK
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Rehan Ullah
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  • Just a sidenote, most new notebooks do not charge from "unverified" sources. – po.pe Jun 28 '20 at 10:34
  • Yeah maybe but this one does. I have a powerbank built using li-ion cells and it considers it as a fine charger. So that can't be the case here. – Rehan Ullah Jun 28 '20 at 10:37
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    @RehanUllah Stepping up the voltage requires a proportionally higher input current. For 19V 3A out, you'd need to step up by a factor of 4 from 5V. That means the input current would need to be at *least* 12A (probably more with losses). I highly douby a mobile powerbank can acheive that. – Tom Carpenter Jun 28 '20 at 10:40
  • @TomCarpenter I see... Yeah you are right... It won't handle 12A... It would just prefer blowing up instead. – Rehan Ullah Jun 28 '20 at 10:49

2 Answers2

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It highly depends on the power consumption of your laptop. Suppose its current consumption is around 2-3A, so if u boost a 5v source to 20v/3A then your 5v source must be able to provide 12A (with the assumption of 100% efficiency!). So there's two problems: 1) is the power-bank capable of providing 12A? for most power-banks the answer is NO, most of them provide current up to 2A. 2) is the step-up circuit capable of handling such a high current? you have to search more for this. For example LM2577 is a step-up IC (and its module is also available) providing about 2A.

Hamid R. Tanhaei
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  • Naah... The IC that I shall be using has max input current limit of 3A... – Rehan Ullah Jun 28 '20 at 10:46
  • You mean your step-up IC? There's something u should consider when choosing a step-up IC, which is "max-switch-current" which means the mosfet inside it will cut-off at this current. This current should be always be higher than average incoming current, cuz the instantaneous input current has ripples! – Hamid R. Tanhaei Jun 28 '20 at 10:51
  • Got it. Actually its rated input i.e. average incoming is 2A. The max-switch-current is 3A. So won't work. Well if I connect 4 powerbank outputs in series thus making it 20 volt and each powerbank's output is 3A, will it work then? – Rehan Ullah Jun 28 '20 at 10:59
  • Seems not a bad idea. It's worth trying, see what will happen in reality. But when u want to recharge them with a single power supply, you should disconnect them from series. – Hamid R. Tanhaei Jun 28 '20 at 11:06
  • Yes that I shall do. – Rehan Ullah Jun 28 '20 at 11:08
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Consider the size cost and reliability of what you are trying to achieve.

Using the Powerbank for more than one purpose to store charge or extend Laptop runtime, is a futile exercise and wears out 2 battery packs at the same time as well as forcing extreme boost currents on the connection for the step-up converter to a low ESR battery load.

Possible yes, but not for a newbie design. I won't get into all the reasons.

Your best bet is to purchase a spare laptop battery pack and use that.

https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2546172.m570.l1313.TR9.TRC1.A0.H0.Xtoshiba+laptop+battery.TRS0&_nkw=toshiba+laptop+battery&_sacat=0

p.s. The more you learn, the wise person will realize how little you know.

Tony Stewart EE75
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