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Probably the most basic portable laptop pack
#1
I wonder how many blokes have come on this forum to post about their portable battery packs for laptops.

Anyways, I've been playing around with making a spare battery to connect to the charge port of my Asus N56JN, the battery on it only holds ~50Wh max, and there's been some wear on my battery. I'd love to have a pack I could just whip out while I'm in class and charge my laptop while I'm working, without having to hook up to an output.

At first, I was going to use 9 LGEAMF11865 cells wired in series, with a DC-DC "buck" converter to step it down to 19V. The laptop charges at roughly 17.6-23v, and the actual charger supplies 19v. However, I've gone through 5 DC-DC converters (4 of the same model), 1 due to a fault on my end, and one couldn't output enough (1.5A) amperage, but 3 of them have failed due to overheating (even after extreme heatsinking).

I used my electric bike battery to test it (36v nominal, 42v full), but I had to drive the bike first because if the battery was too full (above 38v), the converter would spaz out and not output anything. The configuration I worked with was as follows:

eBike battery -> 2 buck converters -> 3A diodes (to link the converters together) -> barrel connector cable -> laptop

Attached is a picture of the old config, after converter 2 gave out. When that happened, I moved the heatsinks to converter 1 and it kept going for a bit, but it ended up giving out later.
I'm not too proud of the wiring if I'm honest. 

 

So buck converters won't work because they're not very portable, they get really hot, and there's a lot of exposed bits and pieces that could short out. 

Next best thing? Just wire the batteries to the wire, what could possibly go wrong? /s

If I use 5 batteries in series, that makes my voltage range roughly 17 to 21 volts. 
So with a nominal voltage of 3.65v and an expected capacity of 2,150mAh, each cell would hold ~7.8475Wh, so across 5 cells that'd be ~39.2375Wh. That's roughly 78% the capacity of the laptop battery, and I'm quite happy with that number, but I could always do more (remember, the original 9 cell config would have ~70.62Wh, near double the amount we have now (well duh, almost double the number of cells...)

The new wiring config will just be a 3 cell holder wired in series to a 2 cell holder, then wire the output of that directly to the barrel connector cable. I might throw in a battery meter too. 
Now it probably won't be able to use all of the energy in the cells due to the voltage getting too low (~17.6v), so let's say I can use 85% of the capacity (random number ig), that's still 33.35Wh to work with. 

Thoughts? Any way I can make this better? 
Thanks,
~CS
Aren't you too young to be playing around with Lithium-Ion batteries?
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#2
Just curious, why'd you post in General Offtopic instead of in Battery Builds??  It's not an offtopic thread
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#3
(06-01-2020, 08:21 PM)Korishan Wrote: Just curious, why'd you post in General Offtopic instead of in Battery Builds??  It's not an offtopic thread
I'm new here, it seemed like the best place to put it Smile
Aren't you too young to be playing around with Lithium-Ion batteries?
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#4
You lose power on those diodes. Also, splitting the load equally between those 2 converters is probably not easy. Much better solution is to just use a higher rated buck converter that can handle the load, such as this one. Packaging will be easier, too - make sure there is air flow over the heatsinks.
https://www.aliexpress.com/item/32805882664.html
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Modular PowerShelf using 3D printed packs.  60kWh and growing.
https://secondlifestorage.com/showthread.php?tid=6458
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#5
(06-01-2020, 09:43 PM)ajw22 Wrote: You lose power on those diodes.  Also, splitting the load equally between those 2 converters is probably not easy.  Much better solution is to just use a higher rated buck converter that can handle the load, such as this one.  Packaging will be easier, too - make sure there is air flow over the heatsinks.
https://www.aliexpress.com/item/32805882664.html
I'll check it out, thank you for the pointer!
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Aren't you too young to be playing around with Lithium-Ion batteries?
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#6
Quick update:
5 cells won't work too well, I've figured out. I put 5 cells in series (without a holder) and it's not outputting enough amperage (I think). I'm not sure the cells were full, but this laptop is a bit picky when it comes to amperage. If the amperage is too low, it starts cycling between "plugged in" and "not plugged in", making it not charge. (I have an Asus power supply at 19v and ~3A, and it does the cycling thing. But if I use the included 19v ~6.32A power supply it works just fine. What's more, If I plug my barrel connector plug into my variable power supply and set it to 19v, I don't think it goes above 2A but it charges just fine.) The workaround is to shut it off/put it in sleep mode, then it will charge off that lower amperage. I bought the buck converter that ajw22 linked, and knowing AliExpress, I'll update you guys come 2022 ( kidding Smile ).
Aren't you too young to be playing around with Lithium-Ion batteries?
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#7
Series = Voltage
Parallel = Amperage

(06-03-2020, 10:10 PM)THEWHITEBOY503 Wrote: Quick update:
5 cells won't work too well, I've figured out. I put 5 cells in series (without a holder) and it's not outputting enough amperage (I think).

I'm going to assume you meant you only connected up 5s1p and need to put more in parallel to increase available current.

When connected and it's not charging, what's happening is the laptop is using the available power from the connector and supplementing from the battery. When closing in on 3A output, it's getting close enough that there's enough power to run the laptop and overflow into the battery. This would only happen when the cpu is idle, though. Ramp up some workload and there goes the balance.

If you need 4+A sustained, don't go with some cheap converter. You'd want to get a beefy one. The ones that are fully enclosed in a metal housing are usually rated for like 5A, 10A, 15A, etc. They have been known to fully handle the output. However, they usually not adjustable.
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#8
(06-03-2020, 10:27 PM)Korishan Wrote: I'm going to assume you meant you only connected up 5s1p and need to put more in parallel to increase available current.
Plan 2 was to use 3 batteries in series to series connect to 2 other batteries in series so I had 5 batteries in series, providing a good voltage range. While this is providing a good voltage, it's still only 2,150mAh, which isn't enough to sustain a, say, 6A power flow. I only have 13 of these batteries to work with (20 were in a recycled pack out of a hoverboard (yuck), 14 would charge, and 1 of which is being used in my 18650 USB power bank), so I should have enough batteries to get up to 4,300mAh, which probably still isn't enough. I do have some other batteries I could work with that only hold ~1.6Ah, so if I get 3 packs (2,150 + 2,150 + ~1,930 mAh), that will bring the capacity to roughly 6.23Ah, which is a great number. The only thing that is stopping me from doing that would be battery holders, but I can always buy more! (Except for I bought the battery holders I have coming in a few weeks ago and they're "not gonna get here until July 24th", so it may take a while...)
Here is a quick diagram I made to show what the circuit would look like wiring wise.
[Image: soFxhC.png]
Aren't you too young to be playing around with Lithium-Ion batteries?
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#9
Another update! (Oh boy) 

(06-04-2020, 04:44 AM)THEWHITEBOY503 Wrote: The only thing that is stopping me from doing that would be battery holders, but I can always buy more! (Except for I bought the battery holders I have coming in a few weeks ago and they're "not gonna get here until July 24th", so it may take a while...)

Forgot I bought these. These are 18650 cell tabs (I call them leads). There's more than shown here, but this is how much I'd need for this project. (15 - and 15 +).

[Image: image0.jpg]
I've got the proper holder here and I'll be printing out 15 of the single holders and taping/glueing them together. 
Here's the wiring config:

[Image: 1L3Re0.png]
Aren't you too young to be playing around with Lithium-Ion batteries?
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#10
(06-04-2020, 04:44 AM)THEWHITEBOY503 Wrote: it's still only 2,150mAh, which isn't enough to sustain a, say, 6A power flow.

Rated mAh has nothing really to do with Amps. One is capacity, the other is force. Capacity is run time, amps is work load.

Adding cells in parallel allows for greater amps available. This also increases overall capacity (as long as all parallel groups in the series has the same amount)

Considering you are using used cells, and they range in individual capacities, you really should look into using a bms (even a cheapo one) to keep them from going out of wack on voltage.
I'm guessing the reason you are using 3 banks of cells connected in parallel is because you will use 3 different holders and then connect them to the load? I'd recommend connecting all parallel cells together first, then connect those in series. Not only does it make the wiring easier, it allows the bms to work easier and the need for only 1
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