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30 Cell Backup Battery( Powerbank if you may )
#1
Hi, I need any advice I could get at the moment, I made a 30 cell powerbank, 3S 10P Configuration. It charges phones as well as laptops, using buck and boost converters respectively. Phone charging works fine, although the laptop has a bit of an issue. My battery pack drops in voltage once a load gets connected, I think that's pretty normal but it drops so much whenever I try to charge my laptop, which trips the low voltage disconnect. Could this be a problem with the pack?, I used harvested cells from Old Laptop batteries. I tested them and they were pretty decent.
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#2
If you have a 3S config, the voltage is nominal approx 3x 3.7 =11.1V
The laptop will need 19V & be trying to charge its batteries, etc.
It will be using approx at least 45W (check the voltage & current on laptops original mains power supply).
So 45W/11.1V = approx 4A before boost converter losses, maybe 5A with losses.
So a 10P pack would be 0.5A per cell if they are all good & similar.
See if one section eg test each 1S/10P section to see if one is dropping more under load.
Is your soldering on the cells good?
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#3
Difficult to remotely troubleshoot that without further details. Does "low V disconnect" refer to undervoltage protection on the BMS or instead something on the laptop end?  How much power did the laptop draw in your test? What is the IR of the pack or series-cells (or, did you test voltage drop under high current loads?). What BMS & boost (to 19V?) are you using? 

Note that charging some laptops (e.g. Dell) requires a proprietary charger which can communicate its power capabilities (typically via 1-wire). Without such it will only power the laptop, but it will refuse to charge the laptop battery (it needs to know the charger's  power capability in order to implement good power path control, e.g. to optimally balance power between the charger and CPU at various loads).

Also charging laptop batteries externally requires using the Smart Battery interface. Further, you may need to ground a (system present) pin in order to enable output on laptop packs if you wish to use them as universal power banks (no need to tear them down).
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#4
I would say, with the amp requirement of the laptop, it's the issue with the boost converter. Can it handle 5A on the input to output 45W?

It would of been better to use 4s if you "must" make a "12V" battery. It would of actually been far better to make a 7s battery, then buck down to what you need for both the phone and laptop
6s * 3.7V = 22.2V
7s * 3.7V = 25.9V

There are many good buck converters that work with these voltages to output a stable voltage. You also wouldn't need very heavy cable as it wouldn't need as much amps to do the conversion.
Remember, the lower the Voltage, the higher the Amperage for any given Wattage output
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#5
(07-11-2020, 01:00 PM)Redpacket Wrote: If you have a 3S config, the voltage is nominal approx 3x 3.7 =11.1V
The laptop will need 19V & be trying to charge its batteries, etc.
It will be using approx at least 45W (check the voltage & current on laptops original mains power supply).
So 45W/11.1V = approx 4A before boost converter losses, maybe 5A with losses.
So a 10P pack would be 0.5A per cell if they are all good & similar.
See if one section eg test each 1S/10P section to see if one is dropping more under load.
Is your soldering on the cells good?
My original mains supply power pack states 19.5V/2.31A, I have a boost converter of 18.5V/3.6A.
I tested all three sections like you said under load and my cells were out of balance to begin with
Cell 1 dropped from 4.04 to 3.98
Cell 2 dropped from 4.03 to 3.96
Cell 3 dropped from 3.98 to 3.93
I'm currently charging the cells individually since I dont own a hubby charger.
I think my soldering on the cells in quite good, not the best

(07-11-2020, 01:50 PM)Korishan Wrote: I would say, with the amp requirement of the laptop, it's the issue with the boost converter. Can it handle 5A on the input to output 45W?

It would of been better to use 4s if you "must" make a "12V" battery. It would of actually been far better to make a 7s battery, then buck down to what you need for both the phone and laptop
6s * 3.7V = 22.2V
7s * 3.7V = 25.9V

There are many good buck converters that work with these voltages to output a stable voltage. You also wouldn't need very heavy cable as it wouldn't need as much amps to do the conversion.
Remember, the lower the Voltage, the higher the Amperage for any given Wattage output
I wish I had thought of this earlier, i actually felt i should choose something in between my requirements since i needed 3.7V and 19V, until I started shopping for boost converters. My buck works really fine and I got it easily, my boost on the other hand was a pain in the ass, I wasn't able to lay my hands on a proper one, I'm using a so called 'DC Distributor' takes in 10-15VDC and outputs 18.5V/3.6A and 30V/0.4A, I cut off the 30V wire.

(07-11-2020, 01:30 PM)gauss163 Wrote: Difficult to remotely troubleshoot that without further details. Does "low V disconnect" refer to undervoltage protection on the BMS or instead something on the laptop end?  How much power did the laptop draw in your test? What is the IR of the pack or series-cells (or, did you test voltage drop under high current loads?). What BMS & boost (to 19V?) are you using? 

Note that charging some laptops (e.g. Dell) requires a proprietary charger which can communicate its power capabilities (typically via 1-wire). Without such it will only power the laptop, but it will refuse to charge the laptop battery (it needs to know the charger's  power capability in order to implement good power path control, e.g. to optimally balance power between the charger and CPU at various loads).

Also charging laptop batteries externally requires using the Smart Battery interface. Further, you may need to ground a (system present) pin in order to enable output on laptop packs if you wish to use them as universal power banks (no need to tear them down).

I did find a blue wire, I didnt know what to do with it, did a little bit of digging and found out it's meant to communicate with the battery on the amount of amps to draw, any way around this?
It's a HP 15 Notebook
19.5V/2.31A is the requirement
I have 18.5V/3.6A boost converter
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#6
^^^ Is the blue wire much lower gauge (thinner)?  If so that could well be for 1-wire protocol power capability communication, in which case you are out of luck - it won't charge the battery without such communication. I don't recall about HPs, but on Dells the BIOS will complain that it couldn't identify the power supply so it won't charge the battery ("plugged in, not charging").

Please clarify what you mean by "trips the low voltage disconnect".  What/where is this "disconnect" and how quickly does it trip?

When you plug in the power supply there will be a quick huge current inrush as large capacitors charge up. It's possible that your booster can't handle this. You could test that by first powering it on the original power supply, than as quickly as you can switch the power supply to your DIY powerbank (quick enough so the caps don't discharge fully). Or you could wire up something like this "no spark" current inrush limiter used by RC hobbyists. If your powerbank works ok when the caps are already charged up then that implies that the current inrush is tripping protection on your booster (or BMS).
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#7
If you can't get it to run with the dc converter, use an ac inverter. I have a 3s16p (31ah) batterypack and I use it to run my 12 inch laptop (uses about 3 amps). I run through a 150 watt ac inverter with its 19 volt power adapter.

Even though its not the most efficient method, I can still run the laptop 5 days (3 to 4 hours a night) before the bms shutsoff, The inverter works great even at the lower volts. I used a dc wattmeter to measure power usage, and the powerpack put out 31 amps before the bms shutdown.

The problem with boost converters, you need a large one to power the laptop, if you need 3 amps, get a boost controller that puts out 12 amps. Also put a fan on the boost controller they get very hot and might shutdown if too hot. And put a fuse in the boost input side, I had one that overheated and shorted out, and it blew my 15 amp panel fuse, when they fail it shorts out the input plus/neg.
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#8
(07-12-2020, 05:56 PM)jonyjoe505 Wrote: [...] The problem with boost converters, you need a large one to power the laptop, if you need 3 amps, get a boost controller that puts out 12 amps. Also put a fan on the boost controller they get very hot and might shutdown if too hot. And put a fuse in the boost input side, I had one that overheated and shorted out, and it blew my 15 amp panel fuse, when they fail it shorts out the input plus/neg.

My experience differs. Generally such problems are due to poor design / quality and dishonest specs, Much of the garden variety stuff you find on eBay, Ali, etc is low quality and is far from meeting the claimed specs (analogs of Ultrafire 20000mAh 18650 cells, that are really rewrapped recycled cells of capacity 20x less than claimed but nonetheless get thousands of rave reviews from eBay newbies). If you're lucky you could even get a rare Frankenstein battery like that below (fake Sony NP-F970 video camera battery) to add to your museum of Chinese engineering marvels (notice the perfect cell "balancing" there - quite a feat!) Alas, some of the cheap regulators are electronics analogs of that (but there are some good ones too, e.g. those by RD Riden).

[Image: 7hmpl.jpg] [Image: mwf3r.jpg]
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#9
(07-12-2020, 05:04 PM)gauss163 Wrote: ^^^ Is the blue wire much lower gauge (thinner)?  If so that could well be for 1-wire protocol power capability communication, in which case you are out of luck - it won't charge the battery without such communication. I don't recall about HPs, but on Dells the BIOS will complain that it couldn't identify the power supply so it won't charge the battery ("plugged in, not charging").

Please clarify what you mean by "trips the low voltage disconnect".  What/where is this "disconnect" and how quickly does it trip?

When you plug in the power supply there will be a quick huge current inrush as large capacitors charge up. It's possible that your booster can't handle this. You could test that by first powering it on the original power supply, than as quickly as you can switch the power supply to your DIY powerbank (quick enough so the caps don't discharge fully). Or you could wire up something like this "no spark" current inrush limiter used by RC hobbyists. If your powerbank works ok when the caps are already charged up then that implies that the current inrush is tripping protection on your booster (or BMS).

The blue wire is actually the same gauge as the white and black wires. Just to clarify, my laptop actually charges for about 10-15 seconds before it trips, I'm using a so-called 'DC Distributor', for some reason, powerful DC boost converters are hard to find. The DC Distributor accepts an input of 10-15VDC and outputs 18.5VDC and 30VDC, I cut off the 30VDC wire since I didnt need it. With my meter, battery voltage drops to around 11V when the DC Distributor trips off with a kind of low battery indicator, I'll attach a picture of it down below. I'll run a couple of tests on how much my laptop draws and how efficient the DC Distributor is and I'll give a feedback.
All in all I'm really surprised people to get so much help from everyone here, I just want to thank you all, it's really amazing how everyone takes their time to help other people they're in no way indebted to.

(07-12-2020, 05:56 PM)jonyjoe505 Wrote: If you can't get it to run with the dc converter, use an ac inverter. I have a 3s16p (31ah) batterypack and I use it to run my 12 inch laptop (uses about 3 amps). I run through a 150 watt ac inverter with its 19 volt power adapter.

Even though its not the most efficient method, I can still run the laptop 5 days (3 to 4 hours a night) before the bms shutsoff, The inverter works great even at the lower volts. I used a dc wattmeter to measure power usage, and the powerpack put out 31 amps before the bms shutdown.

The problem with boost converters, you need a large one to power the laptop, if you need 3 amps, get a boost controller that puts out 12 amps. Also put a fan on the boost controller they get very hot and might shutdown if too hot. And put a fuse in the boost input side, I had one that overheated and shorted out, and it blew my 15 amp panel fuse, when they fail it shorts out the input plus/neg.

Wow, I actually had one of those hooked up to my powerbank, I decided to take it off because I was skeptical of the square wave such inverters produce, couldn't risk damaging anything, besides the cheap one I got was so inefficient. Did you use new cells?, I keep getting the feeling that I'm getting a much lower power than I should from this amount of cells. I wasn't able to test my cells individually because I dont have a Capacity tester, I'm going to try to get a rough estimate of my pack capacity though. I doubt it'll be anywhere near 31Ah.
I have 5 LGABB41865, 3 SF US18650GR, 1 Samsung ICR18650 22F and 1 CGR18650D(Panasonic) in each 1S10P
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#10
(07-12-2020, 07:46 PM)_Olawale_ Wrote: The blue wire is actually the same gauge as the white and black wires. Just to clarify, my laptop actually charges for about 10-15 seconds before it trips, I'm using a so-called 'DC Distributor', for some reason, powerful DC boost converters are hard to find. The DC Distributor accepts an input of 10-15VDC and outputs 18.5VDC and 30VDC, I cut off the 30VDC wire since I didnt need it. With my meter, battery voltage drops to around 11V when the DC Distributor trips off with a kind of low battery indicator, I'll attach a picture of it down below. I'll run a couple of tests on how much my laptop draws and how efficient the DC Distributor is and I'll give a feedback.
All in all I'm really surprised people to get so much help from everyone here, I just want to thank you all, it's really amazing how everyone takes their time to help other people they're in no way indebted to.

Your booster may be meant to be used with 12V lead acid batteries (or LiFePO4) and they typically have undervoltage shutdown to protect the battery (probably that's the purpose of the red light in your photo but the photo is too blurry to read it - did it light up after shutdown?) 

Note that the voltage under load might be less than you measure because there might be voltage spikes that are quicker than your DMM can measure, but long enough to trip the low voltage protection (also note the battery voltage will quickly rise after the load is removed, so measuring it then won't tell you what it was under load).  Were the cells fully charged before your test?

If you are using barrel DC plugs for connection then beware that some of the cheaper versions can have high resistance so large voltage drop. If possible, be sure to check the voltage just before it enters the booster in order to account for all cable and plug losses (nontrivial at higher currents).
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