Power 'brick' design

Hi All.

I like the idea of a portable power source but larger than a standard 'off the shelf' power pack, to charge phones and other devices while I'm out & about and working remotely.

I'm thinking of something the size of a house brick (215mmx 100mm x 70mm ), which should be able to incorporate 40 x18650s depending on the choice of what else I include inside., which should end up about the 2kg mark. I'm aiming to use cells of at least 2,000mAh or better.

At the moment I'm considering a 4s 10p design built using a 4s BMS to charge it, which means I can power it from pretty much any laptop power supply.

Output: Using an 12v car cigarette lighter type device to convert the voltage from the nominal 14.8v to 5v USB. I like the look of the ones which incorporate both a voltmeter and USB 3.0 / Fast Charge / PD so that I've got all the latest options available.

Does anyone know how efficient these type of devices are? Or is there a better option?

Is there a different design that would better/more efficiently use the 40 x 2,000mAh?

Other considerations:
-I could just parallel all 40 cells and then boost/buck the 3.7v up to 5v, but charging would become slow. Would this be any more efficient?
-If I made it 5s8p I could also tap off 20v to directly feed my laptop and/or incorporate a fully fledged 20v USB PD option.

Thoughts please?

Regards
Adam

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BMS:https://www.amazon.co.uk/SODIAL-Lit...ds=4s+bms&qid=1552122125&s=electronics&sr=1-3
USB output:https://www.amazon.co.uk/gp/product...4d5-a0de44c50a7e&pf_rd_r=4X6KM694QZ1EV09VT0BA

Easiest is to just parallel the cells together and then use the electronics from a powerbank. They are ususally fed from 1s system so that works. Make sure the electronics are from /for a li-ion pack and not li-po (cuts at 3.6v)
If you want to run more devices or be able to power higher powered stuff then build a 4s system and use the usb car things like u described. Then you will need a bms.
For higher current its better and you can also connect a 12v car socket for other stuff too.

Check out my build if your interested: https://secondlifestorage.com/t-HUUUGE-USB-POWERBANK

I got a specific charger/boost in one board.

I would go with a 3s unless you are sure the usb chargers/devices can handle over 14 volts/15 volts. You can always get one of the small cheap (20 dollars) 150 wattinverters, most have built in usb outputs.

Thats how I run my laptop and charge my usb items. You might lose some efficiency with the inverter but its not anything your li-ion pack wont be able to handle.

I recently built a 27ah 3s16p li-ion pack (48 18650) , thats almost like a goalzero (40ah) , 27 ah will easily run your laptop most of the day, at 5 hours of use even with inverter my I5 laptopuses less than 10ah.

At 4s, I would get a 12 volt voltage stabilizer that can keep the voltage output at a stable 12 volts. Lights/fans don't like voltage too much higher then 14 volts.

The-J-Man said:

Easiest is to just parallel the cells together and then use the electronics from a powerbank. They are ususally fed from 1s system so that works. Make sure the electronics are from /for a li-ion pack and not li-po (cuts at 3.6v)
If you want to run more devices or be able to power higher powered stuff then build a 4s system and use the usb car things like u described. Then you will need a bms.
For higher current its better and you can also connect a 12v car socket for other stuff too.

Check out my build if your interested: https://secondlifestorage.com/t-HUUUGE-USB-POWERBANK

Click to expand...

Hi The-J-Man,

Thanks for that, I did see your projectbefore I posted and thought how similar it was. Looking again I notice you're using one of the 12v car / USB adaptors I was looking at & considering as an option. Are you happy with it?

Another question for you ... do you (or anyone else)happen to know if the 12v car sockets reduce the voltage down to ~12v? So if say you've got a fully charged 4s pack @ 16.8v will the 12v car socket supply 12v or 16.8v?

I'm just aware that the 12v 300W car inverter that I have has a maximum input of 16v. Other than that I'd like to go for a 4s option because it gives me more flexibility to efficiently supply higher voltages. Currently looking for a good option to boost to 20v to supplymy laptop.

Regards
Adam

This is a kit that I develop, more towards the Powerwall application, but you can just use one pack (64P), just add a boost converter to 5V for your USB application.
http://bit.ly/416OFPPK

If you are considering charging a laptop, I would opt for 24v. There are plenty of buck converters to drop it down to 12v. You can also buck it down to 20v for your laptop. By doing this you will be able to charge the laptop without having to boost as the battery discharges.

You could build a pack that size or smaller with Boston Power Swing batteries in a 4S or 3S configuration that will give you at least 4400mAh. Iif you did build one with the dimensions you specified it could be 8800mAh .