Advice needed

S

Sunv_revenge

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Dec 13, 2019
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Hey all,

Im new here, but not new to electronic projects.
Im having trouble deciding on a li ion battery pack configuration, Im trying to make a high capability portable power supply about 90-95% of the supply will be used on 5 volt devices and the other 5-10% used as a 19 volt laptop charger Im stuck between two battery pack configurations just using a 3.7v pack and boosting the voltage to 5v and 19v respectively or a 11.1v or 14.8v pack and boosting to 19v and lowering to 5v pack will consist of 140 3000Mah 18650s with cell level fusing and BMS TIA
 
Others can probably give better advice, but something to consider.
How will you charge your final product?
Will a particular configuration suit what you already have at hand?
3.7v strikes me as the simplest from the point of view of no balancing required.
 
Build a pack being at 19v an then Buck to 5v when needed.
 
It expects all from 15-22. Since the computer contain several Buck converters inside.
 
The big problem with Li-ion is they have such a large voltage drop during discharge 4.2 to 3.5 .... 5s would give 21 to 17.5 luckly that is fairly good for 19v , but still the variation is too much to use directly for a lap top

Lifepo4 6s does come out as 19.2 so could be used without circuitry as the voltage is almost constant over 90% of discharge ....

Li-ion is lightest so will be the best ... I don't think it's sensible to have a 3,7 pack ... you will require 3 amps or more at 19V so current drawn from 3,7 will be around 20 Amps , I've never seen a step up with this input current rating , it will be expensive ... much better have 11 or 14 V pack
 
No its not to much to use for a laptop. The Laptop have a buck converter inside and takes a very high variety of voltages. The laptop inside is powered with all from 1.5-5v and a few components around 12v. It uses that high voltage only to be able to charge the battery and then power the rest.

5s works fine for most laptops. I know several that have done it including myself!

I have runned laptops as low as 14 volt easy = Run directly from car outlet... Its easy to test if you want if it will work or not. Under voltage is not an issue but you should not go way to high over and most laptops stating are 19-19.5v and if you meassure them they are 20-22 in real life open circuit.
 
I built a 3s16p pack and use that to run run my laptop. I do use a small 120 volt inverter to run the laptop adapter. I been doing it for years and works great. I do have a 12 volt laptop power supply but never use it. I prefer the AC inverter because it has usb outlets to charge my cellphone. On my 31ah pack I can get anywhere from 2 to 5 days of use of my laptop before I have to recharge it.

The reason I use 3s is because it charges well with solar, (4s would voltage would be too high). Also a 3s for me is easier to build then a 4s or 5s.
I can run all my 12 volt devices with a 3s and don't need any adapters to reduce voltage.
 
Only reason it charges better is that you have a solar charger where you cannot set proper voltages. So dont blame solar for it but the controller you did choose :)
 
The controller I use 20a ecoworthy mppt maxes out at 15.5 volts bulk, with voltage drop to battery that barely charges a 4s lifepo4 (14.6 volts) a 4s li-ion needs 16.8 volts. With my 240 watt panel I can get up to 15 amps into my 3s li-ion, performance is excellent with solar. I seen some controllers that max out at 17 volts for 12 volt system, but most usuallybulk around 15 volts.

A 3s will charge with almost any 12 volt charger. With 140 cells(3000mah) I definitely go with a 3s configuration it will give you a 3s46p 138ah battery pack. Thats as large as a goalzero 1000 which is a 3s (100ah). 3s is serious power for anything you want to run.
 
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