-Looking to make massive battery bank

[007agentHP]

So im looking for some components for a battery bank project. 

 

i need it to be able to support 30-50,000 mah with 4-5 usb ports

 

so i was looking into premade cases like the one below 

http://www.ebay.com/itm/DIY-USB-Mobile-Power-Bank-Charger-Case-Pack-8pcs-18650-Battery-Holder-for-Phone-/252399557148?var=&hash=item3ac42f9a1c:m:mOwOtGQnFyTzjbdBdkAgtfQ

 

it holds 8 18650 batteries. are there ones on the market that can support 16 batteries? 32? 

 

and what brand of 18650 is good (looking for as inexpensive as it can get for good quality batteries)

 

i need some direction with the project. any help?

[007agentHP]

Just now, Jorgen297 said:

be careful as hell when ordering from china on ebay, the mah is almost always lower than is said 

im not a complete noob when it comes to this stuff

 

im well aware that the best of the best top out at 3600 mah. so in looking in the 2000-2500 mah range (where its likely to be legitemate) but i'm asking which brands can be trusted

[007agentHP]

Just now, Jorgen297 said:

didnt imply you're a noob lol just saying in general

sorry for the hostilities. its just im really not aware of good brands for this equipment and i want to make sure i get things right

[mariushm]

Unless you have some weight restrictions (and even then), you wouldn't make such a project with 18650 batteries. The load balancing alone would be a pain in the ***

 

if you don't care about weight, get a 12v 45-50Ah from stores like Amazon for anything between 75$ and $100 plus shipping maybe. The usable voltage will be between 10 and 14v so you can use a simple and very efficient dc-dc converter to produce 5v at as many amps as you wish.  For example, 12v @ 2A is 24w, with around 90% efficiency (which would be low for such a buck meaning step down dc-dc converter ) means a bit more than 20 watts will be available on the output, which would mean 5v at 4A. 

lead acid battery chargers are readily available on the market , the dc-dc converter you can buy off ebay easily...  the only downside is the longer charging time for the battery and the weight.

 

if you want lithium, there's stores selling battery packs with proper cables required for load balancing the cells,if you use the proper charger. For example, hobbyking has loads of batteries.

Here's a good example of a battery holding loads of energy : http://www.hobbyking.com/hobbyking/store/__89616__Turnigy_Graphene_Professional_16000mAh_6S_15C_LiPo_Pack_w_5_5mm_Bullet_Connector.html

Fully charged, it gives about 22v and is rated for 16000 mAh which is a lot, you can go for a smaller pack if you want lightweight... it has standardized connectors including the cell balancing one which makes it possible to charge it up easily using proper chargers like this one: http://www.hobbyking.com/hobbyking/store/__58285__IMAX_B6AC_V2_Professional_Balance_Charger_Discharger.html

You can simply cut the special connectors for the output cable of the battery (the connectors are common on drones and electric toys / helicopters / model planes ) and connect your dc-dc converter to produce 5v and the batter charger.

 

It may be cheaper to buy separate 18650 batteries but again, you don't see battery banks with loads of them because they have to be balanced and that's hard.

 

Here's example of ready made dc-dc converter that can take any voltage between 6v and 24v and output 5v at up to 3A, and it even has USB connector on it : http://www.ebay.com/itm/New-6-24V-12V-24V-to-5V-3A-CAR-USB-Charger-Module-DC-Buck-step-down-Converter-/272320057515?hash=item3f678a50ab:g:AysAAOSwZ1BXeHCv

if you can solder two wires, you're good to g. Maybe if you order packs of 5 or 10, the seller can ship you a row of such circuit boards, without separating them... worth a message to the seller. Then all you'd have to do would be to make a custom box for your diy usb power bank.

 

[Hackentosher]

@CUDA_Cores

@iamdarkyoshi

[iamdarkyoshi]

1 hour ago, 007agentHP said:

and what brand of 18650 is good (looking for as inexpensive as it can get for good quality batteries)

Get yourself some old laptop batteries and do tests on them (or buy pretested cells from me)

 

Nearly everything from ebay will be crap.

[007agentHP]

40 minutes ago, mariushm said:

 

what are your thoughts on the 12v 50ah  sealed acid battery system for this? 

[mariushm]

My thoughts are.... it's damn heavy at over 10-15 kg (don't know in US measurement units) but if a 12v 7-8Ah battery can keep a computer running for around 10 minutes (while using around 40-80w) , imagine how much energy is in a 6-8 times larger battery , and how long it  could keep something powered with 10 times less energy (phones usually charge at up to 2A, or around 10 watts). 

Another downside is that if you manage to discharge such a battery completely (the voltage would be around 10v), it would take at least probably at least  8 hours to charge them, I think more. Lithium batteries can handle faster charging.

As a sidenote, you can also connect these lead acid batteries in series to get higher voltage but then the dc-dc converter would have to support that higher voltage, and same story for the charger. In this application it would make no difference if you use batteries in series (for higher voltage) or just one battery, or if you parallel several smaller Ah batteries for more capacity.

[Huntsman]

Batteries from ebay are all crap. Pretty much none of them are close to what they advertise.

 

Again, as @mariushm said, don't play with 18650 unless you are very very experienced with their usage and maintenance. SLAs are a good choice if you dont care about weight. If you REALLY want to go the 18650 route and want to spare yourself the problem with balance charging, parallel them up instead of series.

[klh2000]

As many have already said, all of the batteries from ebay, aliexpress, and taobao will be garbage. They will NOT meet their rated capacity, and can be possible fire hazards.

Some of the reputable brands of cells are LG, Samsung, Sony, Panasonic, and Sanyo. These will meet their rated capacity, and be much safer.

If you are building power banks, Only use protected cells, They will have over-current, over-voltage, and under-voltage protection built in.

 

I would suggest using a premade case such as this (The one that you linked only held 2 cells):

Diy Power Bank Case 6X18650

 

I would recommend these cells, they're just about the highest capacity protected 18650 cell that you can buy:

Panasonic NCR18650B

 

 

Six of these cell will give you a capacity of 21Ah, or 21,000 mAh. This is the highest you can go with one of those cases, unless you can find one that holdsa more batteries.

The total cost of this project would be:

 

1X battery case - $2.79

6x NCR18650B - $41.10

        Total Cost - $43.89