I know there are a lot of threads about this topic already, but I still have some questions about it. Anyways, I am thinking about making a 50-80 thousand mAh power bank depending on the batteries and how many of them I get to build them up. I will need a protection board if my batteries do not have built in protection. Then I would also need a charging board. If I do not have a protection board or built in protection, then the power bank could catch on fire, a safety hazard. I obviously don't want this power bank to be a safety hazard. So I am just wondering if this will work. So I am thinking I could use this board to charge the batteries:


However, I don't know if it can handle the current. If it can't, where is a link that would have all the nice features that this board has like led indications with at least 1 usb for my phone/devices?

I know the batteries here seem legit and has built in protection, so wouldn't need a protection board:


With these batteries, I would probably buy like 16 of them, so 16x3400 mAh=54400 mah and wire these in parallel. So these batteries I am like 90% sure they're not fake.

Anyways, thanks in advance.


closed as off-topic by Bruce Abbott, Neil_UK, RoyC, Colin, Scott Seidman Aug 16 at 15:41

This question appears to be off-topic. The users who voted to close gave this specific reason:

If this question can be reworded to fit the rules in the help center, please edit the question.

  • \$\begingroup\$ The question raises engineering and design choice concerns. I at first felt the same way about it being off topic but because of these design considerations feel it deserves some airtime. It’s Burning Man season so there’s a lot of q’s like this. Voting to reopen. \$\endgroup\$ – hacktastical Aug 16 at 16:00
  • \$\begingroup\$ So if anyone read my entire post, you will see that I do not just ask for recommendation but rather asking if the power going to the board for example, is to much current? This question is one of the specific problems that I am trying to solve. I am trying to solve weather or not this will be a safety issue/ect. Please read my full post and others post, before putting the thread on hold. \$\endgroup\$ – Bob G. Aug 16 at 16:03
  • \$\begingroup\$ @hacktastical Thank you for understanding. \$\endgroup\$ – Bob G. Aug 16 at 16:03
  • \$\begingroup\$ FWIW: "5000 mAh" 18650s are guaranteed to be fake. The highest legitimate capacity currently available in that form factor is around 3600 mAh, and you will pay a significant premium for that capacity. \$\endgroup\$ – duskwuff Aug 16 at 19:15
  • \$\begingroup\$ Okay so those are fake. Good to know. However, I am sure the other ones, more expensive, are not fake. So would the set up with those ones work, so not the fake but real ones? \$\endgroup\$ – Bob G. Aug 16 at 19:24

EDIT: worked figures.

If you've settled on 16 cells, let's work some numbers.

  • Using a realistic figure for an 18650 cell (3400mAh) we get 219Wh for a 16-cell pack.
  • which works out to 43.8 Ah @ 5V for the pack
  • Weight for the batteries alone: 720g (45g/cell)

16 cells is double the size of a large laptop battery. At 5V @ 2A this battery will take about 20-30 hours to charge. That's a long time. Yes, you could do it, but why? Consider USB type C power delivery at least. That said, a 12V or higher charge input is more typical for a big pack like this.

Now, should you make your own pack? If you wanted to make more than one, and were willing to put the work in to fully productize it, sure. Do consider a balancing solution for your pack. Example (link).

Also have a look here for some DIY Li-ion battery solutions. Seems like what you're after.

Realistically though, for a one-off I urge you to consider another solution: use a pre-made Li-ion motorcycle battery with built-in protection and a warranty.

This outfit makes some good ones. Their 16-cell battery weighs 1.4Kg, so yes it's double the weight of the bare cells. But it's a fully-engineered, robust and warranted solution.

Another consideration: Li-ion batteries are banned for air travel. Check the current FAA regulations.

  • \$\begingroup\$ I have power banks that are small like 15000 mAh and just wanted a much larger one basically. I don't want a car battery/motorcycle battery as that is way to big and heavy. I am not considering usb type C because I have an iPhone 6S. I am not planning on taking it on a plane with me. I don't care about how long it takes for this power bank to charge. So will what I put down, work? \$\endgroup\$ – Bob G. Aug 16 at 15:59
  • \$\begingroup\$ Again, I can't charge my iPhone 6s with a usb type C. Secondly, I don't want a power bank that looks like a car battery. I would also have to get the boards to connect to this battery you suggested and would cost more than making it myself. Also, I am not selling this thing, it is for myself. I would like a power bank that looks like a normal power bank and has at least 50000 mAh and is not fake. I seen youtube videos of people making their own power bank and does not look like a car battery, the mAh is lower of course. So would my plan above work or not? \$\endgroup\$ – Bob G. Aug 16 at 19:00
  • \$\begingroup\$ There’s a couple of things you’re missing. Internally, many power banks use higher voltage and step down to supply current (and step up to charge from 5V.) \$\endgroup\$ – hacktastical Aug 16 at 19:57
  • \$\begingroup\$ USB-C is proposed as an option for charging the battery, as it supports higher voltage as well as 5V, in addition to a 12V in. USB-A would be for the downstream ports. \$\endgroup\$ – hacktastical Aug 16 at 20:07
  • \$\begingroup\$ Finally, the AG batteries I linked are small form factor for special projects. The 16-cell one is not much bigger than the batteries it houses, and it includes all the support stuff to make it safe. Yes it costs money, but it’s not likely to catch on fire. \$\endgroup\$ – hacktastical Aug 16 at 20:08

Not the answer you're looking for? Browse other questions tagged or ask your own question.