Boosting 18650 to 5v 2A

Hello, I am trying to make a battery pack for the Amazon Echo Dot. It comes with a 5v 2A ac power supply.

I thought this is simple but can't find a small DC booster module for converting 3.7 to 5V and hold at least 1A stable.

I tried numerous modules such as these, but they all don't meet their descriptions. Most only handle 0.5a or can't hold 1A either voltage goes down or it just shuts down when the current exceeds 1A eventhough it says it can handle 2A

http://www.ebay.com/itm/222322976078_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Does anybody have any suggestions?

Are you using good 18650's? There are a lot of real garbage 18650 batteries making the rounds. I've got some "9000 mAh"* 18650's that are lucky to hold 500mAh, and some "4000mAh" ones that hold like 600, and some "5000 mAh" ones that hold 1500-ish mAh. These crapola 18650's may not be able to put out the ~3A you'd need to boost to 5V 2A.

Have you measured the battery voltage when the output of the boost converter is drooping?

  • Of course, the fact that they're marked 9000mAh is your first red flag, since Panasonic (the industry leader) 18650s only go up to 3500mAh or so...

Use two cells and buck. Use two 14500s if you want to recharge and stay small footprint, or go through CR123s, maybe gamble with the RCR's.

joefly: Hello, I am trying to make a battery pack for the Amazon Echo Dot. It comes with a 5v 2A ac power supply.

I thought this is simple but can't find a small DC booster module for converting 3.7 to 5V and hold at least 1A stable.

I tried numerous modules such as these, but they all don't meet their descriptions. Most only handle 0.5a or can't hold 1A either voltage goes down or it just shuts down when the current exceeds 1A eventhough it says it can handle 2A

http://www.ebay.com/itm/222322976078_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Does anybody have any suggestions?

What battery are you using in the first place??? is your battery even capable of that much current output???

Your link is not working? So I assume that your using mini/micro boost converter modules. Those modules can't output a stable current above 0.5A. So I suggest you use a regular boost converter module like the XL6009 and you'd get your 2amps if you use the right battery.

Also make sure you use a good battery like an original samsung, panasonic or lg 18650 cell instead of ultrafire crap like DrAzzy said.

Using 2 cells in series and using a buck like INTP suggested is the better choice in my opinion, however a single 18650 cell can be boosted to meet your project demand without any problems.

This Pololu step up regulator can provide 5V at [u]5 A input[/u] current.

From a single Li cell, at 80% regulator efficiency, expect an [u]input[/u] current of 3.2 A @ 3.7 V to provide 5V @ 2A output. You might be able to get that from a good 18650 cell.

The best 18650s currently are panasonic NCR18650Bs rated at 3.4 AH. Anything thats quotes more capacity is a fake.

thanks guys for all the comments and replies

This right now is not a battery issue, as I am using a bench powersupply to supply 3.7v to act as the 18650, I plan to use two in parallel so charging is easier

as for the one i tried here I am posting link again http://www.ebay.com/itm/222322976078?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

you all confirm what I was saying (particularly noobian) that these mini/micro booster do not live up to their specs. hopefully XL6009 does. But even that I see a lot of the listings have varying designs and components, so I just picked one and hope for the best. Will report back if it works

Jremington, the Pololu booster sounds good but it seems really expensive considering the dots are not less than $50, the booster would be half of its price for a simple function. But good to know, if I have a higher spec requirement.

You want ten watts plus upconversion loss ? a single Litium 18650 sounds a little on the small side. Can your application carry a 12V Pb motorcycle battery and downconvert to 2A 5V ? If that is too much weight, then could you downconvert from three or four 18650's in series ?

As jremington usually knows what he is talking about, perhaps 3 to 4 amps is not as unobtainable as I had first thought.

If your need is to save weight then you might also want to look at quadcopter batteries, for example 0.6Ah 3.7V. Those are designed with big flat foils to dump high current in a few minutes, at the expense of a high leakage and requirement for slow recharge.

Using an iMax 6 hobby charger, you can discharge and re-charge the 18650 cells (and mostly anything else that's rechargeable). The display reads out the current in mah used to charge/discharge. It's useful to identify how much current any battery can store. I used them to recover all the 18650's from bad laptop batteries. I also bought some budget 18650's online just to compare. The iMax charger cost like $15 on eBay.

The budget new 18650's seemed to discharge about 300 - 450 mah and rarely found one that went close to 700 mah. None of them seemed to be equal to each other. The laptop batteries worked alot better getting over 1,000 mah on many of them.

Due to the cost of real 18650 batteries and the chances I would get ripped off, I never bought the new real certified ones, so I can't provide any statistics on comparing to good grade batteries. The junk/recycled ones I have used work perfect for flashlights and I use them for Arduino testing.

There are alot of statistics involved with batteries regarding their lifetime, and the amount of current that can be passed at a given time. Some batteries will discharge alot right away and allow themselves to be drained down rapidly - like if you wanted to use them to turbo-boost sprinting on an e-bike. Other batteries will only discharge lower current, slowly - they shut down if too much current draw at one time - like when your power drill suddenly stops, but in 10 minutes you can use it again for small bursts. Anyone can probably spend weeks reading all the details on the different grades and types of 18650 batteries. In order to know what you have, you have to buy makes and models of certified ones from known distributors, which cost a whole lot more then just taking a random chance with cheap or recycled batteries.

joefly: as for the one i tried here I am posting link again http://www.ebay.com/itm/222322976078?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

you all confirm what I was saying (particularly noobian) that these mini/micro booster do not live up to their specs. hopefully XL6009 does. But even that I see a lot of the listings have varying designs and components, so I just picked one and hope for the best. Will report back if it works

Yepp, just like I said, that one cannot do 2amps.

XL6009 will give you 2 amps but not for too long since it needs minimum input of 3.5 volts or so to begin with.