Help making a portable speaker

I'm interested in making a dual purpose portable stereo speaker system/Battery bank

but I need some help choosing components as I don't know very much about speakers and electricity


I'll probably using these 2 in parallel to combine the capacity

and 2 70mm speakers, again I don't know very much about them so are these decent?

so a quick rundown again

I want something I can use as a amplified speaker for my phone, and something to charge my phone with, not necessarily at the same time, the simpler, the better, and I don't know what to get besides the battery I picked out and I'll need to know how to connect it all, I can take care of an enclosure

Edit: since the batteries are 96ish mm tall I guess I can go all the way up to 90mm speakers

Well you could put the drivers in a cylinder like shape and have some regular shaped (but properly rechargeable) batteries down the middle like the Logitech UE Boom. Or you could put the battery packs you listed on the bottom and top and have a square one but still have the driers in the same place.

well the enclosure was going to be the last step, I need more help on stuff like voltage step up converters and where wires should connect to and the amplifier and such

LiPo charger circuits can be a bit tricky. It pretty much needs to be IC controlled because there is an algorithm to charging. You want to slow charge if you can past 80% capacity. Discharge for your phone can be through a 'different' USB port than the port that powers/charges.

Two different lipo cells.. charging gets a bit trickier. Adafruit and sparkfun have 'kits' you can get for the charging circuit:

Check this out also:

To get USB output from the thing. You can probably implement the speakers as something 'powered by USB' (or just Powered by 5v). Do you want bluetooth or just use the headphone connector? if headphone connector, you may be able to get by with a relatively standard op-amp circuit and input.

A couple of double pole, double throw switches would let you toggle between whatever states you want the hardware to have. Sparkfun and Adafruit are incredible resources for these kinds of things. A lot of it is like advanced lego these days.. not much PCB prototyping and that sort of thing.


these are Li-Ion, do I just need to put these in parallel and have a 5.5v>3.7v step down for the input, a a 3.7>5.5v step up for the speaker amp and output charge?  And just the headphone jack, blutooth would probably put more drain on both the batteries

also that one said it had a max charge rate of 500ma, is that the output for charging the phone or is that the input to charge the battery would I need this one for 1a output charging?

it doesn't have the micro usb for charging the battery like the 500 one did

well, you don't want to hook them up in parallel or series exactly.. here is the overview from adafruit on lipo/lithium ion batteries:

The chargers should basically be compatible. Not a lot of difference in lipo vs lion as explained there. There is a schematic there, too, for this circuit. I didn't look too closely at it but if memory serves you never want to put lithium* batteries in series or parallel because there is opportunity for insanity in terms of thermal runaway and fire and meltdown and that sort of thing. That's why the multi cell deal up there isolates each pouch from the other in some way. And these cicruits even have temperature monitoring options if you want to solder that in. If you disassemble one of these packs like you would find in a laptop you will always or almost always find a temp sensor in the middle of the pack for charge/discharge related reasons. And that's why each battery will have its own lead that runs to the PCB in the laptop battery pack.

The multi-cel thing should have some way of then combining voltage or current depending on your application and what you want to do. When you use a circuit like the above, that's designed for multi-cell, then you can combine outputs because the assembly will be fairly well regulated and current/voltage limited 

The circuit also acts as a safety. The ratings on the battery you see on ebay is not 'it will perform like this' but more 'if you ask it to perform more than this, it will try, but then bad things happen, so in your application, build it so it doesnt exceed these paramters' -- hence needing a fairly fancy charge and discharge circuit. Thats also why you see "load" terminals on those charging circuits. they're meant to be hooked up all of the time and supply power to your application, as well as manage the batteries/charge them.

So on the load output on the charger, you could do a step up/step down regulator setup to power another circuit.

The example 1000 boost you linked to uses the much, much safer nimh or nicad batteries which generally won't enter turbo entropy mode unless yo u really, really try.


so I should put each one under a speaker so they are somewhat separate

You could make it interesting by using a tactile/exciter transducer and just stick it to any surface to make the speaker. They are really fun and work quite well. Im going to use a pair for my rear surrounds on my home theater system. My boss brought back one from a tech event several years ago and it blew my mind. Here is a link for some supplies if your not familiar with this company already and want some crossover parts or speakers


 P.S. with one of these you could actually use the housing as the speaker and it may allow you to do some cool designs for the casing.

sounds  cool but I'm looking to spend sub 80 with this, 40 of its going toward the battery

Would that work as the speaker amp? Looks like it should be pretty straightforward to setup and can run off a fairly wide voltage range. I own the 20 watt variant from Adafruit and it works well.

now here is a question, would the 3.7v stepped up to [email protected]~1Ah be enough to power two 90mm speakers or would I need to have circuit made to double the 3.7v to 7.4v for the speakers, does having the circuit in series double both the voltage and amps or just voltage?

wattage is amps times volts right?

Why do you need all that battery power, just use a more efficient amp design, and step up instead of stepping down voltage. A single Li-Ion of the cheap kind is rated at 7.4 V, which is less than 15 V which is what you need for audio that's not clipping. A Li-Ion of the expensive kind is rated at 3.7 V, but in fact will show very variable output voltage between 3.5 and 4.2 V depending on charge status. If You're starving a Li-Ion, it's going to become very hot, and then cause a fatal exothermal event. The protection circuitry adds enormously to the cost, to a point where I wouldn't do it, especially since NiMH batteries these days have very good and consistent performance (Sanyo Eneloop batteries ftw), and are rated at more cycles than bog standard Li-Ion batteries. With standard 1.5 V Ni-MH batteries, you can also stack in series to the desired voltage for your circuit.

Now I would put an STE ARM microcontroller dev kit with a touch display and built-in highly efficient amplifier in there, and small highly efficient drivers with a tuned cabinet with a passive radiator (which are also very cheap... shop around on aliexpress!). These things are cheap (about 17 to 25 Euro), and are fed by 5 VDC, fully programmable, etc... You can easily regulate down from 6 V or up from 4.5 V using AA Ni-MH batteries, or even down from 9V and use Ni-MH block batteries (even though these have less capacity), or you can get a cheap solar power bank (these are like 7 Euro at Aldi or Lidl for over 2000 mAh capacity), and are regulated to 5 VDC output already, and have a built-in Flashlight LED and a charging circuit, plus you can charge them with sunlight). A Tripath amp is so efficient that you need very little amps for a decent output, plus Class T amps are also great performers.

Wiring batteries in series doubles total volts, but keeps the original total storage. Wiring in parallel keeps the original volts but doubles storage. So using the eBay batteries I believe series would make both of them combined 7.4v at 12400mAh, parallel would make it 3.7v at 24800mAh.

So using that boost converter and the batteries and parallel would provide the sufficient voltage (and a very long life), but If I'm mathing correctly, I think the amp might draw more than 1Ah.

(3.7W+3.7W)/5.2v=1.42A, or 1.42Ah.

I'm thinking your best bet might be to see if there's a way to wire it in series to 7.4v then regulate the voltage down to 5v. You can make a simple linear voltage regulator for a couple of dollars, the problem with 5v regulators is that the lowest minimum input voltage I've seen was 7.5v.

I am confused did you check the link I sent? They have speakers for under $3, amps under $9, and crossovers for under $10. They have majority of what you'll need for the sound and amp sections for super cheap prices including boards and electronic components.

oh i didn't have it set to lowest to highest

so which one of these voltages would fit better, both are under 15v but over 3.7

I believe the 11.1v crams more capacity after stepping down to 5.2 for phone charging use, or do I need to step down for speakers also, like I said I know very little about speakers, I'd really like to have more that 9Ah capacity, if you have a better suggestion what do you think

the problem with using 1.5v batteries is that I'd need to use around 4 in a series to get the desired voltage, and I'd need an additional 4 in a series to run the series in parallel to increase my capacity, say each one was 2000mAh, if I wanted a min of 10Ah I would need 20 cells

if what you said about Ni-MH is true then I don't mind using it as long as I have the desired voltage, capacity and doesn't take up a HUGE amount of space

you can probably get a pre-assembled nimh battery pack with C or D size sells for the ah rating you're looking for. And some of the adafruit circuits have built-in efficient step up converters to go from 5v to whatever is efficient for powering speakers (?). 

I think I'll take zoltan's and your advice

they I think I can fit about 10 for [email protected] 19,000mAh or around 22,[email protected] 5.2v

some other amp and speaker option for you

This might give you some ideas.