Suitable battery for a supersmall/light boombox?

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Working on a small 12v boombox project and I'm trying to figure out how I should approach the power part. I have some goals that I want to achieve:
  • Should be able to be charged with an iPhone charger (USB)
  • Should be able to play while being charged.
  • As light as possible
  • Small footprint
At the moment I'm thinking of making a battery pack made out of 10 pcs of Eneloop batteries ( Amazon.com: Eneloop XX AA batteries 2500 mAh NiMH x4: Electronics - Amazon.com: Eneloop XX AA batteries 2500 mAh NiMH x4: Electronics) For me this seems to be the lightest and most easily configurable setup for a small and boombox (if you have any other idea, I'm all open).
But what do I need to set it all up and what do I need for the charger part? The batteries will be built into the box so charging and playing must be able to happen without any interaction with the batteries. How long do you reckon it will take to charge the pack?
I'm a beginner so ideally every step should be explained.
Thanks so much!
 
Actually, I had your same problem.
That was my answer (thzat is ready and will be tested in a couple of weeks, if my job lets me):

http://www.diyaudio.com/forums/class-d/237085-very-simple-battery-charger-ta2020-co.html

That does everything you ask , but needs a 15 V P/S that you can recover from an old laptop. Some of them worked at 15 V, otherwise there are some second souce universal ones that can be set up for that voltage.
I must tell you that simple solution does not seem to be of interest on the DIY Audio community.
Othewise, if you really want to charge through USB, you have the following limitations:

1) You need a step-up DC/DC conerter to at least 14V to charge a 12 V battery pack.

2) The current limitation of a standard USB port (500 mA) limits linits your max ower in output to about 1W on 4 Ohm when playing with a low battery, draining power only fromn the charger.

3) Even if you limit your solution to a 4 cells pack, the 5V supply of the USB is NOT enough to charge them correctly.
You need at least 1.4 V x cell. A fully charged Ni-Mh cell is about 1.39 V.
With 5V you can charge 3 cells, but then your power is limited to about 6 W on 4 Ohm whyile, playing on battery, the previous point limit still standing when battery is low and you play only from the charger.
 
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The best choice for a battery would be Lithium-ion, if you use a dedicated charge controller for safety. Light, small, high energy density, but not easy to use.

Assuming your battery pack is as you planned, there's a way to figure out charge time, assuming that the boombox is not playing. You'll need to charge them to about 14V, and your supply is 5V.

That's a step up of 2.8, which means current is stepped down by that much. Assuming the charger is 90% efficient, that's 32% of the input current.

USB allows 100mA without negotiation, meaning the batteries get 32mA.

2500mAh divided by 32mA is 78 hours. Add in an additional 25% for overcharge and you get 98 hours. We'll call it 100 hours.

With negotiation you can get up to 500mA, but a lot of USB ports can't deliver. So... I wouldn't count on it. This means that it would take about 100 hours to charge those batteries, not using the boombox.

I'd say that using USB to power a charger is an exercise in futility. Get yourself a 15V wall-wart.
 
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I'd say that using USB to power a charger is an exercise in futility. Get yourself a 15V wall-wart.

I concour with most your post, that is thechnically sound (pun intended!) and very interesting .
Only I am not a fan of Lithium stuff.
LI-ion is really dangeros and I want NOT give it to my childrem. Proof enough is that even Boeing could not find out an affordable solution with it and had to keep on the ground for three monts its newest aircraft just for that.
The other Li chemistry, the LI-Fe is much more reliable, (the same used in your top - notch battery drill) bur it is heavier and comes often in automotive standard form factors that add useless container weight to the battery itself.
In practice, a 4 A/h Li-FE, that comes in the the automotive (motorbike) PB SLA 7A/h form factor ) weights the same as a 10 - Cell SUB-C Ni-Mh pack @ 4000mA/h, where you get the pure battery instead..
Only the shelf price of the Li is more than double.
I understand, that in the long term the Li-Fe has advantages (durability, flatness of the discharge curve) but I do not think it is yet the solution for a basically ludic application like a boombox.
 
I saw that you wouldn't advise on using USB, FoMoCo, 100 hours is a very long time indeed. How do you think he solved it with the Minirig? Minirigs | Portable, Rechargeable Speaker
My assumptions are as follows:
1) He uses 500mA in his spec, which is quite optimistic.
2) The output is rather weak and rated at only a half meter. I'm guessing a 2 amp hour battery at 5V, not 12.
3) Like my calculations, the charge time is with the unit not playing.
4) Based on the specmanship that he's playing, the marketing department solved his problem.
5) Look at the frequency response curve on the technical page. There's no scale on the Y axis. That's more proof that he's not being forthcoming.

Most likely the charge time isn't even for a fully discharged battery. And, most USB ports won't provide his optimistic 500mA. If it did, your charge time would be down to 20 hours, and you most likely have a bigger battery to charge.

In my opinion, he didn't violate the laws of physics. He twisted things to say he did, without actually lieing about it.

That thing reeks of Bose type engineering...
 
Would you give a laptop to your children? That's what's in most of them. Li-Fe is definitely an alternative, but Lithium-ion is safe when used properly.

NO, I WOULD NOT f they charge overnight on a chalet (say bungalow).
Li-Ion now are even not transportable in aircraft, as freight or in the luggage.
Their failure mode is not yet well understood, and estinguishing the fire is very difficult (they call a type "D" fire).
Boeing had to make a reinforced, valve vented, external steel container around them in order to get the 787 approved to fly again after a 3 months stop by FAA that costed them multi-millions. Root cause of the battery failure still undetermined.
And we are speaking about Boeing, not the lastcomer. Battery was made by Yuasa, another name thet should be in the know.

I was involved in testing some thousands of units of Li-Ion units for home appliances, and believe me, it is NOT a safe technology. Tolerably safe when kept under watch, at best. I do not let my laptop on the sofa when I go to sleep, call me paranoid if you wish.
 
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... Li-Ion... and believe me, it is NOT a safe technology. Tolerably safe when kept under watch, at best. I do not let my laptop on the sofa when I go to sleep, call me paranoid if you wish.

...true words...
Also I am surprised how relaxed the entire RC model world is acting with huge packs of these energy wonders. :eek:

PS
Still I am not storing my laptop in a sand filled stone box.
 
I was involved in testing some thousands of units of Li-Ion units for home appliances, and believe me, it is NOT a safe technology.
I must disagree. However, that sort of flame war is off topic, as the OP has already decided on a different battery technology. Being that as the case, I won't argue pros and cons of battery technologies. Things get out of hand pretty fast here.
 
I must disagree. However, that sort of flame war is off topic, as the OP has already decided on a different battery technology. Being that as the case, I won't argue pros and cons of battery technologies. Things get out of hand pretty fast here.

You can disagree all you want. Fact is that li-ion batteries not in a device are banned from air transport in any shape or form. Consumers cannot legally buy such batteries anymore if the battery is in another country (for the EU that also means no crossing country borders within the EU). And most shipping companies either refuse to transport li-ion batteries entirely, or charge huge insurance premiums.

li-ion batteries are now considered a hazardous substance.
 
Obviously because a battery in a "device" only takes up a certain amount of volume, and therefore the density of hazardous material per volume is significantly reduced. Furthermore, a "device" is typically packaged for shipping drastically reducing the hazardous material per volumes.

Before, batteries were packed tightly in packages and palleted. Which was then stacked inside shipping containers.

Here's how a container ship looks after a li-ion battery container explosion.

container-ship-fire-2.jpg


container-ship-fire-4.jpg
 

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I belive the thread Opener said he needs a lightweight boombox.

So SLA I believe is really overkill- My thoughts (and my experiments) are that until about 4 Ah Ni-Mh is the most convenient and straightforward. After that, Li-Fe (With integrated BMS) takes place.
In this particular case, I believe a string of 10 x AA 2100 to 2600 mA/h cells could do the job in half a kilo weight.
Such batteries, if you keep an eye on your supermaket can be found on sale for something like 15 Euro total, good brand ones. Or take a same capacity packaged set for RC models , that would sell for around 30 Euro.
This batteries are rugged, tolerate very deep discharge (that normal SLA really don´t) and can be charged with simple chargers, even DIY ones (just google a little bit around and have fun!)
 
I don’t want to start an argument with anyone about lithium batteries. Back in 2002 I almost got into the battery business. This is when lithium batteries first started showing up on the market, and started blowing up and starting fires. What kept me from starting that business was the US government started legislation to regulate all commercial lithium batteries. Part of those regulations was to have the batteries tested at altitude. The testing would have cost about $10,000 for every type of cluster of cells with its control circuits and it packaging. The control circuits for a lithium battery control charge and discharge to prevent the batteries from overheating. The packaging for each cluster of cells had to be impact resistant with measures to protect the control circuit from short-circuiting. This is a very simplified explanation. The actual regulations include weight of the lithium metal used and the Wh(Watt Hour) of the fully assembled cells. That being said I have no problems or concerns using and traveling with any commercial lithium battery sold in the US. However I would not use the lithium cells that you see put together by RC hobbyist as these cells with their control circuits likely have not been tested per the IATA regulations which have since been adopted throughout the world. I believe Saturnus is partially correct in saying "Fact is that li-ion batteries not in a device are banned from air transport in any shape or form" This is partially correct. You cannot travel with lithium batteries that are not in a device, or commercially packaged and tested with a control circuit, and impact resistive packaging such as laptop batteries, cell phone batteries, MP3's, commercially enclosed external battery packs, not exceeding 11lbs or 100 wH. This is for carry on. For cargo there is a whole other set of regulations. Sorry for the long explanation.



Here are some of the solutions I have used in a stereo backpack that I have built. I use it skiing and traveling for work and pleasure.



10 AA Rechargeable Batteries I prefer Eneloops
Amazon.com: Battery Holder - 10 Aa: Camera & Photo

Pros: Cheap, batteries can be used in other devices that use AA batteries, works well in extreme weather cold/heat.
Cons: at full volume only 3 ½ hours to 4 hr before you get distortion. You will need 20 AA’s to play about 8 hours at full volume. Pain to charge that many batteries even with quick 15min charger.


10,000mah Lithium Ion battery. Ankar 5v, 9v, 12v external battery
Amazon.com: Anker Astro3 10000mAh Multi-Voltage (5V 9V 12V) Output Portable Power Pack External Battery Charger for iPads, Samsung Tablets, iPhones, Android Smart Phones, Camcoders, Digital Cameras / DV Recorders (Dual USB Output: 5V, 2A; DC Output:


pros: Weight .6 lbs, can charge USB Device mp3, phone. At full volume will last 8+ hours. Can power multiple devices at the same time.
cons: 12v output is regulated to 2A if your device draws more than 2A when powered on the battery shuts off.I got around this by setting the battery to 9v when I turned amp on then slid the switch to 12v. Not good in extreme cold 10 degrees F or colder



18000mah lithium ion Energizer xpal 18000a external battery. 5v, 12v 20v
Amazon.com: Xpal Power XP18000A Energizer External Battery Blk: Cell Phones & Accessories


Pros: weight 1.2lbs, Capacity, will last 2 days. Can power multiple devices at the same time including ipad and computer and t-amp. Can power Topping TP22 which uses 20v or other amps that require more voltage. Has cables and tips for just about any device you might need to charge while traveling.

Cons: Cost 169.00 if you can find it(Always sold out). Make sure to get the xp18000a because the xp18000 cannot charge ipad. Which require 5v 2.1. Not good in extreme cold 10 degrees F or colder


I have never been questioned by TSA while traveling with any of these batteries in my backpack.

Sorry for the long post. I hope someone finds it useful !

Robert
 
sorry for bringing an old thread do life, but how dangerous is it to use this kind of battery?

https://www.volumerate.com/product/...thium-ion-battery-w-switch-blue-silver-376146

It says it has:
Built-in Protected Circuit Yes
Over Voltage Protection Yes
Short-Circuit Protection Yes
Over-Charging Protection Yes
Over-Discharging Protection Yes


Or is that just troll to make us think its safe?


I just want to make a portable bluetooth amplifier, connect a bluetooth ampboard to the battery and then i can connect any speakers i want to connect.

Just like in this video: https://www.youtube.com/watch?v=N3k9lWz48rw
 
sorry for bringing an old thread do life, but how dangerous is it to use this kind of battery?

I wouldn't trust ANYTHING you read in an ebay description....
Caveat emptor....

If you go with Lithium batteries, better buy from a reputable local seller, who can show you a proper certificate for that battery, which should be legally imported (not "grey market", which is basically the same cheap Chinese ebay junk).
I hear horror stories all the time, and although living in EU, there are still some rather dubious electronic devices (most notoriously laptop or mobile phone chargers) sold even here (in "regular" shops) which tend to spontanously combust without a slightest provocation....

In short: do not buy lithium batteries on ebay....
 
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