Low cost battery supply.

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ahull
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Low cost battery supply.

Post by ahull » Thu Nov 19, 2015 9:38 pm

Strictly speaking this is not STM related, but here is a quick and simple LiPo Battery supply hack based on the ubiquitous TP4221A/TP4221B/TP4221C - 18650 LiPo based "Power Banks" that you can pick up for pennies on ebay. I posted it on Hackaday.io this afternoon.

Image

So far, no magic smoke related incidents have been reported :twisted:
- Andy Hull -

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martinayotte
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Re: Low cost battery supply.

Post by martinayotte » Fri Nov 20, 2015 1:07 am

ahull wrote:So far, no magic smoke related incidents have been reported :twisted:
:lol:

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RogerClark
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Re: Low cost battery supply.

Post by RogerClark » Sun Dec 06, 2015 8:00 pm

Hi Andy

Fyi. I just ordered one of those mobile phone power banks for $10 AUD from eBay, which claimed it is 5600mAH.

http://www.ebay.com.au/itm/5600mAh-Port ... -YsUra2LZA

I very much doubt it will have that much capacity, as the price seems too low. But I will take it apart when it arrives ( hopefully next week) and let you know whats actually inside it.

If it only had 1000mAH that would be Ok, as I have built a Bluetooth audio speaker by fittting a small audio amplifier and Bluetooth audio receiver, inside a Warfdale Diamond speaker (from an old hifi separates system), and it would be good to have it run from batteries.

Actually, I'm going to build a better one with the other speaker, and use a boost converter to step up the 5v to 12v or possibly 18v as the amplifier minimum voltage is supposed to be 6v and Im currently running it on 5v from USB, so the sound starts to distort if I drive the amp to hard.

BTW. I'm building this because the sound quality on most Bluetooth and portable speakers is generally rubbish unless you spend a fortune on kit from Bose etc.
And as I have quite a few Warfdale diamond size speakers kicking around, its more interesting to build something myself that has much better audio quality.

Actually I find Bluetooh audio quality to not be as good as direct input to the amp, from the jack socket on my Android phone, but I think this could be because the Bluetooth audio dongle that I canabalised was only about $3, or its just an impedance mismatch

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ahull
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Re: Low cost battery supply.

Post by ahull » Sun Dec 06, 2015 10:48 pm

I did a teardown of something similar on the CHDK website here... You are right to be sceptical of the capacity of these things, but aside from that, they are pretty useful. The CHDK thread is pretty long, but it has some useful ideas for portable power.
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RogerClark
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Re: Low cost battery supply.

Post by RogerClark » Sun Dec 06, 2015 11:23 pm

Yes. That is rather a long thread !

The battery is supposed to be here by Wednesday as its a local supplier (in Aus), so we will see...

I also decided to go for a higher rated boost converter http://www.ebay.co.uk/itm/Hot-DC-DC-Boo ... 1843934870

I doubt its really capable of 6A, but it looks more substantial than the other one I have one order.

Looking at the amplifier its using a TDA7297 which is rated at 15W stereo, but as its only running one speaker, I'm only using half of it.

I was thinking about running the 2 sections in parallel, from and just combine the incoming stereo together, but as these Warfedale Diamond 6R speakers have a woofer and a tweeter, and an internal crossover network. Perhaps there is a better way to do this and drive the woofer with one channel of the stereo and drive the tweeter with the other.

But I supposed I'd then need to build a "crossover" circuit on the input side of the system rather than the output side.

Or perhaps thats not even necessary if I'm feeding the woofer and tweeter from effectively different amplifiers.

ummm. Not my area of expertise, but I'm sure there would be a forum for this ;-)

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martinayotte
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Re: Low cost battery supply.

Post by martinayotte » Sun Dec 06, 2015 11:58 pm

That make me bring the following question :

What are the best deals all of you, folks, have ever found for batteries, especially for 18650, there are so many capacities and vendors...
I wish to order some, cheapest as possible but with biggest capacities possible.

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ahull
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Re: Low cost battery supply.

Post by ahull » Mon Dec 07, 2015 12:05 am

martinayotte wrote:That make me bring the following question :

What are the best deals all of you, folks, have ever found for batteries, especially for 18650, there are so many capacities and vendors...
I wish to order some, cheapest as possible but with biggest capacities possible.
I liberate all of mine from old laptop batteries, effectively I get them for free, but these are unprotected cells. Capacities are typically between 1600 and 2500 mAh, depending on the age of the battery.
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RogerClark
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Re: Low cost battery supply.

Post by RogerClark » Mon Dec 07, 2015 12:09 am

Hi Andy,

I had an old laptop battery, but when I measured the voltage it was virtually zero :-(

I guess I could take the pack apart and see whats inside and whether any of the cells are OK, but I'd still need some way to change the cells unless the battery pack contains the electronics.

So I think at least to start with I'll take a punt on the mobile phone power pack thingy.

If it is very low capacity, I'm going to complain to the eBay vendor and either get a refund or they get a black mark ;-)
But if its 1000mAh, I'll probably just accept it as a £4 is a fair price for that capacity

PS. I also have a solar torch thingy, and that just contains a large NiCad button cell. I'm not sure what capacity it is, but I'm going to use it as a BLE beacon with a nRF51822.

However when I last checked it, the battery was flat because I'd left it in a cupboard, but hopefully a few hours in the sun should fix that !

(PS. Its not actually sunny here today - which is abnormal .... but its probably bright enough to charge )

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Re: Low cost battery supply.

Post by ahull » Mon Dec 07, 2015 1:40 am

If you don't fancy the Hack I detailed, you can pick up a charger for the cells for pennies.

The fact that the laptop battery has zero voltage doesn't mean any of the cells are bad, simply that the charge protection circuit has kicked on. If you pull the thing apart (carefully), then you will probably find most if not all of the cells are fine. Do take a little care with the unprotected cells though, read my Hackaday posts for some safety tips. They are not particularly dangerous, so long as you don't do anything silly.
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martinayotte
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Re: Low cost battery supply.

Post by martinayotte » Mon Dec 07, 2015 2:00 am

I've decided to order those, but please, tell me if there is better offer ...

http://www.ebay.ca/itm/4pcs-3-7V-18650- ... Sw4UtWRrdL

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