Really cheap true cc/cv usb charging board

[Lynx_Arc]

I've only skim-read the thread, so apologies if I've missed something, but the limited USB output of 500mA is only for USB1.1 - with USB2, you can use the port as a charger by shorting the data pins (2 and 3) - this tells the system that the USB device connected is a charger, and if the hardware is capable it will output far more than 500mA quite happily, and the spec allows up to 1800mA. This is exactly what the iPad chargers etc. do. There is risk to the USB port, and I've seen them fried, by trying to pull more than the 500mA without shorting the data pins, though most smart systems just turn off the port until the system is reset, and you'll get some sort of error reported in your Operating System.

I wouldn't try to draw more than 500ma from a non USB 3 port. If you wanted to charge something requiring more current I would be more tempted to hack the charger and short the pins out on it instead so you won't forget and plug in your hacked cable and fry a usb power supply that isn't smart enough to turn off when current draw is too much.

 

[Norm]

I find it's much more convienient to use my ipad or other USB mains charger, there are plenty around the house.

Norm

 

[Aquanaut]

I find it's much more convienient to use my ipad or other USB mains charger, there are plenty around the house.

Norm

+1

See post #35. By "Apple power cube" I meant a plug in USB power supply. My ipad power cube supplies 2A at 5V (10 watts). iPhone, iPod, etc. power cubes supply 1A.

Be careful buying power cubes. There are many cheap imitation cubes which are worthless.

 

[BringerOfLight]

Has anyone noticed the boards getting properly hot while charging?
...
Follow up: the charger cooled down significantly as the cells voltage increased. I started the charge with the cells at 3.7V, so the charger was having to work harder to bring the input voltage down to the required charge voltage. Once the cells were at 4.0 - 4.1V the resistor was barely warm to the touch.

That charger chip works like a linear regulator, meaning it (along with the resister that gets hot) has to burn the difference between your input voltage and output (battery) voltage. I.e. when your battery is at 3.5V, it has to burn (5V-3.5V) * 1A = 1.5W - which is quite a lot for such a tiny board without heatsinks.

I wouldn't be surprised, if the chip went into thermal protection and decreased the charge current - you might want to check that, if you care about charge time.

\\

There are a lot of boards based on similar charger chips (some with much better specs, i.e. 0.5% voltage accuracy), a collection of them is here:
http://dangerousprototypes.com/2011/11/02/partlist-wednesday-lithium-polymer-battery-charger-chips/

 

[mvyrmnd]

Here's a question for the charger buffs - if I were to wire the outputs of two board in parallel, would I get a 2A charger, or a big explosion?

 

[Shadowww]

Here's a question for the charger buffs - if I were to wire the outputs of two board in parallel, would I get a 2A charger, or a big explosion?

No idea about that one, but there are boards with two of these chips that have claimed output of 1.5A.

 

[czAtlantis]

Here's a question for the charger buffs - if I were to wire the outputs of two board in parallel, would I get a 2A charger, or a big explosion?

You would get 2A charger. But there might be problem with enough current from your PC's USB port.

 

[mvyrmnd]

It's a good thing I'm using a 5V PSU, or an iPad 10W charger instead of my USB port

 

[czAtlantis]

It is fine then. Anyway even from standard PC's USB port it is possible (in most cases) to draw 2A but it has quite high internal resistance - so it won't have 5V but 4.5V which would cause slower charge when reaching CV mode with this charger boad.

 

[nofearek9]

has anyone done the resistor mod to be able changing the current output?

 

[Quest4fire]

In case anyone is interested the charging boards that the OP started the thread over are on sale for $1.99 each. The sale ends in one day according to the listing (Search item # 261043881158). The seller is e-worldseller. There is another seller that has them for the same price, but they have a low feedback count. Couldn't resist getting a few more.

 

[russde]

Thanks for the heads up Quest.
Can someone point me towards a source for magnets to use to attach to the + and - of my batteries?
Cheers!

 

[czAtlantis]

Thanks Quest4fire, it is very good deal! I will buy some

 

[Aquanaut]

Thanks for the heads up Quest.
Can someone point me towards a source for magnets to use to attach to the + and - of my batteries?
Cheers!

I have the following and they are quite strong and nickel plated, so it is easy to solder wires onto them.

Try indigo dot com, part number 44201-7.5.

 

[A987K]

Yeah, it seems fun, I will try to get some soon. LIke it

 

[jk037]

In case anyone is interested the charging boards that the OP started the thread over are on sale for $1.99 each. The sale ends in one day according to the listing (Search item # 261043881158). The seller is e-worldseller. There is another seller that has them for the same price, but they have a low feedback count. Couldn't resist getting a few more.

Fabulous, great find!

I'm ordering 5 from "e-worldseller". They come out to £1.27 each including P&P to the UK, so to buy five is still vastly cheaper than buying the components to build just one charger from scratch. And I get to avoid an evening or two hunched over a soldering iron too - bonus!

For the chap who was asking about magnets: I know it's almost a dirty word to some people, but DX sell various sizes of circular rare-earth magnets for a few dollars per pack of 10 or 20.

ETA: Sort of amusing how fleabay describe the price on this listing as "$1.99, approximately £1.27", yet when you get to the Paypal checkout page that has sneakily crept up to £1.306. Nice to see that the Paypal/Ebay machine isn't above outright lying and deception to make a few extra pence here and there!

 

[RoGuE_StreaK]

If we assume a USB port does limit current to 500mA (as a "lowest common denominator" approach), would sourcing power from two ports be an option? ie. one of those Y cables like some of the cheapie 2.5" HDD adapters use?

 

[czAtlantis]

Yes, why not?

Btw- anyone tried how much "true CC CV" it is? I mean if the battery is at 4.1V if it is still charging at 1A or the current is dropping. Or do I have to do it myself? :-D

 

[Norm]

I really wouldn't bother with your computer USB, buy a cheap mains adapter.

Norm

 

[RoGuE_StreaK]

I'm contemplating using these, or a diy version, as a built-in charger for a small-production product I'm prototyping (have to remove battery holder from product to access charger, to avoid pipe-bomb effect), so wanted to make it as versatile as possible for end-users. Good to know that if you leave it set to 1Amp it should still work on a lowly USB port, just much slower, was a point I wasn' sure of from TI's documents. I too saw these things after investigating the various offerings from Texas Instruments, would be neater to integrate TI chips directly into my own boards, but for now a separate board should suffice.