Anyone know more about these modules?

These little modules off ebay cost about £4, combined with a couple of totem-poled battery-charger transformers they look a great way to bodge a high-current bench PSU.

**LINK**

Naturally I can work out how to get the indicator and current/voltage sense voltage connections onto a panel

But does anyone know anything about the RS232 connections?

I can't find a datasheet anywhere.

The other side of the module seems to have a 2-wire connection to the battery - is this a proprietary format for talking to the BMS in some lithium packs? Almost certainly serial if it is - and possibly gets passed through the module to the other port. Might be worth looking at lithium BMS datasheets?

Don't see any mention of RS232 in that page - do the other ads specify it thus? At that price, perhaps the easiest way to find out is to buy one.

Neil,

TinyuRL, http://tinyurl.com/zbrfb9q

Or see: The Art of Electronics, 2nd Ed. Horowitz & Hill, page 724

Geoff

Neil - are you asking how RS232 works or are you wondering about the format of the control data you need to send to this thing? I rather suspect the latter. I expect the format is semi-proprietary but isn't going to be a well-guarded secret. The vendors might tell you (in Chinglish!) if you ask.

Dunno if you can find any trace of these devices publicly but these are what you find when you rip open a Lenovo L-Ion pack.

Definitely the latter. Past experience shows it can take several hours of trial and error to establish communication with a device with unexpected baud rates or parity.

These sorts of things usually use 0/5V signals but RS232 protocols as it makes 2-way communication with uPs very easy.

The display board has only four connections to the actual power board, the four brass columns which are each Vin +, Vin-, Vout -, vout+. I see the power board has a fat R050 current sense resistor between in- and out-

so... this obviously isn't a control function, I suspect it just reports current and voltage.

If you ask the seller they will probably link you to a data sheet.

I'm loosely reminded of emailing a chinese seller after buying a part of him. He miss understood and replied sorry we will get it right next time we makes some. Maybe the serial interface doesn't work.

If you google the entire listing title a number of links come up. Some are video's. Might be some info there.

John

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As they are so cheap it might be worth buying one in the hope that the underlying chip is marked and its datasheet can be looked up.

The functions available through the interface may be more comprehensive than you expect. For example, this TI chip uses an IC2 serial interface to adjust lots of parameters so that the charger can be optimised for particular batteries.

Please let us know how you get on. It looks like an interesting module.

Cheers,

Dave

I think the only way you get any detailed info is to reverse engineer the schematic. I have used quite a few modules similar to the one you show. The descriptions often have errors and you dont know what you get until it arrives!

On this one it mentions non synchronous rectification but nowhere does it say AC input or what AC frequency.

Not relevant to your bench PSU purpose but some people have assumed that the CV/CC modes meant that it can be used to charge Lithium type batteries, they can do, but they are not really optimised.

The modules I use are mostly DC:DC buck or buck-boost. 10A versions are not much more expensive, some have meters but if not there are plenty of cheap digital V and A modules and since they are not on the regulator board are easier to put where you want on your front panel.

By totem poled do you mean transformer secondaries in series? also what current do you consider high for a bench PSU?

Ian P

Forgot to say, module circuit diagram can often be found by looking at the chip makes application notes, they are usually slavishly followed.

Ian P

Duplicate post removed

Edited By Ian Phillips on 06/02/2016 20:38:15

This f-bay advertisement has some information about their modules

Paul

http://www.ebay.com.au/itm/5A-CC-CV-Adjustable-Power-Step-down-Charge-Module-LED-Driver-W-USB-Voltmeter-EB-/261540641867?hash=item3ce5097c4b:g:gokAAOSwDk5TzyJi

A nice low-stress task.... only 4 screws + google required

Its a simple DC/DC chopper. A 1-chip converter (XL4005), plus a couple of big Cs, a hefty shottky diode and an inductor. An LM358 works the pretty lights on the bottom and takes care of the voltage/current limiting, I assume..

For my purposes, anything over an amp is 'high current'; 4A will be plenty for anything I'm planning.

The display board is effectively separate, just neatly designed so four brass stand offs make the connections. Easily replaced with wire, if required.

Another LM358. LS164 is a shift register - used for the displays, I assume.

Interesting bit is an STM8S003F3. As suspected a microcontroller, so all I can do is fire random ascii at it and see what happens - and hope I don't trigger a bootloader

Think I will just accept as a neat module that will do what I want and not try and add data logging or anything clever

I'd eMail the seller, I've had a quite a bit of 'modules' type stuff from China and the sellers are usually very helpful, assuming the Chinglish isn't a barrier. You might get a good surprise in just how much they are prepared to share.

Steve

Neil,

The module in this video looks familiar:

**LINK**

MichaelG.

Yep, that's the one.

Neil

"This seller is currently away until Feb 16, 2016. If you make a purchase, there may be a delay in processing your order."

Chinese New Year - no point asking for at least a week or so!

Neil

What a pita.....

Why cant they have New Year same time as the rest of the world?

Gosh. What if we have got it wrong?

Hi Neil,
I was wondering if you ordered one of these modules. I ordered one yesterday (20/02/16) but I expect it to take a few weeks to arrive. I would be interested to here you opinion on them when your's arrives. (If you did order one.)

Les.

I'd already got it in my hand when I posted my original query.

I still haven't wired it up as I haven't dug out any big enough smoothing capacitors for my transformers yet.

I've ordered a couple of multi-turn pots from China to replace the on-board ones.

At the price even if the regulator isn't much cop the voltage/current readout is worth having.