Switch mode supply mod

[GGoodrum]

I don't think you need to worry about the fan at all. It is thermally activated, and seems to do the job just fine, if you do the mod to reduce the max current allowed from about 135% of the supply rating, down to 100%. These supplies are typically used in applications that have average power levels under the rating, but might need short duration high current peaks, which is why the supply's current limit is set at 135% of the rating. Since we want to use these as battery chargers, we need the current to be limited to whatever the supply can put out continuously, and not burn up, so that means it needs to come down to the 100% level.

The good news is that there is a single resistor that controls this limit, and the relationship between the current limit and the resistance is linear. The current needs to be 74% of the factory set level (1/135% = 74%...) and so the resistance for this part needs to be reduced to 74% of its current value. The bad news is that there are several versions of the PCBs used in these supplies, so the part numbers can be different and be in different places. On my S-350-24 models, the resistor in question is R33, and is in the location circled below:

S-350-24-01.jpg

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I think in one of the other common layouts, this might be labeled R37. On mine, this is the only part anywhere around this section that was less than about 4k, I think.

The bands say the value is 750 ohms, but it measured 735 ohms. Taking 74% of this means the value needs to be around 545 ohms. Using this parallel resistance calculator, I found I could add a 2.1k resistor in parallel to the existing one and should end up with 545 ohms. the closest I could find was a 2k that actually measured 2050 ohms, so I tacked it onto the existing 735 ohm 1/4W resistor, and now the current limit is down around 13.5A. It was a bit over 20A before the mod.

-- Gary

[methods]

Click for full size - and before you complain - these are from my cell phone

Mean Well
SP-320-24
24V 13A

-methods

[AussieJester]

^^excellent...saves me taking mine apart ....again, for them pics you were after Mike thats the same model i have (albeit the 24v model)


KiM

[mwkeefer]

That actually looks a better design than the old, some of it seems odd or out of place with regard to the old design and smps in general but, ill be receiving a few shortly and will check them out... if things are consistent with Meanwell design... the same resistor on each will be used to limit the current output to 130% as pointed out by Gary, adjusting this by a calculable factor will allow for various power output ratings... I've been asked about the voltage adjustments also and it seems those use the standard resistor + SVR1 for voltage limited in high end range with ZD1 so the same adjustment (or similar) should apply... What I am anxious to see is how far up these new models will go in voltage modification... Time will tell.

Methods asked an important question the other day about Dead Shorting these, unlike a true CC/CV I think dead short will engage hiccup protection (docs list all of these as 1 second short to be removed immediately, auto recovery) so it would seem on totally DEAD short load they would kick in protection mode.

That said, I have used these to go from 35v at connection (24s A123 packs) to 74v without issue and while the current maintained constant (darn close) through that process.... I think that drop alone is enough to demonstrate that these supplies should have no problem providing CC/CV even with cells < 2v per cell, although there will be no connecting 3 in parallel and using jumper cables and nickles for spot welding!

-Mike

[methods]

I poked around a little - I think the current mod could go a little different with this model.

R33 is something like 1.7k (from memory) and there are quite a few resistors in the area that are sub 1k. Gary's suggestion to "look for the resistor that is under 1K" wont fly on this model. I think the best way to globally identify the location of the target resistor will turn out to be a nodal analysis - similar to what was suggested a few back - to go ind look for a signature of nets that tie together - triangulating the sweet spot - regardless of its value or marking.

So - who wants to sit down for 20 minutes and map all of the nodes that tie into either side of (in your case) R33 ?
Even something simple like "One side should tie to an electrolytic and a diode, the other side should tie to a ceramic and ....."

-methods

[mwkeefer]

If noone else does, I will map this one out too when it finally gets here... just reverse from the TL494CN Error GND and + #1 and #2 to trace back, it looks like they have changed the package and gone to dual op amps and even embedded a thermal cutout or ? power reduction within the heatsink on the input diode(s). That unit looks more stout than the ones I have but the principal will be the same, back trace the circuit and find the feedback amp resistor network... measure the voltage present and adjust the network accordingly... In the normal config, one side of the error amp will require increased resistance to decrease the current... the flip side will require a reduction of resistance to reduce the current.

In the end, a formula will be acheivable for this unit also based on other existing components. Is there a reverse side (trace) macro of this unit yet?

-Mike

[GGoodrum]

I have an idea that might be easier. If we can get Kim to take a picture of his 48V model from the same angle and framing as your 2nd picture, all we should have to do is look for the resistor(s) that are different. With any luck, there will only be one.

Gary

[methods]

Dat one Gary is da smart guy!

Kim - get to it mate.
Take a good picture of the section in question - it is only 6 little screws - should take less than 15 seconds to pop the top.
Take the best picture you can - I will take another with my "real" camera.
We can then have a contest for who can find the differences first.

CHOP CHOP!!!

-methods

[methods]

click the higher res pic.

-methods

[AussieJester]

Dat one Gary is da smart guy!

Kim - get to it mate.
Take a good picture of the section in question - it is only 6 little screws - should take less than 15 seconds to pop the top.
Take the best picture you can - I will take another with my "real" camera.
We can then have a contest for who can find the differences first.

CHOP CHOP!!!

-methods

I took pics of that section of the board last week Methy...

sp320-48v.JPG

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Both Gary and Mike have several pics of that section of the board i took.
I been a lil busy with other things so haven't taken it apart again for the pics Mike asked for the rest of the board, i am
topping off the batteries as i type this when thats done ill take it apart again and take more.

KiM

p.s mines doesn't have 'made in Taiwan" either mines "made in China" on the front...

EDIT:

Here you go more pics from the same angle...also pics of the rest of the board...

IMG_4359.jpg

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IMG_4361.jpg

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IMG_4362.jpg

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[mwkeefer]

Aussie,

Did you send the macro shots of the bottom side of the PCB? Those would be most helpful, I check my email again and what I have there are the detailed shots from the top - I will need these even if I am just to make a stab at figuring out the proper / safe way of reducing the current and adjusting the voltage to various ranges.

Everyone,

As I previously posted there are a few aspects of the design which make little sense to me (unless the 48v unit has 4 input transformers each providing an isolated 12v)... - some other things I note, there seems to be a better method of securing single diodes or transistors for heatsinking purposes, the pictures I'm seeing (maybe methods is a higher end unit) are showing dual Input Diodes (not sure I understand that) or maybe it's just a better silicone based wedge to maintain proper pressure on the Diode/Fet, etc. One thing I haven't noted (I've looked) is a shunt? Is there a shunt?

Since I have no idea how long it will be before my sample units arrive (3x S(P)-320-48v, 3x S(P)-320-24v and 3x S(P)-320-12v) I would like to ask if anyone here from the USA on this thread / forums has a 48v unit or a 2 x 24v units (S-320 or even the lower powered S-150 models) ... and who could temporarily part with them (I know how we are, we buy what we need to 2-3 extra for spares ... especially at these price points) I would be willing to pay the cost of the units and express shipping from within the USA just to get test samples in my hands faster to conduct the testing / reverse engineering of the newer (current) models. I would then be happy to return the sellers unit free of charge and not only will I cover the return s&h (yes, express) but I will also modify it to whatever parameters (voltage, current, etc) they so desire - gratis (if I have the connectors, I will happily embed andersons or 3.5mm power connectors into their supply also).

If this is an option doable for someone, I would appreciate it greatly ! -
Please feel free to PM me (or email me if you have my email address)...

If this turns out not to be an option, if a few owners are willing to clear a few items up for me... I will see what I can figure out (but your own your own to test the modifications).

1.) What is the U1 (the 16 pin IC chip)... I can't make out the markings, identifiers?
2.) What are U3 and U3 ? - I assume opamps but I can't make them out properly either?
3.) Do these units have a shunt? - If so how many and where are they located?
4.) Can you remove the heatsinks and list the Diodes and FET part numbers (anything else that may be there) - manufacture (if specified) and any markings or numbers on them.

Thanks in advance!

-Mike

[MrKang]

Just ordered a S350-48V 7.4A unit from china on ebay. I will follow this thread to make a charger for my lipo's at work.
at home i use 4 balancer chargers. it's fast but i cannot drag al 4 ballancers with psu to work to charge i over there to get home after work.

So this will be for a quick charge to 75% for my packs to get sure i will get home.

it will charge my packs unballanced but so far i heard it cannot do much damage to my turnigy lipo's.
I have 4 packs. 3 x 6S4P and 1 4S4P. so i have to mod this charger for two setups. one for a 12S charge and one for a 10S charge
Maybe i can connect the lipo 6S battery medic to balance them a bit while charging.
I think it will take 3 weeks to arive here but i will read all the mods you plan to make on them.

[Hyena]

Maybe i can connect the lipo 6S battery medic to balance them a bit while charging.

Trying to balance with a battery medic while a meanwell is belting current into your pack will be like pissing into a gale force wind!
I have one for monitoring purposes and as a token balancer if I really need one but if your packs get to the point where they actually need balancing the battery medic will take HOURS to balance them

Using a meanwell to top your packs up at work will be fine but don't worry about trying to balance them too. Especially running them 4p, they should remain very well balanced with such a low C rate of discharge. And with 20S4P worth of cells and a single meanwell, hell I'd charge that sitting on top of a 44 gallon drum of premium unleaded and feel safe

[GGoodrum]

First of all, Mike you are talking about two distinct mods, the second of which I don't think is all that useful. The first is finding how to simply lower the CC limit, back down to around the 100% level. In the case of the S-350 series, this simply involved lowering the resistance of a single resistor. The second change you propose is to essentially change models, turning a 24V/13A into a 48V/6.5A, for instance. I think most here that either have a MW supply, or are contemplating getting one, are very interested in the CC limit mod, but I think very few are too interested in "changing models", so we don't need to make doing both mods a priority. I think we should concentrate on figuring out how to do the CC mod, and the CC mod only, to the newer SP-320 models.

To that end, Kim, you still haven't supplied a picture that has enough resolution, and is from the right angle, so that we can read the color stripes on all the resistors in the section of the PCB that has the PWM chip. You came close in this last one, but it is from a shallow angle, and there is much blocking lots of the resistors. If you can, please take one closer to straight above that section of the board, and please use as high a resolution as your camera has. If your camera has an optical zoom, stand back a little bit more and zoom it in to just that section. That should make the blowups have as much clarity as possible.

Patrick, you have some parts hiding as well. Specifically, R40, R32, R46 and R47 are either partially or completely hidden. One part in particular that seems like a possibility is C27. I can't really read the stripes on either picture, but it does look like the may be different values. Also, since they are blue-colored, they might be 1% parts, which would make sense if this is in fact the one that controls current, and they wanted it to be a bit more exact. Anyway, can both of you please verify the value or the stripes on these?

-- Gary

[Tiberius]

First of all, Mike you are talking about two distinct mods, the second of which I don't think is all that useful. The first is finding how to simply lower the CC limit, back down to around the 100% level. In the case of the S-350 series, this simply involved lowering the resistance of a single resistor. The second change you propose is to essentially change models, turning a 24V/13A into a 48V/6.5A, for instance. I think most here that either have a MW supply, or are contemplating getting one, are very interested in the CC limit mod, but I think very few are too interested in "changing models", so we don't need to make doing both mods a priority. I think we should concentrate on figuring out how to do the CC mod, and the CC mod only, to the newer SP-320 models.

Hi Gary,

I agree with you, but up to a point. Lowering the CC limit by changing a resistor is a better method than one I came up with first - cutting a shunt. It has to be worth someone tracing out the various circuits round that current comparison area, because there do seem to be quite a few variations. I've even had nominally identical PSUs with different R values in places.

Where I disagree slightly is in the need for hacking the voltage around. True, turning a 24 V PSU into a 48 V one isn't needed; its better to get a 48 V one to start with. But the native tuning range on each model is only +/-10%; we need to increase that or move the centre around to cover all the voltages needed.

Nick

[GGoodrum]

I agree with you, but up to a point. Lowering the CC limit by changing a resistor is a better method than one I came up with first - cutting a shunt. It has to be worth someone tracing out the various circuits round that current comparison area, because there do seem to be quite a few variations. I've even had nominally identical PSUs with different R values in places.

I agree, but with these new SP-320s, the layouts are identical, and so are the value of the parts that I can read, at least.

Where I disagree slightly is in the need for hacking the voltage around. True, turning a 24 V PSU into a 48 V one isn't needed; its better to get a 48 V one to start with. But the native tuning range on each model is only +/-10%; we need to increase that or move the centre around to cover all the voltages needed.

I agree again, that a greater voltage range will be good, but first and foremost, in my mind at least, is coming up with as simplest a mod possible to get the basic units usable as reliable chargers.

[AussieJester]

To that end, Kim, you still haven't supplied a picture that has enough resolution, and is from the right angle,

I left them at 1080 rez and took it from same angle Methy did have you tried saving them to your PC and zooming in? ...i shall pull the thing apart again, now take more pics for you...

OK..10 pics of front and back of the board left in the rez they come off the camera...21mb worth

http://members.ii.net/~aussiejester/ind ... 48v%20PSU/

I can't get a shot of the resistor in the R33 spot i cant bend the component hiding it i cant even see it myself no matter how i look at it and im NOT de-soldering anything sorry guyz. If there's any others you can't see and need to know ask and ill see if i can read them for you on the board...

Best i can do hope it helps

KiM

p.s Mike...the shots of the back of the board are there for you also mate...

[wookey]

I had 2 of the 48V models arrive last week. I've just got as far as testing the no-load voltages, taking them to bits and trying them in series (all good). I'll take some pics forthwith. I might even try and do a bit of schematic tracing.

<fx: faffs about for q>

OK. I've taken a photo of top and bottom, and merged two bottom pics to remove the flash-overexposed bit.
They are uploaded here:
http://wookware.org/pics/meanwell

I've also drawn a schematic of the control area round the controller chip and put it there too. It's a very scrawly bit of paper so far laid out like the PCB rather than anything comprehensible, but it may help a bit. I can tidy it up and measure a load of values if that'll help.

I realise this is a poor substiture for having one in your hands, but I can't help there (being in the UK).

I note that my ZD1 (under the big transformer) is actually two diodes with the tails wrapped together, but not soldered! Tres crufty. Think I'll improve that a bit.

[Velocipede]

Hi, just read this entire post with interest and this looks like an interesting way to go.

Are we aware of a model that have SVR2 already populated so we can adjust amps without any mod?
My local shop lists: SE-600, SE-1000, SP-500, SP-320, S-320.

If I buy a lower power rated unit like S-240, the amps will be naturally limited lower, is that right? Or I will blow it or throw it in protection mode by plugging my battery to it?

If the details are clear about a particular model, I may try the mod.

Something like this is awesome with the display and all, but at 3x the cost...
http://www.gwinstek.com/en/product/productdetail.aspx?pid=38&mid=76&id=178

[Hyena]

My new meanwell arrived yesterday, sure electronics eventually agreed to replace it under warranty. (this was the completely unmodded one that blew up 2 minutes after I took it out of the box)

I tested it briefly with a lipo pack connected and it was putting out 10a (~500w) straight out of the box.
I opened it up and tried the resistor mod but instantly got the buzzing sound. After blowing up 2 SMPSs I wasn't willing to risk a 3rd so I decided to mod the shunts instead. Mine is the model that has 3 large shunts and by cutting one it drops the current to 6.9a - pretty much exactly their rated output.
So, if anyone is looking for a quick and easy fix to the over-current problem, snip through one of the shunts.
I decided to bump the current back up just a little to 8a, so around 400w (one of my other 350w units has been used daily for 6 months at 450w without any problems) I soldered 2 strands of fine wire across the gap - it's a good way to tune the exact current, get a piece of 20ga wire or similar, untwist the strands and fan them out with both ends soldered across the shunt you've just cut. Fire up the power supply with a max load connected and snip through the strands until you get the desired current.
Yeah it's a bit ghetto, but that's how I roll
Replacing R33 with an appropriate pot would probably be the better way to go but it still results in the buzzing and it requires messing around taking the board out which involves removing the glued in fet mounts and reapplying thermal paste afterwards (if you bother)

Also, re: the earlier topic of making the fan stay on, I measured the thermistor and it was reading about 1500 ohms at ambient temperature (about 26 celcius at the time) and when heated with a heat gun turned on the fan when the the resistance dropped down to about 700 ohms. I replaced it with a 500 ohm resistor and now the fan starts up immediately when you power up. If you short it it shuts down, so there needs to be some resistance there. I actually tried putting another resistor in parallel with the thermistor, so it'd just kick in earlier but bizzarely when I put a 500 ohm resistor in parallel with the 1500ohm themistor the resistance actually increased to 2200 ohms. Curious... I'm far from an electronics genius but I know that putting 2 resistors in parallel lowers the resistance. I guess it must be a property of thermistors that their resistance increases at a fixed temperature if you put a resistor across them ??

[dozentrio]

I liked your approach to having the fan on constantly. I was able to do this by putting a 1k resistor in parallel with the thermistor though. My thermistor is labelled 502. I am sure if you're curious you can discover what that means. I was not curious enough, being happy that the 1k resistor did the job.

I have some questions about the current limit. First of all, where are these shunts and what do they look like?

Also, what is a good way of measuring the max current output of my supply? The multi-meters i have access to are limited to 10 amps. Which is about what the output will be at 130%. So, if I am willing to risk the fuse on my multi-meter, do I simply connect the two probes of the multi meter across the powersupply + and - and then plug it in? Something tells me this is not the best or proper way of doing it. Something about inrush current... ? I also have a watt-meter I could use, which has a higher current rating.

[Hyena]

I liked your approach to having the fan on constantly. I was able to do this by putting a 1k resistor in parallel with the thermistor though.

Yeah that should work, as it is doing for you, but for some bizzare reason my resistance actually increased...

I have some questions about the current limit. First of all, where are these shunts and what do they look like?
Also, what is a good way of measuring the max current output of my supply?

These are the shunts - there's 3 of them in my unit (as for most 48v 350w models I believe) and cutting one will result in it safely operating at its rated power output of 7 amps

mw350shunt.jpg (141.34 KiB) Viewed 1381 times

I use a TURNIGY WATT METER FROM HOBBYCITY
They're $24 and measure voltage, current, wattage, ah etc.
I'm in the process of building it into the charger permanantly so I can accurately and easily adjust the voltage to charge a range of packs without connecting up a multimeter. Seeing the current is a bonus as it lets you know once it starts tapering off that the charge is nearly done.
You could also use a cheap analog panel meter, that's what I have one one of my other power supplies. A 10a unit should be sufficient, any more than that and the meanwell will have a short life.

[MrKang]

I have a 5A lifePo4 charger for 48V.
If i measure the output it's 60.1V which is normal. But i want to modify the chargers voltage output to charge my 12S lipo.
I allready found the pot.meter to adjust the output voltage. what is the safest voltage i have to adjust it to?
is it 12 x 4.15V ? or 4.20 volts? so that leaves me a total output to 49.8 or 51V

This charger i could use at work.

[dozentrio]

Well, I connected my watt-meter and did some messing around. There is only one shunt on my power supply, and I didn't want to cut it because it would have been difficult to replace. The resistor (R37 on my 48V 350W clone supply) says it is a 390 ohm, and I modified its value to 200 ohms. Now the power supply outputs around 5 amps, which is just what I would like for charging my pack. The supply supply buzzes/crackles under load, though, and I wonder if it is safe to allow it to do that for hours and hours on end.

[wookey]

SO. My R33 measures 740R in circuit, which matches the colour code. The layout is such that you can fit R37 and SVR2 instead of R33 in order to have an adjustable resitance here. Probably the neatest mod. I'll buy bits for say 360R plus 500R variable and try it out.

Personally I'm interested in mwkeefer's flavour-conversion scheme as well as the simple current-limit mod.

No-one seems to have answered his questions about labels so here's what my board says (same layout as Ggoodrum's, I think mwkeefer actually wanted to know details for the other layout aussiejester has pics of, but nevermind, might as well write it down):
U1: 98AZTLM TL494CN and a TI logo, so that makes it a TL494CN SMPS chip: http://www.alldatasheet.com/datasheet-p ... 494CN.html
U2 is HA17358 (hitachi dual op-amp)
Heatsunk devices: Q2 2 x 2SC3320 (fat transistor) at the end, and D13 is D92M-03 (low loss high speed rectifier) at the side.

RG1 is 7812CT (even I know what that is: 12V regulator
BD1 is D15XB60 (600V 15A bridge rec)

(I've just discovered that LED strip-lights are really good for reading part numbers with)

Now I've got that SMPS datasheet it ought to be relatively siple to make sense of the circuit. I'll do some more documenting and schematic-decoding over next few days. Then hopefully someone who actually understands this stuff can say something sensible about it all.