Gangster way to limit current on meanwells?

Hey hey...
So i've been reading a lot about how to limit current on meanwells lately. Want to get a 48v and run it at 41v.

Seems like the approach of lowering/adding current to a certain resistor is a bit flawed as it will cause an audible buzzing in the system ( generally not a good sound, right? )

Now i hear that cutting off one shunt from the newer models works, is that correct?

If so, how about shaving material off both shunts instead? do they have a different material in their core? Or is it all just one big piece of lead or aluminum etc?

There is so many damn meanwells and and clones all of these threads seem irrelvant unless all the supplies are sourced from the same spot. I just had an IM ealier about how I modded my meanwell. 15 min of mods and mines been rock solid at 400-450w for 8 months now. With none of this BS buzzing and I can go 18-56v. Current limiting set at 10A

hm, i'm referring to the one from sure electronics btw.
Should be genuine, or very close

Meanwell them self has like 20 revisions.

My genuine early Meanwell looks nothing like my late model Meanwell inside, both have the same model numbers.

They're all different, but use the same part codes. Even on my s-150 it's the R33 resistor that controls the current limiting. An no, it doesn't buzz. Best bet is to get the unit, and have a look for yourself. I'm by no means intelligent, but I could figure it out. It took all of 15 minutes to install the current limiting pot. Why even bother wih the shunt? The time it took you to make this post could of figured that out.

15 min of mods and mines been rock solid at 400-450w for 8 months now. With none of this BS buzzing and I can go 18-56v. Current limiting set at 10A

Click to expand...

You run your 350 at 450w? Extra cooling or anything?

Well i have read instances of these power supplies buzzing with the variable resistance level and / or fechter's board. I thought shaving the shunt would be a cleaner way to do it.

You also have a different power supply than i'm looking at. I want the 350 48v model from sureelectronics.

I've read so much varied info on this forum; that's why i wanted to do it the simple way.

auraslip, did you get the sure-electronics one or the stoneined one?

Post a picture of the board for us to be sure

Depends what you mean by simple. Electronics and construction wise, doing the R33 R37 SVR2 is quicker and simpler than building the fechter cc cv board, and it does not buzz with current limiting.

In operation, the cc cv board is simple and nice and easy to use, but far more complicated to build than the SVR2 'mod' But you do get end of charge notification via LED and float/maintenance voltage at end of charge. But, in my case in know that if you use this board for current limiting it does create buzzing

But I can confirm that on S-350-48 meanwells I have, originals, not clones, no buzzing using the R33 mod. Well The R 33 current limiting, is not really a modification it is just adding parts that SOME meanwell models had fitted as standard.

The Fechter / ggodrum boards do cause buzzing when current limiting is at work, as they work to limit the current by different means.

I did both, added the SVR2 pot and use the cc cv board


Add a resistor or potentiometer across R 33, if you are lucky, the places for thes parts will be on the board, but empty...if you are even luckier, you may have a board with these parts already on. Look for R37 and SVR2

Then still use the fechter board for float voltage, end of charge shutoff. What the board does is monitor the output current and when it drops below a figure you set with one of the pots on the cc/cv, it causes the output voltage of the Meanwell to drop between 2-4 volts and the LED changes green to orange

Fechter seems to be too busy to put 'em together and ggoodrum is not responding.
So i kinda have to go without that.

Float voltage? Wouldn't the lack of voltage differential make the charger float the battery at an extremely low amp rating?

I'm OK with manually monitoring my batteries during the charge.

You may have to go back up and re read my last post, I edited it while you posted yours

Gary will respond given time and prompting, he does seem very busy. I just received notification that he has posted me two new cc/cv boards, I still have not ordered the components yet though.

I got my first one by posting in the Wanted section here, and got one ready made.

I would like to offer to build one up for you, but you could be waiting 6 months or more the way things are going for me at the moment, and I could not guarantee them or anything like that

Well i ordered mine from sure electronics and resistor mod will be done. We'll see how it goes !

For the resistor Mod, I would use multi turn potentiometers, like these

http://uk.farnell.com/bourns/3006p-1-502lf/trimmer-15-turn-5k/dp/9352384



This sort will fit directly on the board, but yo will not easily get to the adjustment screw
http://uk.farnell.com/vishay-sfernice/t63xb502kt20/trimmer-15-turn-5k/dp/1141433

http://uk.farnell.com/productimages/farnell/standard/42253963.jpg

I used the top type, and mounted them externally with flying leads running inside the case to the board., a 5K is ideal for both voltage and and current limiting.

I actually used two for both current and voltage, and a switch, so i can switch between one or the other...giving me two different voltage limits

neptronix said:

Float voltage? Wouldn't the lack of voltage differential make the charger float the battery at an extremely low amp rating?

Click to expand...

You use the first pot on the board to adjust the float voltage. So once you have the pack connected and fully charged, and once the Orange LED has come on, you adjust VR1 on the board, so that there is no current flowing to the battery


If you get one of these boards, the instructions are misleading. I believe fechter is re writing them.

The instructions at the moment make it sound complicated, and in places are in fact wrong for the current version of the board. But once you understand what the board is doing and which of the three adjustment pots on it do what, it is v easy to set up.
With a lot of PM'ss from Gary and fechter, they finally hammered it through my thick skull

Yeah those pair are not exactly great at describing things to common laymen like us
Well, they are electrical engineer types so go figure.

Anyway i will hook up the turnigy watt meter to mine and see if it acts as expected. I think i won't need the fechter board immediately. The LED is a big plus but i can live without it. I think the current will taper off gradually as the voltage of the pack stabilizes ( little to no voltage differential ), just as it does with the iCharger.

Good thing i ordered this because my iCharger started doing that shit where it likes to randomly turn off again over 2 amps again. No longer acceptable now that i have a 20 amp hour pack instead of a 5 amp hour.

Yes, you are acorrect, th Meanwell just tapers off to zero volts as the pack comes up

The boards are not necessary but nice. As I say, I just ordered two more...basically because I fried the first one the other day. Connected the pack to the charger the wrong way around. Meanwells ok, but zapped the board.

The terminal I was trying to connect just vapourised in my hand.

this is a good reason to make sure you turn on the PSU BEFORE connecting it to the pack. if it was all connected up when I applied power, then it would have smoked the Meanwells

Note to self...things to do ...fit fuse in charger lead and fit polarised connectors to the Meanwell output!!

Thanks boostjuice. Glad to know the sureelectronics supplies are legit and take this mod well. That's the info i was looking for.

I read your link, and your mod that involves snipping R33 amd fitting another pot next to the original. One question, Why did you find the need to put another trim pot? Did the one already fitted not give enough adjustment?

NeilP said:

I read your link, and your mod that involves snipping R33 and fitting another pot next to the original. One question, Why did you find the need to put another trim pot? Did the one already fitted not give enough adjustment?

Click to expand...

In a nutshell, my versions didn't come standard with any current limit trimpot at all.....

It's true there is provision on the PCB for limited range current limit adjustment (SVR2 in series with R37) however for the versions i received, they were not installed by the factory, probably as a cost cutting measure. It's also true that their intended component positions lie directly beneath the trimpot i installed as shown in my pictures (although with SVR2's 3 legs installed properly ie. through the PCB rather than jury rigged to the remaining legs of the snipped R33).

Standard S-350-27


The installation of R33 is done to set a fixed current limit, and if doing so, SVR2 in series with R37 are omitted (Its legs are wired in parallel with SVR3+R37). For my particular Sure-electronics batch S-350-27's, R33 has a value of 520ohms as standard. Lower resistance values set a higher current limit, so as i installed a 0-500ohm trimpot across R33, even with it dialed up to the highest resistance, i am slightly exceeding the 350W power limit when the output voltage is >27V. However this is fine as the power electronics have a bit of headroom built in and so can withstand above the conservative factory power rating of 350W.

The value of R33 is likely to be different for the S-350-48, so it is essential to check its default value, and select a replacement trimpot that has a max resistance value that is above the value of the standard fixed value resistor R33, or if your willing to stress the supply a bit more like me choose one that is only slightly under it.

Further theory to understand how current limiting is achieved in these MW PSU's.

R33 forms a voltage divider with the heavy duty shunt resistor jumpers that look to be made of nichrome wire. Depending on voltage specification of the supply, between one and five of these heavy duty shunts will be installed (J1, J2, J3, J4, J5). Lower voltage, higher current units have more of them, whilst higher voltage, lower current units have less of them. The amount of these in parallel will affect the ideal value for R33 when wanting to limit current to the factory rating that caps power output to around 350W. This is why R33 can vary in value between the different voltage specifications, but will likely still hover around the 0-1k range.

In a nutshell, my versions didn't come standard with any current limit trimpot at all.....

Click to expand...

Ah ok, I saw your picture and thought SVR2 WAS in place and you were adding another pot across that!!!

Now i am on the computer and not the iPod, i can zoom in closer and see what you have done, just did not zoom in enough before.




From memory, my S-350-48 R 33 value was 330 ohm. I fitted leads to the board and brought them out the case and fitted a 5 k 16 turn cermet trimmer in parallel with R33. This gives almost full current ( 135% ) at 5 k, down to as low as needed at the other end, the mult turn giving precise adjustment