Switch mode supply mod

[AussieJester]

How about with the current limit set to 100% and a pot for voltage adjustment? Seems like a unit with those features would be worth a small premium.

They already do have a 'pot' for voltage adjustment, they have -+10% their rated voltage.

I think Gary must series his 24 volt supplies up to charge 66v packs at 70 odd volts and high
amps?

KiM

[MitchJi]

Hi Kim,

I think Gary must series his 24 volt supplies up to charge 66v packs at 70 odd volts and high
amps?

Thanks! Are they isolated so this is easy?

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.

How about with the current limit set to 100% and a pot for voltage adjustment? Seems like a unit with those features would be worth a small premium.

They already do have a 'pot' for voltage adjustment, they have -+10% their rated voltage.

I should have specified with a greater range than +/-10%.

[GGoodrum]

Kim is right, I like to use these in series, as I have different setups. I use a 24s3p Turnigy setup on my full-sized Townie, an 18s2p packs on one folding bike, and a 12s3p setup on the other. They are completely isolated, and each are capable of putting out 14A. What I do is use two, three or four of these in series, but I only did the current limit mod on one of them.

-- Gary

[Hyena]

Behold, my new 400w 5S-14S charger

Its a meanwell s350-48. Zeners are left untouched so it has an upper limit of 58v.
The thermistor has been replaced with a resistor so the fan is on constantly. That should keep things cool.
Current is fixed at around 8 amps at the moment with a shunt mod, I don't really have any need for variable current at this stage.
What I do need is variable voltage, so I removed SVR1 and replaced it with a precision 2k pot. I'm not sure how many turns it is but one complete turn gives me a resolution of about 1.5v so I can quite accurately set it down to 10 millivolts. With the 2k pot alone i was able to turn the voltage down to 31v, but I needed to go lower if I want to charge individual 5 and 6S packs. So I added a switch (the second knob) that adds another 2k resistor in series. This drops the voltage down to a minimum of 20.5v. You could achieve the same with a single 5k pot, but I didnt have one handy and I actually like having a high and low range switch and then the fine tune.

I don't think anyone has had one of these 48v units running voltage this low before so I'll report back if I have any issues.
The only thing I've noticed so far in a quick test is that the fan speed drops when I flick to low voltage mode

[Hyena]

Well, here's another hot tip for those converting their meanwells. Unfortunately it means I now have another one in my parts bin...

Soooo as I mentioned previously I'd modded the shunt to lower the current, it was putting out around 8 amps at 50v, down from about 10.5 out of the box. With the modded svr1 I was able to turn the voltage all the way down to 20v, and it was happy doing this for a few charges but the current was still limited at 8 amps making the charger output at 6S voltage only around 200w. I got a bit impatient with this as I needed to charge up a 6S6P pack so decided to add a few more strands of wire back into the shunt which upped the current to about 11.5 amps. The wattage read 270w which I figured would do so I hooked up the pack and went about my business. A few minutes later there's a pop and a flash and it goes dead. The case is warm but the back is hot enough to burn your hand if left there. The internal fuse is blown and instantly blows any replacements I fit. Shiiiiiit. Exact same symptoms as the other one that blew up straight out of the box. Hyena the destroyer!

So there you have it, if you want a highly adjustable voltage range you can achieve it by modding svr1. If you want high current at lower voltages you're better off buying a 12, 24v model. My S350-24 has been putting out 17 amps on a daily basis for the last 6 months without missing a beat.

[cell_man]

Good info Hyena.

I'm gonna get onto the case with some similar supplies soon. Hoping for fairly high current for single cell chargers. I've seen some pretty high current 5V units so they might just do the trick with a couple of mods as you've outlined.

[AussieJester]

The internal fuse is blown and instantly blows any replacements I fit. .

Soz to hear that mate You going to try one of the newer models this time round or stick with the 350?

My 320 seems to be going fine :: touch wood:: doesn't get at all hot pushes out 8amp for all but the last 1.5v of the charge i guess then drops off to under its rated 6.7amp obviously takes alot longer but no biggy for me...

Also Mr Hyena... how does one series up two of these puppies is it same as connecting batteries in series or is there more to it than that? AND is it ok to connect two different models e.g a 48v and a 24v ?

KiM

[Hyena]

That's probably the normal CC taper off at the end Kim, its just you're using alot of packs in parallel so you see the current drop hanging around for longer. And yeah they're isolated supplies so you can just series them up like you do with batteries. You should only need to adjust the current on one and the other will be limited to the same

I dunno what I'll replace my dead one with, its a 3rd charger anyway - I have one at work set for parallel charging 6S packs and one at home set to 5S voltage - I'll probably just get another 350-24

[MitchJi]

Hi,

AND is it ok to connect two different models e.g a 48v and a 24v ?

And yeah they're isolated supplies so you can just series them up like you do with batteries. You should only need to adjust the current on one and the other will be limited to the same

But a 24v and a 48v have different amperage. If limiting one makes the other match wouldn't you need to limit the current on the higher voltage (48v in this example) supply?

[AussieJester]

wouldn't you need to limit the current on the higher voltage (48v in this example) supply?

Actually the tother way round buddy, the 24v actually has the higher current I was curious about this also..
I have decide when the time comes i will go with 2x36 meanwels as the charging time will be reduced due to the higher current...the 48v models (sp320 meanwel) have 6.7amp output while the 36v output is 8.8amp.. Price wise would be the same as i will purchase off ebay for
thses not local, local 99 dollars each ebay 45 each...in no hurry this time so can do the delivery time wait

KiM

[Hyena]

Yes if combining a 24 and 48v unit then current would be limited by the lower output 48v unit - out of the box it may do 10amps - which would limit the 24v unit to the same (which would have otherwise been probably 15 amps) Ideally you want to turn the 48v unit down to around 7 amps though, which would limit them both to 7a. As aussie jester said though if you're going to do this then 2x 36v supplies is the way to go - set one at 10 amps and away you go.

[wookey]

I just got my 48V charger tweaked to charge a 16S3P pack. Turning the voiltage up to almost max gives 56.7V and setting the current control resistor to 255ohm sets it to 6A (about 330W). I originally set it to 330R and that puts the minimum current limit at 8.3A (~450W). I also found that putting it up to *high* (by fitting a 22K resistor instead of a 220R one - oops!) set it to a bit over 12A or 660W. I guess it wouldn't last long at that rate, but it didn't blow up immediately either. It appears to tail off perfectly to about 0.02A. How long can one leave headway 10Ah LiFePO4s at this rate? Indefinately? I assume it's fine overnight (until I have a BMS to actually cut the current)?

I'm slowly putting the meanwell circuit into geda. I'll post that when it's done.

[Hyena]

Drawing 12 amps they'll last about 2 minutes, which is long enough for the big fets at the back to heat up the case enough to burn your hand. Unfortunately I learned this the hard way. Twice Although it was under 2 different circumstances so I'm not totally stupid

As for leaving it on overnight its probably best not to but I do it every second day and thats with lipo batteries which most would argue are more dangerous than headways. What I do now is put my charger on one of those $5 mechanical timers and set it for 2 hours after I get off, and then to turn back on half an hour before I leave for work in the morning. The reason for that is with the PSU connected to your battery but the power turned off it will actually drain a bit of power back into the PSU. It's not alot but I wouldn't go away for a week and leave the batteries connected to a powered down charger.

[DaveAK]

Still working through this thread, but thought it worth mentioning that I just purchased, (but not yet received), four Mean Well SP-320-48 at $25 a piece. Get 'em while they're hot!

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 0337565662

Now all I need you guys to help me with is setting them up as a 96V charger for a Goodrum/Fechter BMS.

[mwkeefer]

Hyena,

Sorry I've been absent, I would have warned you about turning a 48v down below 33v or so... I have toasted 2 of them doing this and 33v seems the limit for the 48v unit on the low end - I had one I ran at (no BS) 16v but that went up in smoke fast (worked a few hours, I was using it to power my iCharger).

I have on hand 3 of the 24v 320s and one of each of the 350s for experiments + the 48s I use as 5.5A chargers (15S) and about half a dozen other models (mostly S-350 but a few S-145 and so on).

Also, props on the resistor mod for the thermistor - that is probably the simplest mod to get the fan to spin at all times, I have other methods but they are complicated and require an MCU to control them... I like the simple approach.

One note about calibrating the output current, it should be done after:
1.) the resistor mod to get the fan to pop on
2.) the fan lid should be connected
3.) The unit should be run for a moment (not long without heatsinks) but enough that those transistors are hot (not burning but hot) to ensure accurate calibration when unit is in service.

That will ensure trouble free operation - I agree with your observation (I see the same thing) that even without current limiting mods... as long as your not going wildly beyond the shipped range, I have had great success with the 48v units allowing them to run 400-480watts, yea they make noise and sound like bacon in the pan (just a little) but the 48 I have been testing this way has been fine for the last 3 months and I charge about 4-5 packs daily with it (15S2P/1P).

For the price - they are hard to beat, even if 1 in 6 goes bad or is bad on arrival. Where else can you get a 15S 63v 5A charger in a single unit for 25.00? Or for that matter a 20S 10A charger? Exactly.

Regards,
Mike

[amberwolf]

Still working through this thread, but thought it worth mentioning that I just purchased, (but not yet received), four Mean Well SP-320-48 at $25 a piece. Get 'em while they're hot!

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 0337565662

Looks like the vendor (Nationwide Surplus) is here in Phoenix down at 7th Ave & Grand, so anyone local might be able to save the 11 bucks shipping.

[mwkeefer]

Still working through this thread, but thought it worth mentioning that I just purchased, (but not yet received), four Mean Well SP-320-48 at $25 a piece. Get 'em while they're hot!

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 0337565662

Looks like the vendor (Nationwide Surplus) is here in Phoenix down at 7th Ave & Grand, so anyone local might be able to save the 11 bucks shipping.

Hmmm.... who want's to be our Power Supply Smurf? (that one is for you Methy)

-Mike

PS: If you understand what a Smurf is in this context, you will get the joke... I won't elaborate because it would put this thread into the toxic basement.

[amberwolf]

Ah, well, if those things are as big as they look they'd still cost the flat rate shipping for the bigger box, if shipped USPS. No idea if it'd be cheaper for UPS or Fedex, or some other option (if any exist).

Oh, also, it'd add 8.3% of the price as sales tax, locally, which is a bit more than two bucks.

[mwkeefer]

I think you could get 3 of them maybe more into the largest USPS box... roughly with packaging. The flat rate is 14.95 (I think) from USPS... with a bulk domestic express service account from Fedex or UPS, the cost across the country would be about 9.00 USD assuming a weight of 12lbs.

-Mike

[DaveAK]

So what are the chances of being able to parallel the output on the SP-320s? I'd like to take the four I ordered and set them up as a 96V/13A charger. Maybe even get two more and make a 20A charger, although I don't know if I have the space for that.

[mwkeefer]

So what are the chances of being able to parallel the output on the SP-320s? I'd like to take the four I ordered and set them up as a 96V/13A charger. Maybe even get two more and make a 20A charger, although I don't know if I have the space for that.

Dave what core voltage are your SP-320s, if they are 48v... turning then down to 48v each and running series/parallel you end up with 2S2P in supply terms and have about a 13a charger (limit the current circuit, that's covered in the thread). The reason I ask if they are 48s, the 48s have 100v caps in them and would hold up better (imho) over the long run.

-Mike

[DaveAK]

Dave what core voltage are your SP-320s, if they are 48v... turning then down to 48v each and running series/parallel you end up with 2S2P in supply terms and have about a 13a charger (limit the current circuit, that's covered in the thread). The reason I ask if they are 48s, the 48s have 100v caps in them and would hold up better (imho) over the long run.

-Mike

Yup, they're the 48V ones. I'll actually need them slightly under 48V a piece I think, but well within the normal adjustability. (26 cells @ 3.60V per cell giving 93.6V, plus a little extra. OK, so 96V as near as damn it. ) I was thinking 2s2p like you say, but I've heard words of caution that they might not like running in parallel. What's your take on this?

[mwkeefer]

Wired properly the work fine in parallel (I've done it, not to 90+v) - one other caution, all my old units S-350 are stamped on the circuit board with 0-94v which could simply mean that individual possible range points are 0-94v each (don't try it).

You will need to limit the current on 2 of the units so that they only provide approx 6.8A then, you will series each of those modified units to the non-modified units (the lower limit will be the regulating limit)... and you will have your 90+v 13AH charger.

I would also suggest that you look at the posts in this link about Hyena's resistor mod (replace thermistor with resistor) which will keep the fans on all the time (this is good) and I would perform this mod to each of the 4 units prior to calibrating the current on 2 of them.

Sounds like your running LiFePo4 cells which have a max charge above what you spec (not much above) so I will assume it's intentional and correct (26 Series @ 3.60v per cell = 93.6v) for the 93.6v... each unit (S-3X0-48) must be configured for exactly 46.9 (well within their range) ... though I suggest replacing the SVR1 with a 10 turn 1K (check the existing value first) precision so that you can get the voltage as accurate as possible.

Finally... hook up the two modified for 6.8A units in parallel for 46.9v @ 13.6 A Charger. Now hook the remaining two supplies in parallel (Negative to Negative, Positive to Positive) and last, connect the limited and non limited 2P parts into a 2S (Positive to Negative) and you have your charger.

How many AH capacity is your pack and what is the actual chemistry... 13.6A seems alot for LiFePo4 which seem to like 1/4C which means 13A would be best suited to 40-45A LiFePo4 packs and that would be rapid charge.

Hope it helps!

-Mike

PS:

Feel free to PM with questions, I'm happy to help.

[DaveAK]

Thanks Mike. Excellent instructions which are a huge help. My pack will be LiFePO4 60AH cells, and I believe 1/4C charge rate is well within their specs. I got the 3.60V per cell from the latest specs of the Goodrum/Fechter BMS. I must have missed the thermistor to resistor post, but I fully intend to reread this whole thread before attempting the mods!

[Eric]

[quote="mwkeefer"]...all my old units S-350 are stamped on the circuit board with 0-94v which could simply mean that individual possible range points are 0-94v each (don't try it)....

You might want to double check the stamping on the PC Board. 94V-0 is a flammability rating that's stamped on most bare boards.
Eric S.