Downsides to using a meanwell type power supply instead of benchtop psu?

[Dzl]

Lately I've been pondering the merits of using a simple current limited power supply like the Meanwell HRPG (or RSP or HRP) for top balancing or capacity testing. But I'm not knowledgeable enough about this type of thing to feel confident in my ability to judge its suitability.

Far and away the biggest upside that makes this worth considering is high current at a reasonably low cost and a reputable brand. Voltage is configurable from 2.8-3.8 Volts, and current is configurable from 0 to the nominal current, and the HRPG series has some useful features like remote voltage sensing, and remote on/off. For under ~$150 you can get a 120A power supply, for under ~$100 you can get a 60A power supply, cheaper if you go with the HRP series or an off-brand. Compare this to the little $40-100 chinese 5 and 10 amp benchtop power supplies that are common.

I'm curious what downsides there might be to this approach that I'm not considering.
Are these a suitable tool for a top balance?

@Maast @gnubie @smoothJoey @DJSmiley @HaldorEE @JeepHammer I feel some of you may have some good insight on this topic.

 

[Maast]

Only two downsides: No way to limit current other than getting a smaller power supply, some models don't have backfeed protection and you can cook the output mosfets in a second. Of course the models have to be current limiting like the ones you've mentioned.
The upside is that you can get a whole lot of amperage fairly cheaply at a very precise voltage.

 

[Dzl]

Only two downsides: No way to limit current other than getting a smaller power supply, some models don't have backfeed protection and you can cook the output mosfets in a second. Of course the models have to be current limiting like the ones you've mentioned.
The upside is that you can get a whole lot of amperage fairly cheaply at a very precise voltage.

So if I'm understanding correctly, both issues could be avoided with the proper model of power supply?
(1) no way to limit current, could be solved by getting one of the current limiting models/families? On the datasheet I see for the 120A model it shows 0-120A under "current range" I interpreted this as the ability to limit current.
(2) backfeed protection could also be avoided with the right model? Is there a line on the datasheets that indicates this or a term to look for?

Another thing I was wondering about is precision/resolution. I'm not totally sure how to read/interpret the datasheets, I see for voltage tolerance 2% and for line and load regulation 0.5% and 1% respectively, and for ripple and noise 100mVp-p. I don't know how to interpret any of that but I'm hoping you might.

 

[John Frum]

I looked into the HRPG
I don't think its current is configurable.
It has voltage sense leads which will be handy to allow it to compensate for voltage drop.
It also has pins for external control.
From memory the external control pins are shorted to terminate the charge.
So with a suitable voltage sensitive relay that allows to automatically terminate the charge on voltage at the cell terminals I think it would make a good way to top balance cells.
I'm reasonably confident that it can adjust its voltage low enough to maintain constant current for a battery that is discharged to 2.5 volts.
For 280 amp hour cells in parralel using the 450 watt version it would be...
280ah * 8 cells / 90 amps * .5 SOC = ~12.4 hours
For a single cell it would be ~1.5 hours although the rubber band effect will be more pronounced.

In another thread I was looking at using a battery pack with bms and an SSR + meanwell psu on a single cell within the pack to top balance.

First things last...
I believe charging individual cells with a charge voltage of ~3.66 volts at ~.2c until the cells reach ~3.65 volts is all that is required to prepare cells "close enough" for usage in a serial pack.
I think its more important to get the cells deterministically to the same point on the high knee than it is is to get them all perfectly full.
Further to this I believe that the cells diverge less and converge better if the pack will not be drawn down too far and/or too fast.

tl;dr
Voltage is a pretty good indicator of state of charge at the very top(3.65 volts) and the very bottom(2.5 volts).

 

[DJSmiley]

The RSP versions are not suitable for charging. An empty LiFePO4 takes whatever current is available. Thus maxing out any powersupply: Hence the need for CC, (Constant Current)

A normal powersupply, or a very basic one with a fuse, will stop working, or blow its output fuse, since the load is trying to pull more than it can.
In the datasheet of the RSP series: Overload: Protection type : Hiccup mode, recovers automatically after fault condition is removed
So if an empty cell is connected, which can draw more than the rated ams of the power supply, it just will shut down.

For the HRPG, its different: It will go into CC mode, providing its max amps continuously (Thus charging) and once the cell becomes full, the current will drop and the power supply will end at it's set voltage (Thus changing into CV). That's exactly what you want to archieve, and is also explained in many video's regarding top balancing with a regulated power supply.
From the datasheet: Overload: Protection type : Constant current limiting

For the HRPG, current is not adjustable. There is only 1 small potentiometer so you can adjust the voltage. (within it's adjustable range)

I think there is 0-120A in the datasheet meaning the power supply is capable of powering small loads. If you look eg at some switched power supplies used for halogen lighting, those can have issues when switching to LED, since they require a minimum current draw to work properly, which isn't met with a few LED lights.
These don't have that issue.

The voltage sense leads are a bonus, since, especially at 120A, there will be voltage drop due to wire and connectors. With this, you can compensate for that. But for top balancing, it's not nessecary. If you set the voltage to 3.6V or so, once it's finished you can check directly on the cells, and increase the powersupply to 3.65V or even slightly higher, while checking the cells voltage. The last part doesn't take long so it's highly recommend to continously check that anyway.

However, is 120A what you need? Yes, its nice, but using it also requires thick wires, or multiple wires in parallel. These are harder to handle...

You can also get the less powerfull versions of eg 60A. Also, the HRP will work as just as fine as the HRPG, the only differences if I see it correctly is that the HRPG provides an additional 5V / 0.3A standby output and the higher versions (600W+) allow load sharing, so you can set multiple in parallel to increase the current even more.

Personally, I think 60A is great. 120A is overkill, unless you're going to do it daily, or have a very large bank. With 4 cells in parallel, you have 1120Ah to charge, would take 18 hours if they were completely empty in worst case. Still acceptable imho.

120A would half that, but higher currents are more sensitive to bad cabling/connectors (heat up pretty quickly) and handling thick wires is a pita.
60A is, imho, the nice workable current between fast, and massive thick annoying wires

 

[ArthurEld]

I have the 120A HRP. The only time I used 120A was for charging 3 batteries at once. I connected the leads direct from the power supply (there are 3 connections). It split the amps evenly between the batteries so each one got 40A. I connected it to batteries with different #s of cells and more amps went to the battery with more cells.
It is easy to control the amps with CV. Just use an amp meter and adjust the voltage until the amps are what you want. It takes a long time for the amps to drop and they go down so not much to worry about.
I have never let this power supply go to the end of the constant voltage mode and I am fairly sure it will over charge if left unattended. You'd have to leave it unattended for hours after the battery reaches target voltage for it to overcharge. I've never let it go until it turned off so I don't know how much it will over charge. I do know that when I did let it go for a while, the battery was higher volts than the power supply was set to.
I saw the 60A HRP for $69 recently.
If you want to charge with less amps, charging serial with 10A is faster for 48V. 120A x 3.65V = 438W 10A X 48V = 480W
The Riden 12A power supply does stop when it reaches target voltage and works for 0V - 60V so I use it much more than the Mean Well.

 

[Maast]

Actually the RSP power supplies are current limiting too. They're the least expensive current limiting power supplies by meanwell.

Current limiting means the power supply will reduce its output to prevent itself over-amping and melting something. It does this by reducing the output voltage until the supply is at its designed amp output.
This is the "constant current" portion of the charge cycle.

As soon as the battery voltage has raised enough to not pull too much amperage from the power supply it starts raising the voltage to the limit you have set.
This is the "constant voltage" portion of the charge cycle. Bit of a misnomer though because the voltage is actually increasing as the battery rises and fairly quickly will then output at your set voltage.

Look again at the RSP datasheet

 

[Maast]

I have the 120A HRP. The only time I used 120A was for charging 3 batteries at once. I connected the leads direct from the power supply (there are 3 connections). It split the amps evenly between the batteries so each one got 40A. I connected it to batteries with different #s of cells and more amps went to the battery with more cells.
It is easy to control the amps with CV. Just use an amp meter and adjust the voltage until the amps are what you want. It takes a long time for the amps to drop and they go down so not much to worry about.
I have never let this power supply go to the end of the constant voltage mode and I am fairly sure it will over charge if left unattended. You'd have to leave it unattended for hours after the battery reaches target voltage for it to overcharge. I've never let it go until it turned off so I don't know how much it will over charge. I do know that when I did let it go for a while, the battery was higher volts than the power supply was set to.
I saw the 60A HRP for $69 recently.
If you want to charge with less amps, charging serial with 10A is faster for 48V. 120A x 3.65V = 438W 10A X 48V = 480W
The Riden 12A power supply does stop when it reaches target voltage and works for 0V - 60V so I use it much more than the Mean Well.

I've used a HRP the exact same way, but I always let it raise all the way to the set voltage (3.65V) and it never overcharges. Used this way hundreds of times when it was charging cells in my DIY loop cycle tester for the 280AH cells.

 

[newbostonconst]

Meanwell supplies are constant current usually for LED's.... The supply will up the voltage to high levels to keep the current flowing...
Thus once a cell is charge and not taking current the voltage is going to go through the roof and fry the cell.

That is my short winded explanation and sorry I didn't read the long winded ones above.

 

[Maast]

Meanwell supplies are constant current usually for LED's.... The supply will up the voltage to high levels to keep the current flowing...
Thus once a cell is charge and not taking current the voltage is going to go through the roof and fry the cell.

That is my short winded explanation and sorry I didn't read the long winded ones above.

Er no. Maybe their cheapie LED drivers might but their real power supplies do not. They have excellent voltage regulation. I've used them for years to charge battery packs and cells. Right now on my bench I have a PSP-600-27, a HRP, a HRPG, a LRS (not current limiting) and 8 RSP-100s. I've got a stack of others on the shelf.

 

[ArthurEld]

I am perfectly capable of making my Mean Well HRP 120A do what I need. But it does some odd things so I can't recommend it.
I didn't destroy any cells but I can see how others might.
I can recommend the Riden because it did everything well and nothing unexpected.

 

[Dzl]

The RSP versions are not suitable for charging. An empty LiFePO4 takes whatever current is available. Thus maxing out any powersupply: Hence the need for CC, (Constant Current)

Actually the RSP power supplies are current limiting too. They're the least expensive current limiting power supplies by meanwell.

Actually I think you are both part right. I previously thought the RSP line was current limiting (because that is what I saw on the datasheet for the RSP-750-27 which I was looking at for other reasons). But then, after DJSmiley stated it wasn't current limiting I took a look at a datasheet for a smaller lower voltage version (RSP-320-3.3) which does state the "hiccup mode" protection that DJSmiley mentioned. I assumed maybe the low power variants were not constant current limiting. But now it looks like the even smaller ones like the RSP-100-3.3 that Maast mentioned are current limiting. Weird.

 

[BiduleOhm]

Another thing I was wondering about is precision/resolution. I'm not totally sure how to read/interpret the datasheets, I see for voltage tolerance 2% and for line and load regulation 0.5% and 1% respectively, and for ripple and noise 100mVp-p. I don't know how to interpret any of that but I'm hoping you might.

Voltage tolerance is just that: real voltage can differ from nominal spec by X % (2 % in your example).

Line regulation is how much the output will change given the specified input change (or over the whole input range if not specified). Unless you have a really unstable mains supply (from a bad generator for example) you can just ignore it

Ripple and noise is the amplitude of the AC component superimposed on the DC output, often expressed in Vrms (RMS) or Vp-p (peak to peak), the later being prefered for the user as more informative (you can have a low RMS value but a pretty high p-p value for a given PSU) but some manufacturers only give the Vrms because it's more flattering for them.

Unless you have super high ripple (which you'll not with MeanWell PSUs) it doesn't matter for charging batteries so you can ignore it.

NB: in datasheets every tolerance/drift/error/... is cumulative unless stated otherwise (for example the 2 % voltage tolerance doesn't include the 0.5 % line regulation, so in this case the total error can be as high as 2.5 %).

 

[ArthurEld]

The problem I was having with the Mean Well was at the end of CV mode when it was supposed to turn off.
It kept stopping the charging then it would pump out 10 or 15amps for a second then stop charging again.
Even though the voltage was still at 3.65, this pulsing of amps caused the volts at the battery to go higher.
The Mean Well makes clinking noises and the light goes on and off during this pulsing.
I stopped it after about 10 minutes so I don't know for sure what it would have done if I left it going.

Another time, I had it connected to 3 batteries and I let it get to the end of CV mode when I wasn't watching. I come out and a 100amp fuse was blown and the power supply was off. I don't know what the heck happened. The amps were spread between the batteries when I was watching it.
None were getting more then 10amps the last time I looked at it and they should have been going down.

Maybe my unit is defective or maybe I'm doing something wrong but this topic is about downsides and for me those are downsides.

People have said that you can't leave power supplies unattended and I don't with the Mean Well.

But the Riden does it's thing like it's made for charging batteries. The absorb seems about right to me for a top balance.
And I am comfortable leaving the Riden unattended.

 

[BiduleOhm]

MeanWell PSUs are pretty reliable, they're not TDK-Lambda of course but they're still high quality.

What you describe first makes me think to a thermal shutdown, but what you describe next doesn't make much sense and makes me think your unit is defective, but I can't be sure of course.

Also MeanWell PSUs are not lab supplies who are made to operate with lots of very differents loads, made to operate in CV/CC all day long, etc... So unless your MeanWell PSU is explicitly a current limited one (usually made to power LEDs), then the current limit safety is a safety only and not made to be used as a CC supply.

 

[ArthurEld]

I have read elsewhere that these cells do something strange when they get to the target voltage that causes the power supply to keep charging.
As SmoothJoey said, it is possible to turn it off with a relay. And some people feed the power through their inverter so the inverter can control everything.

 

[Dzl]

Arthur, what specific model do you have?

 

[ArthurEld]

HRP 3.3V 120A
The 60A is a better choice in my opinion.

 

[Maast]

HRP 3.3V 120A
The 60A is a better choice in my opinion.

I agree, if you need more current you can parallel them and the HRPs are designed for current sharing.

 

[John Frum]

I agree, if you need more current you can parallel them and the HRPs are designed for current sharing.

Is a blocking diode necessary to prevent backflow with the hrpg after charge termination?