PSU vs charger

[jai134]

I wonder if there is any benefits from using a PSU, a MeanWell or similar compared to an "ordinary" charger like this one: 20S - 72V (84V) 12amp Lithium Battery Charger ?
Two MeanWell, I'm building a 20S li-ion pack, costs about 400$ together, the one I linked to costs 150£.
According to this thread, #8: chargery spam consolidated from discussion threads Chalo states that a PSU is better.

 

[glennb]

I think it boils down to mean time to failure, failure mode, and EMI. Efficiency’s barely significant with the quantity of power most people use.

I’m biased toward anything with a data sheet, and against anything encased in plastic, but that’s not valid reasoning, purely bias.

 

[jai134]

Ok! A high quality PSU is better than a good charger but a good charger isn't a bad choice, then?

 

[glennb]

Sure. PSUs more come into play for high current.

A 2A charger can be built out of any old junk, and typically is. High current necessitates better design and components, and a high current charger from a reputable manufacturer ought to be alright.

If you’re dubious, and/or want to maximise longevity, it’s best to operate it well away from the edge if it’s ratings e.g. if it’s rated 10A, run it at 5A.

 

[amberwolf]

I wonder if there is any benefits from using a PSU, a MeanWell or similar compared to an "ordinary" charger like this one: 20S - 72V (84V) 12amp Lithium Battery Charger ?
Two MeanWell, I'm building a 20S li-ion pack, costs about 400$ together, the one I linked to costs 150£.
According to this thread, #8: chargery spam consolidated from discussion threads Chalo states that a PSU is better.

The "only" difference between the two (assuming it's a CC/CV PSU, like an LED PSU or Lab(oratory) PSU)**** is that a charger is designed to turn off when current drops below some preset limit.

A PSU will "never" turn off completely. (you can change this by buying a board that will cut off the output or the input when a certain time has passed, or when current drops below a certain point, or voltage above a certain point).

****If it's a typical PSU like laptop power brick, computer PSU, or other fixed-current/voltage-output PSU etc., it's probably hiccup-mode current limiting, and is not useful as a charger.


As far as which is better, it depends on your specific usage case.

For instance, on my SB Cruiser trike, my "charger" is bolted to the bottom of the trike, where it gets shaken and vibrated quite intensely, heated to >130-140F by the hot asphalt roads, chilled <freezing a couple nights a year, submerged in flash flood waters every so often, etc. So rather than a typical charger that would probably have failed and been replaced several times by now, I use a Meanwell HLG-600H-54A, because it's solidly potted.

But because it never turns off, I try to make sure not to leave it charging longer than the actual charge time; manually turning the system off when it's full.

If you're not carrying the charger around, and it's in a clean cool environment, you can use a typical charger, and just monitor the fan so that when it starts making noise as it ages you can replace the fan (or the charger) before it fails and causes overheating.

Cheap stuff is usually made cheaply, so...don't buy cheap "junk" and it will work well enough, whichever way you go.

PSUs that are well-made, like the Meanwells (not necessarily any of their clones), Sorensons, etc., are likely to last for a long time (years, at least), so people using these well-made PSUs as chargers are likely to recommend them over the typical cheap charger.

A good well-made charger will be just as good as the well-made PSU, as far as that goes. I've never had a good well-made ebike battery charger, so I can't provide any brand names like I can for the PSUs. The best one so far was made by Modary, but I'm not sure it's really any better than Kingpan, etc.

 

[amberwolf]

If you’re dubious, and/or want to maximise longevity, it’s best to operate it well away from the edge if it’s ratings e.g. if it’s rated 10A, run it at 5A.

Unless the charger has a current-adjustment intended for the user to set, there's no way to do that. It will run at the max current it can until the battery charges to a high enough voltage to not draw that much.

If it's a lab(oratory) PSU with adjustable current (and voltage, usually), then it can be turned down.

 

[glennb]

Yes, that’s the expectation, the ability to reduce the preset current limit. Unless it’s complete junk with only an internal fuse, it has to have one, and it will be able to be adjusted, whether or not it’s “intended for the user to set”. The effort required mightn’t be worthwhile though, definitely simpler to stick with designs with embedded trimpots.

 

[amberwolf]

There are *some* that do have adjustments...but not all, regardless of quality. Depends on the designer's intent, and whether they built a self-regulating system with preprogrammed limits using an MCU or SMPS managment chip, or whether they went old-school analog all the way with the SMPS limiting / feedback parts. The analog stuff often *has* to have some sort of adjustment, but this could be a simple precision resistor choice rather than a pot. The MCU or SMPS MC designs use internal software to do this stuff, and don't need the external adjustments, so they dont' often have them. (if you had access to the factory programmer and software, you could change these limits yourself, but that's not generally available).

Many of the chargers I've seen the internals of, even decent ones, don't have an adjustment for anything in them other than sometimes the top voltage limit (not always even that).

Many of the Kingpan chargers of years past have had voltage adjustments, some have had current limit adjustments, but there is usually a fairly narrow range that these can effectively change. Sometimes the pots have more physical adjustment than you can use, because the device malfunctions when they're adjusted outside some narrow part of that range. There are some threads about various Kingpan chargers; there are a lot of clones of these, but not all of the clones include the adjusting bits (or even all the protections).

Most plain PSUs don't have any adjustments at all--the SMPS chips in them are designed for a specific voltage (or set of them) and specific overcurrent shutdown, and they regulate to those, shutting down if they go beyond the limits and can't regulate back.

For those without adjustments a user could hack one in for many designs, and it's been done...but that's not something most users are capable of or willing to do (even with help or instructions, and reverse engineering the charger or PSU to figure out how to do it...well, almost no one can or will).

 

[jai134]

That was a lot of useful information. Thank You!
I charge my bike at home in the barn. I don't have the space for an onboard charger so I have a portable one. It works great but it is for my 48V pack.

 

[batteryGOLD]

PSU is not a Charger! but in some cases could work as a charger.. but make sure U know what U'r doin..
PSU is a power supply unit, constant Volts
Charger is current supply, constant Amperes

Soo when chargin a battery, remember to limit those Amps.. so better ideia to use a charger..
a 42V/10A charger limits amps to match battery voltage, constant 10A and voltage goes from 27V to 42V @ max10A rate

if U'r lucky U have a PSU with current limiter mechanism.
once reach max amps, it switches from CV to CC, but this is a smart PSU.. (switched auto to charger mode..)
if U use a 10A 42V PSU to charge a 42V/36V battery max 10A rate,
maybe U could use a series 10A fuse @ charge line, just in case..

 

[jai134]

I ordered a charger from China. I neither can afford two high quality PSU's nor a high quality charger at the moment but I have battery cells for a bigger pack, infact two bigger packs so this will do for now. My dream is two MeanWell in series mounted onboard my bike but that'll have to wait until I convert my Triumph Daytona. There's not enough room on my Husqvarna SM610.