Benchtop Power Supply for under $100.

[FilterGuy]

I am looking for a low cost Benchtop power supply to charge assembled 12V & 24V LiFePO4 battery banks that have BMS systems installed.
The features I am looking for are:

• Variable Voltage (Up to 30 V)
• Variable Current (10 Amp or more)
• I would like good accuracy (.01V) on the built in volt meter, but I do not plan to push my batteries to 100% charge so I am willing to give this up for price as long as the voltage does not drift.

Note: Since I will be charging batteries that have a BMS already incorporated I do not need a Ballenced Charger like they RC hobbyists use.

I am looking at THIS on amazon (https://smile.amazon.com/Yescom-Precision-Variable-Digital-Adjustable/dp/B00SWK6M0M)
This is obviously a mass produced Chinese knock-off, but sometimes that is good enough. What do others use?

 

[krby]

I posted in the Favorite Tools forum, I have an Eventek 0-30V, 0-10A power supply. If I remember correctly, I picked it because folks smart than me at EEVBlog forums thought it was an ok low end bench power supply.

But, I haven’t thought about usIng it as s charger. I’m not sure how accurate and fast the current clamping is, but it might work. When I first wrote this post I said it wouldn’t, but thinking it thru it a bit, it might work I'll test this on an old lipo this weekend (I'll be safe and baby sit it and keep everything well below limits. I still think is a job best left for s dedicated LFE charger.

Buy the adjustable PSU just to have it. If you only want 300W of charging power, buy a dedicated LFE charger or a lower end R/C charger, at that level you can find ones that plug into AC. Or you can power it from your new adjustable PSU!

 

[electric]

I buy my stuff from this supplier, never been disappointed

Switch-Mode Power Supplies - Circuit Specialists

www.circuitspecialists.com

 

[Supervstech]

If you have a little skill, a pc power supply and a boost converter will do most tasks... under 20.00

 

[April]

99.98US $ |Fine Adjustment 4-digits Lab Power Supply 60v 5a Mini Adjustable Switching Power Supplies Input 110v 220v For Family Factory Use - Switching Power Supply - AliExpress

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$60 30V 10A blow up 5 for the prices you can pay

I have a couple of these and balance charge all the cells in parallel first with them then let the solar controller do its job from there.

33.75US $ 25% OFF|CHUX LRS350 Switching Power Supply DC 3.3V 4.2V 5V 12V 15V 24V 36V 48V LRS 350 5 LRS 350 12 LRS 350 24 LRS 350 36 LRS 350 48|Switching Power Supply| - AliExpress

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[SolarRat]

I use a RC hobby balance charger for my small LiPos that are up to 6 series cells but it can only handle about 4-5 amps. It does great for the smaller packs, but am now looking for something that can handle up to 16 cells series and 50+ volts at higher amps. My benchtop power supply goes up to 300v DC but is not robust enough to handle high amps for long periods so I've been looking at a new PS that I''ll dedicate to just charging.

The 0-30v supplies are easy to find but I need one that goes up to 60v+...most of the low cost 60v stuff is only up to 5 amps, even when turned down to 12 or 24v, so for charging my bigger batteries I'm thinking of using a basic cheap high-amp 60v PS like below and feeding it into either a cheap solar charge controller's PV input, or a DC-DC charger. The 600w version should be able to charge a 12/24v battery at near 50/25 amps, or double that for the 1200w version. The CC or DC-DC charger can then handle the charging parameters instead of relying on a monitor-to-cut-off relay (which would be wise with just a PS) to terminate the charge.

Robot Check

I'd hook the above to a cheap 20-60amp max PWM or MPPT that has user configurable output settings.

I also thought about just using one of my computer power supplies and feeding a boost charger like this, but I'd be limited to 10 amps with this one:

Amazon.com : Fuhuihe MPT-7210A Charge Controller Battery Solar Panel MPPT with LCD Display for 24/36/48/60/72 V Battery : Garden & Outdoor

Amazon.com : Fuhuihe MPT-7210A Charge Controller Battery Solar Panel MPPT with LCD Display for 24/36/48/60/72 V Battery : Garden & Outdoor

www.amazon.com

None of these solutions are ideal, but I figure within a few years actual lithium chargers with adjustable output will be much more common, and much cheaper. I really love the little $20 1-6 cell hobby balance chargers, I just wish they'd make them bigger for a reasonable price, and I bet they will soon. That would also shake up the BMS world.

 

[FilterGuy]

99.98US $ |Fine Adjustment 4-digits Lab Power Supply 60v 5a Mini Adjustable Switching Power Supplies Input 110v 220v For Family Factory Use - Switching Power Supply - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

$60 30V 10A blow up 5 for the prices you can pay

I have a couple of these and balance charge all the cells in parallel first with them then let the solar controller do its job from there.

33.75US $ 25% OFF|CHUX LRS350 Switching Power Supply DC 3.3V 4.2V 5V 12V 15V 24V 36V 48V LRS 350 5 LRS 350 12 LRS 350 24 LRS 350 36 LRS 350 48|Switching Power Supply| - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

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Tell me more!
> I have a couple of these and balance charge all the cells in parallel first with them
Two questions:
1) What voltage supply do you have (The link had several options)?
2) Do you have any kind of controller between the power supply and the battery?

>then let the solar controller do its job from there.
Is the solar controller actually on solar panels or are you driving it with a power supply?

 

[FilterGuy]

The 0-30v supplies are easy to find but I need one that goes up to 60v+...most of the low cost 60v stuff is only up to 5 amps, even when turned down to 12 or 24v, so for charging my bigger batteries I'm thinking of using a basic cheap high-amp 60v PS like below and feeding it into either a cheap solar charge controller's PV input, or a DC-DC charger. The 600w version should be able to charge a 12/24v battery at near 50/25 amps, or double that for the 1200w version. The CC or DC-DC charger can then handle the charging parameters instead of relying on a monitor-to-cut-off relay (which would be wise with just a PS) to terminate the charge.

This is along the lines of what I am considering as well. Has anyone else tried this? Did it work?

Like you I am charging a bank of cells (not individual cells) and the bank already has a BMS. Using one of the RC Balanced Charge controllers would be awkward at best.

I also thought about just using one of my computer power supplies and feeding a boost charger like this, but I'd be limited to 10 amps with this one:

Amazon.com : Fuhuihe MPT-7210A Charge Controller Battery Solar Panel MPPT with LCD Display for 24/36/48/60/72 V Battery : Garden & Outdoor

Amazon.com : Fuhuihe MPT-7210A Charge Controller Battery Solar Panel MPPT with LCD Display for 24/36/48/60/72 V Battery : Garden & Outdoor

www.amazon.com

I looked over the description of that boost charger and it looks like the output voltage is a single setting. No 'charge profiles'. Is that the way you read it? Would that be a problem?

 

[krby]

In my (limited) experience, a higher powered LFE charger is less likely to be adjustable. I assume it's a reaction to market demand. Most folks want to charge the bank they have, which is at a specific voltage. R/C chargers (even non balancing ones) are different because most R/C folks have many battery packs in a variety of voltages. Even solar charge controllers and inverter/chargers are usually built around a single voltage "range" (like 12V, 24V, 48V, etc)

The problem (I think) is that high power devices are more expensive and heavier than lower power devices. a 2000W charger will be bigger and more expensive than 500W one. Separately, adjustability adds to the cost, either it's a simple adjustable bench top power supply, or it's got a notion of charge profiles (like an R/C charger) in which case you need a more complex user interface and a more capable microcontroller in the charger.

When I was shopping for bench top variable supplies, I discovered really quickly that even 0-10A was less common than 0-5A or 0-3A supplies. Apparently the primary market for these things doesn't often want more than 5A at 30V or 60V. They get very expensive quickly, and then the quality units end up having REALLY good regulation because the primary marker for these wants a really stable supply. But we're just looking for a CC/CV battery charger.

 

[SolarRat]

Like you I am charging a bank of cells (not individual cells) and the bank already has a BMS. Using one of the RC Balanced Charge controllers would be awkward at best.

You don't have to use the balance function. My SkyRC B6 clone has a non-balance mode also which I'm using on packs that don't have a balance cable, works great. But add a 20 cent balance cable and a BMS for each battery becomes unnecessary (for some applications anyway). Also, just because you have a BMS doesn't mean you can just feed it any charge profile willy-nilly...a BMS should be a failsafe, not a charge controller.

I looked over the description of that boost charger and it looks like the output voltage is a single setting. No 'charge profiles'. Is that the way you read it? Would that be a problem?

That's pretty much how I read it too, but that is what I'm looking for, set a desired voltage and let it terminate there. I just want it to constant current bulk charge up to a set voltage and then shut off. I don't want or need the extra 5-10% capacity of a "top-off" CV absorb stage, although I think it has that too. I may just order one and find out. I have a million 12v power supplies and battery chargers I could run this thing on, so it won't cost much to try. If it doesn't work for this purpose it would be nice to have a boost converter laying around for other projects anyway (like charging a 48v golf cart with a single PV panel).

Looks like the best deal on it here:

42.49US $ 30% OFF|7210a Solar Panel Charge Controller Aluminum Alloy Lcd Display Mppt Adjustable Solar Lithium Battery Pack Charger Regulator - Solar Controllers - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

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EDIT: What the hell, just ordered one. Will let ya know how it works in a couple weeks.

 

[FilterGuy]

You don't have to use the balance function. My SkyRC B6 clone has a non-balance mode also which I'm using on packs that don't have a balance cable, works great.

That is good to know. However, it does not look like the SkyRC B6 will charge a 24v (8s) bank of cells. Do you know of one that will?

But add a 20 cent balance cable and a BMS for each battery becomes unnecessary (for some applications anyway).

I will end up deploying the battery bank in an off-grid system so I will be building the BMS into the battery. Consequently, I want to be testing it with the BMS.

I just want it to constant current bulk charge up to a set voltage and then shut off. I don't want or need the extra 5-10% capacity of a "top-off" CV absorb stage, although I think it has that too.

That is pretty much what I want to.....and that brings me back to my original thinking. The power supply I listed (https://smile.amazon.com/Yescom-Precision-Variable-Digital-Adjustable/dp/B00SWK6M0M) seems to have a constant current control. It also has a Voltage control. If you can set both max current and max voltage, it might do most of "constant current bulk charge up to a set voltage and then shut off. "

1. At the beginning, the battery would not be at the max voltage and and the PS would supply as much current as it could up to the max current setting. (I would probably set it at around .5 C).
2. The voltage would eventually rise to the max voltage and the supply would reduce current to keep from going over the max voltage.
   (I would probably set it to something around 3.3v or 3.4v per cell)
3. What the power supply doesn't do is that last 'little' step of "and then shut off". So what happens if the power supply holds the voltage at a voltage that is a little less than the max voltage for the pack of batteries? It seems that if the battery and supply voltage are equal, no current would flow. Does this hurt the battery somehow? A lot of times the recommendation on setting the charge controllers 'float' to a little less than the max charge voltage because the controller requires *something* to be set..... isn't this the same thing?

Note: I am guessing at how the power supply works and what it does when it can't do both max voltage and max current. I would verify my assumptions before I tried to use it this way.

Note2: Everyone has been pretty firm about needing the correct charge profile, but I am unclear what 'correct' really means. Best I can tell, the Constant Current part of the profile just means "Don't exceed the Charging C Rate for your battery) and the Constant Voltage part of the profile just means don't exceed the max charge voltage for your battery. The 'and then shut off' part of the profile is the part that is not always discussed and I am not understanding the need for. (Since people are firm about needing the shut off, I will do it..... I just wish I understood the reasoning better)

 

[krby]

That is good to know. However, it does not look like the SkyRC B6 will charge a 24v (8s) bank of cells. Do you know of one that will?

Any 6S LiPo Charger will go to 25.3V, some a little higher. But there are several 8S chargers available, all those would have cover at least up to 33.6V
A few:

• Revolectrix PowerLab 8, FMA GT8
• ISDT T8 (1000W for $100!)
• iCharger X8, 208B, 3010B <--- This is last one is 10S lipo or 12S LFE

Or this!!!
Charge ANY battery from 24-63VDC

 

[krby]

Note: I am guessing at how the power supply works and what it does when it can't do both max voltage and max current. I would verify my assumptions before I tried to use it this way.

I have a 0-30V 0-10A variable supply and I tried charging a 3S 4Ah LiPo last weekend, because of this thread. It absolutely works as you expect. Here is what I did:

• Setup
  • Set current limit to 4A (4Ah battery, charging at 1C
  • Set voltage limit at 12.6V (4.2V max per cell for LiPo x 3S)
  • Hooked up a LiPo checker to the LiPo that showed me all the cell voltages. They were about 3.8V per cell, for a total of 11.55V
• Charging
  • Connected power supply to the LiPo. I regular banana to XT60 R/C Charge lead works perfectly
  • The power supply immediately switch the C.C led on and the C.V. off. The voltage readout immediately changed to 11.5V, the current readout stayed at 3.0A.
  • <Waited a few minutes>
  • The LiPo checker showed the cell voltages increasing, the PS voltage was slowly rising.
  • <Waited more, did other stuff on the bench.>
  • Eventually I heard a click and the PS had switched indicators back to C.V being on.
  • Current readout on the PS started dropping from 3.0A, while the voltage remained at 12.6V
  • I waited until the current dropped to 1.0A and then decided the experiment was over. This wasn't fully charged, but close enough for my test.

Here's the one problem, the PS won't turn off, I would have to do that manually. That's the bit I think is required for LiPO and LFE batteries.

 

[FilterGuy]

Thanks krby!! That is what I expected. Thanks for verifying!

Here's the one problem, the PS won't turn off, I would have to do that manually. That's the bit I think is required for LiPO and LFE batteries.

And that is the bit I am unsure of. When do you know the Constant voltage part of the cycle is done? By current going to some level? By time? I would think that eventually the battery would be fully charged and quit taking charge....and you can just let it sit at that voltage..... but I don't know.

 

[Maast]

I am looking for a low cost Benchtop power supply to charge assembled 12V & 24V LiFePO4 battery banks that have BMS systems installed.
The features I am looking for are:

• Variable Voltage (Up to 30 V)
• Variable Current (10 Amp or more)
• I would like good accuracy (.01V) on the built in volt meter, but I do not plan to push my batteries to 100% charge so I am willing to give this up for price as long as the voltage does not drift.

Note: Since I will be charging batteries that have a BMS already incorporated I do not need a Ballenced Charger like they RC hobbyists use.

I am looking at THIS on amazon (https://smile.amazon.com/Yescom-Precision-Variable-Digital-Adjustable/dp/B00SWK6M0M)
This is obviously a mass produced Chinese knock-off, but sometimes that is good enough. What do others use?

I had one of those and it died within a few weeks. Ended up getting one of these but it breaks your budget

Robot Check

 

[krby]

And that is the bit I am unsure of. When do you know the Constant voltage part of the cycle is done? By current going to some level? By time? I would think that eventually the battery would be fully charged and quit taking charge....and you can just let it sit at that voltage..... but I don't know.

I know a bit about this from the LiPo charging for R/C world. Every R/C LiPO charger I'm aware of does this:
- The terminal voltage (the end of the CV phases) is a bit above 4.2V per cell, something like 4.205V
- The CC stage ends somewhere between C/5 and C/20, depending on the charger, and some chargers let you set this yourself. To put this in English. If max charge current is 5A, C/5 = 1A, C/10 = 0.5A, and C/20 = 0.25A. So the CV stage ends with the charger senses that the current drops to that limit.

Generally, a C/20 setting is considered "more accurate" while C/10 or C/5 is considered more of a "fast" charge, because they'll end faster (and put less energy in the battery)

Your point about the current eventually dropping to 0 should be true, but I believe the battery needs to rest, and not be floated at that level for long periods of time.

 

[FilterGuy]

Interesting.

I found this in the manual for the Cycle Satiator charger.
https://www.ebikes.ca/documents/Satiator_Manual_V1.0FW.pdf

With batteries that have a constant voltage end of charge mode, it is possible for small currents to continue flowing into the battery when the output says complete. CHARGE COMPLETE does not mean that the output is disabled, just that the full voltage has been reached and the charge current has decayed below the charge complete amperage threshold specified for the profile.

So this is saying 'charge complete' is based on reaching some low charge current, but the they do not turn off the voltage.

 

[Maast]

I do tons and tons of LFP battery charging with power supplies stacked in various configurations and I'm a big fan of the Meanwell current limited power supplies (HRP and PSP line among others), if I need more voltage I stack them in series, if I need more amperage I parallel them. They hold the voltage settings REALLY well and I've never cooked one, even the used ones I've got off of ebay.

Since each one has a 10-15% voltage adjustment range it give a really wide range of voltages available. For example the 22A PSP-600s I posted earlier in the week go from 24-30V so when I series them that gives me a range of 48-60V at 22A, or if parallel 24-30v at 44 amps (which is what I'm using them for. If I stacked 3 in series it'd give me 72-90v. Etc

If I want to reduce amperage I just use a smaller power supply.

 

[Mars]

I have one of these

30 Volt Adjustable Switch Mode DC Power Supply, 5 Amps

www.circuitspecialists.com

It works well for charging all kinds of batteries, except large flooded lead acid batteries.
The built in volt meter is not very accurate but I just use a separate multi-meter to set the voltage.

 

[SolarRat]

That is good to know. However, it does not look like the SkyRC B6 will charge a 24v (8s) bank of cells. Do you know of one that will?

If I did know of one, at a good price, I wouldn't be cobbling one together with power supplies and charge controllers! I think someone will come out with a beefed up RC type charger soon...heck, I may even try and reverse engineer one that can handle 20+amps and at least 16s capability.

I don't see anything currently on the market that will be as versatile as I want. If you just need one of a particular voltage, that would be pretty easy.... But making it variable V and I is the tricky (expensive?) part.

In the meantime I think that 7210a device may be the easiest/cheapest solution for me. I'll know soon enough.