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Feb 20, 2004, 09:01 PM
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Programmable vs. Non-Programmable Power Supply?

I'm trying to decide between a programmable and a non-programmable variable voltage, variable current power supply. The two uses I know I will be using this power supply for are to charge lithium cells and bench test motors. I imagine there will be other uses that I'll discover along the way.

What I'm puzzled about is what exactly a programmable power supply can do for my purposes that a non-programmable unit can't. For instance, I don't think it's necessary to program anything in simply to charge lithium cells -- just set current and voltage and go. Same with bench testing motors, right?

If anyone can explain some of the potential benefits of a programmable power supply in simple layman's terms, I'd really appreciate getting a quick education. I don't want to pop for a non-programmable unit and find out later I'm missing out on features that would really be useful to me.
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Feb 20, 2004, 11:24 PM
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thazy2's Avatar
I dont exactly remmember it has been a while since i did my reasearch. But I do remember that we dont need that programming stuff for our level of usage.

My first choice was the SPS-1820

then after further research i'd decided on the BK1690. Not as nice as the Instek but this baby has a little more "back" and price friendly too. No amp control but voltage is more important. I think it peaks at 35 or 40 amps. Never really needed anything over 25 amps. I'v the Isl8 and Turbo35 running full load at the same time and the unit didnt hardly get warm.

Last edited by thazy2; Feb 20, 2004 at 11:29 PM.
Feb 21, 2004, 01:23 AM
Castle Tech
Joe Ford's Avatar
thazy2...who makes the BK1690??? NICE lookin power supply...cost? BTW also a NICE Cham!!! I KNOW that set you back a pretty penny.
Feb 21, 2004, 07:32 AM
Registered User
Originally posted by thazy2
... BK1690... No amp control but voltage is more important...
While voltage is critical when charging LiPos, amperage is important, too. Current should not substantially exceed LiPo's C.

A constant-voltage power supply wiil cause C to be substantially exceeded when charging a LiPo that has been discharged below 3.7 volts or so.

A switching power supply (one that starts out charging at set C with voltage set to 4.2 nominal times the no. of cells in series, which then tapers down the current at the set voltage as the battery "fills"), is the way to go.

The Mastech HY 3020 @ about $290 including shipping, has worked fine for me - 30v, 20a, big enough to charge 7s and/or 10p 2000mah LiPos.

- RD
Feb 21, 2004, 07:50 AM
Registered User
To return to Dave's original question, I don't think I would have a use for programming capability - hope someone who does will post.

- RD
Feb 21, 2004, 10:35 AM
Registered User
I've been scouring the internet looking at hundreds of different variable voltage, variable current power supplies in the 10-20A range with digital readouts (meters are not accurate enough for charging lithium cells) for under $300. There aren't many, believe me!

RD, you mentioned one of the two I'm trying to select between -- the non-programmable Mastech HY3020D:

The only programmable variable power supply I've found in the 10-20A range for under $300 is the Instek PSP-2010:

The advantages of the Instek are that it is programmable, its specifications suggest that it is more accurate than the Mastech and it has a key lock to avoid errors during operation. That last point can be critical when charging lithium cells. Wouldn't want the cat to rub up against the adjustment control on the power supply while charging lithium cells!

The big advantage of the Mastech is that it can go up to 20A while the Instek is limited to 10A. While I plan to be focused on smaller motors running at less than 10A, if I ever decide to purchase a motor that runs at higher than 10A, the Instek would not be able to bench test it. But there is a big gap in price between the 10A Instek and any 20A programmable power supply, which generally cost more than $500. I want to stay under $300.

So I'm trying to find any possible uses for programmability that might affect my decision. I'm leaning very slightly toward the 10A Instek over the 20A Mastech, and any additional programmability advantages could make the final decision a lot easier.

Of course, a 20A programmable power supply for less than $300 would be the best solution. But I haven't been able to find one of those.
Feb 21, 2004, 02:37 PM
Crash Master
Gene Bond's Avatar
Keep up the search, Dave... I've been contemplating the same purchse for the same reason Heck, maybe we should share a brain, we seem to be on the same wavelength, and one of us could rest I think I'll take my turn first Zzzzzzzzzzzz...

Actually, though, here's a possible candidate: I also found it at Hosfeldt, but not as much data, and a higher price.
Feb 21, 2004, 03:23 PM
Registered User
So I'm trying to find any possible uses for programmability that might affect my decision.
IMO, programmability is useful in connection with an RS232 interface and a computer.

It allows you to implement ANY charging algorithm in software on your PC with a few lines of code. For example, charge your NiCd pack until you see the first couple of cells peak, then reduce current to C/10 and trickle charge for another 30 minutes to equalize the pack.

Also, it allows you to calculate mAh in Software, which is nice when charging LiPos. Just write a little programm that reads current every second, accumulates the values and divides by 3600. Voilą - capacity!
Feb 21, 2004, 04:10 PM
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thazy2's Avatar
It is made by:

I will eventually purchase the Instek but this will do for now. The most influential factor that pushed me toward the BK was tech support. The friendly folks at BK spoke w/ me for almost ONE HOUR to answer all of my questions. They also explained a bounch of different things about power supplies which i'd never knew, kinda like a telephone crash course. It was very imformative. Service like that is seldom found.

price paid was $350.

BTW........this is NOT one of those weak switching power supply. It weight about 20 pounds w/ a big transformer inside. The power is VERY tight and clean. Ripple and Noise is rated at a low 5mv. which is the same as Instek. Jason
Feb 21, 2004, 09:49 PM
Registered User
Gene, I know we think a lot alike on motors, so it's no surprise on the power supplies. I had seen the All Electronics power supply. It has a small problem: "25 Amps continuous." Gotta have adjustable current, too.

Jason, don't know why you'd need the Instek after buying the BK. They have very similar ratings, so I don't think the Instek would give you anything you don't already have with the BK. My problem with the BK is that it's $100 more than the Instek. The Instek, by the way, is a switching power supply, and about half the weight of the BK. I'm not sure that makes a big difference for what we're using them for. But maybe someone has some thoughts they'd like to share.

Suzanne, easy for you to say "just write a little program!" I've never written a program before, but I'm sure I could write enough bad code to burn up a pack in no time. I can see where programmability would be a huge advantage for someone who knows how to write proper programs.

Still thinking the Mastech HY3020D is the best bargain for a 20A non-programmable power supply, and the Instek PSP-2010 is the best bargain for a 10A programmable power supply. There may be higher quality units out there, but they sure are expensive.

EDIT: Hmm, not so fast on the Zurich power supply. The All Electronics description makes it sound as if current is not adjustable. But I found it at MPJA Online for a few bucks less, and the description says 0-25A. Sounds like a heck of a bargain for a high-current power supply if you can live without programmability. Not sure about that switchable volt/amp meter, though.
Last edited by Dave Hederich; Feb 21, 2004 at 10:13 PM.
Feb 21, 2004, 10:59 PM
Crash Master
Gene Bond's Avatar
I don't know... It doesn't specifically say adjustable current limit. May be worth a call, though. I can't find Zurich anywhere else with a Google... may be Chinese? Seems like a strange name, though...
Feb 21, 2004, 11:45 PM
Registered User
thazy2's Avatar
how about these if you want something simple.....

I got 2 of these over the net before getting the BK. They are SMALL switching w/ volt adj. RATED at 25amps. I have pushed them both to 20 plus and they seem to run very well. However, it will not run the isl8. Just too much initial draw upon connecton. Fail safe kicks in. sales them for $170 each.

But i got them some where over the net for I think $85 each after many hours of search.

Had them both for over a year and they run great!


Feb 22, 2004, 12:02 AM
An Original!
What about this one.
Feb 22, 2004, 08:09 AM
Registered User
In order to charge lithium cells directly from a power supply without a charger, both the voltage and current of the power supply must be adjustable to dial in the precise voltage and current required for the lithium cell or pack being charged. The last couple of power supplies posted here appear not to be adjustable for both voltage and current.

Gene, I agree it's still questionable if the Zurich really has adjustable current. It's certainly priced way low for an adjustable 0-15VDC, 0-25A power supply. It appears to have two adjustment knobs at right top and right center. But the right center "knob" doesn't appear to have a scale. So it may not be a current adjustment. I can find no definite reference anywhere that specifically states that the current is adjustable on the Zurich, which is definitely a "mystery brand."

The worst part I see with the Zurich is the single switchable volt/amp meter. For Li charging, I think separate digital volt/amp readings are a huge safety feature. I would put a label on each Li pack with the pack's volt and amp requirements as they would appear on the power supply's digital readouts. Just match the label on the pack to the digital readouts on the power supply, and you will get a safe charge rate every time.

MPJA does offer a real bargain on a small adjustable current/voltage power supply that would make a great Li charger for all but the largest cells, but wouldn't be much good for testing motors. It's a 0-18VDC, 0-2A Mastech I hadn't seen before -- just $59.95. At that price, it's tempting to buy as a stand-alone Li charger.

EDIT: Just found a pdf user's manual for the little Mastech:
Last edited by Dave Hederich; Feb 22, 2004 at 08:17 AM.
Feb 22, 2004, 08:50 AM
Registered User
Having actually used the Mastech 30 20 for some time now, after having used the Triton, B-P-P-SC2, and the Kokam LiPo 4-cell chargers, I can say that I prefer the Mastech, except that I occasionally use the Trton when I want to measure battery capacity.

Why? Well, in addition to its power (no worries abou reaching C at required voltage) after I'd used it awhile and learned to allow for an acceptable amount of inaccuracy in its volt and amp displays, it was informative and, I must say, comforting to be able to monitor the changes in current and voltage into the LiPo as it charged.

The other switching power supplies mentioned heretofore do not have the power to charge up to 7 LiPos in series and/or 10 2ah LiPos in parallel. Most are more expensive.

I have not used it for motor testing, for the reason mentioned in post #12: electric motors can draw a large instantaneous current on startrup. Why not use a charged LiPo to test motors? It is somewhat like a large low-impedance capacitor. That current spike won't hurt it.

Incidentally, for testing motors with a battery pack and ESC, and accurate charging with my Mastech, I find a Sears clamp-on ammeter and a radio Shack digital voltmeter indespensible.

- RD
Last edited by RD Blakeslee; Feb 22, 2004 at 09:15 AM.

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