hand held variable p.s.

I remember some time back, someone came here asking for assistance with a hand held lipo powered variable power supply. IIRC they had found the build instructions somewhere on the web. I need something like that. Like your traditional 0-30v, 0-'x'A benchtop power supply, but battery powered hand held form factor. Single channel is fine. I cant seem to find anything like that for sale, nor can I find that thread or any mention of a handheld power supply on google. Any leads?

How about one of these with a couple of 12V batteries? This will get pretty big though... might as well lug around a bench power supply, really - unless you're wanting the isolation.

http://www.digikey.com/product-sear...=1&stock=1&quantity=0&ptm=0&fid=0&pageSize=25

Maybe fleabay has what you're looking for.

strantor said:

I remember some time back, someone came here asking for assistance with a hand held lipo powered variable power supply. IIRC they had found the build instructions somewhere on the web. I need something like that. Like your traditional 0-30v, 0-'x'A benchtop power supply, but battery powered hand held form factor. Single channel is fine. I cant seem to find anything like that for sale, nor can I find that thread or any mention of a handheld power supply on google. Any leads?

Click to expand...

I was working on a breadboard power that I was going mount in a altoids can..

Maybe you could buy an adjustable buck module from ebay (DC to DC converter) and attach it to a decent sized LiPO battery pack? It should be a real easy project.

THE_RB said:

Maybe you could buy an adjustable buck module from ebay (DC to DC converter) and attach it to a decent sized LiPO battery pack? It should be a real easy project.

Click to expand...

Something like this? I can see that working nicely. Won't go down to zero, but hey whatever. Desolder the pots and segment displays and replocate with wire leads mounted inside an enclosure like this (probably larger). Could even do 2 channels! I wonder why this doesn't exist already...

$15 less, same supplier.

http://www.ebay.ca/itm/321305750981?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649


Dirt cheap, Hong Kong. $3.49, shipping included.

http://www.ebay.ca/itm/360807123891?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

This is the one I'm looking at right now. Separate V & I displays, current limit LED, pretty much just what you would expect in a benchtop model. Only small con is it only goes up to 24V where the others go up to 35v. But I don't think I'll need to go that high.
Lipo (X3)
Enclosure option 1 would look sexy with rubber boot.
Enclosure option 2 would be required if going for 2 channels.

Now I just have to decide if this is something I really want to do. It would be a distraction from my other endeavors and then there's the issue of charging it; I would need a legit lipo charger with balancing.

I just had a bright idea to nix the enclosure, the batteries, and the balancing lipo charger. I'll try to find a broken dewalt 20v cordless tool charger, remove the guts, and replace them with my buck/boost converter. Plug one of my dewalt batteries into it, and instead of chargi g the battery, the battery powers my supply.

....aaaaand in the spirit of legendary oneupmanship, I nix the previous idea and present the new idea:

I just opened up my DeWalt charger and found that it is largely empty. I took some measurements and compared to those of the constant I/V converter in post #7, and it will actually fit (only just) with the existing electronics intact, and there is room also for banana jacks and pots as well.

So I'm planning to just modify the charger that I already have, to be a multipurpose tool; cordless tool battery charger, portable 0-20V, 0-2A supply that can operate on battery or wall power.

I am a little bit curious what will happen if I try to use the power supply while the charger is charging. It is a fairly smart charger which gives a number of indications of battery faults. The additional load may register as a battery fault. I will have to see. Also, I do not know if it has constant current overload protection; if not, and the load of the battery charging and power supply overload it, it may just just shut off... or burn up (doubt it).

Any predictions what will happen?

That's a "multipurpose" tool for sure!

And that $21 SMPS Buck module from ebay (in your link, post #7) looks like a real winner for building a quick PSU with high energy efficiency;

It should arrive from China within a couple of weeks. I'll post the results, illustrated with pictures, or maybe a video.

@ STRANTOR, What do you think of this one for $8.99.
5-30V in and 5A

http://www.ebay.ca/itm/97K-5A-Adjus...233?pt=LH_DefaultDomain_0&hash=item5d4963d271

pilko said:

@ STRANTOR, What do you think of this one for $8.99.
5-30V in and 5A

http://www.ebay.ca/itm/97K-5A-Adjus...233?pt=LH_DefaultDomain_0&hash=item5d4963d271

Click to expand...

I did see that one in my search, and did not pursue it because of the underwhelming amount of info provided. Dimensions? Measurement signifiant digits? Etc. I saw one that looked identical, and it claimed a width of 114mm which is too big.

Shame on me for not checking things thoroughly. I *assumed* it should arrive in a couple of weeks, because that's how long my other chinese ebay purchases took. Turns out it has an estimated arrival in April. Phooey. I don't want to wait that long. So I took to amazon looking for something similar, and look what I found! This thing is going to be downright swanky!

Crap, this thing is coming in april also. Oh well. I guess I will have to wait on china.

OK, so I've ordered yet another buck/boost module. This one is just like the swanky one above, but is actually a buck/boost module. It can output up to 25V, even if my battery drops to 18V or less. It's shipping from HK instead of China, and comes as early as 13MAR. I will have some spare buck modules for future use. I'm blowing up all that money I made on eBay last week.

Why the big delays fron China? I order bits from HK/China and they generally take 7 to 12 days. Sometimes 3 weeks if I get unlucky. Most of these little things go air parcel mail.

THE_RB said:

Why the big delays fron China? I order bits from HK/China and they generally take 7 to 12 days. Sometimes 3 weeks if I get unlucky. Most of these little things go air parcel mail.

Click to expand...

The few things I've ordered direct from China get to the US fast. But then sit in customs waiting to get released.

Yeah I don't know. I've ordered plenty from china before and been surprised how fast it got here. Maybe these sellers are just erring on the side of caution, and my items really will be here in a few days.

In any case, I'll be able to do a side-by-side compare/contrast/review of 3 different buck/boost modules for other people in the market for such things.