Useing power supplies for charging

[Elias lector]

I need some clarification on an idea I have.
So I already use a 120v 30a power supply to charge all of my batteries and I love it because I can adjust it to a single cell or a 96v pack. But at over $300 it's hard to buy another when I know I can buy a few cheaper ones and combine them. So here's my question. If I were to get 2 60v 3a units then add a 5v 30a unit would I really have the ability to charge 125v at 36a? Aside from the resistance issue atleast. It seems like a rather stupid question maybe but then I start to overthink it like, will the 30a only be carried through 5v. I have packs that I can charge at upto 400amps but I'm not trying to do all that but at 3a it takes a very long time. I do that from time to time just because I feel it's good practice to do a slow charge once in awhile. Sorry if this is a rediculious question and thanks for any clarity.

 

[E-HP]

You can charge at 3A with the setup described.

 

[amberwolf]

Keep in mind: Volts in series add. Amps in parallel add. You can't series and parallel at the same time.

All PSUs placed in series must be electrically isolated from each other; if they are not then the more positive ones will short out the more negative ones, along with whatever (your battery) is connected between the total + / - of the series set, with what could be spectacularly catastrophic results.

If the PSUs (or chargers) you use are not specifcally marked as being electrically isolated, then I recommend looking up the term and how to test all of them for it.


FWIW, there are a number of threads with further details on seriesing multiple PSUs / chargers (and/or paralleling them), if you need more info on the various potential gotchas. I dont' have any direct links, unfortunately, but I have posted in many of them if you search for PSU and/or Charger in my posts.

 

[scianiac]

I don't think it's really worth it at this point, if you have to float them because they are not isolated that can be a pain and you also have to figure the quality of the PSUs, if you are talking about cheaper units even if just 1 is it weakens the whole system. Meanwhile you can find those converted 120-130v 20-30a telecom PSUs for cheaper than $300, I ordered one a little while ago for $150 and then are generally considered to be quite high quality units.

 

[Elias lector]

I reread that first paragraph like 6 times before it kinda sunk in. And you know that feeling where your like "you dumbass you knew that" yeah that just happened to me, once again. Like I said I was sure I was overthinking something so simple. Thank you and now I know what term/s to use I will quietly do more research. I'm sorry sometimes with the ten bazillion other things I've got going on I have a complete breakdown between my memory and common sense. For now I'll blame it on my broken left arm, right wrist, and type 5 separation of my left shoulder coupled with insomnia and a horrible case of food poisoning I'm getting over now. Thank you again.

 

[Elias lector]

I don't think it's really worth it at this point, if you have to float them because they are not isolated that can be a pain and you also have to figure the quality of the PSUs, if you are talking about cheaper units even if just 1 is it weakens the whole system. Meanwhile you can find those converted 120-130v 20-30a telecom PSUs for cheaper than $300, I ordered one a little while ago for $150 and then are generally considered to be quite high quality units.

Could you share a link??

 

[scianiac]

Sure, there seems to be tons of places on aliexpress modding these PSUs. Honestly probably would be even cheaper if you just bought one of the PSUs surplus and modded it yourself although I didn't see many on ebay, not that I looked that hard.

https://www.aliexpress.us/item/3256...t_main.53.53ad1802PB0k8D&gatewayAdapt=glo2usa

 

[raedy07]

to charge up to 96V batteries (109V when full) i'm looking for a 0-120V/ 0-5A Lab power supply on ebay, ali; can't find anything >360W (3A), is that some kind of limit? i'd like at least 500W, better 1000W. battery will be 10-12kWh.

 

[amberwolf]

to charge up to 96V batteries (109V when full) i'm looking for a 0-120V/ 0-5A Lab power supply on ebay, ali; can't find anything >360W (3A), is that some kind of limit? i'd like at least 500W, better 1000W. battery will be 10-12kWh.

If you want 1000w you'll have to look for higher current; wattage is voltage x current, so 120v at 5A is only 600w.

If you search for higher current supplies you'll find them out there. If I change that 5A to 50A and search for your otherwise exact phrase of "0-120V/ 0-50A Lab power supply", several are found on the first page of results. Most are manufacturer page results, so you would have to then search for those model numbers to find places actually selling them to individuals (unless you want containerfuls of them).


You will be limited by your AC supply source. What is the wattage available from your wall outlet? (keep in mind you can usually only get that with no other devices on that circuit breaker). Typically 15A is the max for a 110vac outlet (in the USA), so 15 x 110 = 1650w; realistically 1500w or less on the DC side depending on PSU efficiency.

For that reason, Sorenson makes them up to about 3kW to be powered by "household" 220VAC, like a dryer or stove outlet, like the huge and heavy DCS 55-55 I have (which will probably run you several hundred dollars used, couple thousand new). Beyond that, you'll need a better AC supply, usually 3-phase, such as industrial or high-current EV-car charging stations.



A good quality lab PSU will probably cost more and be much larger and heavier than a dedicated charger for the same wattage, if you don't have any need for the complete range of adjustability of voltage and current of the lab PSU.

An LED PSU would probably be a cheaper slightly adjustable way than a lab PSU, but it will probably still cost more, though it may be around the same size/weight as the charger. Meanwell makes the CSP series that includes one that goes up to 120vdc output, about 3kw total power, if you have an AC outlet capable of providing that.

A charger also has a feature neither of the others will, of being able to shut off below a certain minimum current draw, which is better for the battery over it's lifetime than letting it keep trickling current thru the cells all the time.

 

[raedy07]

here AC supply source is not my limit, Spain has 230V/16A socket outlet. =3680W.
i thought it's a good idea to have an adjustable charger, as i have 12, 24, 36, 48V batteries and planning a 96V one.
i know 5A@120V is only 480W, that's because i lost hope to find anything stronger. and i still can't; limiting my search to EU 360W is highest i get

anyway, my problem, this place isn't about how to use a search-engine

 

[scianiac]

So are you against the converted telecom PSUs already mentioned in this thread, they are often 1000s of watts adjustable voltage in the ranges you are looking for, much cheaper than a lab power supply. You can find them all over aliexpress, just search for like "battery charger 120v" or something like that, they normally come in various different voltage and current ranges. 120 and 130v seem common so those will come up in the search. They are often converted Delta PSUs. Like This

 

[raedy07]

So are you against the converted telecom PSUs already mentioned in this thread,

absolutely not, thanx for pointing them out - i have to admit i wasn't aware such a 'thing' exists and that there is a difference to lab power supplies.