Winding transformer

[camerart]

I was going to say toy cars but really the helicopters cars and other items which use large batteries have gone over what one would call a toy.

Some of the drones used to take photos are quite large devices and clubs tend to run events where rapid charging is really required.

1000W for 5 minutes is not that much when compared with liquid fuel pouring in the two stoke mixture used with compression ignition engines is so much quicker than a recharge.

Looking at electric cars it would seem a lot of work is going into rapid recharge.

The problem is to get 24 volt DC at a reasonable cost one needs to use high frequency and so reduce the size of the transformer so one is looking at a ready built unit rather than a collection of parts in order to use the switch mode technology and high frequency transformers.

The PC power supply does seem the most likely unit.

Hi Eric,

You are correct regarding the need for the 1000W, when charging multiples of large LI-ON cells.

I'm also looking at PC power supplies, LED lighting power supplies and other machine power supplies. They can be quite expensive though, this is why I'm looking at this option.

C.

 

[camerart]

JohnW2. That post added nothing, are you on a mission to increase your post count?

I don't think I have any need to

I suppose that I was more-or-less implying the same about your post as you are saying about mine. I had already pointed out/implied that the OP almost certainly would not need anything like 30A at 24V to charge his RC cells - and you then wrote essentially the same thing, more verbosely, with analogies about 400W halogen lamps!

"I agree with stupic"

Who is stupic?

Kind Regards, John

So it's a charger for RC cells - nothing exotic. Quit your dangerous dicking about with microwave transformers and get a PC power supply. I used to use a Schumacher CCD20 with a PC Power Supply and it's ideal. link the green sense wire to any black on the ATX connector and it comes to life.

These chargers are designed to clip onto a car battery, if you start shoving full wave rectified DC into it, you might find it's none too happy.

Nozzle

If you know of a tried and tested 24V 30A PC power supply please send a link, I would prefer to buy one, than make one.

C.

The input range is so wide, there is no need that have it at 24volts. Also, you cannot sink 1000W (product claim), 720W (24V x 30A) or anything like that into some RC car cells and expect them not to melt. Admittedly, my experience is used NiCds that is now old technology, and although the charging current (pulsed, not sustained) could be adjusted up to 10 amps, anything more than 4 Amps would cook the cells. Even top-of-the-range matched and conditioned sets. Just think how much a 1000W is. Two and a half halogen lamps worth, if you've ever sat next to a 400W halogen lamp you'll know how hot that gets.



Nozzle

@12V the charger will output 500W, @24V 1000W. (Of course, I expect less!)

C.

 

[JohnW2]

@12V the charger will output 500W, @24V 1000W.

It might well be true that the charger can output up to 41.7A (i.e. 500W @ 12V or 1000W at 24W). What current, hence power, it actually does 'output' in any situation will depend entirely on the charge management circuitry (and settings) and the nature of the connected load (battery) - in some situations, it could be a tiny fraction of the ('maximum') figures you are quoting.

As I've asked before, do you know what charging currents you actually want for your batteries?

Kind Regards, John

 

[camerart]

@12V the charger will output 500W, @24V 1000W.

It might well be true that the charger can output up to 41.7A (i.e. 500W @ 12V or 1000W at 24W). What current, hence power, it actually does 'output' in any situation will depend entirely on the charge management circuitry (and settings) and the nature of the connected load (battery) - in some situations, it could be a tiny fraction of the ('maximum') figures you are quoting.

As I've asked before, do you know what charging currents you actually want for your batteries?

Kind Regards, John

Hi John,

Yes, 3-5Amp+ X9, in this case, but I want the power supply for other uses too.

C.

 

[JohnW2]

Yes, 3-5Amp+ X9, in this case, but I want the power supply for other uses too.

Thanks. What voltage are these batteries you will be charging? Do I take it that the 'charger' you have ordered has the ability to charge multiple batteries simultaneously, with independent charge management of each?

Kind Regards, John

 

[camerart]

Yes, 3-5Amp+ X9, in this case, but I want the power supply for other uses too.

Thanks. What voltage are these batteries you will be charging? Do I take it that the 'charger' you have ordered has the ability to charge multiple batteries simultaneously, with independent charge management of each?

Kind Regards, John

Yes, multiple batteries. 3X 3.7V cells = 1 battery X3 in series, X3 in parallel. All cells balanced while charging.

C.

 

[JohnW2]

@12V the charger will output 500W, @24V 1000W.

Yes, 3-5Amp+ X9, in this case, but I want the power supply for other uses too.

Yes, multiple batteries. 3X 3.7V cells = 1 battery X3 in series, X3 in parallel. All cells balanced while charging.

Thanks. If one assumes that a 3.7V cell is charged at about 4.5V, nine such cells being charged at 5A, would theoretically represent a total power of around 200W, so a pretty small proportion of that charger's capabilities. If you were to supply the 'charger' with 24V DC, then, ignoring inefficiencies and losses, you would need about a 8.3A (at 24V) supply to charge those 9 batteries at 5A each. Unless the 'other uses' you have in mind would require much more power, a relatively modest (hence not too expensive) 24V supply (maybe about 15A) would therefore probably be adequate.

Kind Regards, John

 

[camerart]

@12V the charger will output 500W, @24V 1000W.

Yes, 3-5Amp+ X9, in this case, but I want the power supply for other uses too.

Yes, multiple batteries. 3X 3.7V cells = 1 battery X3 in series, X3 in parallel. All cells balanced while charging.

Thanks. If one assumes that a 3.7V cell is charged at about 4.5V, nine such cells being charged at 5A, would theoretically represent a total power of around 200W, so a pretty small proportion of that charger's capabilities. If you were to supply the 'charger' with 24V DC, then, ignoring inefficiencies and losses, you would need about a 8.3A (at 24V) supply to charge those 9 batteries at 5A each. Unless the 'other uses' you have in mind would require much more power, a relatively modest (hence not too expensive) 24V supply (maybe about 15A) would therefore probably be adequate.

Kind Regards, John

27Cells!

C.

 

[JohnW2]

27Cells!

Apologies - I misread/misunderstood. That's probably about 600W, then - about 25A at 24V. What probably confused me were these "3.7V cells" - I probably subconsciously assumed that they were batteries consisting of three 1.2V-ish cells (the usual cell voltage). What exactly are these 3.7V 'cells'?

Kind Regards, John

 

[ericmark]

Now I am confused. 3.7 volt per cell? Lead Acid 2 volt and NiCad plus NiMh 1.3 volt did find some odd alkaline cells at 1.5 volt and the non rechargable cells used in computers at 3 volt but what cell can produce 3.7 volt?
I would have expected a battery of 3 cells to get 3.7 volt?
As to charge capacity it clearly depends on the design and size of the cell. The cells used in forklift batteries can take 100 amp each.
But in general one tries to charge cells is series. Although we can parallel cells the problem arises should any cell go short circuit it can either cause other cells to get too much current or its self take too much current and I have seen the explosive results.
So if I data from a single AA cell it tells me 1.2 volt 2100 mAh and max charge rate 420 mA over 7 hours. So it does not matter how many I have I can't set charge rate to over 420 mA and from flat it will take 7 hours. I have others with different max charge rate and clearly can't mix and match.

With model batteries you may have the rapid charge type and the cells may be larger but once the cells are combined into a battery then that battery has to be charged as one unit not with other batteries specially with the NiCad and NiMh types. The DeltaV charger monitors the voltage peak to detect when the battery is fully charged and if that battery has cells of different capacity or state of charge the DeltaV will likely fail to detect the fully charged point.

I had this with two way radio batteries we had both DeltaV and temperature sensing chargers. If I repaired a battery by renewing a faulty cell it would work OK with the temperature sensing chargers but not with the DeltaV type.

The charger you show looks like a DeltaV type so the battery must contain cells all of the same age and capacity so the idea of using the charger to charge 6 batteries in parallel for example is flawed. It can only be used with one battery at a time.

To charge 6 batteries with my two way radios the charger had a single power supply but 6 separate DeltaV charging modules supplied from that power supply all housed in the same metal box.

 

[bernardgreen]

While I do not disagree with ericmark's comments about charging cells / batteries in parallel I would add that some battery packs have built in "intelligent" chargers that manage the series / parallel connected cells in the pack during charging.

 

[JohnW2]

Now I am confused. 3.7 volt per cell? Lead Acid 2 volt and NiCad plus NiMh 1.3 volt did find some odd alkaline cells at 1.5 volt and the non rechargable cells used in computers at 3 volt but what cell can produce 3.7 volt?
I would have expected a battery of 3 cells to get 3.7 volt?

Quite so - you're not the only one who is confused. As I wrote:

What probably confused me were these "3.7V cells" - I probably subconsciously assumed that they were batteries consisting of three 1.2V-ish cells (the usual cell voltage). What exactly are these 3.7V 'cells'?

Kind Regards, John

 

[camerart]

For anyone confused with battery technology, please Google them.

This thread is about winding transformers.

C.

 

[ban-all-sheds]

What exactly are these 3.7V 'cells'?

Lithium polymer.

 

[JohnW2]

For anyone confused with battery technology, please Google them.

The discussion about batteries has only arisen out of our attempts to ascertain exactly what your power requirements are.

This thread is about winding transformers.

It is, and I think it was made fairly clear early on that it is not a very advisable approach, at least for someone who does not have the appropriate experience and knowledge. As was also suggested early on, some sort of switched mode power supply (along the lines of a computer PSU) would probably be more appropriate for your purpose (and much cheaper) than a 50Hz transformer-based 1000W power supply. If you Googled for them, I'm sure you would find something. If 12V were enough (which I assume it isn't), there are countless ATX power supplies around which cost next-to-nothing which provide 30-40A at 12V. Some have dual or triple 12V supplies but, unfortunately, I doubt that it would be possible to combine them to get higher voltage.

Kind Regards, John