transformer chargin and why arent the lights flickering?

[Hummina Shadeeba]

what are my obstacles in going direct from the 120v ac and stepping down to 4.0 volts at the secondary, rectify, and charge? and do all the cells connected to the secondary in parallel and get balanced.

why are the lights not flash at 60hz with the ac current?

 

[Gregory]

Is this an isolated single cell charger to avoid balancing?

what are my obstacles in going direct from the 120v ac and stepping down to 4.0 volts at the secondary, rectify, and charge? and do all the cells connected to the secondary in parallel and get balanced.

For starters
1. Its a non regulated supply, the Voltage at the secondary will vary with line voltage changes and load.
2. No current limiting, and there will be a lot of current.

why are the lights not flash at 60hz with the ac current?

What lights? Yor incandescent house lights on AC? Because the filament has heat inertia, and the lights are flashing at 120 Hz.

 

[kdog]

whats your set up? what lights?
60hz is usually to fast for your eye to see but not always
all cells connected to 4v in parallel will balance but they will also present a pretty low impedance unless they are almost at 4v. if you have no current limiting you will have a large current flowing through the transformer, rectifier and cells, this will be larger when the cells are flatter ie greater V difference.

 

[Hummina Shadeeba]

Great I have responses. Thank you.
I'm wondering what bits exactly one would need to go from the outlet in my wall and transform it and rectify and plug into a single cell at 4v. Yes no balancing is a big attraction. I want to make this immediately so, you could save a life if you tell me the right way! Otherwise I'll just see what happens. I'm only 13. HELP ME.


So 120hz is USA Ac frequency.
Heat enertia. Of course. Never heard the term. would we perceive the flickering if it actually were at that frequency for that period. How much darkness do I need to be in to know I'm in the dark? Is there any period seen as off in the Ac cycle. Between positive and negative.

 

[Gregory]

No the US uses 60Hz, but look at a sine wave (AC) and see how it crosses zero twice per period.

Thermal inertia is probably a more correct term.

Don't build this. Buy one or multiple isolated CC/CV 4.2v power supplies.

 

[Hummina Shadeeba]

why not build this? iv'e looked up the single lipo chargers using usb and it's nice and convenient but i wWANT TO BUILD THIS!! hAHAhaooho. seriously I at least want to know what's involved and why someone would not want to build it'.

 

[kdog]

13yo seriously? HS of the hub motor threads over in skateboard forum? Jeez you're doing well...
Gregory is probly right don't build it. Why, cause no-one wants to help you kill yourself working with 120v.
But if you are going to do it anyway then that's a problem...
Firstly you need to be absolutely sure not to fry yourself or start a fire.
The rectifier you'll need will be difficult to source or expensive. All the cheap ones are grossly overrated. As in a 50amp one wil do maybe 4-5 amps. it'll be heavy cause the low freq transf are big and as Gregory stated good V control is hard. There are some transformer based circuits that have better VControl but you need big inductors that are expensive and heavy and big.
Maybe build a DC-DC converter that works on ~12v instead. Lots more efficient, you'll learn more, prob cheaper and it'll be heaps better. You can run it off a car battery or any other 12v supply. Input voltage can vary which is useful. Output is stable under load. Heaps of circuits online.
Goodluck

 

[Hummina Shadeeba]

ok i lied for more help.

assuming I don't build it all and just buy it, which is a lot easier, what's the highest power 4 volt power supply available and why don't more people do this?

this being charge all the cells in parallel to balance them.

so far this is the most powerful:
http://www.trcelectronics.com/View/Mean-Well/RSP-500-4.shtml
360 watts. close. really want a 400 watter


this is the cheapest but its stated for LED which I don't get:
http://www.trcelectronics.com/View/Mean-Well/NEL-400-4.2.shtml

but could i use these and put all my cells in parallel and they would balance? I fear not as these are using pulsed power I believe as apposed to a traditional straight voltage off of the transformer method after it's rectified and smoothed

 

[markz]

Maybe a computer psu, or a server psu. I was looking at a 240V unit 1500W or so, it had different voltage lines, but I shied away from it because I'd have no clue what the frock to do. If its not in RC forum group on the hobbyking website with loads of info, then I aint interested. Maybe you can down convert from a Dell 12V 80A, those units I have boughten for as cheap as $2 each. Which reminds me I gotta see what they got.

 

[amberwolf]

ok i lied for more help.

Why should we help a liar?

 

[Punx0r]

There are good reason most li-ion batteries are charged with the cells in series and with a balancing function. You'd need a good reason to depart from this well-trodden path.

Who needs a ~100A (400W) single-cell charger?

 

[Hummina Shadeeba]

i was joking amberwolf

a high power 4.1 volt charger could allow me to balance with one plug. that's the reason. would a typical pwm charger work or must a true steady voltage be used such as with a transformer if all the cells will be in parallel?

 

[Punx0r]

You can't parallel charge the cells in a pack without first breaking all the series connections, else the result is a short-circuit. Are you really going to electrically disassemble the entire pack to parallel charge it on every cycle?

 

[Chalo]

There's a catch when rectifying wall voltage. The peak voltage of nominal 120V (RMS voltage) is about 170V. You can probably sort out the implications for yourself.

You'll want a voltage regulator rather than just a transformer.

 

[Hummina Shadeeba]

I still want a transformer because then I can keep my series connections on the battery and still charge in parallel as there will be no electrical parallel connections with the transformer just magnetic. I'm still more than interested in this..except my "stereo fixer" from Craigslist hasn't called back. It's hard to find an electronics person

 

[Punx0r]

No, you still can't do that. If you parallel the cells in a series connected pack to the output of a transformer they are still shorted. Sketch out the circuit...

The only way is to connect each cell to its own isolated charger, but then they're not in parallel with each other and you just invented the "suitcase full of phone chargers" charger or certain models of RC hobby chargers that charge via the balance leads.

To be fair to the guy on Craigslist I don't think there are many people who would call back if presented with the enquiry you've made in this thread. Your question is confused and sounds kinda crazy.

 

[Hummina Shadeeba]

https://www.google.com/patents/US5659237

exactly what Im talking about

trying to put much power through would require a large and expensive contraption but a small version just to balance with a very small current would work to balance as the lower the cell the higher the current. maybe never get near full charge (since I still can't confirm if lithium ion can sit on full charge or anything close with a true voltage like this would produce as apposed to pulsed power).

no coupling between the secondary coils sounds like the challenge but this could be solved with a primary and secondary coil for each cell.

the big plus with this is being able to balance while all the cells were still in series. yes I could just use a suitcase of phone chargers but thats not as attractive and at least in theory I should be able to get it made cheaper and more powerful with this simpler setup.

here's a good circuit:
http://www.learningaboutelectronics.com/Articles/How-to-build-a-DC-power-supply.php

12 of these would work no?
actually I'm liking doing a multiple secondary core on a toroid:
https://www.youtube.com/watch?v=lyZ7nM6Fo94


and one more balancer for cells in series which uses the higher voltage cells to charge the lesser and no outside supply is necessary. neat:
https://www.google.com/patents/US5594320
why don't we have these around?