Alexkor Air Core Coil Radiant Charger

[SeanK]

Hi Tyson,

Hi Tyson, thanks for replying.
Sorry about the terminology... I meant base voltage and not gate voltage.

I also noticed that the transistor heats up at the higer frequency and is just luke warm on the lower frequency/bigger spike.

I still have much more testing to do. Just getting familiar with its operation. The 12v/100ah battery got up to 13.2 volts, but then over night lost some of that charge (11.38 after 6 hours resting). Ofcourse its a 14 year old battery.

My interest is two fold:
1. desulphate and condition my deep cycle lead acid batteries on the solar system
2. assess if I can charge more batteries with less power (i.e. 1AA -> 4AA)

My initial results iindicate tht 1AA -> 1AA does not work. So will try 1 -> 3 and see how that does.

[SkyWatcher]

Hi sean, thanks for sharing your results.
Would say that the higher spike is best for desulphating, though probably something in between is best for charging and desulphating.
Yes the NTE2300 NPN transistor used here gets hot also when using anything much over 8 volts input, 6 volts input never gets hot.
Found this to be common with the joule thief type circuit, though sometimes, with the right coil, capacitor, transistor combo, can be greatly reduced at higher input voltages.
Not sure about the gate voltage, since not using a mosfet here.
Hope that helps for now.
peace love light
tyson

[SeanK]

Hi Folks, Hi Tyson,
Below are two screen shots as in the previous post. I am now trying to charge a 12v/100ah NiMh.
Appreciate your feedback on the following question:

Is it better to have a lower frequency hivoltage spike (as in the first photo 200+KHz) ?
Or a lower voltage spike but higher frequency (1+MHz) ?

In both cases, the Transistor heats up quite a bit. Tyson do you experience that ? Besides a large heat sink or cooling fan, is there anything else to lower the temperature ?

Notice also that the gate voltage is high (18volts)... is this normal ?

Lower frequency Sharp skipe


Hi Frequency, Less Skipe

[SeanK]

Hi Tyson et al,

Attached some screen shots of the wave form with 2 different caps (Tysons 100nf and Alexkor 2200pf)
Have not done enought testing yet. But trying to figure out which results in a better bang.
The 100nf cap Tyson uses puts a higher voltage across the charge battery with a 32v sharp spike
I also noticed the scope show a higer frequency for the collector compared to the gate waveform. Is this due to the large ripple ?

The 2200pf (cloest to the 2700pf specified on page 1) is a blunter wave (yellow in photos) putting out about 20v.


primary volt = 5v (old pc supply)
secondary = 9v NiMh
RED = gate wav form
YELLOW = Collector waveform

100nf (shows 9.81v across the secondary bat. and climbing)


2200pf (shows 9.66v across the secondary bat. and climing):

[SeanK]

Hi Tyson, Thanks for all your help, I finally got it firing.. used a .37uF Ceramic cap but found a 1200pF and a few others worked too. The .37uF resulted in a low drop in the primary battery and a bigger spike (~20-30Vc).

I have also noticed that changing the cap results in a more ripely gate signal which increase the frequency of the spike (15 - 50KHz)
I am using a single AA to charge another. This is usually resulting in a dead primary and a charged secondary. Not sure if this is a fluff charge yet.
More test to do... but exciting its firing.

[SeanK]

Thanks Tyson, really appreciate your help.

[SkyWatcher]

Hi sean, thanks for the reply.
As far as charging, usually just check the volt meter every hour or so, since prior charges have shown generally what to expect time wise, though this could vary, if charging old sulfated cells.
As far as the alkaline type of cells, if they have been discharged already and haven't been sitting around too long, they will take a charge very well.
As far as nimh, etc., they will also take a charge very well, as long as they have not been sitting around too long in a discharged state.
Then yes, if a cell is sulfated, they will need to be cycled a few times at least.
This is usually seen with the cell showing higher than normal voltage when charging, then it starts to gradually drop back down to a more normal level, because the cell has a higher resistance with the corrosion.
Hope that helps for now.
peace love light
tyson

[SeanK]

Hi Tyson, thanks for sharing your experience.
How do you determine the end of charge ?
Are you monitoring the voltage or using a predetermined time ?
Do I have to cycle these batteries using the charger to "condition" them for this type of charging or will any battery recharge immediately ?

Sean

Sean

[SkyWatcher]

Hi sean, thanks for the reply.
Not sure what we're supposed to see, because have no scope here.
Recharged 2 AA alkalines a week ago and have been using them every other day in a portable cd player, so at least 8 hours of re-use so far, which is a plus with this high frquency setup.
At least 3 recharge cycles of used alkalines, should be easy to achieve.
Never noticed the non-rechargeable alkalines get warm, though nimh wil get warm if charged too long.
Also, when charging the alkalines, used a 6 volt DC wall wart here to charge the 2 AA's in series.
Hope that helps some.
peace love light
tyson

[SeanK]

Hi Everyone, Hi Tyson,
I finally managed to see something I have replaced the Diode with a UF5408 rectifier (I think its rated at 75ns) and a 100mF cap in the RC stage. I used a POT to adjust between 1-5k ohms. My primary and secondary are single AA NiMh.

Using the scope, I adjust the collector voltage to 11.4v @23KHz its a sharp noizy square wave. Increasing the ohms increases the frequency but reduces the amplitude of the pulse at the collector. I have played wih the settings to find a balance between the magnitude and frequency.

Is this what I am suppose to see ?
When does one know to stop the charging with radiant chargers ?
What happens if you don't (i.e. its not hot charging so can you damage the battery) ?

Sean

[SkyWatcher]

Hi sean, thanks for the reply.
The 100 nanofarad replaces the 2700pf, at least in this setup, yours may need a different value capacitor, have a bunch around here to try, from all sorts of gutted devices, like cfl's, etc..
Yes, the test charge capacitor would be placed where the charge battery would be, though maybe the oscilliscope will also tell you if it is oscillating, if it's fast enough to see the spikes.
The only silly question, is one that is not asked.
peace love light

[SeanK]

Many thanks for your reply Tyson.
Got my oscilloscope today( OWON PDS6062 ) Hoping it will help with my experiments.
Just to clarify:
The 100nF is in place of the 2700pF in the diagram at the start of this thread ?
Is the "test" charge cap to be placed where the charge battery would go ? (sorry if these are silly questions, I'll get it eventually).

[SkyWatcher]

Hi sean, thanks for the reply.
The coil used here, is on a 1-1/4" diameter cardboard tube, 5 inch long coil and is using 24 awg. bifilar.
The base resistor also has a 100 nanofarad capacitor in parallel with it, because it would not oscillate without it.
So, check to see if your coil is even oscillating.
Maybe charge a small capacitor to see if the voltage is rising above the input voltage, that should tell you if it is oscillating, since you probably can't hear the high frequency.
Found your transistor online, that seems like it will work good, though could not find information about that 1n5006 diode.
You'll need a fast (reverse recovery time) diode for good charging, 50 nanoseconds or less, as even if your coil is oscillating, if it is a slow diode, you will see poor performance or charging.
Hope that helps for now.
peace love light

edit: the diode is off the collector to positive of charge battery and the other end of coil is to negative of charge battery, using this NPN transistor

[SeanK]

Hi Tyson, many thanks for your continued encouragement and inspiration throughout this forum. I see so many wonderful post from you, its really exciting.

I made the coil using a 1/2 inch pvc conduit (~1.9omhs) and am using IN5006 as the diode with a BU2508A which I ripped from an old monitor. Results are not so great -- horrible actually.
You placed two HER303s in series in your setup (initial version) and I was wondering why you did that ?
Is that across the collector and the secondary battery +?
Sean

[SeanK]

I am particularly interested in replicating this. I have a 48v battery bank (~350AH) and would be cool to charge from 12 V. I also have a 280v 100AH NiMh bank. Wondering if I could scale such a charger up to that voltage.
I'll start with AA size . PK's book, suggested scaling up with more drive circuits and coils. IS more copper expected to yield more A/Pulse or more V/Pulse ?
Its awesome you're so open to sharing. Thanks alot.