Alexkor Air Core Coil Radiant Charger

[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.
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 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.
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]

Thanks Tyson, really appreciate your help.

[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]

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 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

[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 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.

[SeanK]

Reconditioning NiMh & Alkaline

Thus far, its a slow process but:

1. a 100ah 1.2v Nimh battery (14 years old) takes about 8ah and over the past 3 days is steadily showing improvement (tiny). It discharges 120ma @1amp. This is close to 50% improvement from day 1. The input voltage is 12vdc.

2. a 9 volt battery is now keeping an LED lit for more than 10 mins (started with 2 mins).

Observations on 1:
The CAP size affects the spikes, frequency of the spike and current into the battery on charge and temperature of the transistor

So far 100nF seems to be a good all rounded value outputting about 1amp @140v to the charge battery.

Notes on 2:
This is a smaller toroid core driven by a 4.5volt battery pack.

[SkyWatcher]

Hi sean, thanks for sharing.
Have never seen a 1.2 volt 100 amp hour nimh, what was it used in?
Sounds like it may be working good for you.
Any pictures of your setup, thanks.
peace love light
tyson

[SeanK]

large capacity NiMh batteries

Hi Tyson,
Sorry for such a late reply. I was revisiting the thread today only to notice that my reply was never posted.. strange.


screen shot pc


These NiMh batteries are 10 X 1.2v 100ah cells. They are used in my RAV4-Ev. You can't get them anymore. I am motivated to see if a radient charger can revive them.. so far no luck.

In the set up shown, on the left is the air core coil I am using. Recently I have switched to a 50 turn toroid which puts out abour 1000v @25K to see if that makes any difference. I have not measured the current yet..

Sean

[SkyWatcher]

Hi sean, thanks for the pic and information.
From my experience, you'll need to use more current input and probably thicker gauge wire to handle it, maybe even multiple air cores setup like bedinis mutli pole, if you wish to still use air core that is.
It takes some powerful spikes to rejuvenate the size capacity you are trying to recover.
Hope that helps.
peace love light
tyson

[SeanK]

Reviving Large Capacity NiMh

Hi Tyson,
thanks for replying and your suggestion.
Its worth a shot as the batteries are not available anymore.
I'll try a ferrite core too. Would just changing the coil to a heavier guage wire pull more current or do you anticipate my having to play with the RC stage ?

sean