Hi,
Your technical advice seems advanced. Being a home made DIY engineer (hobbyist) I cannot do as you are saying. But it's a new thing to study. Thank you.



Hi
I tried 6% dutycycle, the FET and the pump capacitor (across Gnd to Inductor) was VERY hot. Then I tried 2% and it still hot and then I tried 1%. And it was still hot so I used VERY BIG heatsink.

Maybe 20/50 % pulses will help, personally i think it's the back emf suppression that needs improved, or lower inductance values.

 

Willen,
hard to say what may be wrong unless you can scope things. beyond simple passive components i found that having a scope, even a cheap one like Owon or the like, was needed when i got into semiconductors and digital. there are just some many parameters and variances that can cause a problem.

 

Willen,
hard to say what may be wrong unless you can scope things. beyond simple passive components i found that having a scope, even a cheap one like Owon or the like, was needed when i got into semiconductors and digital. there are just some many parameters and variances that can cause a problem.

Maybe reason of my many failure circuits is this one, as you said. Most of the time I think about replacement of parts due to lack exact accessibility and them I start to mess/modify circuit according to my access of llimited parts. Thank you again.

 

From what I remember (back in about 1982), the modified atx psu I used, had the feed back voltage controlled from the 5 volt line and the output for the 12 volt was modified to be halfwave rectified with no smoothing, which was then connected to the battery. It was the high frequency that de-sulphated the battery but I can't remember if it was pulsed or not. It took over a couple of weeks to restore, but it was a big battery.
I just wish I could think where I put it.

There was a blog about recovering salvage lead acid for off grid use, the author claimed to be using RF - possibly somewhere around 2MHz, but I can't find the blog to check it.

The 12V rail on an ATX PSU won't actually add any charge to the battery, I'd go for a voltage doubling rectifier with capacitor input - Xc gives some pretence of constant current. Use a regular fast recovery for forward rectification so Trr causes a negative spike on the charging current. A Shottky barrier shunt rectifier interferes least with the Trr spike.

ATX PSUs tend more toward about 50kHz, but some could be as low as 20kHz.

 

There was a blog about recovering salvage lead acid for off grid use, the author claimed to be using RF - possibly somewhere around 2MHz, but I can't find the blog to check it.

The 12V rail on an ATX PSU won't actually add any charge to the battery, I'd go for a voltage doubling rectifier with capacitor input - Xc gives some pretence of constant current. Use a regular fast recovery for forward rectification so Trr causes a negative spike on the charging current. A Shottky barrier shunt rectifier interferes least with the Trr spike.

ATX PSUs tend more toward about 50kHz, but some could be as low as 20kHz.

I think we altered the feed to the control ic, disabled the overvolts shut down and with no smoothing caps, we had something like 14.5 volts when connected to a good battery. I think the one we used was a 250watt from a cheap old H.P desktop that had run Win 2000. the thing had a very hashy output with all sorts of harmonics riding on the ripple output. Frequency was around 30kHz

 

I think we altered the feed to the control ic, disabled the overvolts shut down and with no smoothing caps, we had something like 14.5 volts when connected to a good battery. I think the one we used was a 250watt from a cheap old H.P desktop that had run Win 2000. the thing had a very hashy output with all sorts of harmonics riding on the ripple output. Frequency was around 30kHz

My results with lead acid were less encouraging - mostly I used it on 4.8V Ni-Cd packs - the 5V output fed through a current limiting resistor added a small DC charge complement and kept the PWM chip spinning. With ATX; you have a 3.3 that needs loading as well.

You can usually tweak the voltage regulation a bit - and also find out how much margin you've got on the electrolytics voltage rating..............