HS gate drive transformer?

[Grant]

Strange thing is, the fluid level inside is ok. It's one of those
supposedly maintenance-free ones but one can pry off the lid assembly to
peek inside.

Sulphation, do the plates look white? High impedance batteries due to
sulphation can be recovered, hardly worth the effort though as the success
rate has been reported as low as 30%. Leave it at 17V for a long time,
or get one of those pulse/spike units that are supposed to break down the
sulphate.

Car batteries often are used in a chronically undercharged state due
to short trips, and if you happen to have a regulator at low end of the
loose spec auto range.

Since you took the lid off, try adding some battery restorer? Try some
phosphoric acid -- some web searching will hint at the dosage. I've only
read about this acid, not tried it.

Why is it that this brand name battery is dead after 5-6 years, the gel
cell in my StatPower emergency kit also died after 5-6 years, while the
gel cell in my over 10 year old big $10 Chinese flashlamp is still fine?

5-6 years is an okay life for car battery, design life is 4 years.

Poor charging techniques, old fashioned charging regimes that didn't get
updated with the newer battery technology?

Grant.

 

[Joerg]

Sulphation, do the plates look white? High impedance batteries due to
sulphation can be recovered, hardly worth the effort though as the success
rate has been reported as low as 30%. Leave it at 17V for a long time,
or get one of those pulse/spike units that are supposed to break down the
sulphate.

They look the usual dull silvery color. But the battery does slightly
bulge at both ends so you may be right, there could be sulphation
further down inside of the cells.

Car batteries often are used in a chronically undercharged state due
to short trips, and if you happen to have a regulator at low end of the
loose spec auto range.

Since you took the lid off, try adding some battery restorer? Try some
phosphoric acid -- some web searching will hint at the dosage. I've only
read about this acid, not tried it.

I think I'll give it to the recyclers. But it may have to wait until I
buy a replacement. Because there is a high tax on batteries in
California and you only get it back if you hand over the old one. If you
just bring a battery without buying a new one that refund is lost. I
made that mistake once.

5-6 years is an okay life for car battery, design life is 4 years.

Poor charging techniques, old fashioned charging regimes that didn't get
updated with the newer battery technology?

Has the technology change that much on car batteries?

 

[Grant]

Grant wrote: ....

Has the technology change that much on car batteries?

Not a lot, calcium and silver additives? But the car has changed heaps,
more standby loads but still the crappy 13.5V to 14.5V or so constant
voltage charging regime that usually under or over charges the poor
battery. Short trips like the high voltage, long trips the low -- then
there's battery temperature compensation done by ambient but rarely at
the battery. Sloppy, battery will last the warranty period...

Grant.

 

[Joerg]

Not a lot, calcium and silver additives? But the car has changed heaps,
more standby loads but still the crappy 13.5V to 14.5V or so constant
voltage charging regime that usually under or over charges the poor
battery. Short trips like the high voltage, long trips the low -- then
there's battery temperature compensation done by ambient but rarely at
the battery. Sloppy, battery will last the warranty period...

Mine's a run-of-the-mills battery, maybe Sam's Club. The car is also a
rather mundane SUV. Since I do not trust electronics in cars much I
purposely bought a vehicle that has no electric this, that and the other
thing. No power windows, not even central-lock.

 

[legg]

I wound a toroid to use as a HS gate drive transformer for a 100W two
switch flyback. I'm using the typical DC restore technique AC couple
the transformer.

Here's my schematic;

http://i42.tinypic.com/9gvyow.png

I'm using a PIC and a FET driver to simulate the extremes of the PWM
controller duty cycle and drive level and it works well with the
exception of Burst Mode. Burst mode is when the controller modulates
the original gate signal at light load for anyone who doesn't know.

A picture is worth a thousand words.

Here's my gate waveform at 90kHz 70% duty. A little sloping but
acceptable.

http://i39.tinypic.com/25kieyq.jpg

Now here's where the fun begins I'm modulating the 90kHz to simulate
burst mode.

http://i44.tinypic.com/qy5l69.jpg

Here's a zoom of one of the burst.

http://i43.tinypic.com/2eumxbk.jpg

My primary and secondary are 1:1 ; inductance of 1.5mH.

Is there anyway to clean this up?

In reality, a burst controller would be 'bursting' at a minimal duty
cycle - not as is programed in your PIC here.

This is more a power-limit/hiccup type of simulation; the symptoms at
the gate drive will be similar, but are unlikely to repeat as
frequently.

To avoid backswing effects on discontinuous drive trains;
C1 must not be large enough to support saturating voltseconds.
Reduce C2 to ~ 10xCgs.
Reduce Rgs to produce 30% gate voltage droop under full load low line
conditions.
Tailor D2 characteristics (as ~ back to back zeners) for a few voltes
of 'off' bias.

For lowest power loss in bipolar ouput drive circuits, schottkies
should be applied from drive output to both rails, to recover mag
energy.
Rc is probably mislocated here.

RL

 

[JosephKK]

Sounds like electrolyte dry out. See if you can find a way to "juice"
the cells again.

Strange thing is, the fluid level inside is ok. It's one of those
supposedly maintenance-free ones but one can pry off the lid assembly to
peek inside.

Why is it that this brand name battery is dead after 5-6 years, the gel
cell in my StatPower emergency kit also died after 5-6 years, while the
gel cell in my over 10 year old big $10 Chinese flashlamp is still fine?

[...]

Oh yes, I remember Peak Meaningless Pretend Output from the 1960s. A
play value created by inventive misapplication of theory that cannot be
duplicated in the real world. And look at the thin cord that carries it
from the wall wart to the device, better than room temperature
superconductors it must be.

They probably rely on the fact that the majority of shoppers does not
have an engineering degree

While i am not young i had not yet celebrated my 15th birthday when i
recognized that crap (mid 1960s). OTOH i had been building electronic
kits for years by then.