Boost-Buck Regulator Device

Of course. I had forgotten about that old warhorse.

Jim

Forgot the "and thanks" in the previous reply.

Jim

Gee, I dunno, let's do the math. About half the time I go into the hangar the "charge" light is on with the linear design I did 25 years ago, so I think a 50% duty cycle would probably be a good approximation.

And I current limited the charger at 150 mA at 13.4 volts, or about 2 watts when on; 50% duty cycle reduces that to an average watt.

So 1 watt an hour 24 hours a day times 365 days a year times 25 years is 219 kWh times $0.10 per kWh is $21.90.

You're on. Of course I expect on-site service for this sum.

No problem. Radio Shack is just down the road.

Lesson #1 in business ... never bullshit with a bullshitter.

Jim

No, but the more I think about it, the more I'm just going to go with a buck switching converter. THis turkey solar cell is going to have enough trouble keeping up with leakage current with a winter sun than enough and I can't afford to throw linear power away during periods of good sunshine.

Jim

Switching from boots to waders. 8-)

In many cases you may find only a small advantage gained in the end from a smart power converter between the solar cells and the battery. Go ahead if you wish, but if you're working with a substantial number of small stations, the direct connection with a diode may prove best.

I'm a consultant, and I'll design, build, and install a solar-powered airplane battery charging system for you in exchange for as many dollars as the cost of the electricity you've been stealing for the last 25 years. What's that, maybe $10,000? $25,000?

Plus parts, of course.

You can email me by concatenating my first and last name, Rich Grise, and appending the usual shift-two and "yahoo.com".

Looking forward to hearing from you! Rich

Absolutely not. If the device has to be removed before flight, there isn't even a requirement for a logbook entry, much less an STC.

Rutan beat me to it by twenty years. He used to sell a small solar cell that mounted on the top of the forward fuselage when you were parked to keep the VariEZ battery charged. He simply chose a solar cell that didn't have enough poo to overcharge the battery.

Jim

Well, it has to work the same in winter AND summer. Say you get a nice couple of weeks in June and July where you get 10 hours of decent sunlight a day. 150 mA over a 10 hour span is 1.5 amp-hours. Over 10 days this is 15 amp hours on a battery that is only 35 amp hours to begin with. And gas recombinant (sealed) to boot. With only a few mA per day of keep-alives like clocks and such. I have seen damage like this under the right conditions.

Jim

On 04/12/2005 the venerable RST Engineering (jw) etched in runes:

The good old MC33063 will do the trick. Look at

or the original app note is available at:

On 04/12/2005 the venerable RST Engineering (jw) etched in runes:

No Problem. Before I retired, I used the 33063 in every uP design I did as 24V->5V converter. Very robust chip and despite all sorts of abuse we never had a failure. Blew up a few current limiting resistors but never managed to torch the 33063.

Hello Jim,

The real pros squeeze the last drop of electricity out of solar via maximum point point tracking (MPPT) but that would go a bit far here. A

Heck, you could turn this into a hot seller and make one for mounting on top of the fuselage, for airplanes in the tie-down area. Of course, you'd have to get STC and all that ...

Regards, Joerg

Hello Win,

However, Jim said that 150mA trickle could already fry an airplane battery over time. Which really surprised me.

So there would have to be some kind of precise voltage limit. If a linear regulator drops too much a shunt regulator around a TLV431 might work. Maybe some circuit that routes the excess into a large resistor or light bulb. The only thing I'd never do again is an LDO since the stability of some of those is the pits.

Regards, Joerg

While you *can* use a boost-buck device, its hardly worth it for the application. A silicon solar panel acts mostly like a constant voltage source ( typically around 18 volts ) in series with a resistor. The resistor value is inversely controlled by the solar radiation. At radiation levels where the available voltage is less than your required

Your main concern should be a really reliable way of limiting the float voltage to stop overcharging, and a linear series regulator does that pretty well.

Section 21.303 (b)(2) of the FAA regs allows an owner or operator of an aircraft the right to make parts for that aircraft. THerefore, everything we sell we sell "Heathkit" form and let the owner "make" it.

JIm

Consultant: Abreviation of Con and Insulting ....

I stuck one in a 1,000,000W 3-phase light dimmer (oh OK, soft-starter). it worked well.

Cheers Terry

At colder temperatures the voltage a solar panel delivers is higher than when hot.

Rene

ROTFLMAO!

Cheers Terry