regulated-output dc-dc converter

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Dave 19 years ago

I've got an electronic device which operates, at least it used to operate, using a car battery as a power source. Over time it has begun to complain about low battery voltage which causes the unit to shut down. The battery voltage is fine... when I hook it up to the battery in my car and leave the car running (~14.4VDC while charging) the device will run indefinitely. So... it would appear that whatever is sensing the input voltage is sensing the voltage incorrectly.

So... my options are to open up this device (it's a sealed, ruggedized, evacuated of air, computerized survey total station so this would be my 2nd choice) to have a look at the (no doubt) SMT microcircuitry within, or to find a device which will give me a regulated, say, 13.8VDC from my 12V wet cell.

Can anyone point me at a retailer who sells 12V-12V converters with regulated boosted voltage? I've only found one at

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but a) they are in Australia and I am in Canada and b) these units are 8A and up whereas I only require maybe 1A max. Otherwise the description of this device is EXACTLY what I want.

Somebody must make these things, maybe for RV's or sailboats or so solar-powered survivalists can write their manifestos on laptop computers...

Any help greatly appreciated.

Sorry about cross-posting to the repair group but there's no sci.electronics.workaround group.

Dave

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Joerg 19 years ago

See if something like this could work:

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The PTK15-Q24-S12 from Cui is around $50 at Digikey, in stock and the Digikey P/N is 102-1078-ND.

I believe TI has numerous modules as well.

Regards, Joerg http://www.analogconsultants.com

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John Fields 19 years ago

Another possibility is that your battery is coming to the end of its useful life and its capacity has been diminished. To find out, connect a voltmeter across the load without the engine running and track it until your device shuts down. Track it, because as soon as the load shuts down the battery voltage will rise and you want to know where it was when shutdown occurred.

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Dave 19 years ago

Thanks, John, but that was my first hunch too... I tried several fully-charged different batteries and got the same results.

Given all the other projects I've got on the go right now, I'd as soon buy one as my employer will pay for it, but if I've got to build one, so be it.

Thanks for the link.

Dave

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Fred McKenzie 19 years ago

Dave -

Yours is a common problem faced by Ham Radio Operators, as some transceivers are voltage-critical. There was an article published a few years back in the QST magazine, on how to build a DC-DC converter to convert a range of input voltages to a steady 13.8 Volts. I believe it was also offered in both kit and finished form. However, I don't recall the company.

I searched Google for 13.8 dc-dc and came up with several hits. One of the first was

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which had two models, PST-DU500 and PST-DU700, that appear to do what you need.

Fred

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Rich Grise 19 years ago

Leave the car battery in the car, and get a deep-cycle (marine, golf-cart, etc.) battery for your device, and a proper charger.

Car batteries are for starting car engines, and don't like long-term "moderate" loads, and discharging them very much shortens their life.

A deep-cycle battery would be seriously overloaded if you tried to start a car with it, but they can provide a few amps for a surprisingly long time, and they're not damaged by a deep discharge. (well, within reason - the point is, they tolerate it better than a motor-starting battery.)

Good Luck! Rich

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Dave 19 years ago

The device only draws a few hundred milliamps, and I've tried deep cycle, gel cel, and AGM over the years.

the drain on the battery isn't the problem.

I've got several smart-chargers for the different types of batteries and generally get several years out of a battery.

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ehsjr 19 years ago

How about a simple "Rube Goldberg" solution - add a 1.5 volt battery in series. That will at least buy you some time until you find or build the DC-DC converter.

Ed

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kell 19 years ago

at

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a) they are in

Go to bgmicro.com and search for PWR1245 here is a link if it works:

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The device puts out 1A positive and negative 15 volts (for driving op amps), obviously you will only use the positive. Only costs $9, surplus. It would cost a chitload more than that if you bought it retail.

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Rich Grise 19 years ago

OK, so, then, what was the question? ?:-/

Thanks, Rich

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Dave 19 years ago

Where might I procure a voltage boosting device to feed >13V to my device from a 12.6V (or less) source? There were a couple of suggestions, I ordered one yesterday.

thx

Dave

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Dave 19 years ago

Thanks, Fred, that's just the ticket. Overkill with 36A continuous ability, but I ordered up the 500W model yesterday.

Dave

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regulated-output dc-dc converter

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