High Current 12 to 24 VDC Voltage Doubler

[CDirenzi]

I need to power a 24 volt motor with a 12 volt car battery. How can I step the voltage up to 24 volts and allow for a possible spike of 250 amps at 24 volts? I found a 5000 watt DC voltage regulator that would work, but it is $7000! I don't need a very precise regulated voltage, if it fluctuated a couple of volts that would not be the end of the world. To make it more of a challenge, I need to keep it cheap, I am going to need 10 of these for the project I'm working on.

Thanks for any advice, it seems like it should be simple but I can't think of a good way to do this.

 

[OperaHouse]

You don't have to power it with a 12V battery. Adding an extra battery will take up less space than an inverter. I see no practical reason for your request. A 12V battery to run this would already be quite large. RV centers sell inverters to charge an additional 12V battery from a 12V charging system.

 

[itsmoked]

OperaHouse is likely on the right track.

You need to tell us more about the application as your solution is likely the direct one, but the most expensive, and unneeded. If you can give us better details we can hit all the alternatives. Likely one will be much better than a 12->24V converter.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[CDirenzi]

I have a device that essentially 'jump' starts planes when the battery dies. At many remote airports there are no AC outlets, but there is always a car to leave the airport. If the battery dies (which happens occasionally after a long landing that the alternator could not keep up because you are at idle for most of the landing) you can start the engine with my device. Unfortunately, most newer planes (and flying club of 10 who right now is interested in my product) run on 24 volt batteries. It is not realistic to carry an additional battery, just so you can jump it with 2 12 volt batteries. This part is part of a much more sophisticated product, and I'm afraid I'm going to lose out on the sale if I can't get this to work. (and I'm a poor college kid, I need the sale!)

Thanks!!

 

[itsmoked]

Two issues.

If a plane's battery is dying just because of a long landing with engine at idle. Then the battery is sulfated (bad) and should be replaced before a more serious problem occurs.

Secondly to run a starter with an inverter you would need a monstrous thing certainly costing a fortune. Your 250A is likely even low.

On the other hand if the user could stand a 10~20 minute charge period, far less expensive devices may work.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[CDirenzi]

My idea was to do something like charge up some big capicitors and flip a switch where it puts them into series and disconnect them from the car. I have no idea how long it will take to discharge, it could take a good 30 seconds of cranking to start the engine. It is not unreasonable to wait a bit to 'charge' up, but the quicker the better. What were you thinking?

By the way, it is not uncommon for plane's batteries to die, even if they are brand new without. A lot of the older planes do not have alternators, they have generators that don't output much when you are at idle. If you are coming in at night with all of your equipment on, landing lights etc, and you begin your descent from 10,000 feet, you will easily be descending for 20 minutes... the older planes can't handle that. Trust me, there is a need for it, I used to work at an FBO and we had a couple planes a week come in looking for a charge.

Thanks for the help!

 

[roydm]

Option A) Jump start with two cars in series?
Option B) Mount a 24 V alternator on the car, 10 minutes charging @ 50 Amps should start anything.
Option C) Couple a car starter motor to a 24 V alternator drive it from the car with jumper cables.
Option D) Buy or build a 24 V charger.

Roy

 

[itsmoked]

Battery charger... Hmmm I remember one I worked on recently that took 24VDC and put out what it takes to charge 12V or 24V batteries. It could probably be coaxed into taking in 12V and putting out 24V. It's actually way more than 24V to charge a 24V battery. Like 28+ volts.

Drop me an email maybe I can connect the dots. (not sure though)

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[roydm]

Keith,
My first thought, a voltage doubler, but you would need some pretty hefty components.
I still think the starter motor driving an alternator has some merit e.g. readily available used hardware. It's interesting that aircraft still use generators though, don't work well at all at low revs. With all the radios and navigation equipment sounds like a serious problem.
Roy

 

[CDirenzi]

How would you do a voltage doubler circuit? I like the starter motor driving an alternator, but that seems like it is going to be big and heavy- not just something you can throw in the back of the plane.

The new planes have alternators, I fly a 1966, and that is by no means the oldest on the field.

Thanks!

 

[CDirenzi]

Are those portable car jumper boxes capacitors or batteries?

 

[itsmoked]

Hi Roy. The big problem with a voltage doubler is that they never actually "double" the voltage as they have a lot of impedance issues. It is a fairly simplistic technique if it could be made to work. Perhaps a tripler with no voltage control at all. Not real efficient either.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[roydm]

CDirenzi,
No I just thought if you had one at the airport you would drag it out to the plane, or have it mounted on whatever runabout they use.
Is 24 Volts common for light aircraft?
Roy

 

[fsmyth]

Charge 'em in parallel, switch to series for
jump-starting. Use battery switches available
from any decent auto parts store.

OR

Swap out the alternator regulator for a 24v
version, and add a second identical battery
in line with the original.

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