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Author Topic: How may I drop voltage from 14.4 to 12 volts?  (Read 197 times)

Online frank mccune

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How may I drop voltage from 14.4 to 12 volts?
« on: March 09, 2020, 06:02:35 PM »
              Hi Folks:

              I purchased a 14.4 volt battery, li Po battery to power my starter.  Good idea? Not!  The starter works great via an 11.1 v LiPo.  I now have a very powerful starter that I can not use. 

               Is there a way that I may shed the excess voltage?


                                                                        Tia,

                                                                        Frank McCune

Offline Dave Hull

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Re: How may I drop voltage from 14.4 to 12 volts?
« Reply #1 on: March 09, 2020, 07:25:16 PM »
I don't think using line drop (long, smallish wires) is going to work well for you. It would seem that any practical wire size (durability) is going to need a lot of wire coiled up in your box. If you are just curious and want to screw around with this, just jumper the whole deal to use a household extension cord and see what you get. But remember, poor connections also cause line drop.

You might try to find an 11 or 12 volt zener diode with a high amperage rating and connect it across your battery. You may still need a dropping resistor. Does your starter give a stall current rating? You want to be a safe margin above that value.

Good luck,

The Divot

Offline bill bischoff

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Re: How may I drop voltage from 14.4 to 12 volts?
« Reply #2 on: March 09, 2020, 07:52:20 PM »
If you feel confident in your ability to do so, remove one cell and rewire your battery as 11.1volts. If you have ANY uncertainty or misgivings, though, DON'T try it. It could go real bad real fast. My experience has been that starters will take 4 cells without complaining, especially with the short duty cycle.

Offline Igor Burger

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Re: How may I drop voltage from 14.4 to 12 volts?
« Reply #3 on: March 10, 2020, 01:10:45 AM »
Looks like you have LIFE battery, simply do not charge it to full 100%. In that case the voltage will drop to 13V under load and your starter will think you have fully charged acid battery.

And if it is still too much, simply use long wire and you are down at 12V under load.

Online frank mccune

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Re: How may I drop voltage from 14.4 to 12 volts?
« Reply #4 on: March 10, 2020, 08:21:22 AM »
          Hello All:

          Thanks for all of the help!

           The reason that I found that the higher voltage was a bad idea was that the starter became a wild beast.  It would throw the starter cone off to parts unknown and shake the plane to a point where the structural integrity was threatened.  I replaced the battery with one that is 11.1 volts and all is well.

            Any way that I may use the higher voltage starter without all of the jumping and bucking?  I am thinking about using the higher powered starter to turn my .40 Diesel. 

            Comments or suggestions?

                                                                           Tia,

                                                                           Frank McCune

Online Fredvon4

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Re: How may I drop voltage from 14.4 to 12 volts?
« Reply #5 on: March 10, 2020, 09:35:59 AM »
Frank this sounds like follow up to your "my nose cone chatters" topic...

I sincerely believe you just need practice....My el cheapo 12 V DC HobbiCo starter is currently driven by 2 NiMh 8.4 VDC  RC car batteries in a NiMh type battery holder....so 16.8 VDC.....

I briefly pre prime--- then use nose of hand held battery starter to rotate prop to near TDC clockwise...place starter 90/90/90 on prop spinner and give a burst of 16.8 VDC......

OH BY THE way my sonic tronic OR RCATs glow heater always initiates a very white hot glow element.....the trick is.....fuel up to the NVA......

yes sir it is indeed your stuff...trying to tame a 14+ vdc battery to you can motor motor down to 12v dc is doable...but..IMO why?

oh and BTW....two factors...RPM/vs/torque....torque is pretty much voltage dependent in a ferromagnetic, copper wound core electric motor....a mouth full....more juice is much more gooder brother...ifing top rpm is tough on you, and chatters too much...up the battery volts much more and/or, buy a gear reduction starter or adapter....

"A good scare teaches more than good advice"

Fred von Gortler IV

Offline Tim Wescott

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Re: How may I drop voltage from 14.4 to 12 volts?
« Reply #6 on: March 10, 2020, 03:14:37 PM »
...  I am thinking about using the higher powered starter to turn my .40 Diesel. ...

I haven't owned a Diesel engine bigger than an 049, but the word I hear from Diesel fanatics is -- learn to start the engine by hand, and do not attempt to start it with a starter.  Diesels are high-compression by design, it doesn't take much of an over-prime to lock them up; if you've hydraulic-locked a diesel and you manage to turn it over, you've just bent the rod.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Dave Hull

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Re: How may I drop voltage from 14.4 to 12 volts?
« Reply #7 on: March 10, 2020, 09:53:35 PM »
Now c'mon, Tim. What we hoped to get from you was a list of the components to make a voltage regulator setup. Part numbers and where to buy 'em. And the official schematic showin' all the polarities. Eh?

If yer gonna be startin' big dieselly things, always remember to take out (a lot) of compression before you get after it. They bite. Hard.


"Three Finger" Divot

Offline Dennis Toth

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Re: How may I drop voltage from 14.4 to 12 volts?
« Reply #8 on: March 13, 2020, 05:17:01 PM »
Frank,
With the 40 size diesel (or any diesel) using the electric starter has a very good chance of either ripping the nose off the airplane or bending the connecting rod. As Tim mentioned diesels run high compression around 18.5 - 19: 1. There is not lots of room for excess fuel from an over prime.

First rule for diesel operation is to have fresh fuel. Ether boils at 75 - 80F so keep the fuel cool (I have some cooler ice packs the I have in a foam cooler were I carry my fuel container). The usual start approach for diesel is to pull the fuel up to the NVA with a finger choke. Pull the prop through the compression stroke a couple time (not choking the venturi) then flip hard and fast. A couple flips should get it running if the needle is close. Once running back off the compression (about 1/2 turn) as the engine warms then adjust the needle to smooth out the run, re-adjust compression and fly. It is usually better to be a little under compressed then over (if over it will sag at the top of the eights).

If it doesn't fire increase the compression 1/8 turn and start flipping - no fire, repeat. After a few tries you might need to do another choke. You can look on YouTube for some videos on model diesel engines and see the process. Once you get the needle and compression set only very small changes are needed to account for weather changes.

Best,    DennisT

Offline Tim Wescott

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Re: How may I drop voltage from 14.4 to 12 volts?
« Reply #9 on: March 13, 2020, 05:51:36 PM »
Now c'mon, Tim. What we hoped to get from you was a list of the components to make a voltage regulator setup. Part numbers and where to buy 'em. And the official schematic showin' all the polarities. Eh?

For some reason, that reminds me of my days as a street rod parts salesman.  People would come to me at shows and say "how much money does it take to build one of these here street rods?"  My answer was usually "how much money do you have?".

So, how fancy a regulator do you want?

Igor's long wire works, and is easy to tune.  Then if Frank likes the result, he can replace it with a resistor of the right size (resistance and power).  Problems that I can imagine cropping up with that approach are the resistor getting hot (but you won't be starting for long), and the starter having poor starting torque.

You can get almost infinitely fancy (hence my comment about how much do you want to spend -- it's a bottomless well).
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Wolfgang Nieuwkamp

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Re: How may I drop voltage from 14.4 to 12 volts?
« Reply #10 on: March 14, 2020, 12:42:14 PM »
Three power diodes in series would also work. They have a voltage drop of approx. 0,65 V each.
But they will have to cope with the maximum current!
Regards,

Wolfgang

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