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>> Home > Forum > Electrical Related > Voltage increasing via regulator
Voltage increasing via regulator
(263 views)
Author Message
EricMB
(Commander)





Forum Posts: 27
19th Oct 2018 19:18  
>> Permalink
mdlbt.com/47249

Evening all, I have a voltage regulator I’d like to fit to my Southport tug (currently running on 7.2v Ni-MHs) in order to get it up to 12v. I’m after more speed/power and would particularly like the bow thruster running a bit faster than it does on 7.2v. So, the questions are, where to fit it in the wiring loom, and what will the effect be on the battery life? Advice please!
Thank you in advance...

RNinMunich
(Fleet Admiral!)





Forum Posts: 2484
19th Oct 2018 23:29  
>> Permalink
mdlbt.com/47258

A somewhat confused question if I may say so Eric!😲
You can't 'regulate up' only down.
The regulator's job is to produce a constant lower voltage from a range of higher voltages. I often use one to produce 5V for the RX and servos from a 12V SLA drive battery. A little 3 legged device (type LM7805) which looks just like the power FETs in a high current ESC. My version of a UBEC! 😉

What is this 'regulator' you have? Type number? Manufacturer? Photo?

To get 12V from 7.2V you would need to use a Voltage converter (also known as an inverter). This works by converting the DC input from the battery to an AC voltage which can then be increased using a transformer.
More elegant (and expensive!) versions use a transistor oscillator and amplifier. This uses hi-power transistors instead of the transformer.
The AC output of the transformer (or amplifier) is then rectified back to DC.
All this is very inefficient which is why it is normally only used for very light currents, where the losses are not so significant, and when there is no other alternative, not often the case!
You can't beat the physics and you will never get the same power out that you put in.
This leads to a basic design question:-
What is the total current consumption of the load? I.e. the motors.
A simple example:-
Let's say that at 7.2V the motors draw 10Amps total, i.e. 72W (or VAmps). Assuming a utopian 100% efficiency at 12V this would equate to 6A.
Due to the three stages of conversion; DC to AC, transformation / amplification of AC to 12V, AC back to DC, you'll probably be lucky to get an efficiency of around 60% to 70%.
Thus if you stick 720W in you'll get around 430 to 504W out.
Not much of a gain is it!🤔 Your battery would be exhausted in about 2/3 the time it is now 😡
If your motors draw more than 10A the problem just gets worse.

So what is it you really want to do?
If you just want to up the volts to your motors stick a 12V SLA or an 11.1V LiPo (3S) in and hope that you don't cook your motors!
Frankly I don't really know why you're bothering, tugs aren't sprinters!

If you want more pulling power with the existing setup try experimenting with prop sizes and pitch. Will probably achieve much more than fiddlin' about with voltage converters.
BTW: All this assumes that the RX has it's own separate 5V battery supply or from a BEC in the ESC.
Some clarification needed from your side.
Cheers, Doug 😎


Young at heart - slightly older in other places 😉 Cheers Doug
EricMB
(Commander)





Forum Posts: 27
19th Oct 2018 23:50  
>> Permalink
mdlbt.com/47262

Thanks for the in-depth answer Doug, much appreciated! The component was incorrectly labelled - my fault.. it’s a Voltage Booster! Pic attached... to clarify, it’s really the bow thruster (a very small one at that!) I’d like running a bit faster, you’re right about tugs not being sprinters!
Regards,
Eric


Attached Files - Click To View Large

EricMB
(Commander)





Forum Posts: 27
19th Oct 2018 23:51  
>> Permalink
mdlbt.com/47263

Sorry, photo wrong way up!


Attached Files - Click To View Large

RNinMunich
(Fleet Admiral!)





Forum Posts: 2484
20th Oct 2018 00:46  
>> Permalink
mdlbt.com/47269

OK, Understood, I think!
If you just want to boost the bow thruster why don't you just fit a small 12V (or 11.1V LiPo) just for that? Frankly I might start with an 9.6V batt before I jump from 7.2 to 12V.
I assume it's just either On or OFF, i.e. no ESC.
As you can see from the specs of your Booster, as the output volts increase the deliverable current (for a given input volts) decreases inversely, as I predicted! Ya don't get summat for nuttin!
Soooo, you need to carefully check the specs of the thruster motor;
max voltage, current at maximum efficiency versus volts applied!
That will tell you the max volts battery that you can safely and most efficiently use, and you can check if your booster can deliver the required current at the voltage needed. I'd just use a separate battery and a servo operated micro switch, but then I'm just a dumb engineer!😲
Bon chance mon ami👍 Cheers, Doug 😎


Young at heart - slightly older in other places 😉 Cheers Doug