Boost converter loses voltage under load

Thread Starter

Knowlittle

Joined Mar 16, 2016
45
20160507_122120.jpg

USELESS VOLTAGE !!

why does this circuit loose its volatage under load ?, can anybody help please. would like to use it to power a scooter starter motor from a solar panel (12v .56amp), motor uses a little more than the solar will provide, hence the attempted booster
 
Last edited:

jlnance

Joined Dec 31, 2015
6
You can't create power, my guess is that is the root of the problem.

A starter motor takes a lot of current. If you use a boost converter to raise the voltage, then you're going to need to draw even more current from the solar panel. If you step the voltage up at the output, you step the current up at the input by a corresponding amount.

You probably need to use the solar panel to charge a battery which is capable of supplying the current the starter motor needs.
 

bertus

Joined Apr 5, 2008
20,653
Hello,

What does the relay do in your schematic?
The output voltage is reduced by ca. 2 Volts by the diodes D2 and D3 and the Zener Z1 (wich acts ads a normal diode).

Bertus
 

Thread Starter

Knowlittle

Joined Mar 16, 2016
45
The relay acts as a switch, clicking on and off instead of me pushing a switch all the time. Ok so how exactly then can you utilize a voltage booster. Seems all it does then is just "up" the voltage on a dmm and nothing more (nothing useful) !
 

Thread Starter

Knowlittle

Joined Mar 16, 2016
45
Trust me the relay oscilates !, im using the nc and no linked to the caps. Either way can someone tell me what exaclty you can use a booster for, seeing as soon as you connect load to it, the voltage disappears?
 

Alec_t

Joined Sep 17, 2013
11,520
as soon as you connect load to it, the voltage disappears?
Not if the booster is properly designed and is being used within its design limits.
A typical booster use is to operate mains-rated gadgets from 12V (or lower) battery supplies. But the output power (Volts times Amps) can never be more than the input power, and would typically be ~85% of the input power because of circuit inefficiencies.
 

Thread Starter

Knowlittle

Joined Mar 16, 2016
45
Is there any way i can regulate the output voltage to give a constant feed on this circuit, and mabey store some additional power in caps so the stored power can release slower ?
 

Thread Starter

Knowlittle

Joined Mar 16, 2016
45
Please bear in mind i am very new to this, will a switching regulator be able to be intergrrated into my circuit and regulate the output voltage ? Or is it a stand alone circuit?
 

bertus

Joined Apr 5, 2008
20,653
Hello,

Wich motor do you want to drive?
What are the specifications of that motor?

You say that the solar panel is 12 Volts and 0.56 Amps.

Bertus
 

Thread Starter

Knowlittle

Joined Mar 16, 2016
45
Yes on the solar panel. The motor i dont know, when i connect the motor straight to the solar panel i notice that it wants to run, when helping it it spins about once then stops ! So i summise that it is probarbly looking for around .9amp or so, with regards to the 12v feom the solar panel i also suspect that is fine (i accidentally built a circuit a few days ago that acually spun the motor ), but dismantled it before recording my findings. Ps:it spun well. I used a lm317 and some other chip i had lying around (cant say wich one it is as i have about 20 different salvaged ones, and i used 1 of those) !
 

AnalogKid

Joined Aug 1, 2013
8,536
A boost converter boosts the voltage at the expense of the current. If you have a 5 V source capable of delivering 2 A, and boost converter can turn this into 10 V, but at only 1 A. Actually, at about 0.8 A because the converter circuit is not 100% efficient. This is very useful in multi-voltage electronic systems, but not so much in power systems because of all of the various converter topologies, boost is one of the least efficient.

Power equals voltage times current, and it *never* increases as it goes through a system. You have a 6.72 W source. If the motor needs more than that, no circuit will help.

ak
 

Thread Starter

Knowlittle

Joined Mar 16, 2016
45
Ok guys, now we have my circuit and my solar panel. What purpose would a voltage boost converter serve ? I dont see point that if a power source is strong enough to bear a load why would you build a booster ? I really still dont understand the concept. Its similar to someone using a transistor as a switch but manually switches the circuit on and off ! So can someone please explain in laymans terms the purpose of the booster.
 

bertus

Joined Apr 5, 2008
20,653
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