Alternator voltage regulator without battery

Thread Starter

SailCS33

Joined Mar 18, 2021
37
Hi everyone,

Im building a remote controlled mower that uses 24v alternator to power the motors. I'd like to do away with having to buy a battery and would much prefer to only use alternator powering all the electronics. I've been looking at off the shelf regulators which seem to be $30-50 for the amps i need. If not too complicated I'd like to build my own.

Option 1 to use LM7824 in parallel to achieve the desired amperage.
Option 2 to use LM338 also in parallel. Fewer required but they cost more.
Option 3?

Any input is very welcomed!

Thanks

Val
 

MrAl

Joined Jun 17, 2014
8,259
Hi everyone,

Im building a remote controlled mower that uses 24v alternator to power the motors. I'd like to do away with having to buy a battery and would much prefer to only use alternator powering all the electronics. I've been looking at off the shelf regulators which seem to be $30-50 for the amps i need. If not too complicated I'd like to build my own.

Option 1 to use LM7824 in parallel to achieve the desired amperage.
Option 2 to use LM338 also in parallel. Fewer required but they cost more.
Option 3?

Any input is very welcomed!

Thanks

Val
Is it really an alternator or a generator?
If it is, what kind of alternator is it? I ask because many have regulators built right in. How they work without a battery though i dont know because the last time i did anything like this was back in the 1970's when trying to make a battery charger with an alternator and 120vac electric motor.
Very modern alternators may get some control from the onboard computer though too.
There must be something on the web about this.
 

dendad

Joined Feb 20, 2016
3,840
Well, I'll rephrase the question..
What are you going to use to rotate the alternator?

Is whole thing powered via a long mains lead as you do not want batteries?
And if so, why have an alternator at all?
 

dendad

Joined Feb 20, 2016
3,840
Ah! That is ok.
It was starting to sound like another post that wanted to use the motors to drive the alternator to drive the motors......
Using an alternator with built on regulator and adding a small 12V battery may just make it all a lot easier.
A small car battery makes a really good power supply filter!
 

Thread Starter

SailCS33

Joined Mar 18, 2021
37
Ah! That is ok.
It was starting to sound like another post that wanted to use the motors to drive the alternator to drive the motors......
Using an alternator with built on regulator and adding a small 12V battery may just make it all a lot easier.
A small car battery makes a really good power supply filter!
I'd need two car batteries for 24v and besides their cost, it would add lots of weight and the space on top of the lawnmower is very limited.

Since the mower engine is on anyway for the cutter, i thought I'd just power the electronics with it and not have to deal with the batteries.

Hence the need in normalizing the alternator output.
 

dendad

Joined Feb 20, 2016
3,840
I wonder if a mains alternator may be a better way t go, then use an off the shelf universal input switch mode 24V power supply to run it all would be better.
A 120VAC alternator driving a 90 to 260VAC input power supply would give lots of headroom for speed and load variations.
By the way, what is the power requirements of the motors? And you need to allow for stall and startup currents, not just run.
 

Thread Starter

SailCS33

Joined Mar 18, 2021
37
I wonder if a mains alternator may be a better way t go, then use an off the shelf universal input switch mode 24V power supply to run it all would be better.
A 120VAC alternator driving a 90 to 260VAC input power supply would give lots of headroom for speed and load variations.
By the way, what is the power requirements of the motors? And you need to allow for stall and startup currents, not just run.
Hmmm... good point about inrush currents.
The motors are rated at 22amp. I need to look into this more because i imagine that would be at 12v. My guess at 24v it's half of that..the motor does run on 12 but slower.

Didn't know about 120vac alternator. I'll look but wouldn't that be a generator then?
 

dendad

Joined Feb 20, 2016
3,840
A "Generator" is usually a DC device, while an "Alternator" is AC. But these terms are often used loosly.
And if your motors are 12V, when you run them on 24V, they will draw at twice the current, not half.
A same power rated 24V motor running on 24V will draw half a similar 12V motor running on 12V would but the one motor on higher voltage will draw more than on a lower voltage.
Look into a electronic washing machine BLDC motor as an alternator. You may be able to pick one up from a tossed out washing machine.
Do a bit of research about using them as generator/alternators.
 
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