# Alternator voltage regulator without battery

#### SailCS33

Joined Mar 18, 2021
40
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 8,980 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.

Joined Feb 20, 2016
4,134
What are you going to use to power the alternator?

#### SailCS33

Joined Mar 18, 2021
40
What are you going to use to power the alternator?
Lawn mower engine will be used to drive the alternator.

Cytron controller to drive the two wheelchair motors and also Arduino through a step down adapter.

Joined Feb 20, 2016
4,134
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?

#### SailCS33

Joined Mar 18, 2021
40
Well, I'll rephrase the question..
What are you going to use to rotate the alternator?
Sorry i edited it after replying. The lawn mower 145cc engine will drive the alternator.

Joined Feb 20, 2016
4,134
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!

#### SailCS33

Joined Mar 18, 2021
40
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.

Joined Feb 20, 2016
4,134
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.

#### SailCS33

Joined Mar 18, 2021
40
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?