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Multipurpose Automotive Battery Charger - Discrete

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Asc3nti0n

New Member
Hi All,
I'm a newbie to this forums but been designing electronics circuits for many years, and my bro doing it for a career. My current project is an autosensing 12-24V Intelligent Battery Charger for basic Lead Acid batteries.

I'll be designing it with freeware principles in place,circuit design notes, construction details and full schematics posted online, so open input won't go punished.

I have a few ideas, and about an hours study under my belt at this point, mostly Google searches and links to circuit design archives that have previously been referred to elsewhere on this forums.

Anyhow, I have a couple of design restrictions on my setup so far and i'll list them out for comment, rebuttal and input;

- Input AC (230-240Vac Australian GPO) transformation to a centre-tapped 0-12-24V 750VA transformer.

- Essentially discrete components, ATMEL microcontroller preferred monitoring/control brain, but I would like to see options for analogue outputs from this device for each stage of the charging process.

- **broken link removed** is the specific URL that I have take nas gospel for this project, but wish to simplify it without needing to know all the details of the exact battery specifications etc.

- So, basically the microcontroller needs to control two different circuit stages, a constant-current driver capable of say 20A, and it be capable of 24 (28.2V Float). And then; depending on the maximum voltage at which the bettery has plateaued out to, the charger should attempt the middle stages at 13.8V or 28V etc. according to the ideas on the above site. It should revert to a trickle charger after which it decides that he battery it not taking any more charge.

- Each of the 4 stages should have timers in the programming, but i'm not so worried about arguing those ideas here. I want to work on the controlling of a Vref and Iref from a microcontroller. Noone needs to here that we're reinventing the wheel here, it's the doing that is interesting.

- I have a feeling that the transformer mightn't do 28Vdc even after rectification, little worried actually, so should I put a voltage pump to get a 30Vdc max ability.... what currents can i get with basic power diodes?

That'll do, i'll think about it for a few hours, see who else is interested in brain storming, and i'll blog a bit more here soon.
 

Hero999

Banned
Isn't his a bit overkill for such a simple project?

I would build a simple power supply with an switchable output (13.8V and 27.6V) and include current limiting to whatever you want the charging current to be. When you first connect the battery the current limiting will kick in, then when it reaches the set voltage on the power supply it will float charge.
 
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