How to connect a 12VDC Alternation with 2 12VDC batteries in Series

Thread Starter

Jay L

Joined Dec 6, 2019
2
Hi Y'll:

I have two 12Vdc batteries connected in series producing 24Vdc, I would like to use a 12Vdc alternator with signal lamp included to recharge the batteries. I've heard about the use of diodes or Isolators integrated into wiring, but not sure exactly what should be correct components / connection. Any ideas about how should be the correct conection?
 

Papabravo

Joined Feb 24, 2006
13,484
I don't think it would be possible to charge two 12V batteries in series with a 12V alternator. Why do you think such a thing is possible? Have you been watching you tube videos?
 

Reloadron

Joined Jan 15, 2015
5,339
The only way this can work is if the batteries are taken from a series configuration and put in a parallel configuration for charging and then, only if, the batteries are identical. Otherwise they should be individually charged. The best approach would be to have a 24 volt alternator for a 24 volt system.

Ron
 

bassbindevil

Joined Jan 23, 2014
86
You can get way more than 12v from an alternator. See the book, "Alternator Secrets". I expect what you need is an alternator with an external regulator, then swap the 12v regulator for a 24v version.
 

Thread Starter

Jay L

Joined Dec 6, 2019
2
Acknowledging my ignorance - I'm a newby on this. Giving by granted there is no way to charge the two batteries (in series) to produce 24V froma 12V alternator...

What about to convert the 12V alt to a 24V? - I'm using a Delco ad230 Series IR/If 105 Amp/12 Volt, Clock Wise, internal regulator. Any idea how to convert to a 24V output? To give Y'll some background; I'm building a R/C lawnmower using two 24V motors to move the wheels (there is why do I need two batteries in series). Answering dl324, Yes. The idea it's to connect the alternator to a pulley in order to recharge the batteries while gas engine it's running.
 

Tonyr1084

Joined Sep 24, 2015
4,369
I've wondered if it were possible myself for a very long time. I've never found a solution other than switching them from series to parallel for charging. To do that with a switch would require a very complex switch (or set of relays) that could handle the amperage those batteries can produce. It's not just the charging amperage the switch would have to handle it's the load you will put on them as well.

You can get way more than 12v from an alternator. See the book, "Alternator Secrets". I expect what you need is an alternator with an external regulator, then swap the 12v regulator for a 24v version.
I would LOVE a link to that "Alternator Secrets" book you mentioned. Otherwise I have to wake Google up and search myself. Way too much trouble. Not really, just wondering if you have a link and I can be lazy.

I have two alt's in the garage right now. A small 80 amp unit hooked to a small gasoline engine and a much bigger 170 amp unit sitting on the shelf. I think it's 170 amps. I'm sure if I pulled the internal regulator out of it I could get an unregulated DC voltage out of it. But even DC at high volts can be dangerous to human life, so it sits there on the shelf for now. I've even considered the idea of removing even the diode pack and getting three phase AC out of it. It would take a small excitation voltage to get it going but then I'd have a lot more power - depending on what kind of drive motor I put on it.

But no - you can't charge a 24 volt system (two 12V bat's in series) with a 12 volt source.
 

Audioguru again

Joined Oct 21, 2019
1,270
An Alternator produces AC, not DC. A Generator or an alternator with a rectifier produces DC.
I assume your batteries are heavy old lead-acid? Then they need more than 12V each to charge them, maybe 14V each for a total of 28V. A boost converter module can use the 12VDC from whatever makes it to boost to 28V and some can even limit the charging current. The charging current is usually limited by a charger circuit that you did not talk about.
 
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