Rotary selector switch to parallel or series two batteries?

Good morning,

Many years ago I printed off a schematic from the web of a wiring diagram that described how to wire two batteries to a rotary switch that achieved a 12v-off 24v selectable parallel and series wiring arrangement of two batteries to satisfy the intermittent need of 24v devices (windlass in this case).

I recall that a master circuit isolate switch was described in a simple circuit to protect 12v devices from a 24v switch selection and that a less complex switch/circuit offered 12~24 volt circuit isolation at a hardware/switch level by a specific Siemens brand rotary switch. Switching from off to 24v isolated the 12v circuit and vice versa.

I can't recall exactly the specification of the rated amps of this switch/circuit/arrangement, but a value of 350+ amps is bouncing around my head.

Beyond these details, I'm at a loss. I dread that in a garage clean-up I've thrown out this valuable document. I've tried many combinations of internet search terms, I've even called Siemens Australia... To no avail.

Might anyone have thoughts, clues, a solution, or the document I've described?

Regards,

James.

 

I think this is what you are looking for:
http://boatprojects.blogspot.com/2011/06/24v-from-12v.html

 

Awesome, thanks for the link!

It more-or-less offers a solution. I can't understand why those lights seem to be so important to this circuit.

 

Why are you using a two voltage system ?

 

Oh... I'm not. An elderly gentleman, a member of my yacht club, is finding it difficult to lift his anchor. Arthritis apparently makes it difficult for him to grip the rope.

Another boat owner gifted him a second hand powered windless which happens to be a 24 volt device.

He is a pensioner and a few of us are keen to help him continue enjoying the bay on his meagre income.

The cheapest way for us to achieve this goal is to create a temporary 24v system from his otherwise 12v boat to get this "free" windlass up and running for him.

Frankly, if I had the money, I'd buy him a 12v windlass, but that is hardly endorsing of a spontaneous community centric helping hand to a guy that deserves it.

Unless... You'd like to donate a groovy new 12 volt windlass to the cause?

 

I see......

 

The circuit looks simple but is in fact very clever. The light bulbs (halogen) have a very low resistance when cold, so the 2nd battery can be fully charged.
When the switch is closed the bulbs are lit and draw only 4.2 Amps, almost nothing compared to the current drawn by the winch.

 

James, What a nice thing to do for a person who is getting older and a bit cash strapped. The world could use more people who think like you.

 

Jamie. I'll be starting a thread momentarily called "Us old guys" if you want to help some more.
Good Oh onya!

 

Thank you for the compliment. I make it a point to exchange a gift received of an idea, technical solution, recipe idea etc etc etc, with a gift of one sort or another, not necessarily financial to someone else in need of a little help.

It's not a difficult thing to do. By way of follow up, we built the unusual circuit offered here and it works. I still don't understand exactly how, but it does.

We'll be installing it on Friday.

 

That sounds like an awesome idea.