24v output from 12v system

Best way is get a 12V to 24V Stepup Converter

LINK

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That was a British site

Here's an Aussie one

A lot of Jap Prime Movers are 24v so owners use a step down 24v to 12v so as not to have to change trailer light bulbs , but having said that today with LED's it don't matter.

Also try the 12v shop in WAHERE

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Yep, I would leave them as they are, just put your isolator in and make one of them your main battery and the other for the AUxiliary.

Get a 12 to 24v converter thingy and run with your 24v equipment from the Auxiliary battery.

Or just ditch the 24v stuff all together?

If you connected them up to be 24v, you would need to change your Alternator !

Craig,

did a circuit idea just for fun.
Have a look at the components first, before you decide to go ahead.
Some slightly expensive bits in there, like a couple of double pole changeover relays and a commercial battery isolator solenoid.
The changeover from 12V to 24V and back is done with one switch, both batteries will see the full charging voltage from the alternator if switch is in the 12V position.
Will post the diagram if interested....
A..alternator
M...main batt
IS...isolation switch
AUX...second batt
MR...(master) 12V double pole changeover relay, contact rating determined by your 24V load current, and max charge current for AUX
SR....(slave) 12V double pole changeover relay, follows MR with a delay, max contact rating is the sum of all 12/24V load currents or max charge current for AUX whichever is greater
P...24V pump
SW...heavy duty changeover switch, to be rated at max charge current for AUX batt
D1...diode rated at sum of all 12V and 24V load currents
D2...diode rated 1A
C...electrolytic capacitor 25V/330uF
R...10 Ohm, 1W

How it works:
looking at the 'picture' as it is, the engine is off, AUX battery is disconnected from main batt, only 12V loads can be switched on, draining the AUX batt.
If SW is thrown into 24V position, MR and SR are energized, 12V loads can now drain the main batt via D1, and 24V loads can drain both batts via D1 and sr1 (sr1 prevents a reduced (one pn voltage drop 'above' AUX batt voltage) drain of main batt in the 12V position)).
D1's purpose is to block cranking current flowing over relay contacts, yet to allow current through the 24V series configuration.
IS allows the full charging voltage to reach AUX, if the alternator spins up. For this to happen, the switch has to be in the 12V position.
SR's purpose is to prevent the 12V loads draining the main batt while switch is in 12V position, and to provide delayed fall back of sr2 when switching from 24V back to 12V. This is a safety net in case the switch makes contact before r1 and r2 can break the 24V configuration. R and D2 and C are responsible for the delayed action of sr2.

Let me know if you want the circuit diagram.
regards, mr.batteryvalue

We have a 12V to 24V Dc to DC charger that will accept 12V 50A input and produce 24V in boost absorbtion and float with battery type selection and temperature compensation.

It is called a BB122450 and is made by Sterling Power Products of the UK.

It is a quality product and not cheap but is efficent.

Ian

I would definitely love to see a schematic for this circuit if you would be kind enough to post it.

I had an idea there would be a way of doing it - just not quite enough electrical knowledge for all the components.

thanks for your time in describing the proposed layout

regards

Craig