<SNIP>
> Your 24v requirement will connect by using the positive of the now added 12v
> battery, and the negative of the existing 12v battery to give you the 24v
> you want. Again, you daisy-chain your batteries to get the 24v, tapping the
> first 12v battery to get the 12v you need, and separately charging each of
> the two batteries with 12v chargers to keep them charged.
This works with the separate chargers.
>
> Now you could use one 24v charger to do all this, and still just "center
> tap" the batteries for your 12v needs, or using one diode, you could charge
> both 12v batteries with one 12v chargers, and still daisy chain the
> batteries for your 24v needs and center tap for your 12v needs.
The single 24 volt charger works poorly unless the batteries have
exactly equal loads. Early new generation JD diesel tractors used 24
volts with a single generator and every one who added accessories (like
a 12 volt radio or some lights) had troubles with one battery going
dead. When airconditioning and cabs came along the factory switched to
12 volts.
>
> You should use care and caution by marking your wires with gray duct tap and
> a black sharpie pen to keep track of your volts, and polarity as you wire
> since it won't be long after wiring you can easily confuse which wire was
> what. Use pieces of cut off hose to keep wires from chaffing sharp edges.
> Use cardboard on top of exposed battery terminals to keep things from
> falling onto/into avoiding sparks, etc. The cardboard will eventually crumble
> but easily replaced. Remember 12 and 24 volts is a lot, will a lot of
> amperage. Take care because mistakes cause wires to glow like the elements
> in your toaster. Just use common sense and care. Yes, you can very safely do
> your 24v goal, but you really should do it with two batteries, not just
> daisy chaining two chargers.
LOTS and LOTS of amperage, probably a couple kiloamps. Enough to melt
significant wires after burning the insulation off.
>
> Finally, daisy chaining just two chargers won't be very successful because
> chargers by nature get their controlled voltage, their full wave DC, and
> controlled ampere output from the battery which also acts as a capacitor for
> the charger. Without the battery, the charger may not work, may run "wild"
> and often cause a radio humming. You won't be happy running anything
> directly off a charger without using the battery in place with it.
There will be mostly AC coming from the charger not connected to a
battery. Chargers often cause a radio to buzz even with the battery
connected.