AutoElectricians - Charging 24v battery pack with 12v charger

If you just connect one 12 volt battery at a time it should be ok.
As long as the charger suits the batteries.
You have given no details of the battery size or type or that of the charger but in theory you can centre trap the batteries and charge individually.
How does it come about that you have or need a 24 volt jump pack and dont have the means to charge them?

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Ozzie, charging one at a time whilst still coupled together is quite OK. Just be sure of your polarity when charging each battery. And in order to maintain balance, charge each battery to the same level. This is most easily achieved by charging each fully.

OzzieCruiser
I understand/know some earlier Cruisers had 24v systems. So did some Nissan vehicles. As Allan has mentioned, simply attaching the clips to each battery in turn Pos Pos and Neg Neg of each battery, you can charge them with no worries. In fact, if you had two chargers one can be attached to one battery and the others clips to the next battery and both can charge simultaneously as the battery chargers are only seeing one battery each anyway. Used to do that when I was a 3rd yr apprentice and had to run the auto elec section for quite a while by myself. Time was of the essence quite often, so being able to charge both, with two chargers, worked out well for me.
If in possession of two identical same make simple ( not smart) chargers, which each can charge a battery, Linking one Pos and One Negative clip together effectively makes a 24v battery charger with the other Pos and Neg clips. Alternatively, if in possession of a solar panel which has an OC voltage of a little above 24v, it too can be used directly for a period of time to charge the 24v starters. Monitored of course. Just a few options, don't know exactly what gear you have. I often have to improvise to achieve an aim.

Alternatively, get a couple of 12V x 5W solar panels from fleabay in series and set and forget.
EDIT - actually, 2 or 3W would be enough.
Cheers,
Peter
OKA196 motorhome

Apart from all the other advice, the ONLY risk I see is in the unlikely event that the chargers' output side is earthed i.e. not fully floating. Straightforward to determine with a multimeter.

Unlikely, but not impossible. Where TWO similar/identical chargers are used to hit up the battery pair, there would be some fireworks!

Good morning Ozzie,
Just as a matter of interest, what sort of vehicle is it ?
There were all sorts of creative systems installed in converted busses before switch mode tech was developed specifically for automotive applications, some successful, some not.
What size are the batteries and charger?
There are some basic rules of thumb to follow that you may already be aware of.
No need for me to go into them unless you ask, pretty sure someone else will jump in now the matter has been raised with lots of technical words and theories, just give him time to google it to become an expert on the matter lol.