iana wrote:

---

How did we get 24v, I mentioned I charge 12v batteries in trucks either 12v parallel or 24 in series, charging each one individually, Re the taking off a 12v supply all done by "Professional" auto electricians, not for me to alter.
If we go to the original post, they have a 120ah agm, and asking if they can install another in parallel, if its an agm and separated by a switch, apart from work what harm can be done.
What is the objection to a bit of work? what do you guys do all day?

---

 oooppppsssss my bad, us old farts (like me) tend to get carried away at times sprouting our own importance... much sorry...lol

iana wrote:

---

How did we get 24v, I mentioned I charge 12v batteries in trucks either 12v parallel or 24 in series, charging each one individually, Re the taking off a 12v supply all done by "Professional" auto electricians, not for me to alter.
If we go to the original post, they have a 120ah agm, and asking if they can install another in parallel, if its an agm and separated by a switch, apart from work what harm can be done.
What is the objection to a bit of work? what do you guys do all day?

---

 We got to 24V when you mentioned charging truck 12V batteries separately. Trucks generally run 24V systems using 2 X 12V batteries in series. Which is why you would have been taking 12V from one battery to run accessories. And I agree with you putting "Professional" in quotation mareks, because if they were professional they would have done the job properly and used a 24V to 12V converter.

Getting back to the original post, there,s no objection to the bit of work, it's just one way of doing it... There are other better ways, which have already been discussed.