Forgive my ignorance (batteries)

[Tookey]

Between my starter battery and my leisure battery is there any unit/gadget (b2b?) that does anything (there are fuses but I understand them)?

I have had instances where my leisure battery has voltage but my starter battery is dead, why does the charge not work in reverse?

I think I've mashed my brain with trying to understand battery set ups, what did seem like a relatively simple topic is now not!

Thanks

 

[wildebus]

Is there? Well if a Leisure battery has been installed then typically some kind of split charging unit will have been installed as well, but not always.

Options would be a
B2B - one way device from starter to leisure. Physically a fairly large unit and you would likely know if you had one.
VSR - Very small device activated by voltage level. Usually bi-directional.
Switched Relay - very small device activated by ignition or D+ from alternator. Bi-directional but only when on, so therefore only when ignition on or engine running
Given the age of your van, unlikely to be a B2B or VSR from the factory.

 

[Tookey]

Is there? Well if a Leisure battery has been installed then typically some kind of split charging unit will have been installed as well, but not always.

Options would be a
B2B - one way device from starter to leisure. Physically a fairly large unit and you would likely know if you had one.
VSR - Very small device activated by voltage level. Usually bi-directional.
Switched Relay - very small device activated by ignition or D+ from alternator. Bi-directional but only when on, so therefore only when ignition on or engine running
Given the age of your van, unlikely to be a B2B or VSR from the factory.

Thanks. I will google image 'switched relay' and then go hunting. Due to the reliance on this unit, whatever I have, I want a spare. I know relays can stick so definitely want one if that's the case

When you wrote 'is there?', what were you asking please

 

[wildebus]

"Is there? " dunno what I was starting to write before I carried on!
VSRs and Switched relays will be small boxes around 2" square so easily tucked out the way and invisible.
Relays can fail indeed. Now bearing in mind all a relay is is essentially a remotely activated switch, as a backup plan you could fit an mechanical isolation switch in parallel - leave the switch OFF and you rely on the relay doing its thing (so usual MO). If the relay fails, you can connect the starter and leisure battery together by turning the switch on.
Get a decent rated switch - say 350A - and you will even be able to essentially join the two batteries together to assist starting the engine - but your cabling needs to be up to that as well of course.