Bongo Fury

We got a new 100a Numax leisure battery about a year ago and got it exchanged as is wasn't holding a charge.
Now got a similar problem, though not as bad, with the exchange one.

When on the van with noting turned on it loses charge to the extent that the radio and fridge don't work, down to about 9.5v after 2 - 3 days from fully charged.
Off the van the voltage stays up, no load on it of course though.
Obviously something is flattening it but putting an ammeter in the circuit it shows nothing so I'm baffled. I think I will have to take it back again and get it checked out. Even if the radio is still pulling a bit of current I can't see it flattening it in that short a time. Every time it goes flat I have to retune the radio the radio as well which is a pain.
Any ideas anyone please.

I had the same problem a while ago, it did turn out to be the radio, it was an ALDI special and was draining the battery within a few days, changed the radio and all is fine.
Another problem can be a faulty centre light in the rear, change the striplight.

Whatever the cause, a cheap isolator switch ought to cure it? I keep meanign to (re)fit one to mine

Thanks for the replies.
I've already got a switch fitted but that's not really solving the problem as like I said every time the battery goes flat the radio loses all it's presets and has to be tuned in again.
I'll try charging it up and then disconnect the radio and see what happens but it's strange it shows nothing on the ammeter and flattens in about 2-3 days which leads me to believe it's another duff battery.