I have a double battery set up (not leisure) as my MPV was built to operate in cold regions - had a little bit of corrosion over time. Last inspection a few months ago I had to replace the earth terminal on one side. I was doing routine check today and noticed the terminal had crud on it. I took it off to inspect and clean the battery. The earth post on one of the batteries has been badly eaten, the clamp has been almost eaten through.

Is this a signal that the battery has had it and is undercharged (refusing a charge)? Other than that no starting problems and no charging light - has me stumped but looks like its going to replacement clamp and also the errant battery. I consider lack of any problem of corrosion of that other battery terminals, earths linked so earth to body is common to both batteries.

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    Welcome to the site. We appreciate you being here. What exactly is your question? – Pᴀᴜʟsᴛᴇʀ2 Oct 2 '16 at 14:19

I think your analysis is correct. The hydrogen gas released as the battery charges leads to the corrosion. As the battery ages and no longer takes a full charge more gas will be released causing more corrosion.

It would also be good to look at how the batteries are fed. If they are just in parallel with the alternator the charging current may be unbalanced (as it is very likely that the batteries will ever be, or stay, identical). Ideally there will be an isolator and each battery will be charged individually.

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    Thanks dlu it is an unusual set up the vehicle is what we call a GREY IMPORT - it was never marketed in the uk however quite a few are buying them used and importing them to the uk as they are RHD. I need to get in there with a meter and assess the charging/discharging but it is looking like a new battery -- could easily bin one but we do get some minus winter temperatures here. will post the eventual outcome. mods - how about a European section - there aren't many sensible sites for the UK and Europe! – Jimhere Oct 3 '16 at 16:03

To prevent or at least minimize terminal corrossion in the future, you could cover them in petroleum jelly (acid-free) if they aren't already. Cleaning them can be done with contact-spray, this dissolves oxidation.

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