During the discussion following Mark’s talk at the November meeting, Absorbed Glass Mat (AGM) batteries were mentioned, with the comment that their enclosure does not have to be ventilated, and that they can be installed in any orientation, even upside down.
By coincidence, I came across the following passage in a book by Collyn Rivers titled “The Campervan & Motorhome Book”: “Solid-gel and AGM (Absorbed Glass Mat) batteries withstand faster charging and deeper discharging than deep-cycle batteries but they are still more expensive on an effective amp/hr basis. “Note that their manufacturers’ previous advice regarding ventilation and orientation has been recently drastically revised. Housing must now be fully ventilated to the atmosphere. Orientation is still as one wishes (i.e. on the base, sides, or ends – but not, as previously claimed, upside down).”
I have bolded the conflicting parts. If you are proposing to install an AGM battery, it would be wise to confirm with the manufacturer their requirements regarding ventilation and orientation. Actually The Campervan & Motorhome Book is an interesting read for us boaties, especially if you are looking to set up a small boat for limited liveaboard. Collyn River’s emphases on keeping it simple, checking the weight and weight distribution, are all applicable to small boats. I tracked the book down on the recommendation of an acquaintance who shares my interest in alternative technologies, by searching the BCC library catalogue on Collyn Rivers – Author. This book, and the companion book “Motorhome Electrics & Caravans too” (concentrating on the electrical installation) are two of an impressive list.