Hi David,
I’m thinking you might have heard about Century Plastics battery boxes from the link on my website since I’ve never seen them advertised and they aren’t readily available through West Marine . . . so I thought the least I could do is give you this response.
In the mid 80's when I was outfitting our sailboat to go offshore, there was still a thriving West coast fishery and a lot of chandleries to serve them. You weren’t getting insurance on a commercial fish-boat without battery boxes . . . the common boxes in the Pacific NW chandleries were the Century Plastic boxes so that’s what we put on our boat. When I sold the boat 23 years later the boxes looked “as new”.
What makes them so great? They are lightweight, and compared to the ones readily available at West Marine, they take up less room, and are much stronger (I weigh over 200 lbs - if jumped up and down on one all day, I’d only hurt myself - not the box). I bought my boxes at Industrial Plastics in Victoria BC for about $30 a piece (I installed a large battery bank in my boat so I used bigger boxes; I don’t know off-hand if group 27 sized boxes - for standard Ranger OEM batteries - are available).
I was surprised at the OEM battery installation on the R27 (with the batteries strapped to an open grid in a situation where battery caustics could get at the straps and the compartment . . . and with the house batteries “paralleled” on their terminals instead of at a buss . . . so I fixed all that). There are many reasons I ultimately stuck with conventional lead-acid batteries, but that is another topic (big, and “traditionally controversial” among boaters). Suffice it to say that all batteries, even AGM’s, have vents and caustics inside.
Hydrogen gas can be an unwanted by-product of the charging process - not from the lead acid reaction that makes our batteries work, but from hydrolysis. In a properly set up system, this shouldn’t happen all that much except with over-charging. If “gassing” (as the problem is commonly called) occurs, it turns out that hydrogen is lighter than air and would escape easily through the holes at the top of the box (unlike a propane box which needs to be airtight inside the boat with a drain at the bottom for outside egress of the heavier than air gas) and thereafter out the R27's “passive” engine-room ventilation system. (You may not have noticed this “system” on your boat, but it turns out that there is a “slot” for air-exchange extending 3/4 of the way around the engine-room hidden under the cockpit combing. We decided to put an additional active “push-pull” blower on our boat, though, as outlined briefly on our web page).
I think the insurance companies (which tend to “learn things the hard way”) are more concerned with a “backup” system for containment of battery caustics; this is precisely why you don’t want to be drilling a hole in the bottom of your boxes. The boxes are traditionally “strapped down” (you can find pictures of such installations on my boat at this link:
http://www.rangertugr27forsale.com/#/r2 ... utfitting/ ) ; look inside the battery boxes at West marine and you’ll find the straps and fittings that are supplied along with the boxes for this purpose.
So what “bad things” could come from caustic leaks? Well, you certainly wouldn’t want to “eat through” a battery tie-down causing a heavy battery to fly around your boat in lumpy seas. But I think the bigger worry for an insurance company is that bluish powder that you might sometimes find on the terminals of your car starter battery - that’s copper sulfate. It happens when battery caustics meet copper (not just any copper, but copper in a “charged state” . . . think “battery cables”). So in this situation, the copper is “dissolved”, then there’s not as much copper there to carry electrical current, subsequent big currents through smaller wire might make it hot, if hot enough it might cause a fire, etc. etc. .
Hope this “treatise” is of some use to you, David.
Take care,
Bob Lynch
R27 M.V. Echo
