My local Costco sells Interstate Group 27 batteries for approx. $75 each --- but they are flooded, lead-acid, deep-cycle batteries; I've asked if they sell AGM batteries or can order them, & they don't & can't. The Group 27 batteries I installed under the bed were Group 27 sealed, AGM batteries, at approx. $200 each.
I fussed & fussed trying to figure out how to install Group 27s into my battery box, & at least with the Group 27s & the battery box I had, the only way I knew how to do it involved cutting off one or more of the top lips of the box, which I rejected; maybe others have a larger box?
I acknowledge that others have opined that installing sealed & unvented AGM batteries inside the trailer "is a no-no." To obtain further information on this issue, I did a Google search on "must AGM batteries be vented?" & found:
The batteries do not have to be in a box but if they are, they should be vented as per ABYC recommendations. AGM's are SVR (sealed valve regulated) batteries.
A vent system or other means shall be provided to permit the discharge from the boat of hydrogen gas released by the battery.
Battery boxes, whose cover forms a pocket over the battery, shall be vented at the uppermost portion of the cover.
NOTE TO 10.7.9 and 10.7.10: These requirements also apply to installations of all batteries whether they employ removable vent caps, non-removable caps, are “sealed” or “maintenance free” batteries, or have pressure regulated valve vent systems with immobilized electrolyte (gel batteries).
Location of Batteries and Battery Charger (see ABYC E-10, Storage Batteries). Consideration should be given to the following:
- Adequate ventilation should be provided to the bank of batteries to limit the temperature rise during the charging. Sealed valve regulator batteries do allow escape of hydrogen gasses during overcharging; therefore, SVR batteries require the same precautions for ventilation as wet (flooded) batteries. During the charging process, fully enclosed battery boxes will result in a greater temperature rise than with an open battery box.
2. From http://batteriesbyfisher.com/agm-batteries
There are two primary types of VRLA batteries, gel cells and AGM. A VRLA battery (valve-regulated lead–acid battery), more commonly known as a sealed battery or maintenance free battery, is a type of lead-acid rechargeable battery. Due to their construction, they do not require ventilation, can be mounted in any orientation, and do not require constant maintenance. The reduced venting is an advantage since they can be used in confined or poorly ventilated spaces. They are widely used in large portable electrical devices, systems and similar roles, where large amounts of storage are needed at a lower cost than other low-maintenance technologies like Li-Ion.
3. From http://www.carquestprofessionals.com...q_myths.html#9
Never install any type of battery in a completely sealed container. Although most of the normal gasses (oxygen and hydrogen) produced in an SVR battery will be recombined and not escape, oxygen and hydrogen will escape from the battery in an overcharged condition (which is typical with any battery type).
For safety's sake, these potentially explosive gasses must be allowed to vent to the atmosphere and must never be trapped in a sealed battery box or tightly enclosed space!
4. From http://www.homepower.com/articles/so...-small-systems
Article 480.9 of the National Electrical Code (NEC) states that provisions for ventilation must be made to prevent the accumulation of explosive gases, but the NEC doesn’t go into the specifics. Under the NEC, sealed battery technologies don’t require venting. American Boat and Yacht Council (ABYC) guideline 10.7.9 recommends a sealed, vented enclosure no matter what the battery type. Some local electrical codes even require power venting of the battery enclosure.
A properly designed and installed power system with a modern, three-stage charge controller keeps hydrogen gas emissions to a minimum (as with your present system), and battery technologies like sealed lead-acid don’t gas during normal operation. But what happens when the situation becomes abnormal? A poorly programmed or malfunctioning charge controller can cause any battery to gas, and even “sealed” batteries have internal valves to release the gas and prevent a case from rupturing.
Here's my situation:
a. Yes, I have installed 2 Group 27 AGM batteries in the storage area under the bed, adjacent to the front storage area accessible immediately in back of the old battery box & propane tanks.. These two areas are open to each other; the plywood that separates them only goes up partially to the top of the storage area, allowing air in the two areas to intermix. The front storage area is not sealed --- it is partially open to the outside. The storage area under the bed is also not sealed --- it is open on both sides to the bedroom area. Therefore, the AGM batteries are not in a "sealed battery box" & vent into both the interior & the exterior of the trailer
b. The two batteries are strapped to the floor & covered on their top by a cover (without sides) that is also strapped to the floor. The AGM batteries are not in a container, sealed or otherwise, so any discharge from them vents into the storage area, which is open to the interior of the trailer & partially open to the exterior of the trailer.
c. When I replaced the lead-acid batteries with AGMs, I also replaced the stock converter/charger with a 3-stage converter charger, specifically made in part to charge AGM batteries, to ensure no overcharging.
All in all, I remain unconvinced that given these circumstances, more venting of the sealed AGM batteries with no battery box is either necessary or recommended.