• Physical dimensions. These can often be expressed as commonly-used BCI "group" sizes, such as "group 31," or also frequently-used but somewhat less standardized "industry" sizes such as 8D or L16.
• Capacity in amp-hours, at whatever voltage you need.
• Terminal configuration. Important if you don't want to change cabling.
• Expected usage. Do you expect to deep-cycle these constantly, or mostly float them?

---

quote:

Folks,

Let's not confuse battery type with battery size (which is also different from capacity).

Asking "What's better, marine or 8D?" is like asking "What's better, 92 Octane or 15 gallons?"

I don't want to irritate anyone by repeating here information that is readily available either in the archives of this board or other bus boards (e.g. BNO), or at various other excellent resources such as:
http://www.phrannie.org/battery.html
http://www.windsun.com/Batteries/Battery_FAQ.htm
and many others.

However, and with due deference to my good friend Jerry, I'd like to note that any type of battery, to include starting, deep-cycle, marine (which is a type of battery that, by definition, attempts to compromise between starting and deep-cycle performance), traction, float-service (emergency back-up batteries), AE (Alternative Energy), etc. can be made in any size, such as Group 31, 8D, L-16, etc.

It is a fact that most batteries in, for example, BCI Group Size 24 will be starting batteries, while most batteries made in size L-16 will be traction batteries. However, there are a number of sizes, notably 8D and Group 31 (among others) that are very popular form factors for a number of different uses.

One can find 8D batteries that are pure starting batteries, strict deep-cycle batteries, marine batteries, and even traction batteries (especially in EV usage) as well as AE batteries. And one can find "marine" batteries in a wide range of BCI group sizes and including 8D.

FWIW, as stated elsewhere in many places, I believe "marine" batteries are never the right ones to use in a motor coach. Use starting batteries for starting, and use AE, Traction, or "deep-cycle" batteries for your house systems. What size (form factor) you choose depends on many factors, including how much capacity (in amp-hours) you need or want, what the shape of the battery compartment will look like, how much weight you want to carry, etc.. Lastly, within "type", you will often be faced with a choice of technology, to include "traditional" flooded lead-acid (which, BTW, includes many "maintenance-free" batteries that are really flooded cells, just without user-accessible caps), gelled-electrolyte, Absorbed Glass Mat (AGM), and even Lithium-Ion (yes, there are AGM starting batteries, just as there are flooded deep-cycle batteries). Choice of technology will be driven by ease of service access, availability of proper venting, laziness of the owner, and other factors.

Choosing the right batteries is one of the often-overlooked "critical" decisions in how well your coach will perform, especially if you spend considerable time away from shore power.

Good luck on your research.

-Sean
http://OurOdyssey.BlogSpot.com

---

---

quote:

... used AGM's ... but they did require a different charging strategy than Gel or flooded as I recall.

---

• Few, if any, people actually do as much maintenance as flooded batteries require -- they require it weekly at minimum and daily preferably.
• Corrosive emissions from flooded batteries wreak havoc with whatever part of the coach they are installed in.
• Hydrogen gas given off during the charging process is explosive.
• They must be located in a vented compartment and can not be in occupancy areas.
• They can not be discharged as deeply as AGM nor as many times as gelled.
• They must be recharged more slowly than AGMs.
• They must be kept vertical at all times.

---

quote:

AGM is for the folks that will pay for the ability to very rapidly recharge them , period,

They can be destroyed as easily as wet cells

---