[Wavery]

Originally Posted by ThePair

Hello all!

I am a prospective TM owner (likely to purchase in the spring, so I don't have to worry about winter storage this year, but that's a whole other issue!). These boards are a big part of my purchase decision--the TM itself is a marvel of engineering, but no less important to me is the strong, cooperative and supportive community that is seen here.

I've been trying to do as much research as possible pre-purchase, and I have a battery question that confuses me. Everything that I've read indicates that a deep cycle battery is best used down to a maximum of 50% before recharging, in order to prevent damage and maximize the life of the battery. This would be ~ 11.9-12 V, according to "The 12 Volt Side of Life" and other sites.

However (here's the confusing part) I came across this: http://www.1st-optima-batteries.com/...e_battery.html which outright talks about bringing the charge down to 10.5 V. On other pages, they indicate that this is the voltage where a recharge is needed, and their AH ratings are based on this as well. But, according to other sites' info, this would be a complete 0% discharge, and would pretty much ruin a lead-acid battery. So, why is Optima suggesting that this is normal, routine use of their batteries? Is there something special about their batteries, or is this my misunderstanding of the information?

In addition, it seems that their battery ratings are ~1/2 of other manufacturers. At first I assumed that they were just cutting their number in 1/2 for the 50% discharge as noted above, but now I'm not so sure.

It's not that I can't understand this stuff (I do have a Chem degree, and a LOT of physics background), but this is simply contradictory information, and I was wondering if anyone could make sense of it all.

Of note, I'm looking at getting a new 2720SL (DW, twins now 2, and a Springer Spaniel.) TV is a Sienna, so I'm not sure anything larger makes sense, plus the extra floor space is desirable for the doggie. Winter storage will likely not be at my home, so a no-maintenance battery solution is very, very high on my priority list--I will not be able to check water levels or keep the thing plugged in all winter, most likely. I am also considering the two-battery approach, and AGM should lead to an easier installation in the 2720SL, as I understand it (no need for vent worries or access issues.)

I have about a billion other questions, but I figured I'd start here!

Thanks!

Marc

Basically, the answer lies in the stability of the electrolytes in the AGM battery..

You can completely discharge the AGM and maintain stability. When one allows the specific gravity get too low in a liquid battery, it destabilizes the electrolytes and it may not recover. This is not an issue in the AGM because of the unique blanket of gel electrolytes that are literally wrapped in thin blanket around the core then the blanket is wound in several layers.

The AGM also excepts a charge at a much faster rate (lower temperature) and it is less necessary to fully charge the battery. As you stated, there is no worry of losing electrolytes due to evaporation.

The other benefits are that the AGM battery can be mounted anywhere in any position (sideways, upside-down etc). The down side is they are expensive to purchase but when you figure the lower "lack-of-maintenance" failure costs, charging time required (if using a generator) and flexibility, they may actually be a more cost effective choice, over time.