Most RVs come equipped with "RV Marine" type batteries -- a sort of hybrid between a true deep cycle and a starting battery (and less expensive for RV manufacturers to use.. These are definitely better house batteries than a starting battery would be -- so use them until they wear out and then replace them with a true deep cycle type.
Flooded lead acid batteries are either lead calcium "maintenance free" types, or lead antimony -- the more traditional type that has caps and to which you need to add water periodically. Most deep cycle batteries are lead antimony, since the "maintenance free" types (lead calcium) are sealed, but have low tolerance for "deep" discharge (below 40-50%). Lead antimony has higher tolerance for deep discharge, but they self-discharge faster. On balance, lead antimony is better suited for RVs, and true deep cycle batteries are of this type.
Lead Acid batteries have changed little since the 1880's although improvements in materials and manufacturing methods continue to bring improvements in energy density, life and reliability. All lead acid batteries consist of flat lead plates immersed in a pool of electrolyte. Regular water addition is required for most types of lead acid batteries although low-maintenance types come with excess electrolyte calculated to compensate for water loss during a normal lifetime.
Gel Cell: Good for boats, where you're in rough seas, since the electrolyte won't leak out as it would with flooded batteries. But some problems, and in terms of utility are now totally replaced by AGM. If you charge gel cels at too high a charge, you'll actually lose some of the elctrolyte through gassing, and dry out the battery (shorter life).
AGM (absorbed glass mat) is a flooded lead acid battery, but instead of gel, it uses a fiberous mat which is 90% soaked in electrolyte. It is sealed, and the electrolyte is so immobilized that it can never come out.
Solar is nothing but a battery charger. Inverter is nothing without a battery. So need to understand batteries before you can understand either solar or inverter.
The only true way to know state of charge of a battery is to check its specific gravity. But very few RVers do this. Another fairly complicated way is to buy a meter for several hundred dollars (e.g., Link 10) that will measure that for you. The other way is to go by battery voltage. Preferred method is digital display, versus analog (needle). The idiot lights (red, amber & green) that come with most new rigs actually mean very little. The key to voltage checks is getting the battery "at rest". Yet that's virtually impossible unless you completely disconnect the battery, since there are always phantom loads (sensors, etc.). If you're plugged in to shore power, or use solar panels, they "charge" and make it impossible to know true voltage. Best time is first thing in the morning when you've not been plugged in (and before any solar influence). 12.65V is "full"; 12.47V is 75%; 12.24V is 50% 12.06V is 25%; 11.89V is just about zero.
How to know battery voltage: Only way to know for sure is to test the specific gravity of each cell. But his is so cumbersone that most RVers want another option. The built in systems of LEDs are at best an approximation. Best time to catch battery in the needed "at rest" condition is in the early morning -- unless you have solar, in which case you need to check before first light.
Primary causes of battery failure: Overcharging is one primary culprit. To charge, you need a source 14.1V ro 14.4V or more at room temperature. That's the gassing threshold for most lead acid batteries. You don't want to have higher voltage causing it to boil or "gas" from excess amperage. Gassing will occur at lower charging rates if the outside ambient temperature is hot -- such as parking on ashphalt during hot weather. Overcharging causes plate corrosion and/or water loss. In colder weather you may need to go above 14.1-14.4 volts to cause the needed gassing to stir the electrolyte. This is called reaching the edge of the gassing threshhold, which is needed to fully recharge the battery. Thus batteries will have longer life if there is a system for changing the charge rate depending on termperature. Lack of temperature compensation on inverter, charger, and solar is very important for RVs. Hot batteries require a lower voltage charge, while cold weather requires using higher voltage to "compensate" for the ambient temperatures. Unless the charging system can adjust the charging voltage either undercharging or overcharging is likely to occur. Temperature compensation is a crucial for RVs. If you don't have temperature compensation and the weather is hot, you'll have to add water more frequently, and keep batteries clean from the effects of gassing and spillage.
Undercharging is another problem, as it results in plate sulfation and electrolyte stratification. You'll know this when your battery used to last for 3 days, but now only lasts a day.
Vibration in an RV can cause some of the lead on the plate to fall
off and piles up on the bottom of the battery. Eventually it builds up
and will short out on the adjacent plate. By Greg Holder, AM Solar, Inc
Selecting a Battery (batterystuff.com) - When buying a new battery look for a battery with the greatest reserve capacityor amp
hour rating possible. Of course the physical size, cable hook up, and
terminal type must be a consideration. You may want to consider a Gel
Cell or an Absorbed Glass Mat (AGM) rather than a Wet Cell if the
application is in a harsher environment or the battery is not going to
receive regular maintenance and charging. Be sure to purchase the correct type of battery for the job it must do.
Remember that engine starting batteries and deep cycle batteries are
different. Freshness of a new battery is very important. The
longer a battery sits and is not re-charged the more damaging sulfation
build up there may be on the plates. Most batteries have a date of
manufacture code on them. The month is indicated by a letter 'A' being
January and a number '4' being 2004. C4 would tell us the battery was
manufactured in March 2004. Remember the fresher the better. The letter
"i" is not used because it can be confused with #1.
Have you ever been to a campground and you had electrical issues… brownouts, blackouts, blown fuses? We have experienced all of these issues, and after it happens it makes you wonder if it affected your rv electrical system in any way. The delicate electronics for your furnace, refrigerator, and hot water heater can easily be damaged! Air conditioner units, microwave ovens, TVs, DVD players, and 12 volt converters can also be damaged by voltage that is too high or too low! Any voltage less than 102 volts or greater than 132 volts is unsafe for your appliances / equipment in your rv.
There is a campground that we spent lots of weekends camping there that had terrible electric. You could blow a fuse just by using your toaster! The campground had several owners and every time an owner was new there was the promise “to fix the problem”. Unfortunately, this problem still exists in older campgrounds.
A surge protector can protect against voltage spikes that can cause severe damage to your valuable electronic devices in your rv, but beware, do your homework before you make a purchase! Surge protectors come in 30 and 50 amps, so first select the correct amperage for your rv. Next check out how the surge protector works. Some are simply a surge protector like the type that you would use for your computer. Others detect not only a surge of electric but also wiring faults and high and low voltage. Some will only work until you receive a surge of electricity, and then need to be replaced. Some will restart themselves after a surge but they are also more expensive. Some are designed to be hardwired to your rv and others are designed to plug directly into your site’s electric box.
There are many choices and many manufacturers for a surge protector
for your specific need to give you peace of mind for anywhere you spend
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