A LEAD ACID BATTERY is a type of battery you heard about but...
There is much more to know!

There is at least one lead acid battery in your motorhome which would be the engine battery to start the motor of the vehicle.

However, you also have house batteries to power all the domestic electrical amenities. Are those of a different type?

Notice that in a RV trailer, you would only have the house batteries since there is no engine.

Let's then have a look at these two main battery categories.


- SLI battery

The lead acid battery for the engine is the standard thin plate 12-volt automotive SLI (Starting Lighting Ignition) battery that starts the motor and powers lights and other functions of any automobile: radio, air conditioning, dash lights etc...

The SLI battery is built to supply large amperage (a lot of current) for a short time to start the engine. These starting batteries are designed with a large number of thin lead plates for maximum surface area.

In their starting function, the SLI batteries are discharged less than 10 % and can last for thousands of cycles. However,they would fail after only 30 to 50 deep cycles when they are highly discharged.

You have at least one lead acid battery (maybe two) of the SLI type to start the motor engine of your motorized RV (or tow vehicle).

- DEEP CYCLE battery

The house battery is a deep cycle battery with the capacity for heavy and repeated discharges, as is the case when boondock RVing

The deep cycle batteries are made of thick solid lead plates versus the lead sponge design of SLI batteries. They have less surface area, i.e. less instant power than the starter battery but have a much longer longevity.

It is important to note that you can not use marine (a hybrid between the automotive and deep-cycle battery) or SLI batteries as house batteries.

You absolutely need to use thicker plated deep cycle batteries to provide power to the living quarters of your RV. This is important to remember.

Always select deep cycle batteries as house batteries.

They are designed to store a large quantity of power and are the only ones that can be charged and discharged down as much as 80 % over and over again. (Note that a maximum discharge of 50% is preferable.)

Since house batteries are the ones we are interested in to store energy power, let's have a look at them.

1) Wet cell or flooded electrolyte battery (with removable caps)

This is a lead acid battery with liquid electrolytes and removable caps (like the SLI) with heavier plates. It needs frequent maintenance and adequate ventilation for fumes.

Sulfuric acid must be handled with great care and the gassing fumes (oxygen and hydrogen) are emitted when charging this type of lead acid battery.

For this reason, these wet cell batteries can not be located in a living space. If you have an inverter , it has to be located in another compartment since the gas emitted is explosive.

Any spark coming from an electrical device, may provoke an explosion. Also, this type of lead acid battery can not be placed on their side since they are not sealed.

They come as a regular 12 volt 6 plate battery or a 6 volt 3 plate battery, called golf cart battery.

Golf cart batteries are often preferred because they have higher capacities. You need to purchase two 6 volt batteries to replace one 12 volt battery which is the voltage of DC current in your RV.

The pair of 6 volt batteries would have to be connected in series with battery cables The wet cell batteries are inexpensive but need maintenance on a regular basis. They are still a great choice for many RVers on a tighter budget, getting the most for their money.

2) Sealed flooded immobilized electrolyte battery

This is the same kind of lead acid battery but with no caps and no need for electrolyte refills. However they have vents for gassing when charging which means that these 'maintenance free' batteries are not really totally sealed and spill proof.

This type of lead acid battery is NOT RECOMMENDED because you can not add distilled water to level the cells and they will, over time, lose water.

That will have for effect that the batteries will die prematurely because of the internal damage done to the plates. In this case, the advantage of 'maintenance free' becomes a disadvantage.

3) Gel cell battery (sealed)

Also a lead acid battery sealed but with electrolytes having the consistency of a gel or paste.

The advantage is that it is impossible to spill acid even when broken. They are more expensive, heavier and require monitoring. Overcharging (limit 14.1 volts) results in excessive gassing (oxygen and hydrogen) and damage to the battery.

They do not need ventilation and require low maintenance. The fact that they charge very slowly and they can be easily damaged with improper charging is a big disadvantage. Gel batteries also loose water in hot climates due to evaporation.

Because they are sealed, the water can not be replenished and the plates will eventually break. They are no longer recommended in RVs and have been replaced by AGMs.

4) AGM battery (Absorbed Glass Mat)(sealed)

This is a new technology using an electrolyte liquid in a sponge, like a material of glass fiber. AGM batteries are sealed, spill proof and maintenance free. They have minimal gassing. Actually, the gas emitted is automatically reintroduced into the unit.

Another advantage is that they do not loose water. The battery will not leak acid even if broken. No ventilation is needed. They can be placed on their sides. It is possible to install an inverter in the same compartment.

They are very resistant to vibration and impact. AGMs are heavier, and 3 to 4 times pricier than wet cell batteries. They are the only battery that can be shipped via UPS or FedEX.

You must be careful not to overcharge them but they charge faster than other types of batteries and are certainly more durable than Gel cell batteries.

Each type of deep cycle battery mentioned has pros and cons. If you can afford it and intend to 'boondock' on a regular basis using solar panels, I highly recommend the AGM battery.

They are suited for RVs. They seem to last longer (4 to 10 years), are maintenance free and can be recharged with higher voltage equipment.

The 12 volt deep cycle batteries come in different sizes. Many have group sizes based on positions of terminal posts and physical sizes plus variable capacities.

Group - Capacity (amp hr.)

Dimensions (ins. L x W X H)

  1. 24 (70-85 amp hr.)
  2. 27 (85-105 amp hr.)
  3. 31 (95-125 amp hr.)
  4. 4-D (180-215 amp hr.)
  5. 8-D (225-255 amp hr.)
  6. Golf cart (180-220 a/h)
  7. L-16 (340-380 amp hr.)
  • 10.87 X 6.58 X 9.97
  • 12.60 X 6.60 X 9.97
  • 12.94 X6.74 X 9.88
  • 20.73 X 8.66 X 10.27
  • 20.62 X 10.95 X 10.17
  • 10.37 X 7.13 X 11.57
  • 11.69 X 7.13 X 16.69

It is possible to buy 6 volt AGMs with the same base size as a 6 volt golf cart wet cell battery. The golf cart batteries are physically larger in height but if you have room for at least 2 of them, they are a great choice.

You can put more batteries in a smaller space with the higher amperage hour rating (more current supplied for a same period of time). They are expensive but are the best to combine with solar panels

These companies offer different options:

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