What is an on-board battery?

On-board batteries are supply batteries. The batteries store electrical energy on an electrochemical basis. The classic 12-volt batteries with lead-acid technology consist of six cells, each with a voltage of 2 volts. Each cell has two sets of plates which are in diluted sulphuric acid. The material of the positive plate sets is lead dioxide, the negative plate (sets) are made of lead.

Supply batteries with lead technology have thicker lead plates compared to starter batteries, are optimized for continuous current drain and have a much longer cycle life. The supply batteries tolerate deep discharges of up to 75 percent better. The other properties depend on the respective battery technology.

Which on-board battery do I need for my motorhome?

The first step is to decide on a battery type. You can choose between classic wet batteries, more advanced lead-acid batteries and the modern lithium batteries.

Wet batteries for motorhomes: the affordable choice for beginners

Motorhome wet batteries with liquid electrolyte are entry-level models. Their design is similar to that of starter batteries. Manufacturers use thicker lead plates to optimize cycle stability. Older models can outgas and require a venting hose. Modern wet batteries, on the other hand, are maintenance-free. They are usually dual-purpose batteries for engine starting and power supply. These classic lead-acid batteries cannot be installed in an inclined position. They should also be installed in an acid-proof tray.

Advantages:

• Low price
• Low maintenance or maintenance-free
• High currents

Disadvantages:

• Not leak-proof
• Higher self-discharge
• Risk of outgassing
• Lower service life

Recommendation:

Wet batteries are suitable for low deep discharge and if the motorhome is usually connected to shore power.

VRLA batteries for motorhomes: maintenance-free, leak-proof and vibration-resistant

VRLA batteries (valve-regulated lead-acid) are advanced lead batteries with a sealed housing. They are non-gassing, suitable for indoor use and require no maintenance. You do not need to and cannot top up with distilled water. VRLA batteries are leak-proof and can be used in an inclined position - under the passenger seat is a typical installation location. The cycle stability of VRLA supply batteries is about twice as high as that of maintenance-free wet batteries. There are two types: Gel and AGM batteries. Gel batteries (VRLA) for operation inside the motorhome In lead gel batteries, silica binds the electrolyte and turns it into a gel-like state. Due to the high internal resistance, this type of battery is not suitable for delivering high currents. The manufacturers optimize the batteries for the constant power supply of small consumers over long periods of time. The advantages of these supply batteries include low self-discharge and cycle stability. They can withstand high discharge depths without premature wear. However, performance drops at low temperatures.

Advantages:

• Maintenance-free and leak-proof
• Can be used in inclined positions
• Vibration and shock resistant
• Tolerates high deep discharges
• Ideal for the permanent power supply of small consumers

Disadvantages:

• Not suitable for delivering high currents
• Less powerful in cold temperatures
• Longer charging time

Recommendation:

Gel batteries are well suited if you want to constantly supply small consumers with power and do not want to connect any power-hungry devices. AGM batteries supply power-hungry devices in motorhomes and when camping Supply batteries with AGM technology (absorbent glass mat) integrate glass fleece mats that absorb the electrolyte. This results in excellent vibration and impact resistance, and the battery can be installed in an inclined position. Due to the lower internal resistance, AGM batteries reliably deliver high currents and, for example, use an inverter to supply power to sophisticated appliances such as hairdryers and coffee machines. Another advantage: the batteries charge comparatively quickly, which is practical for self-sufficient operation with a solar system. In modern cars with a start-stop system, they serve as a starter battery. They are the preferred choice in motorhomes with many devices switched on at the same time. Low temperatures do not affect performance, which is why winter campers usually opt for AGM batteries.

Advantages:

• Maintenance-free and leak-proof
• Can be installed at an angle
• Vibration and shock resistant
• Also delivers high currents
• Can be easily combined with solar
• Fast charging time

Disadvantages:

• Sensitive to heat

Lithium batteries for continuous use and the highest demands in motorhomes

Compared to lead-acid batteries, lithium batteries for motorhomes weigh significantly less with the same nominal capacity. As you can use almost all of the capacity when required and lithium batteries can be deep-discharged to more than 75 percent, you also benefit from the higher energy yield. The energy density of lithium iron phosphate (LiFePO4) batteries is three times higher, and one lithium battery replaces two gel or AGM batteries. Another selling point is the excellent cycle stability. Lithium iron phosphate batteries last much longer, so the higher purchase price pays off over the years. Even when not in use, the lithium battery scores highly due to its minimal self-discharge. If the motorhome is parked in a garage in winter, you should connect gel and AGM batteries to a charger from time to time and charge them fully. Otherwise, sulphation will occur more quickly in a partially charged state. Lithium batteries, on the other hand, can be stored partially charged; around 50 to 70 percent is recommended. Lithium batteries are also intrinsically safe. The lithium-ion batteries in smartphones can deform and catch fire. The advanced lithium iron phosphate batteries for motorhomes have a different design. They are maintenance-free, leak-proof and there is no risk of explosion.

Advantages:

• Maintenance-free, leak-proof
• Can be installed in any position
• Extremely high cycle stability
• High energy density
• Can be recharged more quickly
• Long service life
• Minimal self-discharge

Disadvantages:

• High purchase price

How big does the on-board battery for the motorhome need to be?

The required capacity (Ah) of the body battery for the motorhome depends on how much power the connected devices in the vehicle consume and how many hours you use them before the battery is charged by the alternator, solar system or shore power. The question is therefore how long you would like to camp self-sufficiently in the great outdoors without sacrificing the convenience of electrical appliances. You can calculate the required capacity (Ah) by balancing the average consumption.

To do this, list the electrical appliances with their power consumption values and multiply these by the typical duty cycle. If you also sleep in the motorhome in winter, you should draw up a separate balance for the cold season due to the higher power requirement.

Example for calculating electricity consumption:

• Compressor refrigerator: 40 watts * 8 hours = 320 Wh
• Light: 10 watts * 4 hours = 40 Wh
• Laptop: 50 watts * 2 hours = 100 Wh
• Total: 460 Wh / 12 volts = 38 Ah daily power requirement

With a lead-acid battery, you can achieve the maximum service life if you only discharge it to 50 percent. In the example, this corresponds to an on-board battery with 76 Ah. When operating with a solar system, it is important to plan in a bad weather reserve. After all, the sun doesn't shine every day.

How long would you like to camp self-sufficiently in the great outdoors?

To ensure the power supply for the appliances in the example for three days without shore power and sunshine, you need a supply battery with around 230 Ah. If you decide to buy a lithium battery, a capacity of around 135 Ah is sufficient, as you can discharge it much more deeply. In addition, the lithium battery can absorb energy more quickly in strong sunshine.

Charging the on-board battery correctly

Even the best quality battery is of little use and wears out quickly if it is not charged correctly. The correct charging procedure is essential to ensure that the on-board battery achieves the charging cycles promised by the manufacturer.

• While driving, the alternator charges the supply battery.
• In combination with a solar system, the charge controller ensures correct charging. It must match the battery type.
• When connected to the 230-volt mains, the charger must be designed for the battery technology. Modern chargers with an IuoU characteristic can be adjusted to the battery type. The final charging voltage for wet and gel batteries is 14.4 volts and 14.8 volts for AGM batteries. Lithium batteries charge faster, suitable LiFePO4 chargers are marked accordingly.

Summary

• For a small to medium-sized motorhome with few and undemanding consumers, the performance of a deep-cycle wet-cell battery is sufficient; a gel battery is more cycle-resistant.
• If you want to use a larger inverter with power-hungry appliances such as a hairdryer or coffee machine, an AGM battery is more suitable.
• For the highest demands, it is worth investing in a lithium battery.

Compare the offers from brand manufacturers such asAcconic, Exide or Optima and order the motorhome battery with the technology and capacity for your needs now from our Voltimax.de online store!