Supply batteries -> off-grid power supply

Supply batteries, also known as consumer batteries, leisure batteries or board batteries, are used to provide an off-grid power supply for caravans, caravans and boats, for example, but also garden sheds, alpine huts and much more.

Which battery technology is right for me?

Supply batteries should always be adapted to individual needs and requirements. Different technologies are available for this purpose, each with different advantages and disadvantages. Roughly summarized, supply batteries can be divided into three categories.

1. classic lead-acid batteries (also known as "wet batteries"), which have been the standard for many years.

2. The next stage of development is lead batteries with VRLA technology, such as AGM or gel batteries.

3. the most modern technology is the lithium-ion battery ("LFP battery", "LiFePO4 battery"). These are currently still somewhat more expensive than their predecessors, but offer a long list of major advantages.

An overview of the different technologies

1. lead-acid batteries

Lead-acid batteries, also known as wet batteries, are the classic among supply batteries and are particularly impressive due to their low acquisition costs. They have a liquid core, which is why they are particularly sensitive to inclination and should/may therefore only be installed at low inclines. For safe operation inside the caravan, boat, etc., it is necessary to attach a venting hose to the gas line of the battery.

• Lowest purchase price
• shorter cycle life compared to AGM and lithium
• heavy
• medium deep discharge leads to damage to the battery
• Inclined installation or prolonged tilting can lead to leakage
• May not be gas-free
• may not be maintenance-free (depending on model, acid may need to be topped up)
• Can be charged and discharged at sub-zero temperatures

2.1 AGM batteries

The special feature of AGM technology is the glass fleece built into the batteries, which is able to bind the electrolytes of the battery to itself and also allows high currents to be supplied. Accordingly, AGM batteries are very safe to operate as they do not leak even in the event of damage.

• Very good price-performance ratio
• Longer cycle life compared to conventional wet batteries
• heavy
• High deep discharge leads to damage to the battery
• leak-proof and insensitive to inclined positions
• gas-free
• maintenance-free
• capable of delivering high currents for a short period of time
• Can be charged and discharged at sub-zero temperatures

2.2 Gel batteries

Gel batteries are particularly practical for small consumers with continuous power consumption. With this technology, silica is added to the electrolyte, giving it a gel-like consistency. This also makes these batteries leak-proof and flexible in terms of installation orientation.

• Very good price-performance ratio
• longer cycle life compared to conventional wet batteries
• heavy
• high deep discharge leads to damage to the battery
• leak-proof and insensitive to inclined positions
• gas-free
• maintenance-free
• capable of delivering high currents for a short period of time
• Can be charged and discharged at sub-zero temperatures

3. lithium batteries

Lithium-ion batteries such as LiFePO4 batteries are the solution for the most demanding requirements and the most effective technology of the variants described here. They are particularly flexible in their areas of use and applications and are clearly superior to other technologies in almost every respect. Due to the high demand, prices have fallen significantly in the last two years, which is why an investment in a lithium battery often pays for itself after a short time.

• Very good price-performance ratio
• significantly longer cycle life compared to wet batteries, AGM and gel batteries
• very light (the same usable capacity can be achieved with approx. 20% of the weight)
• the full nominal capacity of the battery can be discharged without damage (thanks to the integrated BMS)
• leak-proof and insensitive to inclined positions
• gas-free
• maintenance-free
• limited in continuous discharge current. Select a size that can cover your desired continuous discharge current
• can be discharged at sub-zero temperatures, but not charged (except special versions)

How big should my battery be? How much battery capacity do I need?

Once you have decided on a particular battery technology, the next important step is to find out how much capacity (ampere hours / Ah) you need. The required quantity and number is determined by the power requirements of the devices that are to be operated.
Take a look at the example below for a better understanding.

1. The first step is to calculate the total power consumption in ampere hours (Ah).
   
   To do this, you should list all the devices that you want to operate with the battery and determine their consumption in amperes:
   
   --> Device power consumption in watts (W) / battery voltage in volts (V) = required current in amperes (A)
   
   
2. Next, you should estimate how long the devices should be in operation until the battery is empty.
   
   --> Required current (A) * operating time (h) = required ampere hours (Ah)
   
   
3. For lead-acid batteries, AGM batteries and GEL batteries, you should include a safety reserve. (You can omit this step for lithium batteries)
   
   Multiply your total ampere hours (Ah) by at least 1.5 (better 1.7) for lead-acid batteries and at least 1.3 (better 1.5) for AGM and GEL batteries
   
   --> Required ampere hours (Ah) * Safety reserve (approx. 1.5 times) = Required capacity
   
   
   

The battery you select should therefore have at least your calculated required capacity.

If a single battery is not sufficient, several batteries may have to be connected in series.

Example

1. The first step is to calculate the power consumption of each device in amperes (A).
   Rounding up is better than rounding down here
   
   
   Water pump 50W --> 50W / 12V = 5 A
   Coffee machine 1800W --> 1800W / 12V = 150 A
   Refrigerator 100W --> 100W / 12V = 9 A
   Total light bulbs 90W --> 90W / 12V = 8 A
   Mobile phone charger 5W --> 5W / 12V = 0.5 A
   
   
   
   
2. Next, you should estimate how long the devices should be in operation (per day),
   
   
   Ww ater pump 5A --> 5A * 0.2h = 1 Ah
   Coffee machine 150A --> 150A * 0.3h = 45 Ah
   Refrigerator 9A --> 9A * 6h = 54 Ah (refrigerators usually only cool for approx. 25% of the day)
   Total light bulbs 8A --> 8A * 6h = 48Ah
   Mobile phone charger 0.5A --> 0.5A * 1h = 0.5A
   
   Total consumption per day: approx. 150A
   
3. For lead-acid batteries, AGM batteries and GEL batteries, you should include a safety reserve. (You can omit this step for lithium batteries)
   
   Required capacity:
   
   Example lead-acid: 150A x 1.7 = 255 Ah
   
   Example AGM: 225 Ah
   
   Example lithium: 150 Ah

--> If the battery is to last me at least one day (without charging by charger, solar, or charging booster), it should have at least the above-mentioned sizes in amperes.

If you need help choosing your supply battery, please contact us by phone at
+49 895 419 6384 - or by e-mail to [email protected] or via our contact form - we will be happy to help you find the perfect supply battery for your needs.