In today's world of overlanding and camping, the importance of batteries has grown exponentially. Gone are the days when camping had to mean disconnecting from all modern conveniences. Nowadays, essential items like fridges and lights have become part of our outdoor essentials, demanding reliable power sources to keep our adventures going smoothly.
What Sort?
The market offers a wide range of battery types, including Gel, AGM, Flooded Lead Acid and the increasingly popular Lithium-Ion batteries. For the sake of this article, let's leave the Lithium-ion batteries for another discussion, as it is, the choice can be overwhelming, however as with most products we purchase, focusing on reputable brands with a nationwide warranty of at least two years can help provide you with peace of mind.
Battery mounting location will play a big part when choosing a battery. For example, battery manufacturers will not warrant their batteries if mounted in high temperature environments, like under the engine bay hood.
My recommendation for batteries mounted in an engine bay would be AGM/Lead Acid Batteries. Now there are many people who would like to debate whether we choose an AGM or Standard flooded lead acid battery, and both have their good and bad features. Let’s leave that decision up to the battery specialist selling you the battery. Remember reputable brands and warranty periods!
For the inside of the vehicle, motorhome, trailer, camper or similar, if not choosing the premium lithium-ion path, then my recommendation would be Gel or AGM batteries. AGM batteries tend to be more readily available and affordable when compared to the Gel type batteries with both offering similar performance and maintenance requirements. Both these battery types are typically fully sealed, meaning they won’t don’t give off that Sulphur-like smell when charging. The smell is associated with the battery’s gassing, and this chemical reaction happens when the battery is being charged. This gaseous smell is a highly flammable hydrogen gas and not recommended for human consumption! It’s also my experience that AGM batteries recharge faster than their Flooded Lead Acid brothers, so keep that in mind.
Learn more on the different sorts of batteries with our guide to auxiliary batteries.
What Type?
This is where you need to decide what you are requiring this auxiliary battery for. Auxiliary batteries are used to preserve your main vehicle start battery for vehicle specific duties, i.e., starting the vehicle. Whilst your auxiliary battery is added to enable you to run your other recreational loads i.e. fridge, lights and inverters.
My recommendation for an auxiliary battery would tend to be a Deep Cycle Battery. This type of battery is designed for many dis-charges and re-charges; we also refer to this as the cycling of a battery. People’s misconception of Deep Cycle Batteries is they can be fully discharged and re-charged. However, caution must be noted as to not discharge your AGM/Lead Acid auxiliary Deep Cycle Battery/s below a level of 50% charge, as this type of continual over discharging will reduce the performance and life expectancy of your Deep Cycle Battery. A rule I try and abide by is not taking my auxiliary battery lower than a voltage level of say ~12Volts, at the very worst 11.5Volts.
Remember also if you discharge a battery for say 12 Hours it will surely take longer than a one-hour drive to recharge it fully again!
How Long?
This is a beauty, as there are so many variables that when somebody tries to answer this question it is an educated guess at best. Below are a couple of examples of battery run times talking in theory using “round figures.”
Example No.1
- 100 A/hr AGM Battery
- Fridge in 77 Degree Fahrenheit ambient temperature
- Minimal opening and closing of the fridge
- Fridge draws 4 amps whilst running
- It cycles on for 25% of the time
This means that in one hour the fridge (only) consumes 1Amp hour of charge from the battery. Remembering we do not want to discharge our battery below a level of 50%, this means we have 50A/hr of usable energy from a fully charged 100A/hr AGM battery. Under these conditions we can run our fridge (only) for almost 2 days without the battery being charged.
Example No.2
- 100 A/hr AGM Battery
- Fridge in 95 Degree Fahrenheit ambient temperature
- Regular opening and closing of the fridge (Thirsty Mates!)
- Fridge draws 4 amps whilst running
- However now in the hotter/more frequent use, it cycles on for 75% of the time
This example shows that in one hour the fridge (only) consumes 3Amp hour of charge from the battery. Again, bearing in mind we don’t want to discharge the battery below a level of 50%, this means we have 50A/hr of usable energy from a fully charged 100A/hr AGM battery. Under these conditions we can run our fridge (only) for a little over 16Hours, a little over half a day!
Obviously, the figures listed above are only an example, the various loads, battery types, ambient temperatures, fridge temperatures and frequent use will affect this suggested power consumption and run time.
You can see clearly from these examples, starting with a battery which is at 100% is so very important. With many of us never achieving our batteries' full potential, run times and battery life will differ immensely. This highlights the importance of keeping your batteries maintained at 100% and not discharging your auxiliary batteries too much!
Article written by Mark Bruce, REDARC Electronics Technical Training and Development Manager – North America. Mark Bruce is a qualified Auto Electrician with over 35 years experience in the trade and wholesale automotive electrical industry.
For more technical advice and understanding your battery needs, speak with Mark directly by contacting us.
