Choosing the Right Battery Types for Your Van Conversion: A Comprehensive Guide

If you have undertook even a small amount of research regarding batteries for your tiny build, then you have quickly come to realise it is a bit of a minefield.

Battery technology is developing faster than you can imagine. They are becoming lighter, more powerful and their life cycles are ever increasing.

So what’s best? Well… how long is a piece of string?

There are a few fundamentals that are worth understanding before we proceed with the types of batteries in which you could fit into your tiny build.

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Depth of discharge

The first being depth of discharge (DOD). Depth of discharge is how far a battery can be discharged relative to its capacity. Different batteries have different depth of discharge ratings, some batteries can be discharged further than others.

We recommend that you always use a battery monitor, such as the Victron BMV, to accurately determine the depth of discharge of your battery. Not only do the battery management devices monitor DOD, they also give you an array of information regarding your battery. Once setup correctly these monitors become extremely useful in your tiny build and help prolong the life of your batteries.

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State of charge (SOC)

A batteries state of charge is simply the amount of charge within the battery.

A fully charged battery would be 100% SOC whilst an empty battery would be 0% SOC.

State of charge is the inverse of depth of discharge. Put another way, if a battery is at 100% state of charge, then its depth of discharge is 0%. The opposite is also true. If a battery is 100% discharged, its state of charge is 0%.

Cycles

The second fundamental is a cycle. A cycle is when the battery has been fully charged, discharged and then fully charged again. Every time it completes this circle of events, that will be considered 1 cycle. Although by completing this cycle the battery is technically aging, it also keeps the battery active and healthy. Different batteries have different life cycles, some more than others.

The number of charge cycles a rechargeable battery can withstand before performance degrades is the method in which we use to measure how long our batteries will last, if taken care of properly.

Battery Lifespan

A batteries lifespan is a time frame given by the manufacturer which depicts how many cycles a battery can perform in certain period of time.

Over time your battery monitoring system may tell you your system is at 100% charge but this isn’t necessarily accurate. This is a depletion in its lifespan, the battery will take longer to charge and be quicker to discharge in some circumstances.

Batteries coming to the end of their lifespan also struggle to hold a charge, so if everything is turned off in your tiny build and the battery is struggling to hold a healthy voltage you know your batteries are on their way out. If we look after our batteries, connect them in the correct way and use the correct equipment to charge them they will live long and prosper!

How can you increase the life of your batteries?

Once you begin to understand how different factors impact your battery’s life cycle, it becomes clearer how you can increase your battery’s life. Following some simple “best practices” can help you get the most out of your battery, regardless of whether it’s a lead-acid or lithium-ion battery.

Best Practice 1: As much as possible, use your battery in moderate temperatures. Of course, this may not always be possible but if you can keep your batteries in a moderate temperatures this can have a dramatic affect on its life cycles. Optimal temperature for most batteries is between 20 – 25 degrees centigrade. Lithium-Ion batteries are particularly sensitive to discharging and charging in colder weathers. To get around this you can surround your batteries with heat pads to keep them warm and operating efficiently.

Best Practice 2: If you have a lead-acid battery (FLA, AGM, GEL) ensure that you minimise how often you discharge the battery below 50% of its capacity. Ideally, the depth of discharge on each cycle should be between 10% and 50%. If you have a lithium battery, you can likely go down to 80% DOD and, in some cases, 100% DOD. Refer to your battery manufacturer’s recommendations to be safe.

Best Practice 3: If you have a flooded lead-acid battery, make sure to keep the electrolyte solution topped up.

Best Practice 4: Ensure you use the correct charging equipment for your batteries. Better yet, ensure the charge equipment that you are using has the correct charge parameters for your battery type. These parameters vary from battery type to battery type and needs to be done correctly. This is something that we, at Tiny Build Electrics, can help you with.

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Battery Types

Batteries is a stage you want to get right, after all, no one wants to be sat in the dark sipping warm beers, right?!
Understanding the types of batteries available, the capacity you need for your van lifestyle, the relative cost and how to take care of them will help when it comes to choosing the best camper van batteries for you.

The four battery types we will be considering are:

• Flooded Lead Acid batteries (FLA)
• Gel batteries (GEL)
• Absorbed Glass Mat batteries (AGM)
• Lithium-ion batteries (LiFePO4)

Each type has a different make up and because of this perform differently under different circumstances.

Flood lead acid (FLA)

Flood lead acid batteries consist of two lead plates, one positively charged, the other negative. The battery is then flooded with a liquid electrolyte, sulphuric acid which covers all internal parts. When charging commences the acid and lead plates react to store electricity.

Pros

• Low cost
• Resilient to occasional over charging
• Proven technology
• Lifespan can be 4-8 years with regular maintenance and careful charging
• Less susceptible to temperature differences

Cons

• As the batteries age the performance will degrade to the point where the battery won’t hold a charge
• Should be stored inside an enclosure (battery box)
• Battery can only be drained to a maximum DOD of 50%, otherwise you’re likely to incur damage.
• Must be vented in an enclosed area as some FLA batteries will emit gases.
• Stricter regulations on how FLA batteries are fitted and how close they are installed to inverters and chargers.
• Require regular maintenance
• Heavy

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Gel

Gel batteries use the same technology as FLA but instead of liquid acid they are filled with Gel. Gel gives us more advantages than FLA as you will see below.

Pros

• Doesn’t emit any nasty gases
• Sealed so can’t leak or produce any gas
• Maintenance free
• Operates in a wider array of temperatures than AGMS.
• Ideal for vans that are stored over winter and not used for long periods of time

Cons

• Very sensitive to depth of discharge
• Do not recover well from a low DOD
• More expensive than conventional FLA and AGM
• Heavy

View All

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Absorbed glass mat (AGM)

AGM batteries work in a similar manner to FLA and Gel. Instead of acid or gel they have electrolyte soaked glass fibres between the positive and negative plates.

Pros

• Long shelf life
• Maintenance free
• Ideal for vans that are stored over winter and not used for long periods of time
• Can be installed sideways as its a sealed unit and cannot leak (unless damaged)
• Smaller than the conventional Gel equivalent

Cons

• Very sensitive to depth of discharge
• Do not recover well from a low DOD
• More expensive than FLA
• Heavy
• Poor performance in colder temperatures

View All

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Lithium LiFePO4 / Lithium-ion / Li-ion

The famous lithium-ion battery. If you have done any sort of research on tiny building or off grid systems then it is highly likely you have come across the lithium battery, currently at the top end of the battery technology market. This is a battery you should be considering for your build, there’s just one downside… £££!

Pros

• 30% lighter than FLA, GEL & AGM
• Smaller frame size than FLA, GEL & AGM
• 90% of their capacity is usable meaning you need less batteries for the same amp hours as FLA, GEL & AGM
• Low internal impedance (resistance) mean these batteries also charge a lot quicker than the other types of batteries.
• Can be installed in various orientations
• Maintenance Free
• Long life cycles if charged and discharged in accordance with manufactures instructions

Cons

• Very sensitive to charging in low temperatures
• Expensive, although prices have started to drop over the past few years
• A battery management system is required to protect the lithium-ion battery bank from excessive discharging, over charging and to control the load and balancing of each internal cell. Most of the time this system is built into the battery itself.
• Some extra monitoring may be required such as battery temperature monitoring

Lithium-ion batteries (LiFePO4)

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Can I use a vehicle engine battery as a leisure battery?

Start batteries are the type of batteries that are used in cars, boats, lorries, buses and generators. Start batteries are not suitable for uses where they are discharged and then recharged again, also known as a cyclical use.
They also cannot be used in connection with an inverter, although technically they can the batteries make up means that it will not last very long while feeding an inverter.

The reason that start batteries are not suitable for frequent deep discharging is because of the way they have been constructed. They have thin plates with a large surface area. They are designed purely for short-term high discharge currents like engine starting.

During an engine starting the battery is exposed to high current draw in a short period of time. This high current draw turns a starter motor which in turns causes the engine to turn over and start. It might be tempting to use start batteries in a battery bank in smaller inverter systems, but please don’t do it. It will only cause trouble in the long run.