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SLA Batteries v Lithium Batteries

Lead-Acid batteries have been around for some 150 years as the first type of rechargeable battery and while there are several varieties, they continue to be the most popular type of rechargeable battery for a variety of devices and they are durable, inexpensive and proven. Lithium batteries are a much more recent addition, dating back to the 1970’s but it really gained popularity with significant performance improvements through the late 1990’s and early 2000’s. It continues to gain momentum.

There are a few types of lithium batteries which are mostly dictated by their chemical compositions. The most common is Lithium Iron Phosphate (LiFeP04) predominately due to its stability but also high current, long cycle life and hardiness; they won’t overheat and can handle a decent amount of abuse and environmental extremes.

Lithium batteries do require closer monitoring so having a Battery Management System (BMS) is important as the cells can be impacted from over or under current, over or under voltage or over under temperatures, all of which can cause permanent damage.

Let’s break down some of the key differences between the two.

Lithium-Ion Batteries

Pros:

  • Longer Lifespan: Lithium batteries can last two to three times longer than their SLA counterparts, depending on care and conditions.
  • Lighter Weight & More Compact: They offer a higher energy density, meaning they pack more power into a smaller and lighter package.
  • Faster Charging: Lithium batteries generally have a quicker charging time compared to SLA batteries.
  • Unaffected by Partial Charges: Unlike some other battery types, letting a lithium battery partially charge will not negatively impact its overall lifespan.
  • Slightly Better Cold Weather Performance: While charging in the cold is an issue, the general performance of lithium batteries is slightly better than SLA in lower temperatures.
  • Maintenance-Free: No need to add water or perform chemical maintenance.
  • Flexible Installation: Can be installed in any orientation without the risk of leaks.

Cons:

  • Higher Upfront Cost: The initial purchase price of a lithium battery is significantly more expensive than an SLA battery.
  • Challenging Cold Weather Charging: Charging lithium batteries below freezing (32°F or 0°C) is difficult, and some chargers will not work at all. Charging in these conditions can cause permanent damage.
  • Sensitive to Damage and Overcharging: They are more susceptible to heat reactions from being dropped or overcharged, which can lead to fires and the release of toxic fumes.
  • Newer Technology: As a more recent entrant to the market, there may be less certainty about their long-term viability compared to the decades-proven SLA technology.
  • Less Common: Lithium batteries can be more difficult to find in common automotive or big-box stores.
  • May Require System Upgrades: When replacing an SLA battery with a lithium one, you may need to consider additional modifications to your system, such as new charge controllers or alternator adjustments.

Sealed Lead Acid (SLA) Batteries

Pros:

  • Lower Upfront Cost: SLA batteries are a more budget-friendly option at the time of purchase.
  • Proven and Reliable Technology: Having been around for a long time, SLA batteries are a well-understood and trusted power source.
  • Resilient to Cold Weather Charging: They are more forgiving than lithium batteries when it comes to charging in colder temperatures.
  • More Durable: An SLA battery is generally more resilient to physical damage compared to a lithium battery.
  • Readily Available: You can easily find SLA batteries in a wide range of automotive stores and large retailers.
  • Maintenance-Free: Like lithium, they do not require watering or chemical upkeep.
  • Flexible Installation: Can be mounted in any direction without the risk of leaking acid.

Cons:

  • Shorter Lifespan: You will likely need to replace an SLA battery more frequently than a lithium one.
  • Heavier and Bulkier: For the same amount of power, an SLA battery will be considerably heavier and larger than a lithium battery.
  • Slower Charging: It takes longer to recharge an SLA battery compared to a lithium battery.
  • Slightly Lower Cold Weather Performance: While they charge better in the cold, their actual performance in cold weather is not as good as lithium batteries.

Is it Possible to Replace an SLA Battery with a Lithium-ion Battery?

Short answer is yes but with many considerations.

Charging System Compatibility – This is the most crucial aspect. You generally cannot use a charger designed for SLA batteries to charge lithium-ion batteries.

Battery Management System (BMS) – A quality lithium-ion battery must have an integrated Battery Management System (BMS). This is a vital electronic circuit board that protects the battery. Do not use a lithium battery without one.

Voltage and Amp Hours – You must match the nominal voltage of the SLA battery you are replacing (e.g., replace a 12V SLA with a 12V lithium). You should also choose an amp-hour (Ah) rating that meets or exceeds your power needs.

Size and Terminals – Many companies now manufacture lithium-ion batteries in standard SLA case sizes (known as “drop-in replacements”) to make the physical swap easier. However, it’s always wise to measure your battery compartment and check the terminal type and location to ensure a proper fit.

High Current Applications – For equipment that requires a large burst of current, such as starting an engine, ensure the lithium battery’s BMS can handle the high amperage draw. Not all lithium batteries are designed for engine cranking.

A successful upgrade may provide some benefits, but an improper one can lead to damaged equipment, a ruined battery, or a serious safety risk. The most critical step is ensuring you have a compatible charging system for your new lithium battery.

Conclusion

So as it turns out, both SLA and Lithium batteries have their own pros and cons so it really depends on where your priorities are. SLA is often an easier option – lower upfront costs, you can find an exact replacement, and is more of a known entity. Lithium batteries – more cost upfront but will last longer. There may be some additional considerations if switching from SLA to lithium like charge controllers, cranking amps, alternator performance which are all worth taking into consideration when researching your options.