When your electric vehicle needs a dependable auxiliary battery, the right choice keeps your systems running smoothly, from start-stop functions to powering accessories. These compact powerhouses ensure your EV stays ready, even in extreme weather.
This guide reviews the top 9 auxiliary batteries, focusing on capacity, cold cranking amps, and build quality, so you can pick the perfect fit for your vehicle’s needs.
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Weize AUX14 AGM Auxiliary Battery, 36 Months Warranty, 200CCA, BCI Group 40…
Best forDependable auxiliary power
- 36-month warranty
- Fast recharge
ConsiderNot for main starting
UPLUS Auxiliary Battery AUX14-UP 12V 14Ah 200CCA BCI Group 400
Best forEfficient low-temperature starts
- Pure lead construction
- Vibration resistant
ConsiderLimited capacity
Mighty Max Battery MM-AUX14 Auxiliary Battery 12V 14Ah, 22RC, 200 CCA Recha…
Best forRugged and durable use
- High discharge output
- Resists vibration
ConsiderHeavier than some
Daakmax Platinum AUX14 AGM Auxiliary Battery – Group 400, 12V 14Ah, 200 CCA…
Best forStart-stop system vehicles
- Wide temperature range
- 2X cycle life
ConsiderPremium price
Goodyear AUX14-AGM BCI Group Size 400 12V 14 AH, 22RC, 200 CCA Platinum ser…
Best forAll-weather versatility
- Flexible mounting
- Spill-proof
ConsiderNo warranty specified
Mighty Max Battery MM-AUX12 Auxiliary Battery 12V 12Ah, 20RC, 200 CCA Recha…
Best forCompact auxiliary needs
- Compact size
- Spill-proof
ConsiderLower capacity
Relistart AUX14 Auxiliary Battery, 12V 14Ah AGM Battery, 200 CCA Rechargeab…
Best forZero maintenance operation
- Sealed and leak-proof
- Consistent power
ConsiderNo warranty specified
UPLUS AUX4039 Auxiliary Battery 12V 1.3Ah For Mercedes-Benz N000000004039
Best forMercedes-Benz auxiliary slot
- Exact fit for Mercedes
- Pure lead construction
ConsiderLimited compatibility
Relistart AUX14 Auxiliary Battery, 12V 14Ah AGM Battery, 200CCA, Rechargeab…
Best forReliable backup power
- Sealed design
- High discharge rate
ConsiderNo warranty mentioned
Weize AUX14 AGM Auxiliary Battery – Reliable Power
Brand: WEIZE
A reliable, warrantied auxiliary battery for consistent performance.
The Weize AUX14 is a solid choice for auxiliary use, delivering 200 CCA for quick starts and consistent power. Its AGM technology ensures a leak-proof, non-spillable design, making it safe for various mounting positions. You’ll appreciate the faster recharge and longer cycle life compared to conventional batteries, which is crucial for modern vehicles.
With a 12V 14Ah capacity and a 36-month warranty, this battery offers peace of mind. It’s specifically designed for auxiliary duties, so ensure compatibility with your vehicle before purchase. If you need a dependable backup that won’t let you down, this Weize model is a strong contender.
- 36-month warranty
- Fast recharge
- Leak-proof design
- Not for main starting
- Check compatibility
UPLUS AUX14-UP Auxiliary Battery – High Performance
Brand: UPLUS NEW TECHNOLOGY BATTERY
A high-efficiency auxiliary battery with excellent cold-start performance.
The UPLUS AUX14-UP is engineered for high performance, using 99.99% pure primary lead for efficient charging and minimal toxic fumes. This AGM battery is maintenance-free and offers excellent leak and vibration resistance, making it a robust option for challenging conditions. Its 200 CCA ensures reliable starts even in low temperatures.
With a 12V 14Ah capacity and compact dimensions, it fits easily into your vehicle’s auxiliary slot. The strong low-temperature starting ability is a standout feature, ensuring your EV performs well in winter. If you prioritize efficiency and durability, this UPLUS battery is worth considering.
- Pure lead construction
- Vibration resistant
- Maintenance-free
- Limited capacity
- Check fitment
Mighty Max MM-AUX14 – Dependable Backup
Brand: Mighty Max Battery
A tough, reliable auxiliary battery for demanding environments.
The Mighty Max MM-AUX14 offers reliable backup power for critical systems when the engine is off. With a 22-minute reserve capacity, it supports longer run times and extends the overall battery lifespan. Its sealed, spill-proof AGM design ensures no mess and steady power delivery, even with high discharge demands.
This battery is built to resist shock, vibration, and harsh conditions, making it a tough companion for any vehicle. The 12V 14Ah capacity and 200 CCA provide ample starting power. If you need a dependable auxiliary battery that handles rough use, this Mighty Max model delivers.
- High discharge output
- Resists vibration
- Long lifespan
- Heavier than some
- No warranty mentioned
Daakmax Platinum AUX14 – Start-Stop Ready
Brand: Daakmax
An ideal auxiliary battery for start-stop technology and harsh climates.
The Daakmax Platinum AUX14 is perfect for vehicles with start-stop technology, providing 200 CCA for quick starts even in freezing weather. It operates consistently from -4°F to 122°F, ensuring reliable performance year-round. The AGM technology offers up to twice the cycle life of conventional batteries, making it a long-lasting investment.
With a BCI Group Size 400 and M6 terminals, it fits standard auxiliary slots. The 20 RC ensures adequate reserve power for accessories. If you want a battery that excels in start-stop systems and extreme temperatures, this Daakmax model is an excellent choice.
- Wide temperature range
- 2X cycle life
- Perfect fit
- Premium price
- Terminal type specific
Goodyear AUX14-AGM – Versatile Performance
Brand: Goodyear
A versatile, weather-resistant auxiliary battery for any driving condition.
The Goodyear AUX14-AGM delivers unstoppable power in any weather, with 200 CCA for reliable starts in freezing winters or scorching summers. Its versatile installation allows mounting in multiple positions (except upside down), giving you flexibility in placement. The 22-minute reserve capacity extends power availability, and the AGM technology provides up to twice the cycle life of conventional batteries.
This battery is spill-proof and resists shocks and vibrations, ensuring dependable performance on rough terrain. The 12V 14Ah capacity is standard for auxiliary use. If you need a versatile, tough battery that performs in all conditions, the Goodyear is a top pick.
- Flexible mounting
- Spill-proof
- Long cycle life
- No warranty specified
- Heavier build
Mighty Max MM-AUX12 – Compact Power
Brand: Mighty Max Battery
A compact, reliable auxiliary battery for space-constrained installations.
The Mighty Max MM-AUX12 offers reliable backup power with a 12V 12Ah capacity, slightly smaller than the AUX14 but still providing 200 CCA for dependable starts. Its 20-minute reserve capacity supports longer run times and extends battery life. The sealed, spill-proof AGM design ensures no mess and steady power, even under high discharge.
This battery is built to resist shock, vibration, and harsh conditions, making it a durable option for various vehicles. If you need a compact auxiliary battery that doesn’t compromise on performance, the MM-AUX12 is a great fit for tighter spaces.
- Compact size
- Spill-proof
- Durable build
- Lower capacity
- No warranty mentioned
Relistart AUX14 – Maintenance-Free Choice
Brand: Relistart
A maintenance-free auxiliary battery that delivers consistent power all year.
The Relistart AUX14 delivers reliable backup power with 200 CCA, ensuring strong starts even in extreme cold or heat. Its AGM technology makes it completely sealed, non-spillable, and leak-proof, offering zero maintenance convenience. You can install it and forget about it, knowing it will perform when needed.
This battery provides consistent power year-round, with a high discharge rate and robust construction. The 12V 14Ah capacity is ideal for vehicles with start-stop technology. If you prefer a maintenance-free auxiliary battery with dependable performance, the Relistart is a solid option.
- Sealed and leak-proof
- Consistent power
- Start-stop compatible
- No warranty specified
- Standard capacity
UPLUS AUX4039 – Mercedes-Benz Fit
Brand: UPLUS NEW TECHNOLOGY BATTERY
A precise-fit auxiliary battery for specific Mercedes-Benz models.
The UPLUS AUX4039 is specifically designed for Mercedes-Benz models, with a 12V 1.3Ah capacity that fits the N000000004039 part number. It uses 99.99% pure primary lead for efficient charging and minimal toxic fumes, ensuring safe operation. Its compact size makes it easy to install in the designated auxiliary slot.
This battery offers excellent leak and vibration resistance, with strong low-temperature starting ability. Note that it’s not compatible with GLK 350, ML350, GL450, or E350, so verify your vehicle’s requirements. If you own a compatible Mercedes, this UPLUS battery provides a precise fit and reliable performance.
- Exact fit for Mercedes
- Pure lead construction
- Compact design
- Limited compatibility
- Low capacity
Relistart AUX14 – Reliable Backup
Brand: Relistart
A reliable, maintenance-free auxiliary battery for consistent performance.
The Relistart AUX14 delivers 200 CCA for powerful starts in extreme conditions, ensuring your vehicle is always ready. Its AGM technology is completely sealed, non-spillable, and leak-proof, providing maintenance-free convenience. You’ll appreciate the consistent power output across a wide temperature range.
This battery is designed for vehicles with start-stop technology and offers a high discharge rate for stable performance. The 12V 14Ah capacity is standard for auxiliary use. If you need a dependable backup battery that performs reliably, this Relistart model is a great choice.
- Sealed design
- High discharge rate
- Start-stop compatible
- No warranty mentioned
- Standard capacity
Buyer’s Guide: What to Consider
Choosing the right auxiliary battery for your EV involves understanding key specifications. This guide highlights essential factors to consider, ensuring you pick a battery that meets your vehicle’s needs and delivers reliable performance.
- Capacity and CCA: Look for a battery with adequate amp-hour (Ah) capacity and cold cranking amps (CCA) to handle your vehicle's auxiliary loads. Higher CCA ensures reliable starts in cold weather, while Ah determines how long it can power accessories.
- AGM Technology: AGM (Absorbent Glass Mat) batteries are sealed, spill-proof, and maintenance-free. They offer better vibration resistance and longer cycle life compared to conventional batteries, making them ideal for auxiliary use in modern vehicles.
- Compatibility and Fit: Ensure the battery matches your vehicle's specifications, including BCI group size, dimensions, and terminal type. Some batteries are model-specific, like the UPLUS AUX4039 for Mercedes-Benz, so verify compatibility before purchasing.
- Durability and Warranty: Consider the build quality and warranty. Batteries with robust construction resist shock and vibration, extending their lifespan. A longer warranty, like the 36-month coverage on some models, provides added peace of mind.
- Reserve Capacity: Reserve capacity (RC) indicates how long the battery can run on its own power if the alternator fails. Higher RC, such as 22 minutes, supports longer run times for critical systems, which is beneficial for auxiliary applications.
Conclusion
Selecting the best auxiliary battery for your EV is crucial for maintaining performance and reliability. From the Weize’s warranty to the Goodyear’s versatility, each option offers unique benefits. Consider your vehicle’s specific requirements, such as compatibility and capacity, to make an informed choice.
For most drivers, the Daakmax Platinum stands out for its start-stop compatibility and temperature resilience. However, if you drive a Mercedes-Benz, the UPLUS AUX4039 offers a perfect fit. Whichever you choose, these batteries ensure your EV runs smoothly.
Erica Steven is the founder and lead writer of WorstBrands, a site dedicated to providing honest and trustworthy reviews about outdoor gear and fashion products.
With a passion for exploring the great outdoors and staying up to date on the latest fashion trends, Erica uses her expertise to provide valuable insights into the products that matter most to her readers.
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