Are we considering a compact, high-performance 24V marine battery solution that aims to replace bulky lead-acid banks while giving us reliable starting and deep-cycle performance?
Product Overview
We’re reviewing the Banshee 24V Lithium Deep Cycle Marine Battery Group 27-2 Pack, which pairs two BCI Group 27M LifePo4 12V batteries to deliver a 24V system. This two-pack is positioned as a true marine-grade replacement for a range of Group 27 and similar batteries, offering 12V 70Ah per unit and 900 CCA per battery — a combination that suits both starting and deep-cycle needs when configured correctly.
What’s included and how the pack works
We get two identical 12V 70Ah LiFePO4 batteries bundled to form a 24V bank when wired in series, which preserves amp-hour capacity while doubling voltage. Each battery is described with dual post true marine terminals and dimensions that fit many Group 27 mounting locations, so the physical fit should work for most boats and personal watercraft that accept Group 27M batteries.
Detailed Specifications
We like to keep data handy, so here’s a breakdown to make quick comparisons and installation planning easier. This table shows the key specs for each individual battery and for the assembled 24V pack.
| Specification | Single Battery (12V) | 24V Pack (2 in series) |
|---|---|---|
| Chemistry | LiFePO4 (Lithium Iron Phosphate) | LiFePO4 (two 12V cells) |
| Nominal Voltage | 12V | 24V |
| Capacity | 70 Ah | 70 Ah (at 24V) |
| Cold Cranking Amps (CCA) | 900 CCA | 900 CCA per battery (starting at 12V) |
| Dimensions (L x W x H) | 12.00″ x 6.81″ x 7.87″ | Each battery same size; plan for two |
| Terminal Type | Dual Post True Marine Terminals | Dual Post per battery |
| Group Size | BCI Group 27M | Group 27M x 2 |
| Typical Fits / Replaces | D27M 8027-127, SLI27MDC, 27DC-2, etc. | Matches dual Group 27 installations |
| Recommended Use | Marine, PWC, trolling motor, accessory | 24V marine electric systems, trolling motors, 24V inboards |
Key Features
We appreciate clarity on features because they drive decision-making when selecting batteries for boats and watercraft. This product touts LiFePO4 chemistry, compact Group 27M sizing, high CCA, and marine-grade terminals.
LiFePO4 chemistry benefits
We see LiFePO4 as a safer and longer-lived lithium chemistry for marine applications compared with many other lithium variants. It typically offers stable thermal performance, a long cycle life relative to lead-acid, and lower risk of thermal runaway under normal use.
High cranking power and capacity
Each 12V battery is rated at 900 CCA, which gives us considerable starting power for engines that require high cranking amps at 12V. When we pair two in series for 24V systems, cranking remains suitable for engines designed for 24V starting when the installation is configured properly.
True marine dual post terminals
The dual post true marine terminals simplify physical connections and secure mounting on many boats. We like the robustness of these terminals for resisting vibration and saltwater exposure when paired with proper corrosion protection.
Compact Group 27M footprint
The Group 27M size is familiar to many boaters, so swap-outs and replacements are more straightforward. The dimensions provided make planning easier, and the reduced weight (relative to equivalent lead-acid batteries) helps with overall boat trim and handling — though exact weight is not specified here, LiFePO4 is generally lighter.
Performance
We want performance to match promises, so we consider starting power, usable capacity, discharge behavior, and charge acceptance. Below we summarize expected behavior based on the specifications and common LiFePO4 characteristics.
Starting power and cranking
With 900 CCA per 12V unit, we get strong starting capability for engines reliant on a single 12V battery. For 24V starters, using the two batteries in series should meet the voltage requirement while preserving the available current capability, provided the starter and wiring are sized properly. We emphasize checking manufacturer starter requirements to confirm compatibility.
Deep-cycle capacity and usable energy
Each battery lists 70 Ah of nominal capacity. LiFePO4 chemistry gives us a higher usable capacity percentage versus lead-acid, since we can typically draw a much larger fraction of the rated Ah without damaging the battery. That means most of the 70 Ah per battery is usable, which benefits long trolling motor runs or powering high-draw electronics.
Runtime examples and practical expectations
We can estimate runtime by dividing available watt-hours by load. For example, each 12V battery offers roughly 12V × 70 Ah = 840 Wh nominally, so the 24V pack gives about 1680 Wh total at 24V. If we run a 400W trolling motor at full power, that equates to about 4 hours of runtime in ideal conditions. We caution that real-world runtime varies with load fluctuations, temperature, and state of charge.
Charge acceptance and charging recommendations
LiFePO4 batteries accept charge more efficiently than lead-acid types and handle higher charge currents without the same gassing risks. We recommend using a charger or multi-stage charging system that supports LiFePO4 profiles or a charger that can be programmed for lithium chemistries. Without proper charging settings, the battery could be undercharged or not reach full capacity.
Installation and Compatibility
We want installations to be painless and safe. Proper wiring, series connections for 24V, and secure mounting are essential.
24V wiring: series connection instructions
To form a 24V bank, we connect the positive terminal of battery A to the negative terminal of battery B, leaving the remaining negative of A and positive of B as the 24V output. We always recommend using appropriately rated cables, fuses, and isolators and confirming polarity before powering loads. If we’re uncertain, professional installation ensures correct wiring and safe integration with charging systems.
Mounting, ventilation, and secure placement
Although LiFePO4 produces less off-gassing than lead-acid, we still mount batteries securely and protect them from excessive vibration and direct water spray. We keep terminals shielded, use marine-grade stainless hardware where possible, and ensure the tray or compartment allows for stable fastening and easy inspection.
Compatibility with existing charging systems
We check that onboard chargers, alternators, and multi-stage systems are LiFePO4-compatible or can be programmed for lithium profiles. If our charger is lead-acid only, we consider adding a DC-DC charger or a dedicated lithium charger to ensure safe and full charging. Using isolation devices and charge converters can make older systems compatible with LiFePO4 banks.
Replacement fit and cross-compatibility
These batteries list replacements like D27M 8027-127, SLI27MDC, 27DC-2, DC27MF, and others, so if our boat currently uses those Group 27 variants, the physical fit and terminal arrangement should match. We still measure our battery compartment and cable reach to confirm that two Group 27M-sized batteries will fit in the planned location.
Maintenance and Care
Routine care keeps our batteries reliable for years. Lithium batteries typically demand less maintenance than flooded lead-acid types, but they still benefit from good practices.
Basic upkeep and terminal care
We keep terminals clean, tight, and protected with a thin coat of dielectric grease or corrosion inhibitor to reduce oxidation from marine environments. We periodically verify terminal torque, check the state of cabling, and inspect for signs of heat or damage.
Charging and state-of-charge management
We tend to recharge lithium batteries promptly after use rather than leaving them in a deeply discharged state for extended periods. While LiFePO4 tolerates deeper discharges better than lead-acid, long-term storage at low state of charge shortens lifecycle and increases the risk of cell imbalance. We also recommend periodically checking voltage and using a battery monitor or shunt-based system to track Ah in/out for accurate state-of-charge readings.
Balance and battery management system (BMS)
A built-in or external BMS that provides cell balancing, overcharge/over-discharge protection, and short-circuit protection is essential for safe operation. If the pack includes an integrated BMS, we still monitor its behavior and consult manufacturer guidance for firmware updates or diagnostic checks. For multi-battery setups, balance charging or periodic balancing may be necessary if the batteries are not identical or age differently.
Safety Considerations
Safety is paramount when dealing with energy storage, particularly in marine environments where corrosion, moisture, and vibration increase risks. We follow best practices to ensure safety.
Overcharge, over-discharge, and thermal protection
LiFePO4 chemistry is more thermally stable than many other lithium types, but it’s still important to use chargers and systems that respect voltage and current limits. Overcharging can be prevented by chargers with proper voltage cutoff and a BMS; over-discharge is mitigated by low-voltage disconnect features in a quality BMS.
Short-circuit and reverse polarity protection
We protect circuits with appropriately rated fuses or breakers placed near the battery terminals to minimize risk from accidental short circuits. We also take care to label and check polarity during installation, since reversing polarity can damage batteries and connected electronics.
Marine environment precautions
Salt spray and humidity accelerate terminal corrosion and can degrade connections. We secure terminals, use marine-grade hardware, and consider waterproof terminal covers to limit exposure. We also avoid placing batteries where they might be submerged and use sealed boxes or trays if splash exposure is possible.
Use Cases and Applications
We consider real-world scenarios where this Banshee two-pack makes sense. Because the product is marketed for marine use and Group 27 footprint, several common applications stand out.
Personal watercraft and small boats
For PWCs and small boats that need a compact high-current battery, the Group 27M footprint and dual-post arrangement are convenient. Two batteries in series create a 24V bank for systems that require higher voltage or to power electric inboards designed for 24V.
Trolling motors and electric propulsion
For trolling motors that can run on 24V, the two-pack provides the correct voltage and substantial usable capacity thanks to LiFePO4 efficiency. We expect longer usable run times per charge compared to equivalent lead-acid setups because we can use more of the Ah without damaging the battery.
Marine electronics and house loads
We find these batteries useful for powering house loads like fish finders, lights, pumps, and refrigeration when configured as part of a 24V distribution system or with suitable converters. Their low self-discharge and high usable capacity make them good for intermittent boating schedules where charging cycles aren’t daily.
RVs, small solar setups, and backup power
While marketed for marine use, the compact Group 27M size and LiFePO4 chemistry make these batteries suitable for RVs, small off-grid solar systems, and 24V backup configurations. We check charger compatibility and mounting before repurposing marine batteries for land use.
Pros and Cons
We weigh positive attributes against limitations so we can decide whether this product fits our needs.
Pros
- Significant usable capacity thanks to LiFePO4 chemistry, meaning more effective runtime for a given rated Ah.
- High CCA (900) on each 12V unit supports strong starting performance for many engines.
- Dual post true marine terminals provide robust, secure connections for marine environments.
- Group 27M dimensions simplify replacement in many existing installations.
- Lighter weight and better cycle life compared to comparable lead-acid alternatives (typical LiFePO4 advantages).
Cons
- Two batteries are required to form 24V, which increases space needs and adds complexity in wiring and balancing compared to a single 24V battery.
- Not every charger/alternator is LiFePO4-ready; we may need to upgrade charging equipment.
- Initial purchase cost is higher than lead-acid alternatives, though lifecycle economics can offset the initial premium.
- Exact weight is not provided in the listing, so we need to verify weight against our mounting and trim requirements.
Comparison with Lead-Acid and AGM Batteries
We often compare LiFePO4 to lead-acid and AGM because boat owners weigh upfront cost against lifecycle performance.
Cycle life and total cost of ownership
LiFePO4 typically offers far more charge/discharge cycles than lead-acid or AGM, which translates into lower cost per cycle over the battery’s life. While the upfront cost is higher, the longer lifespan often justifies the investment for regular users.
Usable capacity and depth of discharge
Lead-acid batteries are typically limited to 50% usable depth of discharge to preserve life, whereas LiFePO4 commonly supports 80–100% usable capacity depending on BMS and manufacturer recommendations. This means a 70 Ah LiFePO4 can effectively deliver more usable energy than a 70 Ah lead-acid rated battery.
Charging behavior and efficiency
LiFePO4 charges faster and with higher efficiency, losing less energy as heat during charge cycles. They also don’t require equalization charges, which simplifies maintenance and reduces charging times. We still need a LiFePO4-compatible charging profile to achieve these benefits.
Weight and installation benefits
LiFePO4 batteries are generally lighter than lead-acid equivalents. Less weight in the boat helps with handling and fuel efficiency and simplifies installation and servicing.
Troubleshooting and Common Questions
We want to be prepared for issues that can arise and address common questions before they become problems.
What if a battery won’t accept charge?
First, we confirm charger compatibility and correct voltage profile for LiFePO4. Next, we inspect connections, fuses, and the BMS status. If a BMS has entered a protective mode due to over-discharge or cell imbalance, following manufacturer instructions for safe recovery or contacting support is wise.
How do we balance batteries in series?
Ideally, we use batteries that are matched in age, capacity, and state of health. Some BMS units support active balancing; otherwise, periodic balance charging or using a balance charger for maintenance can help. If batteries age differently, consider replacing in matched sets rather than mixing old and new units.
Can we parallel more packs for increased capacity?
We can parallel batteries to increase capacity only if they are designed for parallel operation and matched in specifications and state of charge. When paralleling, use identical batteries and wiring lengths to ensure balanced currents. If in doubt, consult the manufacturer for guidance.
Installation Checklist
We assemble the essentials before installation so the process goes smoothly and safely.
- Measure battery compartment to ensure two Group 27M batteries will fit with space for cabling and ventilation.
- Choose appropriate gauge wiring for 24V series connections and load demands.
- Install appropriately rated circuit breakers or fuses close to battery terminals to protect against short circuits.
- Confirm charger/alternator supports LiFePO4 or plan to install a LiFePO4-capable charger or DC-DC converter.
- Secure batteries with marine-grade hold-downs and provide terminal protection against corrosion.
- Label positive and negative terminals and confirm polarity before first power-up.
Environmental and Lifecycle Considerations
We care about responsible use and disposal. LiFePO4 batteries are recyclable and have a longer useful life than many alternatives, which reduces environmental impact over time.
Recycling and end-of-life
When the batteries reach the end of life, we should follow local guidelines for lithium battery recycling. Many recycling centers accept LiFePO4 cells, and some manufacturers or retailers offer take-back or recycling programs.
Lifespan expectations
With proper charging and maintenance, LiFePO4 batteries typically outlast lead-acid equivalents by multiple years and thousands of cycles, depending on depth of discharge and temperature exposure. That extended lifespan contributes to better total cost of ownership when used in frequent-season boating or daily trolling motor usage.
Warranties and Support
We don’t have explicit warranty details in the provided listing text, so we recommend verifying warranty length, terms, and support channels before purchase. Knowing how warranty claims are handled gives us confidence and a safety net if manufacturing defects appear.
What to ask the seller/manufacturer
We typically ask about length of warranty, what constitutes a warranty event, whether normal wear is covered, and whether shipping or diagnostics are part of the warranty process. We also ask whether firmware updates or BMS support are available and how to access technical support if needed.
Price and Value Assessment
We balance upfront cost, expected lifespan, and performance when assessing value. LiFePO4 battery packs cost more initially than lead-acid, but their longer cycle life and higher usable capacity usually yield better long-term value for frequent users. For occasional boaters, careful calculation of expected years of use and charging conditions helps determine whether the premium is justified.
Who benefits most from this purchase?
We think regular boaters, anglers using trolling motors, and owners of boats with heavy electronics loads will see the clearest advantages due to the extended usable capacity and long life. If we’re replacing old lead-acid batteries and want lighter weight and better performance, the Banshee 24V two-pack is an appealing upgrade.
Frequently Asked Practical Questions
We address common practical queries we get from other boaters and sailors considering this product.
Can we charge the pack with a standard 24V charger?
Yes, if the charger has a LiFePO4 profile or is programmable to the correct charge voltage and cutoffs. If the charger is 12V-only, charging each battery individually is possible but less convenient; a proper 24V lithium charger simplifies charging and ensures optimal battery life.
Will two batteries in series require special monitoring?
We recommend a battery monitor capable of measuring total amp-hours and voltage across the 24V bank. Monitoring each individual battery is best practice to ensure balanced health; some systems support individual battery monitoring in series setups.
How does temperature affect performance?
Cold temperatures reduce available capacity and charge acceptance for lithium batteries, similar to other chemistries. We take care not to fast-charge LiFePO4 below manufacturer-specified temperatures unless the BMS includes a built-in heater or temperature compensation.
Final Verdict
We find the Banshee 24V Lithium Deep Cycle Marine Battery Group 27-2 Pack to be a compelling option for boaters and marine enthusiasts who want higher usable capacity, strong starting power, and a modern battery chemistry that reduces weight and maintenance. The two-pack approach gives us flexibility for 24V systems while maintaining the common Group 27M footprint for easier replacements.
We recommend confirming charger compatibility, measuring your battery compartment for two Group 27M batteries, and ensuring a proper installation with fusing and secure mounting. If we want longer life, better usable energy, and robust cranking performance in a compact package, this Banshee pack is worth strong consideration — just be sure to plan for the 24V wiring and charging requirements so we get the full benefit from the LifePo4 chemistry.
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