Collection: LiFePO4 (Lithium Iron Phosphate) Marine Batteries

CMPower LiFePO4 (lithium iron phosphate) batteries use a lithium battery technology that is safe, powerful and plug compatible with most lead acid and AGM battery charging systems. This battery technology offers many advantages over lead acid and AGM technology including high capacity storage, delivery of consistently high power, longer cycle life, less weight, longer shelf life and rapid efficient charging.  LiFePO4 batteries are ideal for use on cruising sailboats, powerboats, fishing boats, and camper vans.

A CMPower (Custom Marine Products) deep cycle lithium battery has two primary components, the LiFePO4 cells and the Battery Management System (BMS).  Both are housed in a sealed (or with a removable top in our latest batteries) battery case.  The quality of each component is key to the longevity and performance of the battery.  LiFePO4 cells are wired in parallel to form a module producing 3.2 volts.  Four of these units are connected in series to form a rated 12.8 volt Lithium battery; eight for a 25.6 volt battery.  The temperature, charge and discharge rate of each cell is monitored and managed by the BMS, a computer of sorts built into each battery.  In addition to cell monitoring and management, the BMS will prevent over discharging of cells by disconnecting the load and will prevent cell over charging by reducing charge current or stopping the charge process. The BMS will also shut down the system if the battery temperature is out of range.

LiFePO4 batteries are also rated as to their maximum discharge capacity; 80 - 100 Amps max discharge capacity is typical.  Most CMPower Lithium batteries have a discharge capacity of 150 to 200 amps continuous draw and up to 600 amps short cycle draw to robustly accommodate most house, engine start, windlass, electric winch and inverter battery power requirements. ​Charge/discharge cycles -CMPowerLithium batteries have an expected life of 2,000-4,000 charge/discharge cycles at a discharge to 95%.  Lead acid batteries have an expected life of 300-500 charge/discharge cycles at a discharge to 50%. 

Discharge profile -CMPowerLifePO4 Deep cycle Lithium batteries stay at a voltage of 12.5 to 13.4 volts during discharge of up to a 95+%.  Voltage then drops off rapidly.  A lead acid battery decreases in voltage from 13 to below 11.5 volts as more current is drawn.  This means many appliances will  operate more efficiently throughout the discharge cycle using LiFePO4 batteries.

Discharge rate - The BMS built intoCMPower batteries has a 100 amp to a 200 amp discharge capacity.  This means the batteries can sustain a heavy charge and discharge without damage or degradation.  Our manufacturer has advised us that the quality of the cells and quality of the BMS is key to the longevity and performance of a LiFePo4 battery.   We have seen this firsthand. Great for running windlasses, bow thrusters, or using on a fishing boat for running the trolling motor/electronics/live well/power pole as well as starting the engine.

Weight/power ratio - A typical 100 Ah LiFePO4 deep cycle battery weighs about 31 pounds.  A comparable lead acid battery is over twice that.  Because LiFePO4 batteries can be safely be drawn down 95% vs 50%-60% for lead acid, fewer batteries are required to achieve the same power.  Battery weight combined with usable power capacity means battery bank weight can be cut by more than half using LiFePO4 lithium batteries.  Also, LiFePo4 batteries will occupy up to 40% less space than equivalent lead acid batteries.

​For example, 3 group 31 110 amp hour lead acid batteries weighing a total of 200 pounds can be replaced by 2 group 31 size 100 amp hour LiFePO4 batteries weighing a total of 62 pounds.  Both configurations have roughly the same power capacity because the lead acid can be safely drawn down 50% (330 amps @50% = 165 amps) and the Lithium battery can be safely drawn down 95% (200 amps @ 95% = 190 amps).  Also, the lead acid will endure 300-500 cycles and the LiFePO4 over 2,000 cycles. Excellent for trolling motors as it is much easier to move the battery on and off for recharging - that is unless you have a portable solar setup on your fishing boat.

Charging Safety - Lithium batteries have a reputation for catching fire.  This is not so with LiFePO4, a very different technology.  The built-in Battery Management System (BMS) monitors the state of charge of each cell group and manages the temperature, charge and discharge rates.  The BMS will prevent over-charging and over-discharging by disconnecting from the source.  There are no toxic chemicals or gases as in many types of lead acid batteries.  The batteries can be mounted in any direction; bottom or side.

Compatibility - While the optimal charging parameters vary between Lithium, AGM and lead acid battery technology, the BMS built intoCMPowerLiFePO4 batteries compensates for this.  Thus, our LiFePO4 boat batteries are compatible with most lead acid battery charging systems. 
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Charging Multiple Battery Types - LiFePO4 and lead acid or AGM batteries are not compatible and should not be combined.  However, CMPowerbatteries used for the house bank and lead acid or AGM batteries used for engine starting can both charged from a single alternator or generator.  This requires some easy to install electrical equipment including a DC-DC charger or a battery isolator.

Bluetooth Battery Monitoring -CMPowerLithium batteries are equipped with Bluetooth for monitoring battery State of Charge (SoC) through a Smartphone or tablet app.  This is important because unlike lead acid batteries, LiFePO4 batteries maintain a constant voltage between 13 and 13.4 volts so a voltmeter is not an accurate indicator of SoC.   A built in Bluetooth capability enables real time monitoring of each battery through an app on either an Android or IOS smartphone or tablet.  The app displays the state of charge (SoC) of the battery, the amp draw and voltage level, the temperature, the time to full charge and the number of charge/discharge cycles.  This capability is nearly equivalent to having a built in battery bank monitoring system like a Link 2000. Have confidence that you have plenty of power and know exactly when you'll need to run your engine. Terrific feature for fishermen using a single battery for both a trolling motor and engine starting battery.

Winter Operation and Storage -CMPower LiFePO4 Lithium deep cycle batteries can be stored in temperatures from -10°F to +104°F (-25°C to +40°C).  It is recommended they not be heavily charged and discharged at temperatures below -4°F (-20°C) .   It is recommended that the negative terminals be disconnected  during winter or long term storage so there is no chance of draining the batteries while in storage.  LiFePO4 lithium batteries should be recharged at a minimum every 6 months while in storage.

Long Term Investment - Keep Them for Life - Because the number of charge cycles of well cared forCMPower LiFePO4 lithium batteries is in excess of 2,000 they can be a long term  investment you can take with you from boat to boat or boat to RV.  Also, because the batteries have a built in cycle recording system, the batteries can be resold at a value based on their number of charge cycles.  For example:  The owner of a sailboat purchased three LiFePO4 batteries two years ago; two for house and one for engine starting.  After two years of cruising the starting battery had 2 charge cycles and the house batteries, wired in parallel, had only 20 charge cycles as shown on the Bluetooth APP.  These batteries are like new and can be taken to their new boat or sold as quality used batteries.  In fact, if and when CMP Lithium batteries become available from our customers, we will post them on our website for purchase.
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Warranty - 7 years +-  Custom Marine Products warrants each branded battery to be free of defects for a period of 1 year from the date of sale as determined by either the customer’s sale receipt, or other proof of purchase plus an additional 6 years prorated.  Within the warranty period CMP will credit, replace or repair the product and/or parts of the product if determined to be defective in material or workmanship.  CMPower batteries are built to last a minimum of 2,000 cycles and still maintain 80% of rated energy capacity.  This warranty applies to the original owner.

Cost -CMPower LiFePO4 deep cycle lithium batteries are 2 to 4 times the cost of comparable lead acid or AGM type batteries.  Cost justification is often based on convenience, performance and longevity.  Factors to consider in evaluating cost include the number of charge cycles, power to weight ratio, charge and discharge efficiency and compatibility.  Over the long term, these batteries are often considerably more cost effective than lead acid or AGM batteries.
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Bottom line - CMPowerLiFePO4 lithium marine batteries have the following advantages:

1. Bluetooth equipped to monitor battery State of Charge with free app - built in battery monitor.

2. Can be drawn down 95+% vs 50% - more usable capacity.

3. Hold steady voltage through 95% discharge - constant power and voltage.

4. Generally plug compatible with lead acid chargers - drop-in replacement.

5. Charge more quickly and efficiently than lead acid batteries - excellent for solar systems.

6. Have up to (and beyond) 10 times more charge cycles than lead acid and AGM batteries - could last a lifetime.

7. Nontoxic and safe, very low fire risk - no toxic gases emitted, many built-in protections.

8. Low self-discharge - easy winter storage, long shelf life.

9. Lighter than lead acid - lightweight, generally less than half the weight of lead acid (~4x the power per pound)​.

10. Cost effective in the long run​.

Lithium batteries are more expensive than lead acid however their many advantages and longevity often outweigh the additional initial investment.