Firefly Oasis Battery – Carbon foam AGM – Group 31 & L15+

Firefly’s award-winning, patented technology is an innovative material science that removes almost all limitations of current lead-acid battery products. Firefly discovered that much of the lead in the traditional grid structure of conventional batteries can be replaced with a totally new type of grid material, carbon foam. The main improvement of the carbon foam construction is that it resists sulfation and corrosion while dramatically increasing the surface area of the battery plates.

Click here for Firefly Battery Prices & Specs or scroll down for more info.

Here is a list of our Regional Dealers

Firefly Oasis Highlights:

  • Unparalleled Resistance to Sulfation – Sulfation is what usually kills AGM batteries.  The Oasis carbon foam AGM can operate or be stored at a partial state of charge for long periods of time without a loss in capacity.  Check out this article by Professional Boatbuilder Magazine to learn more about sulfation.
  • Depths of  Discharge to 80%-100% of rated capacity without any loss of performance
  • Superior Life Cycle – capable of 3X the number of deep discharge cycles than that of other lead acid batteries
  • Strong Performance in Extreme Cold and Heat– performance range is -20° C to 50° C
  • Fast Bulk Charging and topping up is seldom required
  • Greater Usable Capacity– you can replace your existing bank with a smaller Oasis bank due to its deep discharge capability


Available in 2 Sizes:  G31 & L15+

Model # Nom. V

Charge/Dis-charge ratings

Capacity @ 20Hr Operating temp Cycle Life Size (in) Weight Price


Oasis G31

Detailed Dimensions


Max Charge I/V

250A @25°C/


CCA 625A

MCA 800A


-20°C to 50°C

(-4°F to 104°F)

50% DOD ~3600 cycles

80% DOD ~1000 cycles

13.5” x 6.7” x 9.4”




Detailed Dimensions


Max Charge I/V

450A @25°C/



-20°C to 50°C

(-4°F to 104°F)

50% DOD ~4900 cycles

80% DOD ~1475 cycles

10.5” x 6.85” x 17.2”


2V 900Ah



Price Comparison of Oasis G31 vs. other similarly sized deep cycle batteries

How does this compare to other similar batteries?  Not only is the FFG31 priced similarly to other comparable deep cycle batteries, but it is rated to over 3 X the cycles of similar batteries.  So, for a true price comparison, it is best to compare the price in $/kWh over the entire lifetime of the battery.

The results:

Firefly G31: $0.17/kWh

Lifeline GPL 31T: $0.55/kWh

Northstar SPS Silver M110B:  $0.93/kWh

These calculations are based on 50% DOD and manufacturer ratings.


Firefly Group 31 Oasis Testing and Performance

In independent PSOC (Partial State Of Charge) testing of AGM batteries done by Rodd Collins of Compass Marine for Practical Sailor, the Firefly AGM was the only AGM to regain FULL capacity after 30 PSOC (one month) of cycle testing.  For a full description of the testing procedure, see:
For the test results summary, see:

Click on the following graph to see how Firefly performed after 30 cycles of “abuse” during the testing

While these batteries have proven their resilience over the past 8 years in multiple land-based applications, the first well-documented field test of these batteries in the marine environment was done in the summer of 2014 by Nigel Calder.  As a marine systems guru and author of the Boatowner’s Mechanical and Electrical Manual, Nigel Calder’s opinion is respected by boaters world wide.  Here is what he had to say about the Firefly Oasis:

Nigel Calder’s Firefly Testimonial

Check out his recent comments and update after a winter of storage at 38% state of charge.  Nigel’s Spring Commissioning update.

Watch the video from Pacific NW Boater who has had the batteries in service for four years now.



Curious about their charge characteristics?

Check out this test graph put together by the experts at Coastal Climate Control showing the difference in performance between Firefly and a slightly smaller sized, new, high-quality, marine AGM battery.

northstar vs firefly2jpg

General Information on the Firefly Oasis & Pricing

Click here to see our regional dealers in North America

Firefly L15+ Battery Specifications

Test Performance Comparison with other Lead-acid Batteries

Firefly PSOC Partial State of Charge Sweet Spot

Firefly Users Manual G31 & L15+

Firefly warranty G31 & L15+

You can get more information about Firefly Energy International at their website