By the PES Supply Editorial Team — Reviewed July 2026
SimpliPhi Power is a US-based LFP battery brand with military heritage, now part of Briggs & Stratton Energy Solutions. Known for ruggedized, cobalt-free lithium iron phosphate batteries with class-leading cycle life ratings, SimpliPhi's PHI 3.8, AmpliPHI, and SimpliPHI 6.6 product lines serve off-grid homesteads, residential backup, and commercial applications. This guide covers the full SimpliPhi lineup, certifications, warranty, and competitive positioning.
PES Supply carries SimpliPhi products among our catalog of 50,000+ SKUs from 169 authorized brands, with delivery in 7–10 business days. Browse our solar battery selection or shop SimpliPhi at PES Supply.
1. Company Overview
SimpliPhi Power was founded in 2002 in Oxnard, California, originally developing lithium iron phosphate battery solutions for military and off-grid applications. The company's military heritage informs its product design philosophy: ruggedized enclosures, conservative cell management, and a focus on reliability over marketing-driven specs. SimpliPhi uses lithium iron phosphate (LFP / LiFePO₄) chemistry exclusively — cobalt-free for safety and supply chain ethics.
In 2021, Briggs & Stratton acquired SimpliPhi Power, bringing it under Briggs & Stratton Energy Solutions. The acquisition gave SimpliPhi the distribution and support infrastructure of a major US manufacturer while preserving the brand's engineering focus.
SimpliPhi's market position is as a premium, ruggedized LFP battery brand with the highest cycle-life rating in the residential category. The PHI 3.8 is rated for 10,000+ cycles at 80% DoD — a figure that, at one cycle per day, represents over 27 years of theoretical service life. This positions SimpliPhi at the premium end of the market, above EG4 and Pylontech on cycle life but at a higher price per kWh.
2. Current Product Lines
- PHI 3.8 (24V and 48V) — 3.8 kWh LFP battery module in a metal enclosure. 75Ah at 48V (or 150Ah at 24V). Built-in BMS. 10,000+ cycles at 80% DoD. The flagship SimpliPhi product for off-grid and residential storage. Price: ~$2,240–$3,500.
- AmpliPHI 3.8 (48V) — 3.8 kWh LFP battery with integrated BMS and CAT5 communications. 15-year warranty (vs 10-year for PHI). Price: ~$2,590.
- SimpliPHI 6.6 (48V) — 6.65 kWh stackable, outdoor-rated LFP battery module. 130Ah at 48V. IP65 enclosure. Up to 6 modules per stack (19.95 kWh) and up to 6 stacks (119 kWh max). 6,000+ cycles at 80% DoD. Price: ~$2,462.
- SimpliPHI 20 kWh Stack — A complete stack of 3 SimpliPHI 6.6 modules (19.95 kWh total). 390Ah at 51.2V. Max continuous discharge: 13.98 kW DC. Expandable to 119 kWh with 6 stacks. Price: ~$7,000–$9,000.
3. Recent Releases (2025–2026)
- SimpliPHI 6.6 stackable platform — The current-generation stackable outdoor-rated battery system, designed for scalable residential and light-commercial installations. IP65 rated, CAN/RS485 communication, compatible with Sol-Ark and Briggs & Stratton inverters.
- AmpliPHI integrated communications — The AmpliPHI 3.8 features integrated CAT5 communications and a 15-year warranty, representing SimpliPhi's push toward integrated system design.
- Briggs & Stratton integration — Under Briggs & Stratton Energy Solutions, SimpliPhi batteries are increasingly bundled with Briggs & Stratton inverters and ESS solutions, expanding the brand's reach through Briggs & Stratton's dealer network.
4. Certifications & Listings
- UL 1973 — Stationary battery safety certification for PHI and SimpliPHI modules.
- UL 9540 (Edition 3) — Energy storage system safety certification.
- UL 9540A — Fire-propagation testing passed.
- UL 1998 + UL 991 — Software and functional safety certifications for the BMS.
- UN 38.3 / UN 3480 — Transport safety certifications.
- IEC 62619 — International safety standard for industrial lithium batteries.
- BABA compliance — SimpliPhi products, as part of Briggs & Stratton Energy Solutions, are available through BABA-compliant supply channels for federally funded projects.
5. Warranty & Cycle Life
- PHI 3.8: 10-year warranty, 10,000+ cycles at 80% DoD. At one cycle per day, that is over 27 years of theoretical service life.
- AmpliPHI 3.8: 15-year warranty — Extended warranty for the integrated-communications version.
- SimpliPHI 6.6: 10-year warranty, 6,000+ cycles at 80% DoD (16+ years with daily use).
- Efficiency: 96% round-trip efficiency.
- DoD: Up to 100% depth of discharge supported.
The PHI 3.8's 10,000-cycle rating is the highest in the residential LFP battery category by a wide margin. SimpliPhi achieves this through conservative cell management, advanced thermal monitoring, and a BMS that prioritizes longevity over maximum instantaneous power.
6. Popular Products at PES Supply
| Model | Capacity | Voltage | Chemistry | Cycle Life | Price Range |
|---|---|---|---|---|---|
| SimpliPhi PHI 3.8 (48V) | 3.8 kWh | 48V | LFP | 10,000+ @ 80% DoD | $2,240–$3,500 |
| SimpliPhi AmpliPHI 3.8 (48V) | 3.8 kWh | 48V | LFP | 10,000+ @ 80% DoD | $2,590–$3,800 |
| SimpliPhi SimpliPHI 6.6 | 6.65 kWh | 48V | LFP | 6,000+ @ 80% DoD | $2,462–$3,500 |
| SimpliPhi 20 kWh Stack | 19.95 kWh | 51.2V | LFP | 6,000+ @ 80% DoD | $7,000–$9,000 |
7. Technical Comparison
| Metric | SimpliPhi PHI 3.8 | EG4 LifePower4 V2 | Pylontech US5000 | Fortress eFlex MAX |
|---|---|---|---|---|
| Capacity | 3.8 kWh | 5.12 kWh | 4.8 kWh | 5.4 kWh |
| $/kWh (street) | ~$590–$660 | ~$235–$285 | ~$260–$320 | ~$350–$420 |
| Cycle life (80% DoD) | 10,000+ | 6,000+ | 6,000 | 6,000+ |
| Warranty | 10–15 years | 10 years | 10 years | 10–30 years |
| Enclosure | Metal, IP65 (6.6) | IP20 (rack) | Indoor | Sealed |
| BMS | Integrated, advanced | 100A, RS485/CAN | Dual BMS | Built-in |
SimpliPhi's advantage is cycle life and ruggedization: the 10,000-cycle rating is class-leading, and the military heritage shows in the conservative BMS design and ruggedized enclosures. The trade-off is the highest price per kWh among the compared brands — SimpliPhi is the premium choice for installations where longevity and reliability are non-negotiable.
8. BMS & Monitoring
- Integrated BMS: All SimpliPhi batteries include an integrated BMS with advanced cell balancing, over-current, over-voltage, and over-temperature protection. The BMS prioritizes longevity over maximum instantaneous power.
- Communication: CAN and RS485. The AmpliPHI uses integrated CAT5 communications. Compatible with Sol-Ark and Briggs & Stratton inverters for closed-loop communication.
- Thermal monitoring: Advanced thermal monitoring across the cell array — a carryover from the company's military applications.
- Monitoring: Via compatible inverter platforms. The SimpliPHI 6.6 supports CAN/RS485 communication for real-time battery status.
9. Installation Notes
- Stacking: The SimpliPHI 6.6 is designed for stackable configurations — up to 6 modules per stack (19.95 kWh) and up to 6 stacks (119 kWh max). Floor or wall mount.
- Communication protocols: CAN and RS485. Compatible with Sol-Ark and Briggs & Stratton inverters. Verify compatibility with other inverter brands via SimpliPhi's published matrix.
- Temperature range: Charge: -10°C to 50°C (14°F to 122°F); discharge: -20°C to 55°C (-4°F to 131°F). Wide operating range suits off-grid and remote installations.
- Enclosure: PHI 3.8 uses a metal enclosure. SimpliPHI 6.6 is IP65 rated (dust-proof, water-jet resistant) for outdoor installation.
- Venting: Cobalt-free LFP chemistry requires no active venting. Sealed enclosures with passive thermal management.
- Mounting: PHI 3.8 is a standalone module. SimpliPHI 6.6 supports floor or wall mount.
10. Frequently Asked Questions
Is SimpliPhi still the same company after the Briggs & Stratton acquisition?
Yes. Briggs & Stratton acquired SimpliPhi Power in 2021, bringing it under Briggs & Stratton Energy Solutions. The SimpliPhi brand, engineering team, and product lines continue. The acquisition expanded SimpliPhi's distribution through Briggs & Stratton's dealer network.
What is the difference between PHI 3.8 and AmpliPHI 3.8?
Both are 3.8 kWh LFP batteries. The PHI 3.8 is the standard model with a 10-year warranty. The AmpliPHI 3.8 adds integrated CAT5 communications and extends the warranty to 15 years. The AmpliPHI is designed for installations that want deeper system integration and longer warranty coverage.
Is the 10,000-cycle rating realistic?
SimpliPhi's 10,000-cycle rating at 80% DoD is among the highest in the residential LFP category. It is achieved through conservative cell management and a BMS that prioritizes longevity over maximum power. At one cycle per day, 10,000 cycles equals over 27 years of theoretical service life. Real-world results will vary with temperature, discharge depth, and charge rate.
Can SimpliPhi batteries be used off-grid?
Yes. SimpliPhi's military heritage makes its batteries particularly well-suited for off-grid and remote installations. The ruggedized enclosures, wide temperature range, and conservative BMS design are engineered for demanding environments. The SimpliPHI 6.6's IP65 rating supports outdoor installation.
Are SimpliPhi batteries BABA compliant?
Yes. As part of Briggs & Stratton Energy Solutions, SimpliPhi products are available through Build America, Buy America (BABA) compliant supply channels, making them eligible for federally funded energy storage projects. Verify compliance documentation for your specific project requirements.
11. Shop SimpliPhi at PES Supply
PES Supply carries SimpliPhi PHI, AmpliPHI, and SimpliPHI batteries among our 50,000+ SKUs from 169 authorized brands. Delivery in 7–10 business days.
Explore our full solar battery collection or contact our team for SimpliPhi system sizing and off-grid application guidance.