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Get yours today!
In the last 7 days
Get it between Mon, Sep 22 - Wed, Sep 24
Free Returns within 30 Days of Purchase
Unlimited lifetime support, always available.
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Get yours today!
In the last 7 days
Get it between Mon, Sep 22 - Wed, Sep 24
Free Returns within 30 Days of Purchase
Unlimited lifetime support, always available.

Introducing the Fortress Power FlexTower, a pioneering energy storage system designed to meet diverse energy needs across various environments. This innovative solution, leveraging the substantial storage capability of up to 81kWh, seamlessly integrates with solar arrays, offering unmatched reliability and efficiency.
The eFlex 5.4 is engineered with a focus on versatility, handling diverse applications and harsh weather conditions with ease. This market-leading system features a highly advanced Digital Processor Battery Management System (BMS) for precise control.
The patented enclosure design provides exceptional thermal performance, surpassing competitors by four times. This IP65-rated enclosure is also dust and waterproof, suitable for both indoor and outdoor installations.
Featuring Canbus, Modbus, and Wi-Fi communication, the FlexTower supports Internet-of-Things (IoT) compatibility, enabling seamless integration with various digital systems and 48V inverters.
Adapt to different spaces with flexible mounting such as wall mount, floor stand, or standard 19€ industrial server rack mount. The design ensures the system fits perfectly in any setup.
The battery system achieves greater than 98% efficiency at 0.5C and supports up to 8,000 cycle life at 80% Depth of Discharge (DoD), providing long-lasting and efficient power storage solutions.
The Fortress Power FlexTower works by harnessing its eFlex 5.4 lithium batteries in a scalable setup that can expand up to 81kWh. It integrates sophisticated components ensuring reliable performance across various applications.
This BMS ensures the precise monitoring and balancing of cell voltage and temperature, enhancing the battery€™s longevity and reliability, making it ideal for continuous power management.
The unit€™s advanced communication interfaces allow it to work efficiently with most inverters, ensuring optimal performance and intelligent energy management across networks.
The system's modular approach enables flexible scaling, supporting multiple installation scenarios and varying power requirements, from small homes to large commercial infrastructures.
| Nominal Voltage | 51.2V |
| Nominal Capacity | 105AH |
| Rated Capacity @ 0.5C (50A) | 5.374 kWh |
| Efficiency | >98% |
| Enclosure Protection | IP65 |
| Cycle Life | 8,000 (@ 80% DoD) |
| Charging Voltage | 54.4V |
| Temperature Range | -4°F to 131°F (-20°C to 55°C) |
| Max. Surge Power Rate | 130A (6.6 KW 5S) |
| Warranty | 10 Years |
Returns are free in the first 30 days with no restocking or processing fees, although the customer may be responsible for paying return shipping. See our complete return policy on our Shipping, Delivery, and Returns page linked in the footer of this website.
Our returns policy covers all purchases made through Portlandia Electric Supply. For warranty issues, as authorized distributors, we honor the full manufacturer warranty of ALL the brands on our website. See our complete returns and warranty policies on our Shipping, Deliver, and Returns page.
All orders are processed within 72 hours and you can expect delivery on most orders within 5-7 business days. You will receive access to our customer portal after ordering, where it is easy to track all your shipments. See our Shipping, Delivery and Returns page for more details.
We offer several ways to pay to make getting your solar kit simple:
Credit Card: if the purchase is greater than your card’s limit, you can split the cost onto multiple cards as well as Paypal, financing through Affirm, and ACH/bank transfer
You can arrange financing during the checkout process, or scroll further down this page for more details. Please note, if you'd like to finance your order, you can do so instantly, right at checkout.
Our legendary lifetime customer support has helped make us the #1 online solar retailer! We have a dedicated team of solar professionals standing by to help you navigate the world of solar with ease. From selecting the perfect solar kit to installation and beyond, we provide support and expertise at every step of the journey.If you need help with ordering, shipping, troubleshooting, expanding your system, warranty issues, or anything else you have questions about for as long as you own your Portlandia Electric Supply equipment, we’ve got you covered: we’re always only a phone call or email away.
Introducing the Fortress Power FlexTower, a pioneering energy storage system designed to meet diverse energy needs across various environments. This innovative solution, leveraging the substantial storage capability of up to 81kWh, seamlessly integrates with solar arrays, offering unmatched reliability and efficiency.
The eFlex 5.4 is engineered with a focus on versatility, handling diverse applications and harsh weather conditions with ease. This market-leading system features a highly advanced Digital Processor Battery Management System (BMS) for precise control.
The patented enclosure design provides exceptional thermal performance, surpassing competitors by four times. This IP65-rated enclosure is also dust and waterproof, suitable for both indoor and outdoor installations.
Featuring Canbus, Modbus, and Wi-Fi communication, the FlexTower supports Internet-of-Things (IoT) compatibility, enabling seamless integration with various digital systems and 48V inverters.
Adapt to different spaces with flexible mounting such as wall mount, floor stand, or standard 19€ industrial server rack mount. The design ensures the system fits perfectly in any setup.
The battery system achieves greater than 98% efficiency at 0.5C and supports up to 8,000 cycle life at 80% Depth of Discharge (DoD), providing long-lasting and efficient power storage solutions.
The Fortress Power FlexTower works by harnessing its eFlex 5.4 lithium batteries in a scalable setup that can expand up to 81kWh. It integrates sophisticated components ensuring reliable performance across various applications.
This BMS ensures the precise monitoring and balancing of cell voltage and temperature, enhancing the battery€™s longevity and reliability, making it ideal for continuous power management.
The unit€™s advanced communication interfaces allow it to work efficiently with most inverters, ensuring optimal performance and intelligent energy management across networks.
The system's modular approach enables flexible scaling, supporting multiple installation scenarios and varying power requirements, from small homes to large commercial infrastructures.
| Nominal Voltage | 51.2V |
| Nominal Capacity | 105AH |
| Rated Capacity @ 0.5C (50A) | 5.374 kWh |
| Efficiency | >98% |
| Enclosure Protection | IP65 |
| Cycle Life | 8,000 (@ 80% DoD) |
| Charging Voltage | 54.4V |
| Temperature Range | -4°F to 131°F (-20°C to 55°C) |
| Max. Surge Power Rate | 130A (6.6 KW 5S) |
| Warranty | 10 Years |
Returns are free in the first 30 days with no restocking or processing fees, although the customer may be responsible for paying return shipping. See our complete return policy on our Shipping, Delivery, and Returns page linked in the footer of this website.
Our returns policy covers all purchases made through Portlandia Electric Supply. For warranty issues, as authorized distributors, we honor the full manufacturer warranty of ALL the brands on our website. See our complete returns and warranty policies on our Shipping, Deliver, and Returns page.
All orders are processed within 72 hours and you can expect delivery on most orders within 5-7 business days. You will receive access to our customer portal after ordering, where it is easy to track all your shipments. See our Shipping, Delivery and Returns page for more details.
We offer several ways to pay to make getting your solar kit simple:
Credit Card: if the purchase is greater than your card’s limit, you can split the cost onto multiple cards as well as Paypal, financing through Affirm, and ACH/bank transfer
You can arrange financing during the checkout process, or scroll further down this page for more details. Please note, if you'd like to finance your order, you can do so instantly, right at checkout.
Our legendary lifetime customer support has helped make us the #1 online solar retailer! We have a dedicated team of solar professionals standing by to help you navigate the world of solar with ease. From selecting the perfect solar kit to installation and beyond, we provide support and expertise at every step of the journey.If you need help with ordering, shipping, troubleshooting, expanding your system, warranty issues, or anything else you have questions about for as long as you own your Portlandia Electric Supply equipment, we’ve got you covered: we’re always only a phone call or email away.
From hurricanes to blackouts, reliable solar power ensures you're able to keep your home & family safe no matter what comes your way.
Making one-click solar solutions simple since 2018. Whether you’re powering a cabin, charging devices, or backing up your home.
Say goodbye to reliance on the energy companies. Enjoy the same freedom that 50,000+ customers have with their own solar power system.
Troy P
This is the first stage of my three planned purches. I got the eg4 inverter 6000 XP base kit with six 400 watt panels and the two server rack batteries. Did a little online research and followed the instructions and it got set up without any issues. Right now I'm just running it in my garage on a single outlet and have been running dual 750 watt water distillers with it. Once I get the second inverter and a bunch more panels and batteries, I plan on attaching it to my subpanel in my house that has my lights and outlets and appliances on it. Then I'll get a soft start for my AC and blower and run it on my main panel.
Jacob B
Trying to pick the correct solar system for your needs can be very technical and frustrating. I wanted to thank Yvhan and the Portlandia Electric supply team for their patience and helpful attitudes through multiple calls. I feel like we were able to narrow it down to what worked for me and my family. My system works great and I couldn't be happier to have picked Portlandia Electric Supply.
Patrick B
I wanted to get an offgrid solar system for years but didn’t know where to start. I found Portlandia Electric Supply on Facebook and decided to submit a quote. Within 24 hours I had a custom proposal that was almost half the price of the companies I had previously got quotes from. My wife and I decided to order online and the kit came in a timely manner and it was an easy install. Great company to work with!
James Martin
I would like to take the time to express the outstanding service that I was provided with by Portlandia Electric Supply. They provided me with all the answers to my questions, and after reviewing our quote over the phone I felt comfortable proceeding to order my kit. It’s exactly what I needed and they were there to help us over the phone when we had questions installing it. I highly recommend others in need to choose Portlandia Electric Supply.
Brian H
As a professional videographer, I needed reliable power on the go.Portlandia Electric Supply Delta Pro and roof-mounted panels were the perfect solution. Setup was easy, and the kit included everything needed. The Delta Pro powers my cameras, lights, laptop, and a small fridge with impressive battery capacity.
Keith S
You folks have been wonderful guiding me through the ins and outs of going solar. Plus your tech guys Rod and Nelson are the absolute best. They explained all the different aspects of inverters, batteries and how to keep them in top condition. Too much more to put here… but no other company has the 100% tech support you provide for your customers!
Coll A
My experience with Portlandia Electric Supply has been excellent. Before the sales, they answered all my questions to assure that I got what I needed. After the sales they continued to support me with answers and help. I had a warranty issue with a unit, and it was handled as well as possible. I would recommend them to anyone looking to go solar.
Troy P
This is the first stage of my three planned purches. I got the eg4 inverter 6000 XP base kit with six 400 watt panels and the two server rack batteries. Did a little online research and followed the instructions and it got set up without any issues. Right now I'm just running it in my garage on a single outlet and have been running dual 750 watt water distillers with it. Once I get the second inverter and a bunch more panels and batteries, I plan on attaching it to my subpanel in my house that has my lights and outlets and appliances on it. Then I'll get a soft start for my AC and blower and run it on my main panel.
Jacob B
Trying to pick the correct solar system for your needs can be very technical and frustrating. I wanted to thank Yvhan and the Portlandia Electric supply team for their patience and helpful attitudes through multiple calls. I feel like we were able to narrow it down to what worked for me and my family. My system works great and I couldn't be happier to have picked Portlandia Electric Supply.
Patrick B
I wanted to get an offgrid solar system for years but didn’t know where to start. I found Portlandia Electric Supply on Facebook and decided to submit a quote. Within 24 hours I had a custom proposal that was almost half the price of the companies I had previously got quotes from. My wife and I decided to order online and the kit came in a timely manner and it was an easy install. Great company to work with!
James Martin
I would like to take the time to express the outstanding service that I was provided with by Portlandia Electric Supply. They provided me with all the answers to my questions, and after reviewing our quote over the phone I felt comfortable proceeding to order my kit. It’s exactly what I needed and they were there to help us over the phone when we had questions installing it. I highly recommend others in need to choose Portlandia Electric Supply.
Brian H
As a professional videographer, I needed reliable power on the go.Portlandia Electric Supply Delta Pro and roof-mounted panels were the perfect solution. Setup was easy, and the kit included everything needed. The Delta Pro powers my cameras, lights, laptop, and a small fridge with impressive battery capacity.
Keith S
You folks have been wonderful guiding me through the ins and outs of going solar. Plus your tech guys Rod and Nelson are the absolute best. They explained all the different aspects of inverters, batteries and how to keep them in top condition. Too much more to put here… but no other company has the 100% tech support you provide for your customers!
Coll A
My experience with Portlandia Electric Supply has been excellent. Before the sales, they answered all my questions to assure that I got what I needed. After the sales they continued to support me with answers and help. I had a warranty issue with a unit, and it was handled as well as possible. I would recommend them to anyone looking to go solar.
Shop Securely, Trusted Supplier, 100% Satisfaction
Trusted Company, Real Products, Lifetime Support
Avoid Scams, Buy with Confidence, Enjoy Peace of Mind
Manufacturer Warranty, Exceptional Service
Shop Securely, Trusted Supplier, 100% Satisfaction
Trusted Company, Real Products, Lifetime Support
Avoid Scams, Buy with Confidence, Enjoy Peace of Mind
Manufacturer Warranty, Exceptional Service
Shop Securely, Trusted Supplier, 100% Satisfaction
Trusted Company, Real Products, Lifetime Support
Avoid Scams, Buy with Confidence, Enjoy Peace of Mind
Manufacturer Warranty, Exceptional Service
Shop Securely, Trusted Supplier, 100% Satisfaction
Trusted Company, Real Products, Lifetime Support
Avoid Scams, Buy with Confidence, Enjoy Peace of Mind
Manufacturer Warranty, Exceptional Service
Shop Securely, Trusted Supplier, 100% Satisfaction
Trusted Company, Real Products, Lifetime Support
Avoid Scams, Buy with Confidence, Enjoy Peace of Mind
Manufacturer Warranty, Exceptional Service
Shop Securely, Trusted Supplier, 100% Satisfaction
Trusted Company, Real Products, Lifetime Support
Avoid Scams, Buy with Confidence, Enjoy Peace of Mind
Manufacturer Warranty, Exceptional Service
Shop Securely, Trusted Supplier, 100% Satisfaction
Trusted Company, Real Products, Lifetime Support
Avoid Scams, Buy with Confidence, Enjoy Peace of Mind
Manufacturer Warranty, Exceptional Service
Shop Securely, Trusted Supplier, 100% Satisfaction
Trusted Company, Real Products, Lifetime Support
Avoid Scams, Buy with Confidence, Enjoy Peace of Mind
Manufacturer Warranty, Exceptional Service
Shop Securely, Trusted Supplier, 100% Satisfaction
Trusted Company, Real Products, Lifetime Support
Avoid Scams, Buy with Confidence, Enjoy Peace of Mind
Manufacturer Warranty, Exceptional Service
Shop Securely, Trusted Supplier, 100% Satisfaction
Trusted Company, Real Products, Lifetime Support
Avoid Scams, Buy with Confidence, Enjoy Peace of Mind
Manufacturer Warranty, Exceptional Service
When you choose Portlandia Electric Supply, you’re buying real products from a trusted company with established supplier relationships. Enjoy peace of mind with 100% manufacturer warranty coverage and lifetime customer support. In an age where online shopping is fraught with risks, it’s crucial to avoid fly-by-night websites that skirt regulations. Shop with confidence, knowing you’re getting genuine quality and reliable service.
$150 Value - Free Offer (Limited Time Only!) No Strings Attached. Totally Free. Takes Less than 2 Minutes.