Blog Post

PHI Batteries Prove Ideal Drop-in Replacement for Lead Acid Batteries

In 2011, The Ojai Foundation was exhausted with maintaining and replacing the lead acid banks of batteries required to capture all the solar generation on the property that kept their operations up and running off the grid. They had evaluated upgrading to new flooded lead acid batteries in the hope of reducing the burdensome maintenance requirements but realized lead acid, new or not, would continue to add to their maintenance costs, ongoing failure rates and lack of reliable access to power. In addition, the corresponding reduction in cycle life, low depth of discharge, low efficiency rate and sensitivity to high ambient temperatures (typical of southern CA) made the idea of staying with lead acid a losing proposition. As a result The Ojai Foundation chose to replace the lead acid batteries with the SimpliPhi Power PHI 2.6 kWh lithium ferrous phosphate batteries.

Working in partnership with California Solar Electric , SimpliPhi Power replaced the 24 toxic lead acid batteries with eight efficient, non-toxic PHI 2.6 batteries to provide even more accessible, reliable power storage to the Foundation on a 24 hour basis. The new batteries were installed in the same outdoor area as the previous batteries without the need to upgrade the existing inverter charge controllers, making the PHI batteries an ideal drop-in replacement.

As a result, The Ojai Foundation’s power capacity increased from 10.8 kWh, using the lead acid batteries, to 20.8 kWh using the PHI 2.6 batteries. In addition, the weight of the battery bank was reduced from 2,823 lbs to 460 lbs and the overall footprint was reduced significantly. The Foundation was thrilled to eliminate the maintenance, toxic off-gassing and inefficiency losses typical of lead acid batteries.

Lead Acid vs. SimpliPhi Power Technology


Lead Acid Value SimpliPhi Power Value
24 Lead Acid Batteries 10.8 kWh of energy storage 8 PHI 2.6 Batteries 20.8 kWh of energy storage
Weight 2,823 lbs Weight 460 lbs
Replacement Requirement 3 years Replacement Requirement 10 to 20 years
Maintenance Extensive, trickle charging Maintenance None
Optimum Operating Temp 77° F Operating Temp -4° to 140°F (20°-60°C)
Hazard Rating Acute-chronic Hazard Rating Safe & environmentally benign
Depth of Discharge 70% Depth of Discharge 100%
Cycle Life 300 Cycle Life 5,000+
Depth of Discharge 50% Depth of Discharge 98%
Self-Discharge 13% per month Self-Discharge <1% loss per month
Savings None Savings Weight, size, shipping and operating costs

Today, SimpliPhi Power is the only lithium-ion battery manufacturer that offers a direct drop-in replacement option for lead acid batteries that’s, well… simple. For most installers, lead acid is just the only option or “devil we know”.

Beyond SimpliPhi Power, most lithium-ion batteries offer yet another “devil” that is important to to get to know. Overall, lithium ion batteries can offer installers a simple way to transition customers from lead acid, reducing the number of PV panels required to charge the batteries, to improving the cycle life, depth of discharge, efficiency charge & discharge rate and overall performance of their energy storage system. Because of their higher cycle rates, SimpliPhi lithium ferrous phosphate batteries offer five to ten times more cycle life compared to lead acid batteries, without the need for maintenance or temperature regulation. However, most lithium ion batteries in the market today use cobalt (known as Li-on with cobalt) in their chemistry.

Cobalt is a toxic, hazardous and unstable element that has an intrinsically shorter cycle life (500 to 800) and a dangerous potential for what is known as ‘thermal runaway’. Thus, Li-on with cobalt batteries require active management techniques to mitigate heat build-up, such as longer charge and discharge times, shallower depth of discharge and internal cooling or ventilation. Additionally, the ambient temperature of an installation with lithium cobalt batteries also needs to be monitored and controlled, which translates into higher inefficiencies and costs over the lifetime of the battery installation. To avoid issues around temperature sensitivity and the danger of overheating and thermal runaway, most Li-on with cobalt batteries are not rated for outdoor installations, as it’s easier to control temperatures indoors. This leads to further costs and hassles when looking to move a customer off of lead acid.

By combining the LFP chemistry with SimpliPhi’s proprietary cell architecture, raw materials, assembly techniques and Battery Management System (BMS), SimpliPhi has created a deep cycle battery with the highest efficiency rate (98%), longest cycle life (10,000 @ 80% DOD and 5,000 @ 100% DOD), broadest operating temperature (-4 to 140 F), rapid charge and discharge rates (15 minutes to 2 hours – depending on the model) with a 10 year Warranty that holds to the industry standard 80% End of Life (EOL) without the risk of ‘thermal runaway’ characteristic of the cobalt based lithium ion chemistries and battery packs. Combining the LFP chemistry with our proprietary materials, manufacturing techniques, power electronics and architecture, SimpliPhi has created nominal internal resistance such that the flow of electrons is not impeded during charge and discharge cycles and as a result, SimpliPhi batteries do not pose the risk of thermal runaway and fire, do not require ventilation or cooling to maintain capacity or safeguard cycle life, unlike other lithium ion cobalt based batteries. Without the requirement for ventilation or cooling, SimpliPhi batteries can be stored outside in temperatures up to 140 degrees F.

With SimpliPhi Power, you’ll no longer need to take risks with the cobalt based lithium batteries and ‘dance with the devil’, as our customers remark, to achieve your energy storage freedom.