SimpliPhi Basics

All of SimpliPhi’s products are Manufactured in California, USA.

Our batteries have been tested by Intertek and are ETL listed to UL 1973.

SimpliPhi offers some of the best warranties in the industry. The term of the warranty is dependent on the depth of discharge:

  • 80% Depth of Discharge: 10 year warranty / 10,000 cycles
  • 90% Depth of Discharge: 10 year warranty / 5,000 cycles

Further warranty questions are addressed in the Warranty section below. The warranty can be found on our Downloads page.

SimpliPhi batteries have a round-trip efficiency of 98% -- one of the highest in the industry.

SimpliPhi batteries use LFP chemistry, which is the safest, non-toxic and environmentally benign Lithium Ion chemistry available. The raw materials are non-hazardous and recyclable.

Yes. All SimpliPhi Lithium Ion batteries are made with safe and environmentally benign Lithium Ferro Phosphate (LFP) chemistry. SimpliPhi’s LFP batteries pose none of the risk associated with more common Lithium Ion chemistries that use cobalt. Cobalt is toxic, unstable and hazardous. Lithium is not. Therefore, SimpliPhi batteries do not pose the risk of thermal runaway, fire, or exposure to toxic fumes and materials.

SimpliPhi Power has a variety of products in 12V, 24V and 48V configurations. Our batteries are designed to operate only at the nameplate voltage and cannot be wired in series. We will be offering a higher voltage battery solution that can scale from 48-600V to suit the application as needed.

Yes. Simpliphi batteries are approved for all modes of transportation globally. Only SimpliPhi has explicit FAA permission to transport its Lithium Ion battery systems by air globally.

PHI 2.7 and 3.5 Batteries

Our batteries are rated at a standard of C/2 for continuous charge and discharge. For example: each PHI 3.5 kWh 48V battery equates to a maximum charge and discharge rate of 33A continuous. This rating is per each battery unit in the bank, so each time a battery is added to the battery bank the total capacity of the bank increases: The total capacity is the number of units multiplied by the per unit capacity. The batteries are also capable of 60A discharge for short periods <10 minutes. For more rapid discharge use cases, we make dedicated High Output 24V versions of the 2.7 & 3.5 kWh batteries that can deliver up to 160A and 250A per unit.

Yes. As long as the nameplate voltage is the same and the capacity range is the same, then new model PHI batteries can be added to existing systems with older SimpliPhi models. This even extends to legacy OES, OES1, OES2, and OES3 batteries. Just remember to reprogram the inverter charge controller equipment for the new battery bank capacity.


Our batteries are rated at a standard of C/2 for continuous charge and discharge. For example: each PHI 3.5 kWh 48V battery equates to a maximum charge and discharge rate of 33A continuous. This rating is per each battery unit in the bank, so each time a battery is added to the battery bank the total capacity of the bank increases: The total capacity is the number of units multiplied by the per unit capacity. The batteries are also capable of 60A discharge for short periods <10 minutes. For more rapid discharge use cases, we make dedicated High Output 24V versions of the 2.7 & 3.5 kWh batteries that can deliver up to 160A and 250A per unit.

Yes. As long as the nameplate voltage is the same and the capacity range is the same, then new model PHI batteries can be added to existing systems with older SimpliPhi models. This even extends to legacy OES, OES1, OES2, and OES3 batteries. Just remember to reprogram the inverter charge controller equipment for the new battery bank capacity.

Lead Acid Replacement

Absolutely. In fact, PHI batteries are designed to be a direct replacement for old and/or failing lead-acid batteries. Simply reprogram the inverter charge controllers voltage curves to accommodate the different PHI voltage profile and battery bank size.

SimpliPhi batteries use lithium ferro phosphate (“LFP”) chemistry in their cells as opposed to lead-acid. This makes them very different in many ways. SimpliPhi batteries can be drawn down to 80-100% depth of discharge so you can have greater capacity in a smaller footprint. No ventilation or cooling is required, maintenance typical of lead acid batteries is not required and they offer a very broad ambient temperature range for operation. In addition, each battery has an internal battery management system that automatically balances the cells and will protect itself in the event of extreme over charge/discharge. There is also an external ON/OFF switch (80A breaker) for enhanced safety during shipping, storage, installation, and maintenance.

No. Equalization charge is specific to lead-acid battery chemistry, in which sulfate crystals build up on the lead plates in the cells and decrease the battery capacity. This does not happen with SimpliPhi’s lithium ferro phosphate chemistry, so equalization is not required and actually can harm SimpliPhi batteries.

Unlike lead-acid batteries, Simpliphi’s LFP chemistry results in minimal self-discharge (> 1%/month) so they do not require float charging to retain their capacity. However utilizing the float charge capability can help prioritize solar charging and will not harm the batteries.

It is simple to calculate how many PHI batteries to create a battery bank equivalent to your lead acid battery bank:

  • Find the name plate amp-hour (Ah) capacity of your existing batteries.
  • Multiply the nameplate Ah capacity of each lead acid string by the number of strings you have to find the total battery bank capacity. (The Ah capacity of the battery remains constant as multiple lead-acid batteries are connected in series to reach the string voltage.)
  • Multiply this total battery bank capacity by the Depth of Discharge (DOD) factor for the system to find the total usable capacity of your existing system.
  • Multiply the nameplate capacity of the desired PHI battery by the DOD factor to find the usable capacity of each battery. (Simpliphi batteries can only be connected in parallel, so with multiple batteries the voltage remains at nameplate while the total Ah capacity of the battery bank increases.)
  • Divide the usable Ah capacity of the desired PHI battery model into the usable capacity of your existing battery bank to find the minimum number of PHI batteries required. Round up to the next whole battery.

For Example:

  • The existing system uses twelve 12V 80Ah lead acid-batteries.
  • The battery bank consists of three strings of four batteries to reach 48V and yields a total battery bank capacity of 240Ah. (80Ah per string x 3 strings)
  • Operating at 50% DOD means a usable capacity of 120Ah. (0.5 DOD factor x 240Ah)
  • To replace with PHI 2.7 kWh 48V batteries, which each have a 52 Ah nameplate capacity and operate at 80% DOD, means that each battery has a usable capacity of 41.6 Ah. (52 Ah x 0.8)
  • 120 Ah / 41.6 Ah = 2.88. Rounding up, this means you need at least three 2.7 kWh batteries to meet or exceed your existing battery bank capacity. Note: In this example, three Simpliphi batteries create a battery bank with a usable capacity greater than the twelve existing lead acid batteries.

It is important to remember that there are multiple ways to size your battery bank and you should thoroughly evaluate your system to determine the appropriate PHI battery bank size. The maximum load on the batteries should also be considered, as well as the maximum charge capability of your PV array.

SimpliPhi Warranty

SimpliPhi’s warranty is prorated because the warranty coverage is 10 years from the date of purchase or until the batteries have been cycled 10,000 times (at 80% DOD), whichever occurs first. For example, the 10 year term is prorated if 10,000 cycles are achieved by year 8.

A full cycle is defined as: Discharge to programmed DOD, and charge back to 100%. Partial cycles occur when the battery is not discharged completely to it’s programmed DOD setting before it’s fully recharged. With respect to the warranty, this means cumulative cycles totaling the rated DoD settings (per the warranty) are the equivalent of a cycle.

As long as the nameplate voltage of all batteries is the same, and the batteries are in the same capacity range, then adding new batteries in parallel will not affect the performance or warranty of the existing batteries. (Note: Sharing the same capacity range means that mixing PHI 3.5 with PHI 3.4 or PHI 2.7 with PHI 2.6 is supported, but mixing PHI 3.4 with PHI 2.6 (or PHI 3.5 with PHI 2.7, etc.) is not supported.

Basic System Installation & Operation

PHI batteries can be directly integrated with many popular hybrid inverter and solar charge controllers including: Outback Power, Schneider, Magnum, Victron, SMA Sunny Island, Midnite, Morningstar, Selectronics and more. It is also possible to retrofit existing solar-only systems with an A/C coupled system by installing an additional inverter and batteries.

Simpliphi batteries are not currently compatible with SolarEdge and StorEdge inverters because they require 120V batteries. We have 120V solutions in development.

We maintain a portfolio of integration guides for most major brands of equipment. Further information and brand-specific integration guides are available on our Downloads page.

Yes, PHI battery compatibility with Schneider inverters has been tested and verified by both Schneider and Simpliphi Power. Instructions and settings for Li-ion battery chemistry exist throughout the current Schneider XW inverter installation manuals. There is also a FAQ at https://www.schneider-electric.com/ww/en/ that confirms that they are indeed compatible.

Usable capacity depends on your operating parameters. For example, to determine usable Ah Capacity of a PHI 3.4 48V battery set up to operate at 80% DOD, multiply the DOD factor (0.8) by the specified battery capacity (67Ah) to determine the usable capacity of each battery: 67 x 0.8 = 54Ah. Then, multiply this number by the total number of batteries in parallel to find the total battery bank capacity. This simple sizing calculation can be applied to all of our battery models.

PHI batteries are warranted to sustain maximum output of 60A each for up to 10 minutes at a time. If the peak load is expected to be close to the maximum output capacity of the battery bank frequently and/or for sustained periods it is best to increase the size of the battery bank to at least double the kW load to maintain an average sustained output of C/2 for the batteries.

All SimpliPhi batteries can stored and discharged at temperatures between -4° to 140°F (-20° to 60°C). SimpliPhi batteries can only be charged at temperatures between 32° to 120°F (0° to 49°C).
PHI batteries cannot be charged below freezing, please plan accordingly for cold climates. A protocol for charging PHI batteries below freezing can be provided upon request.

No. Wiring any SimpliPhi batteries in series is not condoned and will result in voiding the warranty. SimpliPhi batteries can only be wired in parallel to operate at their nameplate voltage. Wiring in series will cause damage to the batteries and void the warranty.

SimpliPhi batteries have a very low self-discharge rate of approximately 1% per month. As long as they are sufficiently charged before they are left idle, they will remain in good working order for weeks or months at a time. When returning to a system that’s been left idle for some time, it is recommended that the PHI batteries are charged immediately to avoid drawing loads until the batteries are confirmed to be sufficiently charged. Failure to charge the batteries prior to use will void the warranty.

SimpliPhi batteries are much different from lead acid chemistry in that the Voltage-Discharge Curve is very flat. This means that the % SOC can change significantly across even a single volt. As a result, the best way to understand the SOC of the battery bank is by monitoring the Ah-in and the Ah-out. There are a variety of shunt based battery monitoring products that can be used to achieve this.

Appropriate wire sizing should be calculated per NEC (and/or local authority) to be sufficient for the ampacity, the run length, conductor, and wire type. There are no specific requirements regarding wire type (thhn, thwn-2, etc) so long as the rating works in your calculations. The recommended minimum wire size for each parallel run to a PHI 3.5 kWh 48V battery is AWG #4, but it is the responsibility of the licensed installing electrician to calculate and confirm the appropriate wire size. If using a combiners or bus bars, ensure that they are sized appropriately for the total number of batteries combined.

Energy Storage Basics

There are many different applications and use cases for energy storage. Batteries have traditionally been used in off-grid scenarios to store and provide power from solar, wind or diesel generators in remote locations 24/7 long after the sun goes down or the wind stops blowing or your diesel runs out. However, there are a number of advantages to including energy storage in grid connected systems: energy arbitrage, peak shaving, and back-up power in the case of grid failure.

Energy arbitrage means storing excess energy produced by your PV system during the day in batteries so it can be deployed later in the evening and night time when your electrical loads can be higher, solar production has waned or ceased and utility rates for electricity increase in cost. This can be especially valuable for customers who are subject to time of use rates (TOU).

Peak shaving also employs stored energy to reduce or eliminate additional fees associated with peak power demand, which can be quite substantial based on the utility rate structure. By deploying stored energy to supplement grid power, with or without PV, PHI batteries can provide substantial energy cost savings by ‘shaving-off’ your peak usage.

System Design

The number of SimpliPhi batteries you will need depends on a number of factors, including but not limited to:

  1. what the end-user’s energy needs are
  2. what types of loads they want to support
  3. what energy sources they have (solar, wind, diesel, etc.)
  4. what their goals are (back- power for critical loads only, net-zero, demand charge management, peak shaving, TOU, etc)
  5. what project constraints exist

SimpliPhi Application Engineers can work with you to assist with technical support to design your project.

When considering any major purchase or investment, it’s important to consider the lifetime cost of that investment. Often this means taking many factors into consideration, not just the up-front price point. . If you can save 20% of the up-front price of a new roof by purchasing the cheaper of two roofing materials, but that cheaper roofing material only lasts half as long, which is the better, more cost effective choice? The same principle can be applied to energy storage by evaluating the Lifetime Cost of Energy (LCOE) as it relates to a specific battery. . There are many factors that affect LCOE, including but not limited to efficiency, cycle life, depth of discharge, maintenance, shipping, heating/cooling, power density, and replacement costs. SimpliPhi batteries are more efficient, have longer cycle life, greater depth of discharge, and require no heating/cooling or monitoring equipment, making them a better value over time, but even at the point of installation when the cost of ancillary monitoring, cooling and other protective equipment required by other battery manufacturers is taken into consideration.

Power is a rate measured in kW that measures how quickly something generates or uses energy. It reflects the instantaneous consumption of energy. Energy is measured in kWh over a specific period of time. It is the product of the power used and how long it was used. For example, running 1 kW for 1 hour is 1 kWh.

SimpliPhi batteries can be paralleled infinitely. The only practical limitation is the configuration of the inverters. Depending on the manufacturer and model, there are different limits on how many inverters can be stacked together to function with a single battery bank. To date, there are successful installations of up to 88 SimpliPhi batteries paralleled together.

Yes. Adding new batteries to an old system is perfectly okay. Because SimpliPhi batteries require parallel configuration, old batteries will not hamper the performance of new ones that are added to increase the total battery bank capacity. However, you must remember to reconfigure the inverter and charge controller settings to reflect the new total system size whenever batteries are added. More detailed information on the process can be found in our installation manuals.

No. Mixing SimpliPhi batteries with other battery chemistries or types in a single system is not recommended and will void the warranty.

Yes. You can add new PHI batteries to older ones to expand your battery bank size. Since PHI batteries are wired in parallel and each battery has its own BMS, the older batteries will not bring down the performance of the newer batteries. It’s also important to understand the implications of changes to your battery bank size and whether or not you also need to install additional inverters and/or charge controllers. Either way, your settings should be reviewed and adjusted whenever changing or adding any equipment or batteries to your system.

SimpliPhi batteries can be installed safely indoors or out. Outdoors, the batteries are installed in a weather-resistant enclosure, or in any code compliant container and location. Indoors or out, there is no battery clearance or ventilation required. Because SimpliPhi only utilizes the environmentally benign Lithium Ferrous Phosphate chemistry, the PHI batteries do not pose the threat of thermal runaway or fire characteristic of cobalt-based lithium ion batteries, nor do they expose people to hazardous fumes or materials. PHI batteries have been and can be installed inside closets, crawl spaces, attics and other indoor spaces, making them very versatile and safe. Because they are small, modular and scalable, they can be installed in very small spaces in any orientation.

Because SimpliPhi batteries require no clearance or ventilation and no cooling or monitoring equipment, they can be efficiently packed tightly together and/or against existing walls. They can also be installed on their sides or with the terminals facing forward with no negative impact on operation or capacity.

Yes, If you already have a PV array, you can create an AC-coupled system to add energy storage.

An AC-coupled storage system involves adding new batteries and a new inverter to an existing PV system. Most grid-connected PV inverters cannot be directly integrated with batteries, requiring the addition of an inverter to interact directly with the batteries. The interface between the PV array and the batteries occurs through the two inverters, which means that some system efficiency is lost as the solar array charges the batteries because the power must be transformed twice -- i.e. DC to AC and back to DC. If you are planning to install a PV system, it is more cost effective to integrate PHI batteries up-front. In this way, for all grid-tied PV systems, you will have access to power by using the PHI batteries whenever the grid fails. Without PHI batteries, you lose the ability to draw from your PV generation if and when the grid fails, making your investment limited in black-out and other catastrophic events in which the centralized grid breaks down.

Existing PV systems can also be retrofitted by removing and replacing the existing PV inverter with a new hybrid inverter. However, installing a hybrid inverter does require additional work to re-wire and reconfigure the system. Additionally, removal or replacement of the existing inverter could cause problems for customers with grid-connected policy agreements, so it’s generally preferred to a/c couple by adding on and operating with two inverters.

A DC-coupled system is the best option if you don’t already have PV because it’s more efficient in energy and cost. In a DC-coupled system, the DC current produced by the PV array can be used to charge the DC PHI batteries directly by controlling the voltage and current delivered from the PV array. You can have a single inverter interact with the PV array, PHI batteries, loads, as well as the grid and/or generator power where available. For new projects, it is generally recommended to DC-couple. However, there are many factors that determine what’s best for each application, so it’s important to understand the particular conditions and constraints of each project. SimpliPhi application engineers can provide technical support to help you design the best energy system that optimizes the cost and performance of all the equipment for your particular project.

Don't see your question here? Please don't hesitate to contact us to get the answers you need!

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