The NTM Tech Center has been researching lithium batteries for several years. There have been several major obstacles that made lithium batteries a poor choice for missionaries. There were serious thermal runaway issues with Lithium ion (most commonly Lithium Cobalt batteries), very high initial costs, and poor reliability over time. In September 2015 we came across a different chemistry of lithium batteries, Lithium Ferro Phosphate (LFP). These proved to be much safer than other lithium batteries, with no chance of thermal runaway. The initial cost, though still high, is substantially less, and the cycle life is dramatically improved. However, all lithium batteries used on Solar Electric systems require an onboard electronic battery management system (BMS). This helps control and regulate the charge on each individual cell inside a lithium battery. The quality of the BMS, and the manufacturing process of LFP cells, directly affects the expected battery life and reliability. There are quite a few different manufactures of LFP batteries. Within these manufactures we have found a large variation in product. This variation includes:
- Battery cell chemistry
- Cell manufacturing process
- BMS electronic design
- Expected battery cycle life
- Target uses (EV, PV, Standby, Grid Storage, Hobby, Yachting, etc.)
- Charging parameters
- Operating parameters
- Sales strategies
- Warrantee and repair requirements
- Company financial health
- Customer communication
- And the list goes on.
We have spent 100’s of hours researching the field of LFP batteries. We do not have the resources to fully study every battery manufacturer. However, in almost every area, we found ourselves most comfortable with the SimpliPhi brand of battery. This company has a long history providing LFP batteries for the film industry and federal government. During the last few years they have started to broaden their target customer base to include the solar power industry. When we reached out to them for more information back in 2015, they were very willing to answer our questions. Over the past two years we have continually come back to SimpliPhi with questions and concerns. Over the last few months we have seen the Simpliphi brand picked up by every major US solar distributor, as well as numerous international distributors. Their popularity is not surprising, as they have a warrantee that soundly beats any other battery on the market. The SimpliPhi battery specifications, life cycle, charging parameters, target application, and fully incorporated and tuned BMS, puts their battery many steps above the competition.
In 2016 we sent out the first bank of LFP batteries to a missionary in PNG. That system was installed in September 2016, and we have been monitoring that solar electric system over the internet since then. We are very pleased with the results so far.
- Extended cycle life:
- SimpliPhi LFP batteries have an expected cycle life of 5000 – 10,000+ cycles. This is up to 27 years of daily deep cycling.
- Lead Acid batteries typically have a maximum of 3500 cycles. This assumes the lead acid battery is only cycled to 35% Depth of Discharge (DOD) and always kept at 75ºF. The expected life cycle for most tropical installations is about 1500 cycles, or 4 years.
- Higher efficiency:
- SimpliPhi LFP batteries are 98% efficient. This means that when you put 100 amp hours into SimpliPhi LFP batteries, you get about 98 AH back out
- Lead acid batteries (flooded, GEL, AGM) are only about 80% efficient. This means that when you put 100 amp hours into lead acid batteries, you get about 80AH back out.
- Very short absorb time:
- SimpliPhi batteries only need to reach the absorb voltage for a few minutes before LFP batteries are fully charged. (The Absorb time should be set to 1 hour)
- Lead Acid batteries need between 4 and 12 hours of absorb time. This can be difficult to achieve on solar electric systems.
- Not damaged by Partial State of Charge (PSOC):
- SimpliPhi batteries do not need to reach 100% State of Charge (SOC) on a regular basis.
- Lead acid batteries need to be regularly charged up to 100% SOC. If not, they degrade. This may lead to starting up a generator during rainy season, and because of the 4 hour Absorb time, this can result in using a large amount of fuel.
- Long shipping times, furloughs, and extended absences:
- SimpliPhi batteries will not, under normal circumstances, suffer from long shipping times. The SimpliPhi batteries can also be stored unused for up to 6 months with no maintenance.
- Lead acid batteries will degrade after only 3 months in shipping. Furloughs and extended absences can also damage lead acid batteries.
- High temperature operation:
- SimpliPhi batteries can be operated at any temperature between 32ºF and 120ºF, with no degradation.
- Lead acid batteries cycle life will degrade quicker at higher temperatures. For every 15ºF above 75ºF the cycle life of a lead acid battery is reduced by half.
- At 33lbs each, a typical SimpliPhi battery bank (6) will weigh about 200lbs.
- A typical lead acid battery can weight 180 lbs. each, and a battery bank can weigh over 650lbs.
- Add Additional Batteries:
- Additional SimpliPhi LFP batteries can be added at any time.
- You cannot add new lead acid batteries to an existing battery bank, all lead acid batteries should be the exact same size and age.
- SimpliPhi batteries are based on the Lithium Iron Phosphate chemistry, which is one of the safest Lithium battery chemistries, and is not prone to thermal runaway.
- SimpliPhi makes LFP batteries in 12 V, 24 V, and 48 V in several different models to meet different battery needs.
- Price: In most situations it will take between 6 and 8 years before SimpliPhi LFP batteries begin to give a return on investment
- In very warm climates, the ROI may be closer to 4 years.
- If you will only need batteries for 4 to 8 years, lead acid may be a better choice
- Low reserve capacity:
- Because of price and intended cycle depth, LFP batteries will have a very small reserve capacity designed into the battery bank. The NTM Tech Center has a design target of 60% DOD daily discharge, (discharging down to 40% SOC on a daily basis). This leaves very little power left over in reserve. We do not recommend discharging these LFP batteries lower than 85% DOD (15% SOC). This may mean a missionary has to run a generator or reduce loads more often.
- Lead Acid battery banks are designed with reserve capacity in mind. A typical lead acid battery bank for a solar electric system will be designed to be discharged to 35% DOD (or 65% full SOC) on a daily basis. This leaves 65% in the batteries as a buffer. Lead Acid batteries can, on occasion be discharged all the way to 80% DOD (20% SOC).
- May be more susceptible to lightning strikes:
- SimpliPhi batteries have sensitive electronics embedded in each battery. These can potentially be destroyed by voltage spikes and surges from nearby lightning strikes. Surge suppression will be built into the battery combiner box to help mitigate this possibility.
- Lead Acid batteries have a much smaller chance of being damaged by a nearby lightning strike, unless the charging equipment is damaged and the batteries don’t receive adequate charge.
- Shipping: The small and light form factor of these batteries can make them easier to transport. However, these are a lithium battery technology and although they are not susceptible to the thermal runaway and fire dangers that other lithium ion batteries are, they are fully regulated hazardous cargo and fall under UN3480 regulations. All shippers must be certified to UN3480 certification before they are legally allowed to ship these batteries. In some circumstances this can lead to high fees and even refusal to transport.
- A battery combiner box is needed to properly install SimpliPhi batteries. The NTM Tech Center can provide this.
- The voltage on a 12 V LFP battery bank will not change until they are almost empty, and users will have a difficult time determining how much power is left in a battery bank. We highly recommend a State of Charge meter that monitors the amperage going in and out of the batteries and provides a SOC %. The Outback Mate3 (and late model Mate1) can do this with the addition of an Outback Flexnet DC battery monitor and shunt. Victron Energy also has a standalone unit. Either of these can be incorporated into the battery combiner box from the NTM Tech Center
- The 12 V LFP batteries CANNOT be connected in series for a 24 V bank. Order the 24 V LFP version instead.
Please contact the NTM Tech Center, to discuss if SimpliPhi LFP batteries will meet your needs.