Off-Grid Updates: Lithium Iron Phosphate Batteries

2 Lithium Iron Phosphate batteries paralleled together

Lithium Iron Phosphate (LiFePO4) batteries have been a hot topic these days, with good reason. They are claimed by some to be “the future” in energy storage. Some advantages over the more popular Lead Acid (LA) batteries include longer life, greater discharge rate (up to 80% Depth of Discharge claimed as well), and little to no maintenance.

A customer, now a friend of ours, who enjoys testing the latest technology, decided to give Iron Edison’s LiFePO4 Battery a try. We helped with the transition of his previous 48 Volt Lead Acid battery bank (that we installed in 2012), which consisted of sixteen Trojan L-16 RE Bs (740 Amp Hour total), to his current 48 Volt 360 Amp Hour LiFePO4. Normally, with Iron Edison, the Lithium batteries are housed in one large metal enclosure. However, as there were sizing restraints (concerning the entrance of the underground structure where the Balance of Systems is contained), Iron Edison configured the battery system in two separate smaller enclosures. These were easily paralleled together with the provided Anderson quick connect cables to complete the 48 volt system.

Meter afixed to battery showing power, warnings and faults

Iron Edison boasts of their batteries being fully compatible with leading industry equipment, such as Schneider Electric, SMA, Magnum, and MidNite Solar. Our customer was already equipped with a Magnum MSPAE4448 Inverter/Charger and a MidNite Solar Classic 200 Solar Charge Controller. Once the battery set (S/N 011) was installed, it took some time working with the manufacturer to "dial in" the Classic 200's set pionts to completely charge the battery bank from 50% State of Charge (SOC) to 100% SOC in one sunny day. As of today, the change in the "end amp" set point seems to have mitigated the issue.

It’s only been three months since the batteries have been commissioned, but we’ve put together a preliminary list of pros and cons that we have observed during this period. There are some things we cannot comment on, for example long life and increased life discharge cycles, but we’ll continue to update the list if anything of importance arises. 

Pros: 

• Require less maintenance - no checking water levels or specific gravity
• No equalizing needed
• No venting needed
• Can be discharged to a lower level than Lead Acid batteries, 
• Has a Battery Management System (BMS) that protects against over-heating, over-current, over and under voltage
• Can be customized to fit your energy needs as well as dimensional requirements
• Has a smaller footprint than Lead Acid batteries

Cons:

• Upfront cost could be up to three times more than what you might pay for a comparable LA battery
• Must be kept at temperatures above 0 C (32 F). In comparison, we saw battery temperatures of -16 C (3 F) on our LA batteries this winter in our unheated shop and they are still in working condition. This would limit the amount of locations, in comparrison to the LA batteries, that this storage system could be installed in. 
• Even with the Low Battery Cut Off (LBCO) set from the factory at 48.0 volts and our LBCO on the Magnum Inverter set at 48.8 volts, we have still witnessed more than two occasions of having to manually reset the battery bank to bring the system online again. Recently we have installed Magnum’s networked Automatic Genrator Start (AGS) and we are no longer experiencing the issue, since the battery bank no longer reaches the LBCO set point. This does limit the amount of Amp Hours that are available. So it is no longer a 360 Amp Hour battery set that is able to be discharged down to 20%, it is more like a 360 Ah battery set that you can only discharge down to possibly 30% - 40%. (We are still testing this).
• At 48.0 VDC the Iron Edison BMS will shut down the battery bank to protect it from damaging the battery cells. This is a good stratigie for safegurding the battery but makes Solar and Wind production unavailable because there is no battery voltage to power the charge contollers and recharge the batteries. This becomes problematic in remote sites. With LA batteries there is usually voltage present (even at less than 10% SOC) and the ability to charge when the charging resource becomes available (Sun or Wind).

We still have much to learn, test and discuss about Lithium Iron Phosphate batteries in Renewable Energy applications.

Have any experience with using Lithium Iron in the Solar Electric world you’d like to share? Please comment below. We’d love to hear your feedback!