Blog Post

Replacing Lead Acid Batteries with LFP: A Guide for Homeowners

John Hassell is the owner and president of Be Green Solar in Benton, NH. Through Be Green Solar’s work in New England and humanitarian projects in Haiti, John is regularly working with off-grid homeowners and medical clinics to replace their aging and otherwise failing lead acid battery banks with LFP batteries. In part one of our interview, SimpliPhi spoke with John to learn more about what customers are seeking when it comes to upgrading their existing energy storage systems and the lead acid vs. lithium ferrous phosphate (LFP) comparison.

How many lead acid replacement projects has Be Green Solar completed so far?

Quite a few actually, we’re working on them all the time and have replaced lead acid batteries of nearly every make and model — Deka AGM, Trojan FLA, Rolls AGM and more. We just completed one of our largest lead acid replacement projects at a clinic in Haiti where 72 Rolls AGM lead acid batteries were replaced by 40 PHI batteries. In the USA, we recently completed a system where we replaced 12 large Rolls FLA batteries with 10 PHI 3.5 batteries, and are about to expand a PHI lead acid replacement project that we completed two years ago with an additional battery to give the homeowner more capacity as her energy needs have changed. These represent only a small sample of our work thus far.

Why are customers typically looking to replace their lead acid battery banks?

Our phone rings when something goes wrong. Certainly, systems age and the associated lost capacity is often the reason for a call, but unexpected emergencies also arise. Two weeks ago, a customer called explaining that they had tried to equalize 16 Rolls AGM L16 batteries, destroying them all in the process. Other customers simply grow tired of the ongoing maintenance flooded lead acid batteries require. Simpliphi LFP provides a stable power source. Each battery contains a battery management system (BMS) which protects the battery from damaging discharge.

Beyond reliable power, what are customers looking to achieve with a new battery bank?

The most common customer request is for a solution that doesn’t require their constant attention. They want to flip a switch and see the lights come on. They don’t want to be buried in the minutiae of battery maintenance. They don’t want to take off caps, fill out maintenance charts, add water or any of the other maintenance required of flooded lead acid batteries.

Fumes are also frequently a concern — from health, safety and nuisance perspectives. To avoid the dangers of toxic hydrogen off-gassing, flooded lead acid batteries require ventilation and an exhaust fan. But even with that ancillary safety equipment, homeowners with flooded batteries have to contend with an “acid smell” whenever batteries are charging at a high rate.

When it comes to scalability, how do lead acid and lithium batteries compare?

For most homeowners, energy needs grow over time. In some cases, a family grows, in others they add new appliances. In both cases, the answer to “how many batteries do I have to have to sustain me for two days without sun” changes.

With lead acid batteries, the only choice is to double the size of your battery bank with a string matching the size of the original bank. Let’s say you have an initial bank of 8 batteries, you’d need to add 8 more, which of course requires double the space and weight. It’s also a bad idea to mix old and new lead acid batteries because you sacrifice capacity as they tend to “steal” charge from one other.

PHI batteries allow you to grow your battery bank in smaller, incremental steps, which saves space, weight and cost. It’s also not a problem to mix older and newer batteries in the same battery bank.

As you help your customers decide what technology to choose for their battery bank, what aspects require the most discussion and consideration?

We spend a lot of time talking with customers about lifetime cost and usable capacity.

Looking at the cost of FLA vs. AGM vs. LFP, FLA customers are initially drawn to flooded lead acid because its upfront cost is less than LFP. But when you dig into those numbers and do the math of replacing a lead acid battery bank one or two times within the warrantied lifespan of a SimpliPhi system, the economics change. PHI batteries are warrantied for 10,000 cycles, whereas, most lead-acid batteries provide 1,200-2,000 cycles. Given that most homeowners are financing their battery banks, it is worth spending a few extra thousand on the front end to save two times that amount or more over the course of 10 years.

Then there is the concept of nameplate capacity vs. usable capacity. Let’s say you go out and buy eight L16 batteries for your battery bank. You think your capacity is 425 amp hours. However, with lead acid, you shouldn’t discharge the batteries more than 50 percent. So, in reality, you’re only getting 212 amp hours you can use. If you discharge your batteries beyond the 50 percent limit, you reduce their lifespan. With SimpliPhi, on the other hand, there aren’t the same discharge limits – practical limit is usually set at 85%-90% discharge – giving you the benefit of significantly more usable capacity.

How does performance compare?

For a homeowner who is accustomed to a lead acid battery bank, the normal charge process of bulk, absorb and float includes a lengthy absorb phase. With PHI batteries, there is no absorb phase — they go immediately to float. This translates into shorter generator run times and batteries that charge more quickly. Also, with built-in battery protection (BMS) you don’t have to worry about damaging your batteries.

Much of your business is in New England. Are there any cold weather considerations that homeowners should keep in mind?
The biggest winter consideration is snow cover. Problems arise when solar panels are left blanketed in snow and unable to charge the batteries or power battery warming systems. If LFP batteries are not kept above 25℉, they will lose the ability to charge or discharge. If the application houses the batteries in a cold (below freezing) location, they must be in a heated enclosure.

SimpliPhi PHI batteries are designed to be a drop-in replacement for lead acid. Is it really that easy? Can a homeowner keep all their existing equipment?

Absolutely. You don’t have to change any equipment at all. The only changes are to the programming of the existing charge controller and inverter.