The Chemistry

Thinking about which battery to buy is often an arduous and risky task, scrambling to research what you need and what will work. Ultimately, you reach two clear solutions: lithium and lead acid. Lead acid is your best bet if you aren’t really worried about technical aspects and need a cheap method of energy storage but to those that are aware of the world’s ever-innovative power solutions, you understand the absolute beauty that is lithium chemistry. Lithium and lead-acid have different subsets of chemistry, each with its own substrate of power characteristics, but for the sake of simplicity, we’ll narrow it down to an AGM sealed lead acid battery composed of two lead electrodes and a lithium battery composed of a lithium iron phosphate (LiFePO4) cathode and a graphite carbon anode. The cathode is the positive electrode while the anode is the negative electrode.

The Basics

LiFePO4 is just one type of lithium chemistry, commonly thought of as the safest due to its high resistance to thermal runaway. Thermal runaway is the point at which a battery ignites/explodes due to a buildup of excessive heat and gases within the battery. It takes quite an enormous amount of heat to be able to ignite a LiFePO4 battery—270°C to be exact. They offer a conventional lifespan of about 10 years and anywhere from 2500 (100% DOD) – 7000 (50% DOD) full charge and discharge cycles. When comparing that to lead acid’s measly 3 to 5 year lifespan and 300-500 cycles you’d think, “Why not more lithium batteries?”.

Cost

The lithium iron phosphate cathode and graphite anode put a huge strain on lithium’s viability to be more commercially available. Lithium metal alone costs an astounding $7.48 USD per pound. That doesn’t even include the cost of the very specific type of graphite material that you need. In order to effectively flow current through a lithium battery, graphite needs to be “battery-grade” which can be upwards of $10 per pound, an absolutely overwhelming cost. Part of what makes lead acid so appealing is the fact that lead is cheap and easy to mine—its cost? 95 cents per pound. Price tag is just one of the more average consumers’ first thoughts when it comes to buying a battery, the next? Practicality. Rather, do they need it?

Necessity vs Indemnity

For example: the average parent would want their little ones to enjoy their tiny life through miniaturized toy cars. These “power wheel” toys often utilize lead acid batteries and every now and then, they need a replacement. Some curious soul might take the plunge and buy a lithium-based battery-- not so bad right? No more replacing for a long time! Fast forward 4 years and the power wheels toy gets damaged, now what? You’re left with a battery that was 90% the cost of the power wheels. Doesn’t make a lot of sense to spend so much for so little. Lithium batteries are amazing but there’s a line between naivety and ignorance.

Caring For Your Power

All batteries require a certain level of maintenance to keep them from failing prematurely. To make the most out of LiFePO4’s 100% usable capacity, you require a LiFePO4 charger. Using a standard lead acid charger isn’t enough as the specifications just aren’t quite right to take care of LiFePO4’s needs.

(Why Not > Technical - LiFePO4 > Why Can't I Use A Lead Acid Charger)

Luckily, LiFePO4 batteries typically include a battery management system (BMS) to help regulate a lot of the potential damage that can be done to LiFePO4 batteries in the short term so you aren’t entirely in the dark when it comes to maintaining your lithium battery.

Lead acid doesn’t have the privilege of a BMS, they also don’t have 100% usable capacity. Unless a lead acid battery is “deep-cycle”, you should not discharge it below 50%. Discharging it will induce a chemical process known as “sulfation”. Too much sulfation occurs because of things like keeping the battery below 100% SOC when not in use, lack of periodic charging, constant cycling below 50% capacity, and discharging/charging too slowly-- eventually killing the battery.

Your Solution

I’ve discussed only the key differences between LiFePO4 and lead acid to help inform those that are taking time to learn more about what’s best for them. Electric power’s advantage is that it can always be generated and stored in a battery which can be charged using typical chargers or by harnessing the power of the sun through implementing solar panels into convoluted “solar systems” that utilize both the electrical grid and backup power in the form of a battery.

Solar systems provide an excellent source of renewable energy and we will talk about them in the future as well but for now I hope you were able to find this article informative and helpful in your search for the right battery.