Advantages of Lithium Batteries

Cost Effective

Lithium batteries have actually been a solid choice for years now, even when they used to carry a steeper up-front cost. The argument used to be that you might pay twice as much for a lithium battery bank up front, but it would last you four times as long, so ultimately you’d cover your investment.

Of course, with lithium batteries dropping in price in recent years, the value gets even better. Not only are they more efficient over a longer lifespan, they’re now comparable in price to other battery types, so you don’t have to pool up more money for your initial investment into your system.

No Maintenance

The main appeal of a lithium battery bank is that you can “set it and forget it.” Lithium batteries require no maintenance or interaction on the owner’s part. These days they all come with internal computers (called Battery Management Systems, or BMS) to moderate things like state of charge, temperature levels, and so on. Most also have apps to provide automatic status updates and performance data to the owner.

Other battery types carry monthly maintenance tasks, like refilling water and manually monitoring state of charge. Critically, ignoring these tasks can reduce battery performance and, in unfortunately all-too-common cases, destroy the battery bank completely.

Given the choice - and the severity of the consequences - we find most of our customers prefer taking the path of least resistance with lithium batteries.

Longevity

Lithium batteries are simply built to last longer, with the typical warranty lasting between 10-15 years. In comparison, other batteries are warrantied for 3-7 years if properly maintained.

That last part is crucial: we’ve seen flooded battery banks die within 18 months because their owners never maintained them. Not only do lithium batteries have a longer theoretical lifespan - in practice, more of them reach the end of that lifespan because the maintenance requirements are so much less punishing.

Lenient Charge Requirements

“Depth of Discharge,” or DoD, describes the amount of battery capacity that can be used before a recharge is required. Lithium batteries have a recommended 80% DoD, compared to just 50% with other types, meaning that lithium battery banks can operate for longer before they need to recharge.

You can run lithium batteries all the way down to 0% charge with no (or minimal) ill effects as long as they are recharged in a timely fashion. The same isn’t true for traditional batteries - running past the recommended DoD can permanently compromise your battery bank.

You can also let lithium batteries sit unattended for long periods of time at partial SOC (State Of Charge), ideally between 50-80%. They can sit like that for months with no ill effects assuming that all loads are shut off. A lead-acid battery would probably be ruined under the same conditions, since they generally need to be brought to full charge once a week.

Cable Management

In lead-acid battery banks, cables need to be the same length due to Peukert’s Law While the details can be a bit dense (feel free to dive into the Wiki article), it boils down to this: your recharge rate changes depending on the length of the cabling. If you have different cable lengths, batteries will charge at different rates, and the imbalance in state of charge between batteries can compromise the entire battery bank.

Lithium batteries remove this limitation, which makes the design of battery banks a lot more flexible. There’s no more restrictions on the lengths of cables between your batteries, or from your batteries to your inverter, which removes a lot of the headaches from laying out your battery bank design.

Expandability

You can add new lithium batteries to an existing lithium battery bank without impacting the performance of the system.

You couldn’t do this with flooded batteries for many of the reasons mentioned in the section above: new and old batteries will charge and discharge at different rates, and will be cycling to a full state of charge at different times. Some batteries may be chronically undercharged, while others are constantly overcharged trying to bring the rest of the bank up to full.

That imbalance in state of charge is a killer for flooded battery banks - it often causes the new batteries to fail right alongside the old ones.

This probably isn’t nearly as pronounced with lithium, because the internal BMS works to balance the cells automatically, ensuring uniform charging across the entire battery bank. You may still see a drop in performance if you mix lithium batteries with vastly different wear levels, but it won’t actively harm the health of the system, the way it would with flooded batteries.