The time has finally come… 😊 I have been waiting to write this for a while. Lithium has come a long way, and so has the variety in brands and quality. Warning… it may get technical.
As a sailor and an overlander for the past 30 years, I have always had to manage my power consumption. To make sure lights aren’t left on, faucets are opened only briefly so the pump won’t drain the batteries and ensuring the batteries are full before sunset so the navigation lights will last till morning has been constant concerns.
But lately, it seems that people’s views are changing. Suddenly, my customers are asking why they should save or worry about it when all they need to do is spend more money on it and let me resolve it for them. It usually goes like this; let’s replace our current battery bank and upgrade to lithium batteries, we will add some charging sources, and direct our worries to something else.
They are right; it has become possible. In addition to various developments like LED lights and LED TVs, NMEA 2k networks, solid-state radars, fixed satellite antennas, multifunction displays (MFD) that combine information that in the past required 4 different displays/gauges to display a fraction of the data the MFD can and more.
these normal loads we are accustomed to using, just don’t consume that much power anymore.
Moreover, other advancements in charging sources like smart DC/DC charges and curve programable - high output alternators, solar power (with 20% efficiency), charge controllers, brushless motors in the wind vane, and many more have made it less necessary to be cautious about power consumption.
Add a high-density – low-profile lithium battery with 80% DOC (depth of charge) that gives you 10 times the lifespan of a conventional battery, and it really is a no-brainer.
Let’s geek out about it for a second; Take a group 27 Flooded/AGM/Gel battery (the most common size) it usually says that it packs 105 Ah (amp-hours). However, if you discharge this battery to a point where you have used 50%, now you are really eating into its lifespan, which is usually only 350 - 500 cycles from new anyway. So… you try to stay above it; you now only carefully discharge it to 45% - 50% DOC max so it will last you longer, meaning you can only use 52.5 Ah of the 105 Ah.
Replace it with lithium (and I will refer only to LFP or LiFePO4 because it is the safest chemistry so far) of the “same capacity” on the label, but now you can discharge it to 80% DOC. so now you can use 84 Ah. And it will do that for 3,500 cycles (do this ones a day and you will be good for 9.5 years)
And if that’s not enough good news, here is more; they will rest at a higher voltage, roughly 13.8V where non-lithium rest at 12.8V. They will remain at a higher voltage longer into the discharge period where non-lithium batteries will drop their voltage quite linearly throughout. That means your loads (consumers) will be happier with LFP as less current will run in these conductors (or wires) and therefore less resistance. LFP is also able to charge back up faster which means less motor/generator time, and they are also roughly 60% lighter.
But… they are slightly more expensive (although not really if you plan to keep them for more than 3.5 years). Here is why; non-lithium batteries should be replaced every 3-4 years. A decent quality group 27 AGM will cost about $220 - $350 but they only last say 3.5 years. So, after these 3.5 years, you will have to buy another. So now you have spent $440 – $700 on a battery. A good Lithium battery will last you 7 years easily, and they cost $400 - $900. But don’t forget you are still not comparing apples to apples; you are now comparing a battery that can give you 52 Ah with one that gives you 84 Ah. That’s 38% more power every time before you need to recharge it.
That’s good news all around. The last thing worth mentioning is. don’t buy the cheapest without researching it first, there are many Lithium (LFP) batteries out there, and they are not all good. As a matter of fact, stay away from some. I only buy from companies I know and trust. To name-drop a few; Battle Born, Victron Energy, Epoch Batteries, MasterVolt, and GoPower by Dometic. These brands are good, and I have installed them personally. However, they are not equal; every one of them has a different strong/weak side, and I needed to know it before I installed them, which is how I acquired the knowledge with these and other brands.
