To clarify, you mean “House Battery” not a second house battery, you would not want to mix with another technology.
Looking at LiFePO4 or Lithium in general it brings with it some pluses:.
- Weight to Power Ratio
- 80% to 90% DOD without degrading life cycles.
- Not negatively affected by PSC or Partial State of Charger
- Fast Charge Rate
- Long Cycle Life compared to lead acid
- Low Peukert number
- High Cost of ownership
- Acceptable temperature to charge at, specifically cold, but even high temps have some impacts to life span.
- Perceived volatility, sure we have all read about Lithium Battery fires. Any time your storing power you have potentials for problems.
Many people assume that you can’t discharge your Lead Acid Battery below 50%. You can but the number of expected life cycles decreases substantially if you do. 50% just seems to be a good point for capacity vs life cycle.
PSC is the largest driving factor in killing are lead acid based battery systems. After usage they liked to be fully charged to full capacity. Solar especially in the winter months make this worse. Many people look at the voltage and assume that they got it fully charged. LiFePO4 does not suffer from this problem and one could say they almost prefer not to be fully charged.
Fast Charge rate is both a blessing and a curse. In fact, charging LiFePO4 brings its own set of issues. While some manufacturers may say they are drop in replacements, I would not consider that a true statement. Lithium batteries do not take the same stage charging that our lead acid batteries do, there is no bulk, absorption, and float stages, It is better to look for a charge device that specifically has a profile that is set up for Lithium. Even better is one that lets you program the values. The other problems with LiFePO4 is its appetite to consume power so when hooked to your alternator will lead to a early death of your alternator.
ff you want to use your Van system to charge while your driving you need a separate 2nd Alternator with a regulator that has a Lithium setting. Balmar is a common provider of these items. If only using one alternator you should go to a Battery to Battery charger that has a lithium setting. This covers two things, it can limit the charge rate and save your alternator and provide the correct charging profile. Don’t forget about Solar either, you need to make sure that your Solar charger also has a Lithium profile. There are a couple of BtoB chargers that have solar integrated in it, so that is a nice option.
When looking at installing a lithium system, the cost is high, but when you look at the lifespan it appears that the cost becomes closer to break even. The problem is that you need to realize that expected lifecycle increases to make the decision payoff. I think the reality is that we probably won’t realize the specified lifecycles that are specifying on their websites. In general, they probably have limited real life data, and a lot of data that is collected in a “Lab Environment”, there is at least one vendor I saw that states that they have seen X number of cycles in a “Lab Environment”. I appreciate the honesty.
Then there are the temperature issues, not that all batteries don’t suffer from temperature issues. Almost all the lithium vendors have some for of integrated and offer an external Battery Management System, which is a needed item with Lithium batteries. Obviously, the low temperature charging issue is the most talked about problem, especially for people going up to the slopes, or anyone that generally camps in cold temperatures. Here is where their size and weight make them an easier choice to keep inside the van, which would be hopefully help that condition.
Are they worth it? I believe if your building a system from ground up, you don’t have to change any existing equipment it might pan out, It will obviously have a higher cost to entry than lead acid system. I would cut your expectations on life cycles in ½ and see if that is a reasonable cost trade-off. I believe lithium is more of an option if you are looking for high storage capacity and some high current needs.
If I was just trying to get some of the benefits that lithium provides, I would look at Carbon Foam AGM batteries such as the Oasis Firefly.
They also are not prone to PSC issues and have similar Depth of Discharges rates of 80% give you 2X the rate of AGM at 50%DOD. They also are not nearly as costly as Lithium.
Hope this helps get the discussion going.