You need to reduce weight or have limited space for batteries in your installation. You plan to live off your battery system for more than four weeks a year with infrequent use of mains power. You want to regularly run a large (1000W-plus) inverter to power a range of domestic appliances away from mains power.
Let's take an off-road caravan for example, which in today's market, will most likely be fully optioned with things like an air conditioner, microwave oven, washing machine, perhaps satellite TV and will generally be fitted with a large inverter or inverter/charger. People buy this type of van to spend large amounts of time ‘free camping’ away from mains power and owners will often add additional equipment like a coffee machine, hair dryer, toaster, electric kettle, etc… Many carry a small generator with them for the times when poor weather conditions can’t keep the solar up to charge the batteries.
This setup is the perfect candidate for a lithium battery system, where high demand and quick re-charge times will be expected, but where space for a suitably sized lead acid battery bank to cope with these loads is not readily available.
One major factor to consider is the overall weight of the van. With a lithium battery system you will reduce the overall weight of your battery bank by as much as 40% when compared to a lead acid battery system of equivalent power. This could make the difference between having that extra creature comfort on the option list, or being able to carry more water for those more remote adventures.
Other big advantages of lithium batteries when compared to lead acid batteries are:
Re-charge time – Lead acid batteries have a charge efficiency of approx. 90-95%, while lithium batteries have a charge efficiency of nearly 100%. This means that you need to put 5-10% more power (amp-hours) back into a lead acid battery than you took out to fully charge it. Not only that, but it has to be done at a lower charge rate than lithium. All this ultimately means a longer charging time which, when regularly using a generator as your AC power source for charging, means more wear and tear and fuel consumption.
Cycle Life – Typical life cycles for lithium batteries are generally about 3 times those of AGM batteries. The benefit is obvious there, but one additional benefit of lithium that sometimes gets overlooked and can also affect cycle life, is not having to worry about leaving them in a semi discharged state. This is something that can ruin lead acid batteries in a short space of time and is why it is important to always fully charge a lead acid battery straight away after discharge. Leaving lead acid batteries in a semi discharged state is one of the primary causes of premature battery failure.