What are the advantages of a 12v lithium battery, Iron phosphate batteries guide, House electrics design
Advantages of 12v Lithium Battery Guide
7 July 2022
LiFePO4s are extremely light! In the camper we all have to pay attention to the weight. If you want to be self-sufficient and independent of shore power, you need a lot of battery capacity, which in turn means a lot of weight. Lithium iron phosphate batteries are significantly lighter than lead batteries: 200Ah from Renogy weigh 19 kilos, a 200Ah lead battery weighs over 50 kilos.
What are the Advantages of 12v Lithium Battery
Extremely high number of cycles possible! If you travel a lot, you need a lot of electricity. The demands for luxury are also increasing, as people are reluctant to do without televisions and coffee machines on (long-term) vacations. But every discharge of a battery costs a bit of life. So it’s great when lithium batteries wear out only 1/10 as fast as lead-acid batteries.
100% battery capacity is fully usable with lithium batteries! Lead-acid batteries should only be discharged to a maximum of 50%, below which they can neither deliver high currents nor will it have a positive effect on their service life. 12 volt deep cycle battery are completely different here. Even at 100% depth of discharge, the lithium batteries offered here can withstand up to 1000 charge cycles.
Use a battery like a water tank! Lithium batteries do not need to be fully charged! This is an incredibly large advantage over lead-acid batteries. Unlike lead-acid batteries, LiFePO4 batteries do not sulphate and are therefore not damaged if they are not fully charged with solar power. This enables a whole new era of battery power in the mobile home.
The best motorhome battery: definitely lithium
Just imagine if you could use electricity in the same way as the water supply in the RV. Open the tap and water comes out with the same pressure, from the first to the last drop. If you only fill the water tank halfway, nobody cares, not even the tank itself. If you treat the lead-acid battery in this way, it will not last long – for a lithium battery, on the other hand, these are the best operating conditions.
Brief information on how lead-acid batteries work
Lead-acid batteries consist of battery acid and lead. When discharging, the acid “migrates” into the lead plates. This reaction produces electricity. When loading, this connection is disconnected again. The longer a discharged or partially discharged battery is left standing, the stronger this combination of acid and lead becomes.
Sulfate ion is formed – which becomes more and more difficult to dissolve with increasing time. On the outside you only notice it in the decreasing capacity of the battery. It is therefore important to recharge lead-acid batteries immediately after they have been discharged, which is considered the best deep cycle battery charger.
Lithium batteries do not sulfate, they work like the water tank described above. As long as they are not completely full or completely empty, they feel great.
I summarize. Lithium iron phosphate batteries require
No absorption charge for hours
No specific charging current
No special end-of-charge voltage
It is simply the best RV batteries in connection with a solar system. With LiFePO batteries you can realize a really self-sufficient motorhome, which (depending on the design) never has to be connected to a 230V socket.
Two scenarios for using 12V LiFePO4 batteries in motorhomes
Self-sufficient without solar power
If you like to travel a lot, never stay in one place for long, possibly even in winter and don’t want to install a (larger) solar system, of course, you need to know more information about how to live off the grid. The lithium battery in the mobile home is recharged with a charge booster and 230V shore power charge (as a backup). Precise displays such as the BMV712 provide information (on request also via Bluetooth) about the charge status. If the battery cannot be fully charged after short journeys, it doesn’t matter at all. They are only interested in whether there is enough energy in the storage for the upcoming service life.
Almost 100% on solar charging – shore power and charging booster only as a back-up:
That’s how I drive, for example. 98% of my electricity is generated by 400 watt solar panel on the roof of the mobile home. My LiFePO4 batteries don’t get full for weeks in winter. Depending on the weather, the state of charge decreases a little every day or increases again slowly if the weather is good for a longer period of time. This calculation works wonderfully when wintering in southern Europe, in Germany it would probably not be possible. I only think about shore power or charging while driving when my batteries fall below 20% charge level. Then it will be tight for the coffee the next morning.
Is the lithium battery in the RV really expensive?
Lithium batteries are more expensive to buy compared to lead-acid batteries. However, you must not compare the purchase price alone with that of lead-acid batteries. Consider what additional performance you get for the higher price. Lithium batteries are much better suited to demanding applications in mobile homes, cycle numbers speak for themselves, they can not only be recharged quickly, but also discharged much more deeply. Since a lithium battery with half the capacity of a lead battery can deliver just as much USABLE energy, the investment costs are no longer as high as a first glance at a LiFePO4 battery 12v 90ah would suggest. Such a battery replaces a whole 180Ah in lead!
Let’s take it a little further. I plan energy concepts for new vehicles with many customers. Usually it is about a self-sufficient package with solar, charger 230V and maybe a charging booster. If I plan a self-sufficient motorhome based on a lead battery, I have to plan for expensive lead battery chargers. The solar system must be designed in such a way that the batteries are recharged by midday in order to have enough time in the afternoon for the important absorption charge.
Since solar systems only work at maximum power at midday, lead-acid batteries are rarely supplied with more than 10% of their capacity as charging current. GEL battery require 6-8 hours of absorption charging at 14.4V. How is a solar system supposed to do that in one day if it first has to charge the battery in order to get into this charging phase at all? Especially in winter there is usually not enough time for this. That’s why you should drive to a 230V socket for at least 12 hours every 7 days so that lead-acid batteries can really recover and get really full.
Things are completely different with LiFePO4 battery. When planning a solar system, the daily power requirement is decisive, as well as the time of year and country in which a solar system must reach the daily consumption. Since lipos do not need an absorption charge and it doesn’t matter how full they are, it is sufficient to design a solar system in such a way that the daily yield is just reached at sunset when the sun is at its worst.
This leaves the whole day to charge the batteries, which requires less solar power. Shore power or alternator power is only used with a lithium battery if solar is not delivering enough energy due to bad weather. A simple, usually small charger for 230V is sufficient, and you have already saved a few 100 euros. If such a system is consistently planned and optimized, the additional price of a lithium battery in the mobile home is not that far removed from a lead-acid battery system with almost the same performance. However, lead-acid batteries will never beat lithium batteries.
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