While they sometimes seem to get a bad public opinion in the media- most of these news stories stem from NMC (Nickel Manganese Cobalt) or NCA (Nickel Cobalt Aluminium) cells which have their uses- but are certainly more volatile than the more consumer and leisure friendly LFP (Lithium Iron Phosphate) batteries.

With a proper charge system, and a proper BMS caring for the battery, you can get some real benefits over historic lead acid style batteries.

• MORE USABLE POWER - Lead acid batteries have a limited usable capacity- beyond about 50% depth of discharge you run a very real risk of damaging the battery capacity- and if you can't run a desulphation cycle on the battery (like a flooded lead acid), this deterioration is likely permanent. LFP batteries allow up to 100% of the usable capacity without degradation, repeatedly.
• SAVE WEIGHT - LFP batteries are not only more energy dense (more usable capacity in a smaller volume, and a true usable capacity allowing honest capacity to be worked around), but the cells are also far lighter than a lead acid equivalent. A lead battery of 12V 100Ah is ~24kg, versus a modern LFP 12V 100Ah sitting at ~8kg.
• CHARGE UP QUICKER - While this might also be one of the chemistries main limitations (which we will cover later-), LFP batteries can be charged very quickly as their internal resistance is far lower than a lead acid equivalent, allowing current to flow far more easily.
• FLATTER VOLTAGE CURVE - LFP batteries maintain a higher voltage throughout their whole operating range. Their full voltage sits at around 13.4V~ (on a 12V nominal battery), and their ~5% voltage is down at about 12.0V. Higher sitting voltages, and the ability to sustain that voltage under load, means that all of your equipment runs happier.
• LONGER LIFE SPAN - Thousands of performing cycles, even under regular, constant use.
• AGAINST THE RUMOURS... SAFE - While they're not perfect, and there are hazards with all battery types, an LFP battery is one of the safest methods of storing power. They're one of the most stable lithium chemistries (beaten only by Lithium Titanate, which is not often commercially available), and almost always come with a BMS (battery management system) that has pre-set protections for you and the internal cells in place.
• AND FINALLY - LFP is possibly the best way of running a 24V, 36V or 48V system. If you purchase a 51.2V (16S) LFP battery, the internal BMS takes care of the cell balancing for you. You don't need to worry about inter-series balancing between 12V batteries connected in series, where an imbalance is one of the leading causes of complete bank failure and risk, because this is all handled as part of the design of a battery.

If you do decide to go for 48V systems, you do get some good benefits.

• Smaller cabling, due to the lower amperage flow,
• Higher system efficiency and higher inverter efficiency (for much the same reason as above)
• More powerful even using this smaller cabling,
• Utilise 48V appliances (such as domestic style inverters, which can be very powerful and stable)
• And, with a proper 51.2V cell stack and BMS, no worries about manual balancing upkeep.

Some BMS have direct CAN or bluetooth (or both) communications, and can give you a pretty accurate, though not perfect, understanding of the battery state of charge, battery health, and what the battery is doing at any point in time.

I mentioned in the Lithium Advantage tab that there are some real benefits to Lithium- and I foreshadowed that their incredible ability to be charged can also be their primary limitation.

Alternators aren't designed to run at their limit all day long, nor are they designed for Lithium. Bonding an alternator and a lithium battery bank directly or through a relay can put some real stress and limitation on the system.

• An alternator that responds to a load, will try to put as much power through as it can for as long as it can support a voltage higher than what the LFP battery will draw current at... This can mean that you're seeing maximum current flow without a suitable RPM, which means, too, without suitable cooling.
• This can rapidly lead to alternators overheating or degrading. Sometimes in an evening, sometimes over weeks. There are some systems that can support this heat (through explicitly designed cooling-) but this is rare.
• In the event of the lithium battery being the only thing connected to your alternator, you have more issues. If the LFP BMS disconnects half way through a charge cycle (due to being full, or seeing too much current flow) you can see a voltage spike at the alternator. This can put the alternator components at risk, the regulator components at risk, or even other power equipment in your system at risk.
• If your alternator doesn't melt, your battery BMS doesn't shut-down and refuse any charge at all through the entire process causing any horrible spikes and the, you're still not out of the woods. If the battery is full, it will disallow any further charge... which means there's no capacity available for the alternator to provide to, and this can lead to repeated spikes at the alternator output, as it doesn't have a battery or draw there to 'anchor' the alternator.

The best solution for this, and the best method for charging while motoring in general, is to look at DC/DC charging.

From the limitations tab, we address that there are some primary issues we should address-

• Overcurrent putting the alternator at risk
• Overcurrent or over-voltage putting the batteries at risk
• The possibility of spiking DC voltage if a alternator struggles to regulate when a battery BMS turns off.

With a DC/DC charging system that is properly rated, these problems are resolved.

DC/DC charging is something Sterling pioneered in the marine industry years ago. An intelligent DC/DC charger treats an input and an output battery circuit as separate entities, limiting any interaction they may have with each other through the DC/DC charger itself.

They offer some benefits in all DC/DC charging systems-

• Inherently current limiting- allowing us to limit the current flow intentionally, whether because you're conscious of poor cabling inducing voltage drop that never lets your batteries charge, or to limit the load on the alternator.
• Full voltage control at the output circuit, allowing you to make sure that different battery chemistries are charged correctly to the battery manufacturers wishes
• This level of voltage control means that you can even have a 48V leisure battery bank and charge it from a 12V alternator.
• Some of the Sterling DC/DC chargers are even bidirectional, allowing you to distribute charge from the leisure bank back to the starter bank safely, when either there is excess charge at the leisure battery (IE solar, or mains charge), or in an emergency to run a 'Jump Start Assist' sequence, which charges your starter battery for 20 minutes to hopefully mean you don't need to cancel your holiday!

They do mean that you require a lead acid style battery on their input, or our Alternator Linearisation Device (ALD) to clean up the alternator output, which can be 'messy' and put our sensitive electroncis at risk, but that single compromise is all you need to address.

Alternator -> Lead acid battery -> BB rated to no more than 75% of the alternator rating -> Leisure bank.

Drive freely, and explore confidently.