Drop in lithium deep cycle replacement leisure batteries

Leaders in Lithium-ion Phosphate motor home & marine leisure batteries

Replacing Lead with our Lithium Batteries

The Benefits:

  • More power – up to 50% more than a managed lead battery to prevent diminished life. Regardless of the load, lithium provides virtually all the available power at a constant voltage no slow fade out.
  • Ultra-long life, several thousand cycles are possible. Lead batteries fail prematurely when they operate in deficit for long periods. If left partially charged or discharged, failure is even quicker. Lithium batteries do not need to be fully charged. Service life even improves in case of partial charge. This is a major advantage and why we offer a guarantee of up to 10 years.
  • Highly efficient. (99%) Especially off-grid solar energy. Efficiency is extremely important. A discharge from 100% to 0% and back to 100% of an average lead-acid battery less than 80%. The efficiency of a Lithium 96%. Lead batteries become especially inefficient from above the 80% charge. Over several days, such losses can compound to worse than 50% in losses or worse in systems where batteries are operating between 70% to 100% charged state. In contrast, lithium’s achieve over 90% efficiency, even under shallow charge/discharge cycles.
  • Faster charge time – lower resistance. Lead batteries have an increasing resistance as they take on charge, resulting in longer charge cycles. Lithium’s do not suffer with this increasing resistance meaning they stay in a constant current (bulk charge) phase for most of the charge duration leading to a naturally faster charge cycle. This is particularly significant when comparing the last 30% of the charge of a lead battery.
  • Around 40-50% lighter – reduced axle weight creating increased load carrying capacity.
  • Orientation in any direction. We use 32700 type premium cylindrical cells which can be orientated in any position, even upside down. This is especially advantageous in confined areas such as under seats of cupboards. Many lead batteries and cheaper prismatic cells can only be orientated standing.
  • Abuse proof, our lithium’s switch off in the case of over charge or under charge conditions, or attempted charge at low temperature (super series)
  • Environmentally Friendly – There are no poisonous heavy metals or environmentally damaging chemicals in lithium iron phosphate batteries. In contrast lead batteries are toxic to all life and lead pollution is damaging to the environment. The simple fact that lithium significantly outlast lead batteries result in a reduction of repeat manufacturing and recycling. Hence there is a dramatic reduction in the products carbon footprint. 

Lithium batteries cannot just drop in and replace lead batteries can they?

The Answer is: YES!!! no additional components are required:

Lithium leisure batteries are designed to be a direct replacement for lead batteries. They achieve this by having an inherently closely aligned terminal voltage to that of other lead acid variants of leisure battery including wet, gel and agm types.

Our batteries will charge fully to their design capacity at 14.4V (+-0.2V) and this is the output level of the charging circuits of all modern 12V existing split-charge engine wiring circuits regardless whether the manufacturer has used a fixed voltage or smart alternator charging circuit, since they would have already had to account for that prior.

When solar charging, existing 12V MPPT chargers can charge existing wet, agm and gel batteries, and will therefore charge our lithium just as efficiently in the same way. Existing 12V PWM solar chargers are the same. Many modern PWM or MPPT variants have a separate selection for wet/agm/gel/lithium battery variants to “fine tune” their charging efficiency. In the case of variations having no lithium settings it is recommended to select the setting with the closet match to a 14.4V charge voltage.

Existing mains charging/power supplies that were designed to charge existing wet, gel or agm batteries will also charge our batteries too and as is the case with solar charge controllers above, may have a setting to change between wet/agm/gel/lithium. Where this is the case, select either lithium or refer to the voltage output selecting the closest setting to 14.4V.

Some very old chargers may have been designed with a fast charge and/or a desulphurisation mode sometimes referred to a rejuvenation setting. It is important to ensure these settings are never used since this could result in damage over time to the battery.

Charging characteristics, charge algorithms and lithium batteries in detail

Now let us look into more detail why there are no issues, by considering what electrically changes when you upgrade your battery to a lithium.

Prior to fitting:

When a lead battery is recharged using its pre-existing charging methods, in the main it is the internal chemistry that dictates the charging cycle you may have read about, ie bulk, absorption and float charge. Indeed, the charger may even go so far as claim to “intelligently” manage such cycles. Be that as it may, it is the battery that dictates this cycle and simply the charger that regulates the current and voltage as the charge proceeds.

When the battery is discharged, it has a low resistance and the bulk of the charge can occur. During this portion of recharge, a constant current phase is seen, and its resistance rises. The last remaining portion called absorption can then occur at a fixed voltage (usually between 14.2-14.8V depending on battery and charger settings). The voltage remains fixed, the current drawn by the battery decreases and at a preset current, the charger assumes the battery is full. It then switches to a lower voltage called a float voltage (usually between 13.2-13.8V), this protects the battery from self-discharge so that the battery remains fully charged and ready for use.

Post fitting:

When a KS Energy battery is substituted, what happens is just as with the lead battery, at the beginning the internal resistance of the battery is low. The difference is that the resistance remains low. So, the charge remains in the bulk phase just as before, but it continues to remain in the bulk phase for much longer. In fact until the battery is almost fully charged. It is only once it reaches around 95% of its entire charge that the constant voltage (or absorption phase) can begin and the remainder of the cycle completes. The charger then reverts to its float phase.

Float charge:

It is often said a lithium battery does not need a float charge since it is extremely efficient and does not self-discharge in the way a lead battery does. It does therefore not need any protection from self-discharge. If the charger were switched off at this point, the rest voltage of the battery would fall to 13.3V. However, if the charger is left to its own devices to float the battery, the fully charged lithium will fall back to the float level, instead of its natural rest voltage. Within the context of normal leisure use, this is completely harmless to the battery, perfectly acceptable and of no consequence.

Vehicle charging:

Lastly, we look at split charging, in other words charging from the engines alternator whilst driving. Till recently, all RV’s were fitted with a simple relay which simply connects the leisure battery to the alternator when the engine is running. The alternator has a fixed voltage output of 14.4V and this is the perfect level to charge our lithium batteries at. Since it has a low resistance, similar to the level of a lead leisure with a low state of charge, it will recharge extremely efficiently from the alternator because it will effectively be in what would have been the bulk charging stage of the lead over the majority of its charge cycle. Once fully charged, the terminal level will be brought up to and held at 14.4V as the journey concludes. This is again completely harmless within the context of normal leisure use.

Smart alternators:

Increasingly, vehicles are switching to smart alternators. There are several different versions of this technology. The most popular involve monitoring the vehicle battery temperature and voltage and using a pulse charge current to accurately maintain a constant state of charge. This reduces engine load by saving wasted energy the alternator would otherwise have been generating, thus reduced unwanted emissions. There are others including regenerative breaking. It has meant that RV coachbuilders and van convertors are increasingly finding they are having to use what is known as DC-DC charger to charge the leisure battery instead of the conventional split charge relay. This system is a little more expensive for the manufacturer, however it is by no means less efficient than the former system, in fact it is possible to tailor the output current to better suit the manufacturers alternator and has meant for installations where the habitation electrics are fitted some distance from the alternator, natural voltage drops over wiring runs can easily be overcome. This can allow for greater efficiency in leisure battery charging. In the case where a vehicle has one of these types of chargers (some times also know as a B2B or battery/battery charger), the user should ensure it is set to a 14.4V output, since some chargers have slightly higher settings for certain types of lead batteries such as AGM lead batteries.

Some misconceptions addressed:

Let us address some popular miss conceptions in the context of using lithium (Lithium iron phosphate) leisure batteries in place of lead batteries.
  • Lithium batteries are dangerous. This statement can be correct however our batteries are designed to be safe. Firstly, they have in integrated battery management system with a range of features that guard against the dangers. Notably from an external short circuit which a lead battery does not share. Moreover, in the unlikely event the cells themselves were shorted, for example externally pierced or crushed, the cells would not achieve a high enough temperature to combust and any gases given off during this process are inert. A high enough temperature would only be achieved if the cells were electrically damaged, for example by over voltage charging, or charging at a low temperature (below freezing). Our battery management system guards against low temperature charging or high voltage charging. On balance, lead batteries would normally be more dangerous since gases given off in fault conditions are explosive and there is no internal short circuit protection.
  • A lithium battery costs more than a lead battery. This is correct, lead batteries have been manufactured commercially for more than 120 years whilst lithium iron phosphate just over a decade. However there is a proviso. Setting aside the benefits, manufacturing techniques have already halved costs over the period and are now at a price point where the cost per KWh of stored energy over the lifetimes of each now mean that lead batteries will usually work out more expensive.
  • A lithium battery is the equivalent to 2 lead batteries. This is incorrect. A lithium battery delivers its power at a constant voltage for far longer and supplies power to near zero capacity before its voltage significantly tails off. This means they deliver nearly 100% of their stored energy as usable energy. By contrast a lead batteries voltage tails of as it discharges, passing the half way mark certain items such as water pumps start to become notably sluggish or lights dimmer. This is clearly impractical and a recharge becomes a pressing issue for its user. Moreover, lead batteries begin to suffer increasing lifetime degradation around 50% of discharge and it is in the user’s interest to manage a lead battery so that the duration elapsed after this level is kept to a minimum. Lastly, when a lead battery is subjected to large current demand, such as an inverter or motor mover, it suffers from a natural phenomenon called the Peukerts effect and the stated capacity drops by a very significant factor. For these reasons it appears lithium has acquired a reputation for a single battery being the equivalent of two lead ones.
  • A lithium battery wont power my motor mover. This is incorrect. A motor mover requires a current around 50A and the larger ones may rise to 100A particularly on steep gradients. We have a choice of batteries that provide 100A or 150A continues current draws with temporary current draws even higher and so this is not an issue.
  • A lithium battery needs a battery to battery charger. This is simply not true, a lithium battery will charge no quicker or better with a battery to battery charger unless the charger is increasing the current available to the battery by overcoming the natural voltage drop that was inherent in the original wiring. It should be noted that if you did choose to go down this path, be warned. You must also ensure the alternator can happily supply the extra load demanded upon it by that charger! We have also seen an argument that suggests it is needed to increase the life expectancy of a lithium battery, or that even without one the life will be dramatically reduced. This is simply not true and in the context of normal leisure its simply unnecessary and a often a complete false economy.
  • Charging from your alternator can damage it. This is simply not true; a lithium battery has a similar resistance to a lead battery in a low state of charge and will only draw from the alternator what the discharged lead leisure battery would have done. In the context of replacing like for like in the setting of additional manufacturers wiring, the current load on the alternator is comparable, indeed many motorhomes have a capacity to charge a lithium battery at a far higher rate and it is possible to upgrade the wiring to overcome natural resistance and voltage drops of the manufacturers to drastically increase the charge duration of a lithium battery.