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.