Marine Batteries: The Thesis of Trolling Power Solution

Effervescence in the world of batteries ... The revolution of marine batteries  or batteries for electric trolling motor is in progress

Our electric energy tanks are in a state of flux.

Of ancient lead battery lithium batteries to last generations or that future graphene, there is a world, both in capacity, discharge, number of cycles, and weight and especially price.

We evolve more and more from the simple accumulator to a sophisticated system of electronic management and intelligent computer of the electricity on board!

Similarly, the possibilities of better use, desulfation and maintenance of batteries are not yet sufficiently exploited...

Essential notions to understand

Capacity or "storage capacity"

It is the amount of current that a battery in perfect condition (new) is able to deliver by being charged. It is expressed in Ampere-hour (Ah).

For example, a 100 Ah battery can deliver a current of 1 A for 100 hours or a current of 100 A for 1 hour).

The "floating" or "maintenance charge" voltage

This is the voltage to which we must constantly maintain a battery to be sure it is loaded optimally when one should be used: 2.25 to 2.28 V / element by (Elt) At 25 ° C (remember that the basic unit of an accumulator is 2 V).

For example, for a 12 volt battery the "floating" is 14.6 V to - 10 ° C 13.6 V to + 25 ° C and 13.2 V to + 40 ° C.

The absorption voltage

This is the maximum voltage sent to the battery in charging operation (14.1 volts typically for an AGM battery at a temperature of 25 ° C, less for a GEL battery).

Then, this voltage is retained until the battery is 100% charged before switching to the floating voltage.

AGM batteries

Marine AGM Batteries

Effect AGM marine battery (Absorbed Glass Mat)

Recommended Use:

Solar or wind powered solar charging batteries, but also suitable for starting, if sufficient capacity.

General information

In this battery technology, the electrolyte is absorbed and thus immobilized in fiberglass blotters (boor-silicate), placed between the electrodes.

Gas recombination is different from open battery technology: the oxygen molecules diffuse through tissue-separators, the positive electrodes to the negative electrodes to form water it (up to 99% the hydrogen and oxygen may thus be recombined into water).

Manufacturing and Safety
  • Pb alloys - Ca and Pb (lead) - Ca (calcium) - Sn (tin) are used to construct the AGM batteries because these combinations can limit the electrolysis of water (few degassing).
  • Despite their sealing, AGM batteries are pressurized and therefore equipped with a safety valve: When the pressure becomes too high (overload, high temperature ...), the gas from escaping.
  • They therefore, do not like heat, directly linked to a decrease in their lifetime.
Advantages of AGM batteries
  • Waterproofing
  • No maintenance, no addition of distilled water; Enhanced security compared to open lead batteries.
  • Plates always flat

Because their combination with the fiberglass mat, which has a very low resistivity, optimizes the low internal resistance of the accumulator (a few milli Ohms).

This low internal resistance of the AGM batteries allows them to withstand very high charging and discharging speeds, up to 4C (nominal capacity in Amps).

Another advantage of the very low resistivity of AGM batteries is a faradic efficiency of 96 to 98%, whereas for open batteries it is of the order of 90%.

  • Low self-discharge rate

On the order of 1% to 3% per month, this low rate allows storage for long periods without recharging, unlike standard open lead acid batteries.

  • Good resistance to shocks and vibrations

Since the AGM plates are tightly compressed and securely fixed from top to bottom in the cell, this arrangement is considerably superior in this respect to conventional batteries.

  • A good reaction to the gate or to the swell

Its tightness with the electrolyte in its liquid form makes it insensitive to all the phenomena related to the navigation at sea: gite, swell, pitch, roll...

Disadvantages of AGM Waterproof Batteries
  • Low cycling life

This is the main disadvantage of AGM batteries in part due to electrolyte stratification.

Battery manufacturers have attempted to remedy this concern by creating cyclic AGM battery ranges (thicker plates and separators, dense plates, etc.), but their performance is still lower than that of the best Sonnenschein gel batteries.

These AGM deep discharge batteries like the DISCOVER range support 100% discharge and regain their rated capacity if the discharge time is short.

This is not at all the case with standard stationary AGM batteries: recharging is poor and the batteries lose their capacity (never to exceed 80% discharge).

This severe drawback causes the loss of many AGM batteries in solar systems when used with poor quality converters. The cut-off voltage can be 10.5 V and the battery is fully discharged. After a few events of this type, it is the operational end of the battery.

This problem occurs especially for AGM batteries with a floating lifetime of 5 to 6 years (the least expensive AGMs that are often found in solar kits)...

  • A risk of acid concentration of the electrolyte

Since AGM batteries are sealed batteries, they suffer from the progressive loss of water from their electrolyte, which leads to acidification of the electrolyte and higher corrosion rates; Hence the advantage of having models with the tissues of thick separators, for which the quantity of electrolyte is large, which increases the lifetime of the batteries.

Loss of water occurs during overloads: to avoid them, the use of a quality regulator is essential if it is desired to maintain the life of AGM batteries (however, Gel batteries are even more Subject to this problem).


For cyclic and / or deep-cycle applications, preference should be given to:

  • AGM batteries with a floating lifetime of 10 years and up,
  • Cyclic AGM batteries (NPC Yuasa range or equivalent),
  • Deep cycle AGM batteries type DISCOVER.


Like all lead batteries, AGM batteries are very sensitive to temperature rise: any increase of this temperature by 10 ° C divides the life of AGM batteries by 2.

An AGM battery with a floating life of 10 years at 20 ° C will have a lifetime of 5 years at 30 ° C.

But while in the case of an open battery, one can add water, this is not the case for waterproof batteries. This means that the charger or charge controller must take into account the temperature during the charging process (decrease of the floating voltage depending on the temperature, etc.) in order to limit the risk of overloading.

GEL batteries

Marine GEL batteries

The sealed lead acid batteries of GEL technology use a gel electrolyte and microporous Duro plastic separators (the HAZE batteries are in true GEL).

They were developed around 1950 in Germany by Sonnenschein.

The electrolyte is frozen by the addition of silica gel and in some batteries, phosphoric acid is added in order to improve the lifetime in deep cycling.

Cracks are created during the first cycles through the gelled electrolyte between the positive and negative electrodes, which facilitates recombination by promoting the transport of gasses.

Recommended Use

To enjoy its advantages and limit its disadvantages, the ideal would be a recharge with dock, with a charger adapted and well regulated.

Any "engine" load, through the alternator or "solar" would require super-regulators and would only store some of the electricity produced!

Benefits of GEL batteries
  • Total recovery after deep discharge, even when the battery is not recharged immediately,
  • Ideal for repetitive cycles, in daily use,
  • Good performance during long discharges,
  • No lamination by the use of a liquid electrolyte,
  • No equalization charge required,
  • Self-discharge reduced (1 to 3% per month),
  • Protected positive plates,
  • Thick plates to reduce grid corrosion,
  • Good resistance to evaporation with a suitable load configuration,
  • Ultra-stable polymer separation with fiberglass,
  • Good short-circuit resistance thanks to the mechanical performance of the polymer separator
  • Can be discharged even when full recharging has not been carried out, without loss of capacity,
  • High cycling life (500 to 1600 cycles at 80% discharge).
Disadvantages of GEL batteries
  • The price (about 30% more than an AGM),
  • Their relatively high internal resistance means that they do not withstand high charging and discharging speeds; Continuously, the charging current must not exceed C / 10 (one-tenth of the capacity).
  • The gel batteries must therefore, be recharged slowly, which is not necessarily suitable for photovoltaic energy storage.
  • More than for other lead batteries, the load parameters (floating voltage, load and equalization ...) must be respected; For example, a manufacturer's notice specifies that "if the charging voltage exceeds the specified voltage by 0.7 V, the lifetime of the batteries will be reduced by 60%." Note that the charge threshold voltage of gel batteries is 0.2 V lower than other types of lead-acid batteries.20% is considered a safety, much like the reserve of a fuel tank. - As with other lead batteries, the lifetime of Gel batteries is reduced by a rise in temperature (beyond 20 ° C, - 50% for the lifetime per 10 ° C for the Plate plates, - 30% for tube sheets). As the charging voltage varies with the temperature, the gel batteries can be doubly affected if the charger and / or charging controller is not equipped with temperature compensation. This compensation is usually only necessary if the temperature of the batteries varies outside a range defined by the manufacturer (15 ° C - 35 ° C for Sonnenschein).
  • Requires a suitable charger and / or charge regulator, with compensation as a function of temperature.

Which one to choose: AGM or GEL?

On comparative reading of our presentation, many of you are asking the question.

Difficult to answer definitively as the cases of use, load and the upstream or downstream equipment of the batteries may be different on each boat.

We will be content to note that almost all ship chandlers now only offer AGM batteries, both for easements and start-up...

Silicone batteries (ALS)

Aquamot silicone ALS traction marine battery The ALS deep-cycle silicone batteries (developed by Aquamot) are traction batteries whose technology increases durability and performance compared to conventional AGM and GEL batteries.


In ALS batteries, the electrolyte is a silicone gel, which ensures lower internal resistance and therefore less heat loss (Joule losses), resulting in a longer life and safety.

They are presented as being robust, very reliable, flexible to use and more economical (number of cycles greater).

Lithium-Ion batteries

Marine Lithium-Ion batteries


A lithium battery is an energy storage technology of the family of electrochemical cells, the reaction of which is based on lithium (alkali metal of symbol ll, located in the first group of the periodic table of elements).


  • Less heavy and smaller batteries

This technology offers the highest specific energy (energy / mass ratio on the order of 100 to 260 W / kg) as well as the highest energy density (energy / volume).

  • More durable batteries

Lithium batteries can operate up to 15 years (aeronautics, hybrid vehicles, and backup systems). The Galileo satellites are also equipped with Li-Ion SAFT batteries with a verified lifetime of 12 years.

A little technique

One distinguishes the technology:

  • Lithium-Metal where the negative electrode is composed of lithium metal,
  • Lithium-Ion (Li-Ion), where lithium remains in the ionic state thanks to the use of an insertion compound both at the negative electrode (generally graphite) and at the positive electrode (Cobalt dioxide, manganese, iron phosphate, etc.). Unlike other technologies, Li-ion batteries are not linked to an electrochemical couple. Any material that can accommodate lithium ions within it can be the basis of a Li-Ion battery.
Advantages of Li-Ion batteries
  • Have a high energy density for a very low weight, thanks to the physical properties of lithium (very good weight / electrical potential ratio). These accumulators are therefore widely used in the field of embedded systems.
  • Self-discharge rate (1 to 10% per month depending on conditions and technologies) acceptable but less good than AGM or GEL,
  • No maintenance,
  • No memory effect.
Disadvantages of Li-Ion batteries
  • Discharge depth: these batteries wear out less quickly when they are recharged every 10% than when they are every 80%.
  • Lower permissible charge and discharge currents than with other technologies.
  • require some precautions in their handling.


As with all misused batteries, this technology presents potential hazards; In particular, these batteries can degrade by heating above 80 ° C. in a brutal and dangerous reaction.

Must, therefore:

  • Never short-circuit the battery, reverse polarity, overload or pierce the housing.
  • That the batteries are always equipped with a protective circuit to prevent overload or overload, a thermal fuse and a relief valve.
  • The load complies with precise parameters,
  • The elements never fall below 3 V.

Lithium-Polymer batteries

It is actually a trade name for "Lithium-Ion-Polymer" where the electrolyte is a gelled polymer.

Li-Po (or Li-Poly) batteries use a similar operating principle to Li-ion batteries and have similar characteristics while presenting some differences.

Benefits of Li-Po Compared to Li-Ion
  • Li-Po can take finer and varied forms,
  • The Li-Po may be deposited on a flexible support,
  • Lighter weight (Li-Po sometimes makes it possible to remove the heavy metal envelope),
  • Li-Po are safer than Li-Ion (more resistant to overload and leakage of electrolytes),
  • Li-Pos allow more life cycles.
Disadvantages of Li-Po Compared to Li-Ion
  • Energy density slightly lower than the latest generation Li-ion,
  • Li-Po are a little more expensive than Li-Ion,
  • The loads are subjected to a strict procedure or risk of ignition.

A Lithium-Polymer battery is no more dangerous than another rechargeable battery as long as it is of good quality and used properly.


  • Some Li-Po batteries are sold without a protective circuit and must therefore be handled with great care.
  • The essential elements for the proper management of a Li-Po battery
  • An industrial Li-Po battery system must have the following components: a BMS, a PCM, a balancer and a dedicated charger.

The BMS (Battery Management System)

  • It manages the charging and discharging of the battery as never to charge a "Li-po" element more than 4.20 V and discharge it at less than 2.5 V.
  • This BMS component is essential on a Li-Po battery and its quality is essential to the lifetime of these highly technological accumulators.

The PCM (Protection Circuit Module)

  • It is a module linked to each cell that continuously monitors their voltage.
  • If the high (4.2 V) or low (2.5 V) thresholds are exceeded, the PCM sends a signal to the BMS.


  • In case of voltage unbalance between elements of the same battery, the lowest voltage element triggers the stopping of the discharge even if the other elements still contain sufficient energy.
  • The greater this imbalance, the more the available energy decreases.
  • The remedy consists in bringing all the elements back to the same tension.
  • It is the role of the balancer to unload the fuller elements to match the tension of the weakest element.
  • Once these voltages are re-balanced, the charge of the entire battery can continue.

Industrial Li-Ion batteries

There are high-power industrial Li-Po batteries that are very stable and performing, thanks to more advanced chemistry, advanced electronic management and an elaborate balancing system. More and more manufacturers as well as the military use Li-Po batteries in many systems requiring powerful mobile energy storage systems.

Unlike consumer products (which are used even when not in use), industrial Li-Po batteries are better protected and have much less risk of internal corrosion leading to increased resistance; from where :

  • Good safety and reliability,
  • A rise in temperature of less than 30 ° C during a cycle.
  • A lifetime well above 5 years with a number of cycles between 800 and 1200.

Industrial Li-Po batteries

KOKAM manufactures batteries for models (cars, boats, planes) as well as for mobile phones, camcorders, PDAs, laptops...

This company has developed a specific technology (the Superior Lithium Polymer Battery, SLPB) which is used in a large number of electric vehicles: bicycles, scooters, boats, cars, light aircraft and microlight.

Silicon / graphene batteries

What is graphene?

If one begins to know the silicon well, it is not the same with the "graphene".

It is a matter discovered in 2004 by a team of researchers from Vanderbilt University in the United States, made up of carbon particles.

Its promising properties fuel an over activity in technological research.

So that in 2015 the European Commission decided to bet one billion euros over 10 years to develop scientific projects related to applications related to this material.

Marine Batteries

Properties of graphene

In its use as an "electric energy tank", graphene would allow:

  • A considerably reduced loading time,
  • A lifetime is much more important than a conventional battery: 5,000 recharges on average against 1,200 for the current technologies.

Aluminum battery

A team from Stanford University is developing an aluminum battery that will recharge 100% in less than a minute while being very safe (no risk of catching fire or exploding). Likewise, it can be recharged 7,500 times without losing its efficiency, seven times more than the current batteries.

But this technology seems for the moment rather reserved for telephone batteries, since it only stores 40W / Kg, against 100 to 260 W / kg for lithium-ion batteries!

Is it therefore, declinable on units of high power, and for the use of marine traction that interests us?

If these "new races" of battery fulfill their promises, it would indeed be the opening of electrification to many applications...


This type of battery also requires specific chargers, allowing the balancing and management of the cells.

It is also advisable to recharge its batteries immediately after discharge, in order to always store them charged.

For indication, with industrial Li-Po cells, the full recharge of a 3 kWh battery takes only 1.5 hours. The batteries can be used immediately after charging.

The charger must be specially designed to charge Li-Po batteries. The charging takes place at constant intensity until a voltage of 4.2 V is obtained per element and then continues at constant voltage until the charging current falls below C / 20 (the twentieth of its Nominal capacity).

For industrial LiPo cells, the charge can be applied immediately after use. The full recharge of a 3 kWh battery takes 1h30. The batteries can be used immediately after charging.

General note

The question is often asked: should the batteries be charged (connected to a 220 V charger) permanently during a long period of inactivation (wintering for example)?

Except to have a self-contained charging system (photovoltaic or onboard windmill with intelligent charge management) it is better to recharge by monitoring for half a day each month its batteries, than to leave them in permanent charge; In fact, besides a large electrical consumption, this risks exposing your boat to electrolysis (hull and / or power unit), and to electrical accidents.

The future of Lithium batteries Example battery Lithium 48 V - 100 Ah

New battery technologies with mass-energy much higher than Li-Po are currently being tested in laboratories, and in the pre-industrialization phase for some.

Research has intensified in recent years with the development of electric trolling motors...

The Lithium-Air (or Lithium-Oxygen) battery, which uses oxygen from the air to function, could bring a major technological breakthrough.

Indeed its energy density can potentially reach 5 kWh / kg, and in practice (verified in lab), measured around 1.7 kW / kg.

That would be about 10 times better than the current models!


Electrical energy is neither more nor less dangerous than traditional fuels, because a boat fire of hydrocarbon or electric origin is always devastating!

Just follow some basic rules for safe use:

Neither will it happen to you to smoke in the vicinity of the tank, to put a ground connection when refueling nor must to use an inadequate fuel of poor quality ... The users of traction batteries respect rules simple:

  • Correct order of connections,
  • Batteries of good quality and homogeneous (type, year, charging ...) (*),
  • Check the electrolyte level for conventional lead-acid batteries (**),
  • No short circuit,

Result of a forced charge on a battery of which two cells were dry ... - perfect connections...

(*) Never combine batteries of different type and age at the risk of seeing in a few hours the best loss of capacity.

(**) The picture opposite corresponds to the result of a battery recharged intensively while 2 of its elements (right) had enough electrolyte...

Professional battery regeneration

There are now industrial maintenance centers operating in the direction of sustainable development, regenerating the batteries.

Initially, the battery is diagnosed with a specialized tester which highlights the anomalies and indicates whether it is compatible with its regeneration.

Little reminder

A battery can only be recharged if the lead sulfate which covers the plates remains in contact with these plates; if it has fallen to the bottom of the vat, it is over!

You will also conclude that a "delicate" handling of your discharged batteries will avoid to this layer of lead sulfate a mechanical detachment.


Lead-acid batteries

  • It is sulphation which predominantly deteriorates lead-acid batteries.
  • Suitable for batteries: stationary, marine, truck, auto (start) as well as all traction or forklift batteries.
  • Allows to renovate the batteries of 24 V or 48 V (or 2 x 24 V in series), of capacity between 100 and 3000 Ah.

Nickel Batteries

  • Nickel NiCD (Nickel Cadmium) or NiMH (Nickel Metal-hydride) batteries undergo an internal crystallization phenomenon which forms when the battery has not been sufficiently discharged. The crystallization is materialized by the formation of sulfate and becomes permanent between 3 to 4 months after its formation; it results in a loss of capacity.

The regeneration

  • The regeneration process consists of sending micro pulses of high power (up to 13 A) with a maximum voltage per element of 2.6 V.
  • This action will reduce the internal resistance of the battery and bring it back to normal, which will allow the battery to be charged normally afterward.
  • The full capacity of the battery will be reached after a few charge / discharge cycles.
  • The duration of this operation ranges from 24 hours, for a maintenance regeneration to 72 hours, for a regeneration of reconditioning.


  • Restores their original capacity to sulfated batteries,
  • Iincreases the life of the battery which can even be doubled (by regular maintenance regeneration),
  • Ensures a longer use of the battery between two loads,
  • Decreases the charging time (reduced internal resistance),
  • Reduces the number of charge cycles for the same efficiency thanks to a more complete charging with each recharge.

Ecological interest

  • Reduced collection and destruction of batteries,
  • Reduction of waste during manufacture and destruction of replacement batteries,
  • Significant reduction in the gray energy required for the manufacture and transport of new batteries,
  • Reduction of wastage of raw materials and imports...


This can also be done for the preventive maintenance and maintenance of your starter, servitude or traction batteries.

Small battery regenerators

Given the increasing demand and the deterrent prices of both devices and professional treatments, a few firms have embarked on the study and marketing of small electronic assemblies that are supposed to achieve the same result.


  • These devices propose to increase the lifetime of solar, stationary and marine batteries by emitting electrical pulses adjusted to the resonance frequency of lead sulfate for a certain number of hours (depending on the state and Of the battery power).
  • The effect of this treatment will dissolve the crystals that are deposited on the inner plates of the battery.
  • In other words, the "blower" would avoid the crystallization of the sulfate while "destroying" the crystals which would tend to form in the landfill.
  • To complete this desulfation, a chemical cleaning agent (SULFASODIUM), for example, is added to the electrolyte.


The originality of this device is to be connected and installed permanently (with a double-sided adhesive provided) on the battery in use; Thus, rather than desulfation the battery when kneeling, this operation is carried out regularly during the time when the battery is not electrically stressed.

The regeneration is therefore fully automated and without any special intervention.

Technical characteristics

  • Input Voltage: 11,5 - 17V
  • Output current range: 1.6 A (pk)
  • Operating range: 12.5 V
  • Operation indicator: green LED
  • Low Voltage Indicator: Red LED
  • Dimensions: 25 mm x 78 mm x 60 mm
  • Inversion Protection Polarity
  • Short-circuit protection: 3 A auto reset
  • Connection type: Terminals UL1015.


  • The limits specified by the manufacturer are as follows:
  • For batteries less than 10 years old,
  • Inefficient for batteries with "short-circuited" cells (definitely HS),
  • Inefficient for batteries whose voltage does not exceed 10.5 Volts after recharging,
  • Strongly advised on batteries whose case is damaged (cracks, bending), or with batteries whose electrolyte has frozen.

Maintenance of terminals

  • Oxidized terminals (result of acid vapors on lead) frequent on old batteries, poorly charged and in the presence of moisture, are a cause of electrical loss.
  • It is therefore, advisable to clean them if this stigma is not the sign of a battery at the end of life.
  • The use of the wire brush can be advantageously replaced by immersion in boiling water with sodium bicarbonate (for pods) and cleaning with a cloth soaked in this preparation (for the terminals); this treatment has the property of dissolving sulfate of lead.
  • Then, coating the terminals and their pods with petroleum jelly, will prolong their protection.
  • Finally, the carcass of a battery must be dry, in order to avoid the passage of any unnecessary current between the terminals.

The wintering of batteries

  • As many boat owners do not forget to winter their engines and their sanitary water circuit, many of them do not know precisely how to take care of their battery off-season.
  • Some take them away and spend the winter in their garage.
  • When it comes to lead batteries of 60 kg, it is usually quickly seen!
  • Is it really better than leaving them on board? This is not necessarily the case.
  • What intervenes more is to recharge them about every month for about fifteen hours, and of course with a charger adapted to the type of battery and its capacity.

To know

A discharged battery is more likely to have its electrolyte freezing.


Recharging a lead-acid battery releases a significant amount of hydrogen; so do not do so in a room without ventilation and do not engage in activities that could cause sparks before complete ventilation.

Some generalities to know

  • Do not hesitate to look at the date of manufacture (usually coded and hidden in the middle of the lot number) of the battery you buy; in fact, it is discharged (self-discharge) even if it is not used! If she has been lingering for a while with your dealer, she may not be very fit:
  • * Below 12.6 V, it will lose efficiency and duration.
  • * Below 12.45 V, (more than 60% of its capacity of use) it will never regain its full capacity.
  • The enemy of batteries is their variation of temperature:
  • * Stored at 30 ° C, it will discharge 2 times faster than at 20 ° C,
  • * Each increase of 10 ° C multiplies by 2 self-discharge.
  • The state of the electrical circuits of the boat (alternator, charger, cabling ...) will of course, participate in the longevity and the maintenance of the performances of your batteries.

A proposal

A sustainable future would lead to the manufacture and distribution of removable batteries.

Indeed, in a battery, only one part of the plates is used, the other being as new.

Thus, when a battery has lost a little of its active material, one could:

  • Empty it of its electrolyte, reserving it,
  • Clean i from the inside by removing the sludge of lead sulfate accumulated at the bottom,
  • Replace the most "corroded" plate (s) with acid,
  • Reintroduce the electrolyte.

A battery thus treated would find a new use, even if its capacity would decrease a little.

An anticipation of a more elaborate re-use circuit would allow the design of the plates to change the lead plates.

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