How to Make the Trolling Motor Batteries Better Performance

 Make the trolling motor batteries better performance, or I have an electric motor, now I need batteries to make it work! -so how to do? Because is too much important by great water experience! And a battery is characterized by its voltage (generally a multiple of 2V, size of an element) of its capacity which is expressed in ampere / hour: it is the product of a current by a discharge time.

A conventional battery consists of grids of lead plates enclosed in vertical and horizontal bars retaining the active material: sponge lead for negative plates and lead dioxide for positive plates, all immersed in sulfuric acid ‘electrolyte.

Its principle of operation is based on a chemical reaction between two bodies which generates an electronic imbalance by lack and excess of electrons on the plates:

  • During the discharge cycle, the acid contained in the electrolyte combines with the lead of the plates to form lead sulphate. The electrolyte depletes in acid.
  • When charging is the reverse reaction that occurs, the lead sulphate turns into lead dioxide on the positive plate and sponge lead on the negative plate.

Well, that’s for the theory, but it’s not really what we’re interested in here, is it?

Battery starter or slow discharge?

A slow discharge battery is made to provide a long constant current, a starter battery to provide a very strong current in a brief moment: these two applications are totally opposite … in theory.

Caution, a marine battery is not always a slow discharge battery: do not make the amalgam!

Car batteries (60 and 75A) = typical starter battery:

  • Light enough as low power. But more is needed (often 2).
  • Economical with the purchase, especially in occasion (for the breakage for example)
  • Sufficient in many cases.
  • It is more “fragile”, does not have to be discharged as thoroughly (30% to 50% maxi) or else make it unusable, and it supports less the cycles of charge / discharge.

There are some on the forum that uses this kind of batteries for years successfully.

Slow discharge:

A specialized batteries for electric trolling motor is said to be slow and deep discharge: it supports discharges of 80% of the total load. So it allows a better autonomy with equal battery weight.

  • more expensive
  • often distributed in deck fittings

Gel battery:

Lead with gel electrolyte

  • it is very expensive, much more expensive than a conventional battery (ampere equivalent)
  • Actually better
  • Less heavy, but only a few kilos.
  • No maintenance: no need to check the levels.
  • despite the fact that there is no maintenance, the lifetime of these batteries is not infinite, and they are capable, like all batteries, of only a certain number of charge / Discharge: once the gel is dry it is dead
  • Is 100% charged and discharged at 0%
  • The main advantage is to operate in all directions: no possible accident (reversed acid). But unless you try to skimp the Eskimo with the boat, the interest is limited.
  • No need for a special charger: it just needs to be compatible with the amperage of the battery.

Electric fence battery:

  • Exists in 60 AH
  • Can be bought in stores such as “emerald space” or “Gamm Vert”
  • Would be very light and endurable (I have never tested)


The battery life is characterized by its Amps / Hours (AH): the higher the number, the longer the battery life.

With electric motors, the autonomy is not very high and remains a limiting factor, especially compared to a thermal: between 2H and 12H (depending on the chosen speed) for an 80AH associated with a 36lbs of power.

It will therefore be important to save your battery during long sessions, or to take several (for half a day of fishing one can afford to “Cramer” his whole battery by pushing the motor thoroughly to save time) .

We have already mentioned the factors that directly influence autonomy in an article devoted to electric motors.

Since the batteries are also very heavy, the choice of the power of a battery must therefore be a compromise between the desired autonomy and the weight of the battery.

Attention: also provide sufficient autonomy to enter even if the wind rises (forcing to “push” the motor)!

The minimum seems to be 70AH. With this one keeps easily a day of fishing, and saving to the max one can go until a week of session. Similarly, beyond 110AH, it is no longer a battery is … a Calvary to carry!

We can also choose to carry 2 (or more) batteries less powerful, easier to handle. With 2 x 70AH, we already hold a moment, and we can wear them one at a time, which is already heavy but much more feasible.

However, a battery 2 times less powerful is not 2 times lighter nor 2 times cheaper.

The starter batteries are considered to have less autonomy (with equal AH of course), but in view of the testimonies of users, doubt is allowed.

To gain even more independence:

  • Turn the croc clamps of your engine to replace them with car lugs: better contact, less heating and loss.
  • Petroleum jelly to coat all the oxidizable parts: the lug of the car, the screw that connects the wires to the lug and the bare wires. No oxidation at all, less wastage.
  • If the echo is connected to the battery, it is better to turn it off when it is not used.

When using for a long time non-stop, especially at the end of the battery, it is good to let the battery “stand” for a moment: its voltage (and thus its autonomy) will go up a little bit: it is Always that of won.

Even if it is tempting to “push” a bit its battery to hold a day more, a too large discharge will damage the battery more or less irreversibly! Slayer reasonable and finish with the ream if necessary, your battery will return it to you.

How to check the battery charge?

How do you know what is left as autonomy during the session?

The batteries used with our electric motors are 12V batteries, but the voltage varies from about 12.5V when it is full to about 9V when it is empty. The knowledge of the voltage allows us to know if the battery is discharged or not, and to follow its evolution during the fishing time.


Make the Trolling Motor Batteries Better Performance


If an echo is not used or if it does not have a “voltage” function, use a small voltmeter instead (for cheap) to measure the voltage at the terminals of the battery.

Attention! It does not always give the same measurement between the echo and the voltmeter: my echo always indicates less than my voltmeter for example. I think there are variations in the electrical contact between the terminals of the battery and the devices, or it is the intrinsic consumption of the echo itself which lowers the voltage a little.

The voltage also decreases when the motor is pulled at the same time: as soon as the motor is stopped, the voltage rises. Therefore, if one wants to follow the evolution of the voltage and create “markers”, it is better to always take the measurement under the same conditions (same measuring device, and same way of proceeding), and motor stopped!

On my echo, I start with a full battery around 12.5-12.7V, to finish at 10V when changing it (it could come down more, but I could then damage it).

When charged, when the battery is connected to the charger, the voltmeter reads 13.8V.

Battery indicator

Finally, some (not all) batteries have a “charge lamp” indicator in the form of a chip that changes color depending on the load: this gives an indication, but the reliability and precision of this witness is subject to discussion.


It is necessary to count about between 18kgs for a marine battery 70 / 80Ah and 28kgs for a 100/110 Ah.

This high weight of the batteries is a major disadvantage, and a limiting factor of the choice of the power:

  • Choosing an ultra-light inflatable boat to be able to easily handle it and take 30 kilos of lead in addition is nonsense!
  • It becomes in transportable over a certain distance, kind over 50m and worse on the slope. On the way, it goes, but during the returns of session (well fatigued), the distance between the shore and the car appears interminable, especially if one is alone!
  • Fishing only during the day: it will be necessary to carry the batteries morning and evening! So, Matos the lightest possible if we want to hold a week at this rate.
  • The bottom of a Fish Hunter boat would probably not fit under the weight of an 110AH.

This weight must be relativized with a big boat (or big zed), a launch is essential anyway (and therefore no battery to wear).

2 small batteries of 70Ah or 90Ah are much less heavy to carry than one big one of 110 AH, and especially they can be carried by a single person over a certain distance more easily.

But a battery 2 times less powerful is not 2 times less heavy.

Some batteries are equipped with handles practical per the models: a point that can be interesting when it is necessary to carry the battery over several hundred meters.

Choice of charger

Perfect battery charger is the most important element to buy, one that will ensure the proper performance or not of your battery in time!

Whatever battery is chosen, if the charger is bad you will burn it very quickly.

Fast Load / Slow Load:

  • Battery charge overnight for example, under slow charge.
  • Avoid fast charging to the maximum: it is known to shorten the life of batteries.


Must be powerful enough to charge the battery fully (the maximum power must exceed the battery power): low-end chargers hardly mount to 100HA (they are made for “car” batteries), and charging times Become very long.

Do not take too low also in anticipation of replacement in the future by a more powerful battery (it would be a shame to have to change the charger again!).

Automatic load stop:

The most important thing, in my opinion, is to take a “floating” loader:

  • It cuts when the battery is recharged, and maintains it in “maintenance” (= does not charge more but does not discharge either).
  • The battery is therefore always charge, but never heats. So the battery can be left in charge for several days without risk.

Without this function, the battery must be disconnected from the charger after the charging has been completed, which means checking the charge regularly and being available at the right time to turn it off!

Otherwise, at best we risk to burn the battery, and at worst to see it catch fire.


You have to see the power (A / Hours), and the features described above. Afterwards, the brand itself is of little importance in my opinion.

There is no need to put a fortune, nor to buy his magazine in a specialized shop. As long as it is capable of cutting at the end of charging, and keeping the battery charged, and it is not too low in power, it does.

Security: Batteries explode!

  • It is preferable to load them by removing the plugs for long load.
  • Do not smoke or approach a nearby flame.

There are also batteries where it is not necessary to remove the plugs because they have a hole (on the side of the battery for example) for the evacuation of the gases during the reloading.

Do not wait until the battery is completely discharged before recharging: as soon as you return from fishing, connect your battery to the charger without delay. The less time your battery runs out, the longer it will take you.

One can easily replace it even partially empty, quite the contrary!

If your charger is not capable of turning off at the end of charging, or switching to charging mode, be sure to disconnect the battery yourself at the end of charging (see above).


  • Ni-Cd batteries, which must be stored unloaded or emptied, lead-acid batteries must be stored charged.
  • A battery left for too long will not be recharged, and therefore will be damaged.

But beware! During time, the battery self-discharge slowly, even when not in use (in winter, for example): remember to recharge it from time to time, or to leave it connected to a charger capable of regulating and maintaining the charge You are told that the choice of the charger is important!).

Finally, keep the battery away from the cold, especially frost.


It is really the way to use it (no discharge too high) and its maintenance (recharge as soon as the return fishing, storage charged, etc.) that condition the good life of a battery. Hence the importance, once again, of a correct charger.

Thus, well maintained, a battery lasts about 3 to 5 years (unless they are toppled!). Some have their batteries for 8 years!


  • Batteries (marine or other) are guaranteed minimum 1 or 2 years.

Reversed acid

Be careful not to spill the batteries: the skin like the gear does not appreciate the acid!

The gel batteries do not have this disadvantage.

Severe weather

Personally, for years I did not use any special protection for the battery in the boat: it took all the rain on the face without flinching, as well as the winter nights at -5 ° C!

That said, there are now battery “bins” that will protect them effectively.

Connecting electrical devices to the battery:

No problem connecting an echo on the same battery as the electric motor (12V). This avoids lugging with an extra battery (motorcycle battery, or battery box) for the echo.

Similarly, all 12V devices (cigarette lighter socket), especially the laptop, can be connected to the battery of the electric motor, by means of a small tinkering.

Connecting the motor to the battery

  • fast pockets
  • “Crocus” clamps: the most flexible, because they allow to connect directly to the terminals of the battery, or on the lugs if they already exist.
  • But the contact surface is less important than with butterfly screws.
  • Butterfly screws: the most effective, because the contact surface is maximum. Necessary to provide a set of lugs per battery, not to have to be Ch. … to remove the pods when changing batteries during the session.


Before carrying out maintenance of lead-acid batteries several precautions must be observed. By the fact that they contain sulfuric acid and that they can produce gases, their manipulations impose a few safety rules:

  • Ventilate the room before intervention, do not smoke and avoid any naked lights in the vicinity, it is possible to have a release of hydrogen so risk of explosion.
  • Avoid contact with acid (if necessary wear full body clothing and glasses). In case of accidental contact: rinse thoroughly with soapy water or sodium bicarbonate solution and seek medical advice.
  • Check the condition of the terminals and connections, in case of oxidation, clean them with a metal brush and coat them with silicone paste or liquid pure petroleum jelly, never grease.
  • Check the sulfation that is the accumulation of lead sulfate on the plates, due to the fact that the refill tends to leave the innermost parts of the plates. This phenomenon is inevitable as soon as a battery is discharged seriously and becomes worse in the absence of a full recharge. Solution can become irremediable (battery to replace) if no remedy is provided.

The solution consists in regularly equalizing the batteries, if: temporarily boosting it by a controlled amperage.

The indices of sulphation are as follows:

By capillarity the lead sulphate infiltrates and rises to the terminals of the battery. The white powder, which it is not uncommon to find on these same limits, is sulphate of lead.

In addition, the capacity of the battery decreases rapidly.

  • Check the potential difference at the terminals of the battery with a voltmeter, open circuit (without discharge current), it should be about 12.6 V when charged.
  • Check the level of the electrolytic solution, especially after a long period of inactivity.

During the operation of the battery, the sulfuric acid present in the electrolyte never degrades (except accidental overturning or breaking of the tank).

On the other hand, the water in the solution is subject to evaporation, hence the need to re-establish the level of the electrolyte by periodically adding, once a month, only distilled water (never tap water Nor of the acid, nor of the so-called special electrolytes).

The distilled water must be added to a cool and resting battery (20 ° C) until the separators are about 3 mm thick. If the battery is really charged, the height of the solution must be 5 mm higher than the top edge of the separators.

Distilled water must be contained in clean earthen or plastic containers. The funnels and strips that come into contact with distilled water must be of the same material and never of metal.

Of course the gel batteries are not concerned.

  • Control of the venting. Each element has a screw or pressure plug which is generally provided with a small hole allowing the exit of the gases resulting from different chemical reactions. If this hole is blocked, the gases are no longer able to escape and create a pressure inside the element which can be detrimental. It contains therefore to check that it is free every time the battery is inspected.
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