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Battery on the boat: care and maintenance

To get the large starting currents necessary for the starter, it is best to use lead (acid) car batteries: they have a small internal resistance, so that batteries, even of small capacity, can create large currents.

Why does the battery last longer on a ship than on a car? The use of a car battery on a boat — mainly in the summer — has its own characteristics:

  1. it is much easier to start the engine with a starter;
  2. the density of the electrolyte does not need to be increased to 1.27-1.30 g/cm³, in order to protect it from freezing, it is enough to maintain it at 1.25 g/cm³.
  3. during the day, the engine on the boat starts only 1-2 times;
  4. long-term operation of the motor with a constant speed helps to reduce the value of the charging current.

All this allows you to extend the battery life up to 6 years or more.

For vessels with outboard motors and with engines from passenger cars, batteries with a capacity of 45-60 Ah are used, with engines from trucks - 75-90 Ah. The capacity of a fully charged battery is enough for the starter motor to be scrolled for 10 minutes. If we take into account that a few seconds are enough to start the engine in the summer, during parking the battery can be used to power lighting equipment, using up to 50% of its capacity.

How to charge the battery? Currently, all batteries are produced dry-charged, so before you put them on the boat, they must be brought into working condition. With a shelf life of less than a year, it is enough to pour an electrolyte with a density of 1.23 g/cm³ (i.e. 0.02 g/cm³ less than the recommended value), while the electrolyte level should be 5-15 mm higher than the upper edge of the plates. The density is measured with a hydrometer. Recall that to prepare an electrolyte of this density for 1 liter of distilled water, 290 cm³ is needed chemically pure battery acid (92-94%). When acid is diluted with water (acid is poured into water), a large amount of heat is released, so it takes time for the electrolyte to settle and cool down, therefore, it must be prepared 10-20 hours before pouring. After that, the battery can be put on boat. During storage, dry batteries lose their qualities. We can assume that 2-3 years of storage is equivalent to a year of work.

If the battery has not worked for a long time or has been discharged during operation, it must be put under charging. Usually, the first charge is carried out with a current of 0.1 of the battery capacity. The beginning of active gas release, the so-called «boiling», as well as an increase in the voltage on the cells to 2.7 V and the electrolyte density to 1.25 g/cm³ indicate that charging has ended. However, for a more complete use of the active mass of the plates of the elements, it is continued for another 3 hours, while the voltage and density of the electrolyte should remain unchanged. Density measurement should be performed at an electrolyte temperature of 15 °C.

If the charger is turned off, the voltage on the elements will immediately drop to 2.4-2.5 V, and then gradually decrease to 2.09 V. The voltage value depends on the density of the electrolyte and is related to it by the ratio: E = 0.84 + y, where y is the density of the electrolyte at 15°.

The voltage of the discharged battery is 1.95 V and lower. When measuring its voltage with a load plug (recall that a small resistance of 0.02 ohms is used to control batteries with a capacity of 40-65 Ah, at which the discharge current is about 100 A), the voltage of the charged battery is 1.7-1.8 V per jar. When starting the engine, the starter consumes approximately the same current, therefore, the voltage will also be 1.7-1.8 V per jar. (For a discharged battery, this voltage is below 1.4 V).

Battery specifications

Brand Dimensions, mm Amount of electrolyte, l Weight with electrolyte, kg
length width height
3 st-60 PMS 179 178 237 2,4 17,9
3 st-70 PMS 257 194 230 2,5 19,9
3 st-84 PMS 272 188 230 2,7 21
3 st-98 PMS 308 188 245 3,0 22,7
6 st-42 EM 240 179 219 3,0 19,3
6 ST-45 EM (ER) 245 182 230 3,0 20,1
6 st-54 EM 283 182 237 3,5 24,7
6 st-55 ER 260 172 223 3,8 21
6 ST-60 EM (ER) 260 172 223 3,8 21
6 ST-75 EM (TMS) 358 177 238 5,0 30,5
6 st-90 EMS 242 188 230 6,0 35
6 st-95 EMS 475 186 235 7,0 41,4
6 TST-132 EMS — — — 8,0 59
6 tst-140 — — — 10,0 62,3
6 TST-165 EMS 527 280 280 11,5 70,6
6 st-128 586 238 238 15 51

Sometimes, after the first charge of the battery, the density in the banks turns out to be different. To eliminate this, it is necessary to add distilled water to those cans where the density is high, and sulfuric acid with a density of 1.4 g/cm³ to those where it is small. After thoroughly mixing the electrolyte with the pear of the densimeter, the excess electrolyte should be drained and the battery should be charged again.

What is sulfation and how to deal with it? When the battery is discharged, lead sulfate is formed in the form of crystals; however, at low current, crystal growth is insignificant. With a large discharge current, the reaction in the depth of the active mass stops, and continues on the surface. It is on the surface that sulfates are formed, which clog the entrances to the pores of the active mass. In this case, the process of plate sulfation occurs, i.e. blockage of pores in the active mass by large, hard-to-dissolve sulfate crystals, which leads to a decrease in battery capacity and an increase in its internal resistance.

Sulfation is accompanied by a decrease in the electrolyte density of a fully charged battery. Most often, the battery capacity can be restored. To do this, it is necessary to dissolve large crystals of lead sulfate and release clogged pores, i.e. increase the contact surface of the active mass with the electrolyte. Lead sulfate can be dissolved using several cycles of charges and discharges with very low currents of 0.5-1 A, alternating them with long breaks to equalize the density of the electrolyte in the pores and the bulk.

Do it this way. The battery is put on charge for 5-10 hours, then take a break for 3-5 hours and continue charging with the same current. After charging, the electrolyte is drained, distilled water is poured instead, and after settling for 3-5 hours, charging is continued with the same current in cycles of 5-10 hours with stops for 3-5 hours. The charge is carried out until the density of the electrolyte ceases to increase in at least one jar. When the growth of electrolyte density stops in all banks, it can be assumed that all sulfates have passed into solution. In this case, distilled water should turn into an electrolyte with a low density, usually 1.1-1.15 g/cm³. The resulting electrolyte should be drained, and an electrolyte with a density of 1.25-1.26 g/cm³ should be poured into the battery.

Next, the battery must be discharged with the same low current, connecting a 12-watt bulb, and discharge in cycles of 5-10 hours with stops for 2-3 hours.

After these operations, the battery must be re-charged intermittently until the increase in electrolyte density in all banks stops and bring it up to 1.25 g/cm³.

Some tips for using batteries on boats and boats

When the electrolyte level decreases (if you are sure that the electrolyte has not leaked or spilled), distilled water should be added to the jars. We do not recommend using rain and soft lake water, as there is no confidence in its purity, and the active mass is very sensitive to contamination. After adding water to the battery banks, the electrolyte should be thoroughly mixed, putting it on charge. Otherwise, self-discharge currents will occur inside the jar, caused by the fact that the density of the electrolyte in the upper part of the jar is less, and, therefore, will be less than in the lower part, EMF. As a result, an electric current is formed, which will charge the upper part of the jar and discharge the lower one. Self-discharge of the battery can occur through a coating of dirt or moisture on the upper outer surface, so it should be thoroughly wiped and protected from splashing water on the terminals.

If, as a result of sulfation or internal breakage, the resistance of one of the cans has sharply increased and the battery cannot be replaced, then the failed jar can be shorted with a thick (of several turns) copper wire. This will reduce the internal resistance of the battery and make it easier to start the engine.

It is harmful to recharge the battery, i.e. to continue charging with rated current for a long time after the start of intense «boiling». This leads to the decomposition of water and an excessive increase in the density of the electrolyte, which contributes to the warping of the plates and the coloring of the active mass. However, recharging with a small current, except for a slow decrease in the electrolyte level due to the decomposition of water, does not lead to any other undesirable consequences. Such overcharging is much less dangerous than storing an undercharged battery.

If the engine is difficult to start, do not turn the engine with the starter for a long time, as this contributes to sulfation and warping of the plates. This can be avoided if you take breaks in the starter, then the density of the electrolyte and the temperature of the plates are aligned.

At the same time, it is usually not possible to start the engine, especially the outboard motor, turning it with a starter for a short time (less than 2-3 seconds in one attempt). Because of this, the total battery life in starter mode increases. We recommend increasing each start of the starter to 10-15 seconds, especially since individual flashes in the engine, reducing the current consumption, will help the starter.

The degree of charge of the battery, and therefore its service life, largely determines the operation of the relay controller. If the battery is installed in the engine room of the boat, then the generator voltage value supported by the relay regulator should be set within 13.5-13.6 V. If the battery is located outside the engine compartment, the generator voltage should be 13.8 V.

It is not necessary to increase the voltage of the generator above the optimum by 10%: this leads to a 2-2.5-fold reduction in battery life.

It is also necessary to limit the amount of current when charging from the generator, because at the very beginning of charging, especially with a severely discharged battery, due to the low EMF of the battery, the charging current may increase, which will lead to warping of the plates. Therefore, at the initial stage of charging, it is desirable to limit the current to 5-8 A by switching on a small resistance of about 0.2 ohms in series with the battery and a dissipation power of at least 10 watts. You can create a significant load, for example, by turning on the headlight: due to this, the voltage developed by the generator drops. As the charging current decreases, the resistance is shunted by a toggle switch, the headlight turns off, and further charging is carried out in the usual way. The charge time at the same time becomes longer, which is acceptable for long transitions, but the battery life increases. However, when charging from the generator, there is a periodic undercharging of the battery. This can be avoided if you put the battery on full charge from the rectifier 1-2 times a season. It is very convenient, from this point of view, to charge from magdino outboard motors, since their power is low and the charging current usually does not exceed 4-5 A, while the maximum voltage at low load exceeds 16-17 V, which is quite enough for a full charge.

When installing two outboard motors, the voltage from each magdino is supplied to its rectifier and then connected in parallel, while the charging current increases slightly. Thus, in the absence of powerful consumers on the boat on the move, it is enough to connect only one motor to the electrical circuit of the boat.

When charging the battery, sulfuric acid is formed, and the density of the electrolyte increases to normal. As soon as this process ends, further charging of the battery stops. An increase in the density of the electrolyte can occur only by reducing the content of water in it, which will be decomposed by electric current into hydrogen and oxygen.

A mixture of hydrogen and oxygen is known to be called a rattlesnake gas. It must be remembered that a spark is enough to cause an explosion of great force. Therefore, the battery on the boat should be located in a well-ventilated compartment: the total area of the two vents should be at least 0.02 m². The compartment must be ventilated; it is possible, for example, to apply various deflectors, to arrange ventilation openings at different heights. When using stationary engines, the battery is most often installed in the engine compartment, since intensive ventilation occurs in it due to the air entering the engine carburetor. In no case should the battery be installed in the fuel compartment, and for motor boats that do not have special fuel compartments — near gas tanks: when the engine is started by the starter, a spark may form on the oxidized battery terminals.

We do not recommend putting the battery far into the nose, primarily because it is necessary to increase the cross-section of the wire feeding the starter. If, for example, the battery is removed from the starter by 1 m, then the wire cross-section should be 25-30 mm², and if at 5 m — 125-150 mm². In addition (especially this applies to planing boats), overloads and vibrations in the bow of the boat when running on a wave are higher than in the stern. When swimming on a wave through the ventilation holes of the plugs, it is possible to splash out the electrolyte, which, draining, can lead to intense corrosion of the metal body. It is advisable to put a plastic pallet under the battery, preferably on the frames. It is absolutely unacceptable to install it on the lining of the bottom: on a wave, a heavy battery can tear off the sheathing sheet from the stringers and frames.

If a stationary engine is mounted rigidly on a metal boat (without shock absorbers), then there is an increased level of vibration of the hull. In this case, it is advisable to put a sheet of hard foam rubber or soft microporous rubber 20-30 mm thick under the battery. From the same material, you need to cut a gasket under the upper frame of the battery mount to exclude mechanical contact of the battery housing with the boat kit. Naturally, in all cases, the battery mount on the boat must be absolutely reliable.

In winter, the battery is best stored in an unheated room at a temperature from 0 to -30°. Before storage, the battery should be charged to the norm with a 20-hour discharge current. It is necessary to check the electrolyte level and, if necessary, top it up.

The outer surfaces should be wiped from dust, the conclusions should be lubricated with a thin layer of technical vaseline. You can not use medical vaseline: it contains boric acid. It should be remembered that during storage, an electrolyte with a density of 1.25 g/cm³ freezes at a temperature of -50°, and a decrease in density as a result of self-discharge to 1.20 g/cm³ leads to its freezing already at -25°. Therefore, during storage, the battery should be recharged once every 2-3 months to compensate for self-discharge. If the temperature in the room where it is stored is above 0 °C, then recharging should be done more often — once a month.

In the section «Motorboats, boats, yachts — miscellaneous, reviews, tips»

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