Many beginners planning to electrify their boats often wonder whether it is advisable to buy specialized equipment. It would seem that why overpay for expensive deep-discharge traction batteries, if there are affordable ones in the garage or auto parts store. battery-powerThey're basically identical on the outside, the same dimensions, the same terminals and the 12 volt voltage, but that could be a fatal mistake for the entire onboard system.
The fundamental difference is in the chemistry of the processes and the design of the plates, which directly affects the durability and safety of operation on the water. The conventional starter battery is designed to instantly return a colossal current for a few seconds to turn the crankshaft of the internal combustion engine. motorboat It requires a stable but long-lasting power supply of moderate power, resulting in a deep discharge of the battery.
Using an inappropriate power source will not only shorten its lifespan, but it can also leave you in the center of a body of water without the ability to return to shore. In this article, we will examine in detail the physics of the processes occurring inside different types of batteries and explain why. AGM or GEL Technology is preferable to the classic lead-acid starter, and you will understand the emergencies you can still risk and how to minimize damage to equipment.
The difference between starter and traction batteries
The main difference is the design of the internal plates, in the standard car battery, which is marked with the markings. SLI (Starting, Lighting, Ignition), many thin lead plates with a large surface area are used, and this architecture is necessary to ensure maximum initiation current.CCA), which can reach 500-800 amperes in short-term pulse, and these plates are fragile and not designed for cycling.
Traction batteries, designed specifically for electric motors, golf cars and autonomous power systems, have a different structure: they have fewer plates inside them, but they are much thicker and more massive. This allows them to withstand hundreds of deep discharge cycles without significant loss of capacity. If the starter battery after a discharge below 50% can irreversibly lose part of its capacity, then the traction battery calmly gives 80% of charge and recharges.
Technical details of the design of plates
The plates in traction batteries can be as thick as a few millimeters, whereas in starter batteries they are thinner than a millimeter. This makes traction batteries much heavier at the same dimensions, but provides them with mechanical and chemical resistance to vibration and deep discharges.
Trying to use the starter battery in deep discharge mode will cause the active mass to fall off the thin plates quickly, and the sludge will settle on the bottom of the housing, and if it reaches plate level, it will short circuit. battery In conjunction with the electric motor is calculated not years, but only a few dozen cycles charge-discharge.
Why the car battery will quickly fail on the electric motor
When you plug an electric motor into a conventional car battery, you start a process that it's not designed to do. The motor consumes current uniformly over several hours. For example, a 30-40-pound motor can consume about 20-30 amps per hour. In a three-hour walk, you'll give 60-90 amps, which is 100% discharge for a 60-Ah battery.
For a starter battery, a deep discharge below 20 to 30 percent of the rated capacity is a stressful state. Under these conditions, irreversible sulfation of the plates begins. Lead forms a large crystal sulfate of lead, which blocks the chemical reaction. You can't charge the battery with a conventional car charger to 100%, it will show a full charge almost instantly, but under load the voltage will immediately subside.
- 📉 Critical drop in capacity: After 15-20 deep cycles, the starter battery will lose up to 50% of its original capacity.
- 🔋 The effect of voltage memory: The battery will show normal voltage at idle, but under the load of the motor, the voltage will fall below the permissible minimum.
- ⚠️ Bloating: intensive gas formation under incorrect charge regimes after deep discharge can lead to inflating of the plastic case.
The average life of the starter battery in the mode of operation with the electric motor is only 1 season of active operation, after which it will require replacement.
And there are also risks associated with tightness: Many modern automotive batteries are maintenance-free and do not have the ability to top distilled water. When the electrolyte is deeply discharged and then recharged, the electrolyte can boil, and the gases will be vented through the valves, reducing the level of fluid. You can not add water to such batteries, which finally finishes the device.
Comparative table of specifications of power sources
To illustrate the difference, consider the comparative specifications of a typical starter battery and a specialized traction battery. The numbers may vary by manufacturer, but the ratio remains unchanged.
| Parameter | Starter AKB (SLI) | The Dep Cycle (Deep Cycle) | Lithium-iron-phosphate (LiFePO4) |
|---|---|---|---|
| Appointment | Short-term initiation current | Long-term uniform returns | High energy efficiency and cyclicality |
| Depth of discharge (DoD) | Not more than 20% | Up to 80%. | Up to 90-95%. |
| Number of cycles* | 50-100 (deep discharge) | 500-1000 | 2000-5000 |
| Weight (at 100 Ah) | ~23-25 kg | ~30-32 kg | ~10-12 kg |
*The number of cycles is indicated for discharge modes up to 50% and below.
As you can see from the table, the resource gap is huge. When you buy specialized equipment, you actually invest in the number of future fishing boats, and it's not economically feasible to use the starter option in the long run, despite the low initial cost.
Acceptable scenarios for the use of a conventional battery
Despite all of the above, there are situations where the use of a conventional car battery is permissible. emergencyIf your main traction battery fails in the middle of a body of water and you have a few kilometers to the shore, connecting the car is a lifeline. Yes, you risk finishing up the battery, but the goal is to go home, not keep the battery.
You can also use starter batteries in buffer mode or to power low-power consumers, for example, if you have a main high-power lithium motor and a conventional lead-acid battery is connected to power the sonar, the navigator and the LED lights, and in this mode, the currents are minimal, and there is no deep discharge, which prolongs the life of the battery.
If you have to use the starter battery to move, try not to discharge it more than 30-40%. Control the voltage: a drop below 11.5 Volts under load is a signal to immediately stop driving.
Some anglers use old car batteries that have already been used by the car (residual capacity of 40-50%) as a temporary solution for short trips for 1-2 hours. This is a reasonable approach to recycling: the battery is still decommissioned, why not give it a “second life” on the water for short walks? However, you can not rely on it as the main source of energy for a full day of fishing.
Rules of operation and charging in emergency mode
If you're going to take the risk of putting a battery on an electric motor, you have to follow a number of safety and operating rules, and the first and most important rule is voltage control, and you'll need a voltmeter or an on-board computer that shows the charge in real time.
Charging these batteries after running the electric motor should be done immediately. You can't leave the discharged starter battery standing for weeks - sulfation will kill it completely in a couple of days of idleness in a discharged state. Use chargers with desulfation mode or at least with automatic current control.
⚠️ Attention: Never discharge a normal lead-acid starter battery to zero. A voltage drop below 10.5 volts can cause the cans to overpole, after which the battery will have to be thrown away. Also avoid overheating the case while charging.
☑️ Safety rules when using the starter battery
Starter batteries are generally lighter than traction batteries of the same declared capacity (due to thin plates), but their real delivery capacity for long discharge will be significantly lower than passport. Passport 60 Ah will turn into real 30-35 Ah of usable capacity if you discharge the battery slowly, within 3-5 hours.
Choice of alternative: AGM, GEL or Lithium
If you are looking for a balance between price and quality, look for technology. AGM and GELThese are lead-acid batteries, but they are sealed and deep-discharge, maintenance-free, safe (the electrolyte won't spill even when it rolls over), and last 3-4 times longer than normal liquid batteries when running electric motors.
AGM batteries (Absorbent Glass Mat) have an electrolyte absorbed in fiberglass. They hold high discharge currents perfectly and charge faster than gel batteries.GEL) are more sensitive to charge currents and require special chargers with precise cut-off voltages, but they are better able to tolerate deep discharge and have a greater cycle life.
The most modern solution is lithium-iron-phosphate batteries (LiFePO4Despite the high initial cost, they pay off at the expense of life. Lithium battery weighing 10 kg can replace the lead weight of 30 kg, giving a full capacity even in the cold (although you can charge lithium in the cold without heating). BMSIt will not allow the battery to be discharged to zero or recharged.
Why is LiFePO4 better than lead?
Lithium batteries have a flat discharge curve, which means that the motor will run at the same power and speed until the end of the charge, while lead batteries gradually lose voltage, and the motor begins to turn the screw slower at 30 percent of the remaining charge.
Frequently Asked Questions (FAQ)
Will the electric motor burn if you connect a conventional car battery to it?
No, the electric motor itself will not burn, because the voltage is the same (12 Volts). However, the motor may not work correctly: as the battery discharges, the speed of the screw will fall. The risk exists only if the battery completely discharges and there is a deep drawdown, which can damage the motor control, but this is a rare scenario.
Can I charge the traction battery with a conventional charger for a car?
For AGM and GEL batteries, conventional "automatic" charging is often not suitable, as they may give too high voltage in desulphation mode or not have the correct charging completion algorithm.LiFePO4) use of lead chargers forbidden without voltage control, as this can lead to fire.
How long will a motor on a single car battery last?
The operating time depends on the power of the motor and the battery capacity. For example, a 30 pound motor consumes about 30 Amps. A 60 Ah car battery will safely give off about 20-25 Amps (30-40% of capacity), thus, the active life will be less than 1 hour.
Do I need to maintain traction batteries?
Liquid traction batteries (with plugs) require periodic checks of electrolyte levels and distilled water. Hermetic AGM and GEL, as well as lithium batteries, are maintenance-free in terms of electrolyte, but require cleanliness and periodic recharging during storage.