Planning for an electric launch always starts with the question of energy supply, because it depends on the quality and specifications of the power source how far you can swim and how much time you spend away from the shore.
Many beginners mistakenly believe that any powerful battery is suitable for this purpose, but the specifics of the work. traction-battery It is very different from the starter analogues used in cars.
The wrong choice can lead to rapid degradation of expensive equipment or even to an emergency situation in the middle of a reservoir, so the study of technical specifications should be approached with the utmost seriousness.
⚠️ Note: It is strictly forbidden to use conventional starter car batteries (SLI) as traction batteries, as they are not designed for long-term energy output by low currents and can quickly fail.
Difference between starter and traction batteries
The fundamental difference lies in the design of the plates and the chemistry of the processes that occur inside the housing during operation.
Starter batteries are designed to give a huge current for starting the internal combustion engine in a split second, and then immediately replenish the charge from the generator.
In turn, tractor It must provide a stable voltage for a long time, withstanding hundreds of cycles of deep discharge without loss of capacity.
If you use a starter battery for an electric motor, it will quickly lose its capacity due to the sulfation of the plates at a deep discharge.
Traction models have thicker plates and special separation, which allows them to work in mode. Deep CycleIt can be used to deliver up to 80% of the charge without fatal consequences for chemistry.
The cost of such solutions is higher, but the work life is measured not in months, but in years of intensive operation.
- 🚤 Starter batteries are afraid of a deep discharge below 20%.
- ⚡ Traction batteries are designed for cyclic operation.
- 🔋 The resource of traction models is 3-5 times higher with proper operation.
The main types of batteries for boats
The modern market offers several core technologies, each with its own advantages and disadvantages in the context of water use.
The most common are lead-acid batteries, which are divided into liquid (WET), gel (GEL) and made by technology. AGM (Absorbent Glass Mat).
AGM batteries are considered the middle ground: they are sealed, maintenance-free, can withstand vibration and can operate in any position that is critical for a boat.
However, the real breakthrough in the industry was the lithium-iron-phosphate batteries, known as the LiFePO4.
They are much lighter than lead analogues, have a almost linear discharge curve and withstand many times more charge-discharge cycles.
Their only disadvantage is still a high initial cost, although in terms of full service life they are often more profitable.
⚠️ Warning: When choosing lithium batteries, make sure that they have a built-in high-quality BMS board with protection against low temperatures, as charging lithium in the cold is deadly for the cell.
Calculation of the required capacity and power
To understand what kind of battery is needed, you need to conduct basic calculations, based on the specifications of your electric motor and the desired battery life.
The average current consumption of the motor is usually specified in the specification, but the actual numbers depend on the weight of the boat, the presence of wind and current.
For an approximate calculation, use the formula: consumption current (A) multiply by the desired stroke time (h) and divide by the depth factor of the discharge (0.5 for AGM, 0.8 for LiFePO4).
For example, if the motor consumes 20 Amps and you want to swim for 4 hours, you will need a margin of 80 AH.
However, for the lead AGM battery, taking into account the depth of the discharge of 50%, the actual required capacity will be 160 Ah, while lithium will suffice and 100 Ah.
Always keep a small amount of storage, as over time nominal The batteries will go down.
To increase battery life, it is more efficient to connect two smaller batteries in parallel than to buy one huge battery – this will also increase the reliability of the system.
specifications comparison table
To systematize the data and simplify the choice, it is worth considering the key parameters of different types of batteries in a comparative table.
This will help to visually assess the difference in weight, resource and permissible depth of discharge.
| Parameter | AGM (Lead) | GEL (Gel) | LiFePO4 (Lithium) |
|---|---|---|---|
| Weight (at 100 Ah) | ~29-32 kg | ~30-33 kg | ~10-12 kg |
| Cycles (80% discharge) | 400-600 | 500-700 | 2000-5000 |
| Depth of discharge (DoD) | 50% | 60% | 90-100% |
| Self-discharge per month | 3-5% | 2-3% | 1-2% |
As you can see from the table, lithium technologies win in weight and number of cycles, but lose in price.
Lead batteries remain heavy, but they are easier to dispose of and more tolerant to charging conditions.
Charging and maintenance rules
The durability of any battery depends on how you charge and store it in the off-season.
For lead-acid batteries, it is critical to use chargers with the right ones. charge-stage: main charge, absorption and buffering.
Overcharging is destructive for them, as it causes boiling of the electrolyte and corrosion of the lattice, even in sealed models.
Lithium batteries require specific chargers with profile CC/CV Constant Current / Constant Voltage and precise voltage control on each cell.
If you are using an old charger, make sure it does not have a desulfation or pulsed recovery mode that could damage the lithium battery’s BMS.
Store batteries best in a charged state at a temperature of +10 to +20 degrees Celsius.
☑️ Checklist of preparation for wintering
Safety and installation on board
Installation of the battery on the boat should be done in compliance with all safety standards, as water and electricity are a dangerous combination.
The battery must be securely fixed in a special locker or box that has ventilation to remove gases (especially important for lead batteries).
Use only copper cables with a cross section corresponding to the consumption current, and be sure to install a fuse or automatic switch next to the plus terminal.
The terminals should be tightly tightened and protected from spray and salt water, which causes rapid corrosion.
For lithium systems, it is recommended to install a separate mass switch to completely equip the system during long parking.
Why is the calibre of the cable important?
Using too thin a wire will cause the motor to drop voltage and the cable to heat up, which can cause a fire. Always choose a section with a margin.
⚠️ Warning: Never place the battery in a fully sealed box without ventilation, as when charged intensively, lead batteries can release explosive hydrogen.
FAQ: Frequently asked questions
Can a lithium battery be charged with a conventional car charger?
Car chargers often have a high voltage desulfation mode or incorrect charging completion algorithm, which can damage the BMS of a lithium battery or cause it to ignite.
Which battery is better to choose for a PVC boat?
For inflatable boats, weight is critical, so the best choice will be the weight of the boat. Lithium-Iron-Phosphate (LiFePO4) Batteries3 times lighter than lead with the same capacity.
Should I take the battery off the boat for the winter?
Yes, lead batteries can't be stored in cold - the electrolyte can freeze and destroy the body. Lithium batteries are also best stored in heat at partial charge (40-60%).
What is a BMS in a battery?
BMS (Battery Management System) is an electronic control board that controls cell voltage, temperature, charge and discharge currents, protecting the battery from overloads.
The correct choice of battery type and compliance with the rules of its operation can increase the life of your power system by 2-3 times.